Description of the Related Art Surgical ballons are used for procedures such as percutaneous transluminal angioplasty for treatment of stenosis and for occluding blood vessels to prevent release of emboli into the bloodstream during such procedures. During this type of procedure, a guidewire is conventionally used to guide the insertion of the medical instrument, such as a balloon catheter, to the desired treatment site within a patient's vasculature. A hollow guidewire or guidewire catheter with a balloon at its distal tip is often used to anchor the guidewire at the treatment site. A medical instrument such as a occlusion balloon catheter for emboli containment may have multiple lumens and a pair of occlusion ballons. Alternatively, the balloon on the guidewire or catheter may be used for the occlusion of the vessel downstream of the treatment site.

Surgical ballons are typically made of compliant material and increase in diameter with increasing inflation pressure until the balloon burst pressure is reached. Surgical ballons such as occlusion ballons and ballons used for anchoring guidewires must be expanded to contact the blood vessel wall. Clinicians, however, often do not know exactly when the balloon has contacted the blood vessel walls, if uniform circumferential occlusion has been accomplished or whether the balloon has been overinflated. In addition, some ballons may undergo longitudinal expansion, further resulting in balloon inflation in a manner that is unpredictable and undesirable. The longitudinal expansion andlor overinflation of the balloon may, for example, damage the surrounding healthy tissue.

Conventional surgical ballons are inflated with a syringe coupled to the proximal end of the catheter. The syringe, which is located external to the patient, typically has a fluid capacity of anywhere from 1 cc to 10 cc and the clinician uses the syringe to inflate the ballon. The clinician must have considerable patience, skill and concentration to accurately deliver a suitable volume of fluid, such as 0.05 cc, to properly inflate the ballon.

The clinician must also be extremely careful not to overinflate the ballon. Although a pressure gauge is provided on some syringes, the skill required to avoid overinflation is still beyond many clinicians because a very small movement of the syringe piston results in a relatively large injection of fluid. For example, if the clinician desires to deliver about 0.1 cc of fluid to the balloon from a conventional 10 cc syringe, the travel of the syringe piston is less than about 0.7 mm. Thus, it can be readily seen that the control of the syringe to this degree of precision is very difficult. Additionally, unlike therapeutic ballons (which require about 20 atmospheres pressure and can use syringes ranging between about 10 to 20 cc in fluid capacity), typical occlusion ballons require less than about 3 atmospheres pressure and require less than about 1 cc of fluid. Because occlusion ballons are inflated to relatively low pressures with small amounts of fluids, the clinician must be very careful when using a conventional syringe to inflate the ballon.

The risks of imprecision while inflating a surgical balloon with a conventional syringe are substantial. For example, overinflation of the occlusion balloon may cause it to rupture, releasing inflation media into the bloodstream (e. g., fluid, air, gas, etc.), and possibly allowing pieces of the balloon to enter the bloodstream. In addition, the balloon will fail to occlude emboli or anchor the guidewire. Overinflation of the balloon can also damage the healthy tissue adjacent the vessel segment undergoing treatment, even if the balloon does not rupture. The radial expansion of the balloon can also cause undesirable pressure on the vessel wall, and longitudinal expansion of the balloon can create a shearing force which could lead to vessel trauma. Further, if the balloon is overinflated, it may experience a decrease in fatigue strength. For example, if a surgical balloon is overinfiated such that it is approximately two to three times its original working length, the balloon may experience a significant decrease in fatigue strength. Underinfiation of the balloon also causes many difficulties and problems. An underinflated ballon, for example, may allow fluid to flow around the balloon and the balloon may fail to occlude emboli or anchor the guidewire in the desired position.

Thus, there is a need for a low volume syringe to provide accurate delivery of a suitable amount of fluid to a surgical balloon.

It is also very difficult for the clinician to deliver the desired volume of fluid and then maintain the syringe in a fixed location such that the volume of fluid does not subsequently change. For example, once the clinician has depressed the plunger of the syringe a desired amount to properly inflate the ballon, the clinician must hold the plunger in that position until the pressure equalizes andlor it is desired to deflate the ballon. As discussed above, even small movements of the syringe plunger may cause overinffation or underinflation of the ballon. Thus, the clinician must be very careful not to allow the plunger to move even a very small distance after the fluid is delivered because that may effect the amount of fluid delivered by the syringe.

Thus, a need exists for a syringe which delivers a desired volume of fluid and then does not allow that volume of fluid to be unintentionally changed.

In addition to the problems of overinflation, another problem exists when inflating occlusion balloons. As discussed above, even though the pressure required to inflate the occlusion balloon is generally less than 3 atmospheres, the pressure caused by a conventional inflation syringe causes an immediate build up of pressure near the syringe. The build up of pressure can reach magnitudes of 400 psi. This high pressure caused by conventional syringes often causes leaks in the system and it may damage the ballon. Additionally, this high pressure makes it very difficult for the clinician to properly inflate the balloon to the desired size and pressure.

Thus, there is a need for a syringe that does not create the high build up of pressure created by conventional syringes.

It is also common to use a syringe as a vacuum source either during aspiration to remove debris or in the preparation stage to remove air bubbles from within the system. The vacuum is typically created by pulling the plunger away from the body of the syringe and holding it in place to create a negative pressure in the conduit connected to the plunger. The plunger is typically equipped with an internal ring surrounding the inside of the elongated cylinder of the syringe housing. Once the end of the plunger is pulled over the internal ring, the plunger will be locked in place. Pulling the

plunger out to a position near the end of the body of the syringe, however, creates a risk of the plunger being pulled out of the body of the syringe. If the plunger is pulled out of the body, it will cause a complete loss of the vacuum and it may allow the potential entry of contaminants into the system.

Thus, a need therefore exists to create a syringe, or syringe system, that minimizes the risk of losing the vacuum and contaminating the system.

Summarv of the invention A need exists for a low volume syringe which inflates surgical ballons without the above-described problems and disadvantages.

The present invention is an apparatus and method for inflating surgical balloons and, in particular, inflating surgical ballons requiring minimal amounts of inflation fluid. Desirably, the apparatus and method includes a syringe which inflates surgical balloons for proper contact with a wall in a human body, such as a vessel wall, without damage to the wall. Advantageously, the present invention is not limited to occlusion balloons and it can be used, for example, in connection with other ballons, other types of inflatable devices, low volume accurate fluid delivery, etc.

Preferred embodiments of the present invention are illustrated below in connection with a guidewire catheter having an occlusion balloon attached. It will be appreciated, however, that the present invention is readily adapted for use with other medical devices requiring small inflation volumes, for example, to prevent balloon rupture and/or damage to the surrounding tissue. In addition, the present invention can be used with somewhat larger balloons, such as therapeutic ballons for angiopiasty procedures, where the enhanced control of the delivery of the inflation fluid is beneficial. The present invention also provides important benefits for non-angioplasty balloon procedures, as well as certain non-balloon applications where inflationlinjection and/or deflationlevacuation are utilized.

One aspect of the present invention is a low volume syringe for inflating a medical or surgical balloon attached to a distal end of an elongated tube (e. g., a catheter or canula) which is inserted into a patient's vasculature. The syringe includes an elongated body having a proximal end and a distal end. A stop or flange is located at the proximal end of the body and the distal end is adapted for attachment to the elongated tube. A plunger with an elongated shaft is located within the elongated body and the plunger includes a handle located at the distal end of the shaft. A housing is connected to the body of the syringe and the housing includes a locking member which is used to lock the plunger in a desired position.

Desirably, the housing and the handle are positioned to allow the user to easily grip and operate the syringe. The plunger preferably includes a resilient piston provided at its distal end and an annular groove configured to receive the locking member.

The locking member of the syringe advantageously allows the plunger to move a predetermined distance before it is locked into position. This allows the syringe to inject a predetermined amount of fluid, based upon the internal volume of the body of the catheter and the distance traveled by the plunger, into a balloon and then the plunger is held in place. This eliminates guessing or estimating how much fluid has been injected by the syringe. Preferably, the predetermined volume of fluid to be injected by the syringe is matched to a balloon of a given size and shape so that balloon is properly inflated.

Significantly, different syringes may have various sizes and configurations to provide different volumes of fluid according, for example, to the size of the balloon to be inflated.

The locking member of the syringe also advantageously maintains the plunger in the desired position, and this prevents unintentional movement of the plunger. That is, once the locking member locks the plunger in the desired location, the clinician does not have to maintain the plunger in the same location-which can be a very difficult and tiresome task. A conventional syringe, in contrast, requires a force to be maintained on the plunger to keep the plunger from moving once the plunger is depressed. If insufficient force is maintained on the plunger, the plunger will move back (often referred to as "snap back"or"kick back") and this changes the volume of injected fluid. Alternatively, if excessive force is applied to the plunger, the plunger will move forward and this may overinflate the ballon. Thus, the locking member provides accurate inflation of the balloon with a known amount of fluid and that volume of fluid will not subsequently change because of unintended movement of the plunger.

The locking member of the present invention is preferably releasable so that once the plunger is locked into position, the lock can be released to allow additional movement of the plunger. A releasable locking member, for example, allows the plunger to be pulled back to withdraw fluid from the ballon. Thus, the syringe can be used for both irrigation and aspiration. The releasable locking member also allows the syringe to inject additional fluid. For example, the syringe can inject a first known amount of fluid by depressing the plunger a predetermined distance until it is locked into position.

The locking member can then be released and a second known amount of fluid can be injected by moving the plunger another predetermined distance. This allows, for example, the syringe to inflate a balloon with a first known amount of fluid and then a second known amount of fluid. Alternatively, the syringe may be used to inflate a balloon of a first size with only the first amount of fluid, or a balloon of a second size with both the first amount of fluid and the second amount of fluid. For example, a surgical balloon with a 3 mm diameter may be inflated with a first volume of fluid by depressing the plunger until it is located into position. Alternatively, a balloon with a 4 mm diameter may be inflated with a first volume of fluid by depressing the plunger until it is locked into position, releasing the locking member, and then continuing to inflate the balloon with a second volume of fluid. Advantageously, the locking member of the present invention allows two precise amounts of fluid to be injected by a single syringe.

Another aspect of the present invention is a syringe with a flange or stop located at the proximal end of the body. The stop includes an outwardly extending annular ridge and a channel for the plunger shaft to extend therethrough.

The stop preferably includes a generally planar end surface configured to contact and abut the plunger handle when it is fully depressed. The plunger shaft includes an end portion with a narrow shaft which fits through the opening and a centrally disposed portion with a larger shaft that does not fit through the opening. This larger portion prevents the plunger from being pulled back through the opening. Thus, the outer surface of the stop prevents the plunger from being inserted past a specific point and the channel prevents the plunger from being pulled back past a specific point. Thus, the stop limits the travel of the plunger within the body, which limits the amount of fluid that can be drawn into the syringe and that limits the amount of fluid that can be injected by the syringe.

The stop and the locking member preferably work together to allow a balloon to be inflated a first amount and then a second amount, or to allow balloons of different sizes to be inflated a desired amount. In particular, the syringe is preferably filled with fluid and the plunger is fully pulled back. The plunger is then depressed a first amount until the locking member is engaged and a predetermined amount of fluid is injected. The locking member is then released and the plunger is depressed a second amount until the handle contacts the outer surface of the stop. This allows the syringe to provide two different, but precise, volumes of fluid to a ballon. Thus, the same syringe, for example, can inflate two ballons of different sizes or the same balloon with two different volumes of fluid.

Another aspect of the present invention is the syringe which provides precise, low volume fluid control. The syringe includes an elongated, narrow cylindrical body with an elongated plunger centrally located within the body.

Advantageously, because the body has a small inside diameter and the plunger must move a relatively large distance to displace a small amount of fluid, this allows a small volume of fluid to be accurately measured. Thus, the syringe allows small, precise volumes of fluid to be accurately controlled and this is particularly advantageous when it is used to inflate occlusion balloons which have a small volume and contain relatively low pressure.

Yet another aspect of the present invention is a syringe which operates at relatively low pressures of about 200- 300 psi because of the elongated, narrow body and the elongated, narrow shaft of the plunger. This low pressure improves the reliability of the syringe and it makes the syringe easier to use. For example, the low pressure significantly decreases the possibiiity that the syringe or inflation system will leak or that the balloon will be damaged or rupture. In contrast, conventional syringes that operate at pressures of about 400 psi or more are much more likely to develop leaks or damage the ballon. Additionally, it is much more difficult to control the inflation of the balloon with a conventional syringe because of the high pressure. The low pressure syringe of the present invention, on the other hand, provides a desired volume of fluid in a more controlled manner because the low pressure.

In another aspect of the present invention, the low volume syringe described above is combined with a high volume syringe to create a syringe assembly. The high volume syringe provides the capability to quickly prepare the balloon and catheter lumen prior to insertion into a patient and during deflation of the ballon. That is, the high volume syringe has the power to draw out any air or fluid in the pathway to the ballon, which is deflated prior to use. Preferably, the high volume syringe is connected to the low volume syringe by a stopcock or three-way valve which can be operated to allow flow between a) the high volume syringe and the balloon catheter, b) the high volume syringe and the low volume syringe, or c) the low volume syringe and the balloon catheter. Thus, the necessary steps to prepare for and execute the balloon inflation can be accomplished by the appropriate positioning of the valve.

Yet another aspect of the present invention is a low volume syringe with an elongated body including a stop with a radially inwardly extending annular lip. The lip forms a central opening in which a first portion of the plunger is movably located. The central opening in the lip is desirably sized slightly larger than the first portion of the plunger to allow that portion of the plunger to freely move within the opening. The plunger includes a second portion with a diameter larger than the first portion of the plunger. The enlarged second portion is positioned such that when the plunger is withdrawn a predetermined amount, the second portion contacts the inwardly extending lip to limit the withdrawal of the plunger. The

plunger also includes a handle connected to the distal end of the plunger. The handle is larger than the central opening in the stop to limit the inward movement of the plunger. Thus, the stop limits the total amount that the plunger can be depressed and the amount the plunger can be withdrawn. Accordingly, the stop limits the volume of fluid that can be contained within the syringe and the volume of fluid that can be injected from the syringe.

In yet another aspect, the present invention includes filling of the low volume syringe to a limit defined by the stop and injection of inflation fluid by the syringe to a limit defined by the stop. Desirably, the low volume syringe can also be attached to a reservoir syringe and a catheter by a three-way valve. The various settings of the valve allow the reservoir syringe to be used, for example, to evacuate the catheter prior to the procedure, as well as for quick deflation of the balloon for removal from the patient after the procedure.

The syringe or syringe assembly of the present invention advantageously may be used with an inflation adapter and low profile catheter valve attached to the proximal end of the balloon catheter, at a side-access inflation port. In this configuration, the catheter valve is used to open and close the side-access inflation port for communicating fluid from the low volume syringe to the inflation lumen of the balloon catheter, and for evacuationideflation by the reservoir syringe.

Other configurations andlor other devices may also be used in connection with the present invention in order to gain access to the inflation lumen of the balloon catheter or to allow fluid communication between the present inflation syringe and the medical balloon.

The low volume syringe of the present invention is also useful for multiple lumen emboli containment catheters having multiple medical ballons, not just a single ballon. Further, other balloon procedures, such as is used in ablation, gynecological and urological treatments, for example, may reap the benefits afforded by the syringe and method of the present invention. Moreover, other non-balloon applications, such as irrigation) aspiration, drug delivery, transfusion of whole blood, etc., may use the syringe and method of the present invention.

In accordance with a preferred embodiment of the present invention, there is provided a syringe adapted for use in medical procedures requiring relatively accurate volumetric delivery of fluids. The syringe includes an elongated body having a predetermined cross-sectional dimension, a distal end and a proximal end. A plunger with a distal end and a proximal end is longitudinally movable within the elongated body to effect intake and outflow of the fluids. The body is dimensioned such that the cross-sectional dimension has a relatively low profile and the plunger is cooperatively dimensioned within the body such that a relatively long distance of travel of the plunger within the body will result in a relatively low volume of fluid intake or outflow, whereby the amount of fluid delivered in the medical procedure can be accurately controlled by tactile manipulation.

In another embodiment of the present invention, a syringe adapted for use in medical procedures requiring relatively accurate volumetric delivery of fluids includes an elongated body and a plunger longitudinally slidable within the body to effect fluid intake and outflow. The elongated body includes a stop to limit the distance of travel of the plunger within the body and a housing with locking member to maintain the plunger in a fixed location. Preferably, the locking member is releasable to allow additional insertion of the plunger into the body or pulling back on the plunger. The locking

member is desirably located such that a predetermined volume of fluid is injected by the syringe and then the plunger is locked into position. The locking member can then be released to inject a second predetermined volume of fluid.

In yet another embodiment, the syringe of the present invention includes an elongated body having a proximal end and a distal end, and a plunger with an elongated shaft including a handle located at a proximal end and a sealing piston located at a distal end. The plunger is inserted into the elongated body such that the handle is positioned near to the proximal end of the body and a stop is provided at the proximal end of the body for limiting the movement of the plunger.

The stop desirably limits the travel of the plunger into the body and prevents withdrawal of the plunger from the body.

Thus, the stop is used to limit the maximum volume of fluid that can be drawn into the syringe and limit the maximum volume of fluid that can be injected by the syringe.

The syringe of the present invention can also be comprised of a barrel with a tip at one end and a stop at the other end. The barrel preferably has an elongated length and a longitudinal channel formed therethrough. The channel has a diameter sized to received the shaft of the plunger. The shaft is generally cylindrical with an indent section that is sized and configured to cooperate with the stop to limit the travel of the plunger and thereby to limit the maximum volume of fluid that can be contained in the syringe.

Another embodiment of the present invention comprises a syringe assembly adapted for use in delivering fluids during a medical procedure. The assembly comprises a first syringe, a second syringe and a fluid conduit for delivering the fluid during the medical procedure. The first syringe is in fluid communication with the second syringe or the fluid conduit.

The second syringe is in fluid communication with the first syringe or the fluid conduit. The syringe assembly of the present invention preferably includes a connector having two upstream ports, a downstream port and a flow deflector. The downstream port is configured to be attached to the proximal portion of a tube. The first syringe is a low volume syringe with an elongated body and a locking member to retain the plunger of the syringe in a desired location. One of the upstream ports of the connector is attached to a distal end of the low volume syringe. The second syringe is preferably a large volume syringe with a relatively large fluid capacity. The large volume syringe has a distal end adapted to be attached to the other of the upstream ports of the connector and the large volume syringe is configured to facilitate quick evacuation of the inflation lumen and the ballon. The large volume syringe also preferably provides fluid to the low volume syringe as required.

Still yet another embodiment of the present invention comprises a syringe assembly adapted for use in delivering fluids during a medical procedure. The syringe assembly includes a low volume syringe, a large volume syringe, a high pressure valve assembly, and a high pressure fluid conduit. The low volume syringe preferably includes a stop to limit the travel of the syringe and a locking member which releasably locks the plunger in a predetermined location. The locking member more preferably locks the plunger into position after a predetermined volume of fluid has been injected by the syringe. The high pressure valve assembly is in fluid communication with the low volume syringe, the large volume syringe, and the high pressure line. The high pressure valve selectively allows fluid communication between the large volume syringe and the low volume syringe, or the low volume syringe and the high pressure fluid conduit, or the large volume syringe and the high pressure fluid conduit.

The maximum volume of fluid contained in the low volume syringe is preferably in the range of between about 0.01 cc to about 10 cc of fluid and more preferably, the maximum volume contained in the low volume syringe is in the range of between about 0.05 cc to about 2 cc of fluid, but the volume can be larger or smaller. Further, the maximum volume contained in the large volume syringe is preferably in the range of between about 10 cc to about 30 cc. The high pressure line is preferably rated for use at a pressure of 500 psi and even more preferably the high pressure line is rated for use at a pressure of 250 psi. The high pressure valve of this embodiment is rated for use at a pressure of 750 psi. Even more preferably, the high pressure valve is rated for use at a pressure of 500 psi.

Yet another embodiment of the present invention is a syringe assembly adapted for use in delivering fluids during a medical procedure. The syringe assembly includes a low volume syringe, a large volume syringe, a high pressure valve assembly, a high pressure fluid conduit, and a locking means attached to the low volume syringe for locking the plunger of the low volume syringe in a desired position. Preferably, the locking means is releasable to allow further movement of the plunger. More preferably, the locking means is releasable to allow additional delivery of fluid and/or removal of fluid.

Still yet another embodiment of the present invention is a low volume syringe adapted for use in medical procedures requiring relatively accurate volumetric delivery of fluids. The low volume syringe includes a body including a proximal and distal end, and a plunger longitudinally slidable within the body to effect fluid intake and outflow. The body has a small cross-sectional area and an elongated body to limit the pressure within the syringe to a maximum of about 300 psi.

Another embodiment of the present invention is a syringe with an elongated body and a locking member. The elongated body has a predetermined cross-sectional dimension, a distal end, a proximal end, and a plunger which is longitudinally slidable within the body to effect intake and outflow of the fluids. The plunger includes a handle mounted to the distal end and an annular groove located between the distal and proximal ends of the plunger. The locking member is configured to selectably engage the annular groove in the plunger. Preferably, when the plunger is locked into position by the locking member, the plunger is not longitudinally movable within the elongated body, and when the plunger is not locked into position, it is freely slidable.

Yet another embodiment of the present invention is a syringe with a plunger having an elongated shaft. Located at the distal end of the shaft is a handle and located at the proximal end of the shaft is a spring and a piston. The spring has a spring rate which is selected to prevent overinflation of the ballon. Specifically, the spring rate is selected so that once the balloon is inflated to a predetermined pressure, the spring will collapse if any additional pressure is provided.

Desirably, the syringe also includes a locking member to selectively hold the plunger in a desired position and a stop to limit the range of movement of the plunger.

Still another embodiment of the present invention comprises a method of easily and precisely inflating a balloon catheter. The method includes inserting and positioning a tube and balloon at a desired position within a blood vessel of a patient and providing a three-way valve having first and second inlet ports and an outlet port, where the outlet port is adapted to be attached to the proximal portion of the tube. The method also includes a low volume syringe adapted to be attached to the first inlet port of the valve, the low volume syringe including a housing and a locking member for limiting

injection of inflation fluid to a predetermined amount, and a high volume syringe adapted to be attached to the second inlet port of the valve, the high volume syringe has a reservoir lumen. Additionally, the method preferably includes positioning the valve to communicate the high volume syringe with the lumen of the tube and pulling on a plunger of the high volume syringe to effect evacuation of air or fluid within the tube, the balloon and the outlet port of the connector into the high volume syringe. The method preferably also includes positioning the valve so that the inflation lumen of the low volume syringe communicates with the lumen of the tube and pushing the plunger of the low volume syringe to deliver the predetermined amount of fluid to the tube and the ballon, whereby the predetermined amount of fluid inflates the balloon to an appropriate size without rupture of the balloon or damage to the blood vessel of the patient.

Another embodiment of the present invention includes a method of easily and precisely inflating a balloon catheter comprising an elongated tube having a proximal portion and a sealed distal end with a surgical balloon attached thereto. The tube has a longitudinally extending lumen communicating with the balloon for inflation thereof. The method comprises the following steps: providing a three-way valve having first and second inlet ports and an outlet port; providing an inflation adapter assembly attached to the outlet port of the three-way valve and attached to the proximal portion of the tube selectively positioned in a first position to allow fluid communication through the inflation adapter and a second position to prevent fluid communication to the inflation adapter; providing a low volume syringe adapted to be attached to the first inlet port of the valve, the low volume syringe having an inflation lumen and a locking member for limiting injection of inflation fluid to a predetermined amount; providing a high volume syringe adapted to be attached to the second inlet port of the valve, the high volume syringe having a reservoir lumen; positioning the inflation adapter in a first position to allow fluid communication through the inflation adapter and to the tube; positioning the valve to communicate the high volume syringe with the lumen of the tube and pulling on a plunger of the high volume syringe to effect evacuation of air or fluid within the tube, the balloon and the outlet port of the connector into the high volume syringe; inserting and positioning the tube and balloon at a desired position within a blood vessel of a patient; positioning the valve so that the inflation lumen of the low volume syringe communicates with the lumen of the tube; positioning the inflation adapter in a first position to allow fluid communication through the inflation adapter and to the tube; pushing the plunger of the low volume syringe to deliver the predetermined amount of fluid to the tube and the balloon; and positioning the inflation adapter in a second position to prevent fluid communication through the inflation adapter and to the tube, whereby the predetermined amount of fluid inflates the balloon to an appropriate size without rupture of the balloon or damage to the blood vessel of the patient.

Yet another embodiment of the invention is a method of easily and precisely delivering fluids during a medical procedure through an elongated tube having a proximal portion and a distal end. The tube has a longitudinally extending lumen communicating with the distal end. The method includes inserting and positioning the tube at a desired position within a blood vessel of a patient, and providing a three-way valve having first and second inlet ports and an outlet port, the outlet port adapted to be attached to the proximal portion of the tube. The method also includes providing a low volume syringe with a housing and a locking member. The low volume syringe is adapted to be attached to the first inlet port of the valve. Additionally, the method includes providing a high volume syringe adapted to be attached to the second

inlet port of the valve. The valve is then positioned to communicate the high volume syringe with the lumen of the tube and pulling on a plunger of the high volume syringe to effect evacuation of air or fluid within the tube, the balloon and the outlet port of the connector into the high volume syringe. The valve is subsequently positioned so that the inflation lumen of the low volume syringe communicates with the lumen of the tube and pushing the plunger of the low volume syringe delivers the predetermined amount of fluid to the tube and the ballon. Preferably, the fluid is inflation fluid, irrigation fluid, whole blood or a therapeutic drug. More preferably, the fluid is delivered without damage to the blood vessel of the patient.

Further aspects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments and the drawings referenced herein, the invention not being limited to any particular embodiment.

Brief Description of the Drawings The appended drawings contain figures of preferred embodiments of the present apparatus and method for inflating surgical balloons. The above-mentioned features, as well as other features, will be described in connection with the preferred embodiments. The illustrated embodiments, however, are only intended to illustrate the invention and not limit the invention. The drawings contain the following figures: Figure 1 shows a preferred embodiment of a syringe assembly having features in accordance with the present invention and operabty coupled to an illustrative inflation adapter at a proximal portion of a balloon catheter; Figure 2 shows a perspective view of the catheter valve and balloon catheter of Figure 1 placed within an open inflation adapter; Figures 3A and 3B show the closed and open low profile catheter valve positions, respectively; Figure 4 shows the syringe assembly of Figure 1 including a low volume syringe and a high volume syringe operably coupled using a three-way valve; Figures 5A-5C show the various positions of the three-way valve which determine the flow between the syringes and the balloon catheter; Figure 6 shows a cross-sectional view along the longitudinal axis of a preferred embodiment of the low volume syringe of the present invention; Figure 6A shows a cross-sectional schematic view of the stop mechanism of the low volume syringe of Figure 6.

Figure 7 shows an end view of the low volume syringe of Figure 6; Figure 8 shows a syringe having an alternative embodiment of a stop member; Figures 9A and 9B show a syringe having yet another embodiment of a stop member; Figures 10 and 11 show alternative connections of a low volume syringe having features in accordance with the present invention; Figure 12 shows an alternative syringe assembly utilizing the low volume syringe of Figure 6; Figure 13 shows a preferred embodiment of a high pressure syringe assembly with an exploded view of the plunger stop mechanism; Figure 14A shows a plan view the plunger stop mechanism of Figure 13;

Figure 14B shows a cross section of Figure 14A taken aiong the line 14B-14B; Figure 15 shows an exploded perspective view of another preferred embodiment of the low volume syringe of the present invention; Figure 16 shows a cross-sectional view along the longitudinal axis of the low volume syringe of Figure 15, illustrating the plunger in a pulled back position; Figure 17 shows a cross-sectional view along the longitudinal axis of the low volume syringe of Figure 15, illustrating the locking member engaging the shaft of the plunger; Figure 17A shows an enlarged cross-sectional view of a portion of the low volume syringe of Figure 17, illustrating the locking member engaging the annular groove in the plunger shaft; Figure 18 shows a cross-sectional view along the longitudinal axis of the low volume syringe of Figure 15, illustrating the plunger in an inserted in position; Figure 19 shows a cross-sectional view along the longitudinal axis of yet another preferred embodiment of the low volume syringe of the present invention, illustrating the plunger in a pulled back position; Figure 20 shows a cross-sectionai view along the longitudinal axis of the low volume syringe of Figure 19, illustrating the locking member engaging the shaft of the plunger; and Figure 21 shows a cross-sectional view along the longitudinal axis of the low volume syringe of Figure 19, illustrating the plunger in an inserted in position.

Detailed Description of the Preferred Embodiment The present invention involves a low volume syringe and method for inflating surgical ballons. The principes of the present invention, however, are not limited to inflating surgical balloons. It will be understood that, in light of the present disclose, the low volume syringe can be successfully used to control the movement of fluids such as irrigation fluid, blood or therapeutic drugs.

Additionally, to assist in the description of the present invention, words such as upper, lower, front, back, left and right are used to describe the accompanying figures. It will be appreciated, however, that the present invention can be located in a variety of desired positions-including various angles, sideways and upside down. A detailed description of the present invention now follows.

A preferred embodiment of a low volume or inflation syringe 10 in a syringe assembly 100 having features in accordance with the present invention is shown in Figure 1. Also shown in Figure 1 is an illustrative connection of the syringe assembly 100 to an occlusion balloon guidewire catheter 12 utilizing an inflation adapter 30. The syringe assembly 100, comprising the inflation syringe 10 and a larger capacity or reservoir syringe 110, is attached via tubing 216 to the inflation adapter 30 within which a low profile catheter valve 32 and the balloon catheter 12 are engaged during use.

The catheter valve 32, described in more detail below in connection with Figures 3A and 3B, is attached to an open proximal end of the catheter 12. The low volume syringe 10 is used to inject inflation fluid through the adapter 30 and valve 32 into a lumen of the hollow catheter 12, and into the balloon 14. The inflation adapter 30, described in more detail below in connection with Figure 2, is used to open and close the valve 32 to regulate the inflation of the balloon 14

mounted on the distal end of the catheter 12. Nevertheless, it will be emphasized that other types of adapters andlor valves can be employed with the inflation syringe and : or syringe assembly of the present inflation, in order to achieve rapid and accurate inflationideflation of medical balloons or other non-balloon medical devices. Therefore, although the present inflation is illustrated in connection with a low volume occlusion balloon 14, other types of balloons and non-balloon devices can benefit from the advantages of the invention.

The balloon 14 is mounted on a distal end of a hollow guidewire 16 which defines the inflation lumen for the ballon, and the syringe 10 and/or syringe assembly 100 is connected at the proximal control end 33 of the guidewire 16.

Prior to use of the low volume syringe 10 to inflate the balloon 14 to the proper size for the vascular segment to be treated, the guidewire 16 and balloon 14 are first"primed"or evacuated. The reservoir syringe 110 of the assembly 100 may be used for the evacuation. Access to the vascular site is through a port in the patient obtained, for example, using an introducer (not shown). The introducer arrangement for entry into the patient may be that described in assignee's co- pending U. S. application Serial No. 081874,307, filed on June 13,1997, entitled MEDICAL WIRE INTRODUCER AND BALLOON PROTECTIVE SHEATH, which is incorporated by reference in its entirety. A preferred system and method for accomplishing the occlusion balloon inflation is described below.

Generally, the inflation syringe 10 of the present invention is provided with a stop mechanism 20 for limiting both the intake of fluid into the syringe and the delivery of fluid from the syringe. Various embodiments of such a stop mechanism 20 are described in more detail below in connection with Figures 6-9, and alternative embodiments of the syringe are also described in connection with Figures 15-18. As shown in Figures 6-9, the syringe 10 has an elongate cylinder 44 and plunger arrangement 50 which provide for greater displacement or travel by the plunger along the cylinder length than is necessary to expel a relatively small amount of inflation fluid. Thus, with the stop mechanism 20, the clinician is provided with an enhanced sense of whether the fluid in the syringe 10 has been delivered to the ballon, which helps compensate for lack of precision by the clinician. The stop mechanism 20 may be mounted on the syringe 10 during production, or as separate components that can be retro-fit onto an existing supply of syringes.

Overview of Balloon InflationlDeflation Referring to Figures 1-3, a balloon guidewire catheter 12 has a low profile catheter valve 32 attached to a proximal end of the guidewire 16 having a side-access inflation port 17, shown in greater detail in Figures 3A and 3B. The inflation port 17, proximal end of the catheter 12 and distal end of the valve 32 is positioned within the inflation adapter 30 (see Figure 2) to which a syringe assembly 100 in accordance with the present invention has been operabiy coupled.

The inflation syringe 10 is coupled via an injection cap 22 at its distal end to a valve 112 that also connects the large capacity syringe 110 and a short tube segment 216. The tube segment 216 is adapted to connect to a fitting or male luer member 24 of the inflation adapter 30. Thus, the valve 32 is opened and closed by the adapter 30 to allow use of the low volume syringe 10 of the syringe assembly 100 to inflate the balloon 14 at the end of the catheter 12. Preferably, the low profile catheter valve 32 is as described in assignee's co-pending U. S. application Serial No. 081975,723, filed November 20,1997, entitled LOW PROFILE CATHETER VALVE AND INFLATION ADAPTER, which is incorporated by

reference in its entirety. It will be apparent especially from Figures 3A and 3B that the valve 32 is considered"low profile" since it is no larger in cross-sectional diameter than the catheter 12 itself.

Referring to Figures 1 and 2, the inflation adapter 30 comprises a housing having two halves 34,36 preferably formed of metal, medical grade polycarbonate, or the like. The halves 34,36 are attached by hinges 205 to be separated or joined in a clam shell manner. A locking clip 38 secures the halves while the adapter 30 is in use. A groove within the housing has a width to accept the proximal end 33 of the catheter 12 having the low profile valve 32. The male luer member 24 (Figure 1), or other suitable connector, extends from a top of the housing to provide an inflation passageway.

Seals 280 are provided within the housing and around the internal segment 285 of the inflation pathway to conduct the pressurized fluid provided by the syringe 10 attached to the male luer member 24.

In one embodiment shown in Figures 3A and 3B, the low profile catheter valve 32 comprises a movable sealer portion 35 attached at a distal end of a wire segment 37 and positioned within an inflation lumen 15 of the guidewire catheter 12. The wire 37 may be secured to a spring just within a proximal opening of the catheter 12. It will be noted that various spring or biasing arrangements may be utilized, including a zig-zag wire 41 which is formed on or replaces the wire segment and which provides biasing force to the sealer portion 35 due to frictional engagement with the walls of the lumen 15. The sealer portion 35 forms a fluid tight seal with the inflation lumen 15 by firmly contacting the entire circumference of a section of the inflation lumen 15. The sealer portion 35 may be positioned proximally of the side-access inflation port 17 on the catheter to establish an unrestricted fluid pathway between the inflation port 17 and the inflatable balloon 14 on the distal end. As desired, the clinician may move the sealer portion to a position at, or distal of, the inflation port, thereby preventing any fluid from being introduced into or withdrawn from the balloon 14 via the inflation port 17.

An actuator 40, shown in Figure 1 at the top of the adapter housing, controls a cam which operates sliding panels 291 (Figure 2) contained in the housing. Preferably, the catheter 12 is positioned within the housing with the valve closed (Figure 3A), such that the side inflation port 17 is located in the sealed inflation area 285 of the housing. An adjacent proximal portion of the catheter extends outside the housing (and the patient), and a proximal portion 33 of the catheter valve 32 extends out of the other side of the housing. The locking clip 38 is then secured and then the syringe 10 may be attached. The actuator 40 is moved from a first position to a second position, such that the sliding panels 291 within the housing cause the valve to be in an open position to allow fluid flow through the inflation port 17 (Figure 3B).

Closing the valve is accomplished by moving the actuator 40 from the second position back to the first position (Figure 3A), such that the balloon inflation is maintained.

Other inflation adapters may be used with the inflation syringe of the present invention as desired. Other connectors or fittings, such as tubing, quick connects and Y-connectors, may also be used according to the particular application and available supply of equipment, as shown, for example, in Figures 10-11. (in Figure 10, for example, the inflation syringe is connected via the injection cap 22 directly to the guidewire 16 to allow inflation of the balloon 14 on the catheter. In Figure 11, the inflation syringe 10 is connected via a short tubing 216 to a y-connector 210 which is in turn in fluid communication with the catheter 12. Thus, a variety of inflation devices and techniques are available in connection with the inflation syringe 10 of the present invention.)

Occlusion Balloon Guidewire The guidewire 16, or catheter used as a guidewire, has an inflation lumen 15 for communicating pressurized inflation fluid, such as a saline solution or contrast dye, to the balloon 14. The lumen 15 extends from the open proximal end to the sealed distal end which has a side opening for communication with the balloon interior.

Preferably, the hollow guidewire material is stainless steel, or, alternatively, an alloy of nickel and titanium known as nitinol. Alternatively, another metallic material such as titanium may be used. Other biocompatible elongate flexible tubes, made of polymeric materials such as nylon, polyamide, polyethylenes, or combinations thereof, for example, are also appropriate for use with the present invention. Various embodiments of a suitable guidewire and occlusion ballons are described in assignee's co-pending U. S. application Serial No. 081812,876, filed March 6,1997, entitled HOLLOW MEDICAL WIRES AND METHOD FOR CONSTRUCTING THE SAME, which is incorporated by reference in its entirety, and co-pending U. S. application Serial No. 091026,105 filed on February 19,1998, entitled SHAFT FOR MEDICAL CATHETERS, which is incorporated by reference in its entirety. The guidewire 16 is preferably circular in cross-section with an outer diameter (OD) of about 0.010" to 0.044". More preferably, the OD is no more than about 0.020". The inner diameter (ID) of the guidewire 16, or lumen diameter, is preferably from about 0.008" to 0.010", and more preferably about 0.009".

The occlusion balloon 14 is preferably made of a block copolymer of styrene-ethylene-butylene-styrene (SEBS) such as C-Flex (TM) available from Consolidated Polymer Technologies. More preferably, the balloon material is C-Flex (TM) resin grade R70-050-000, as described in assignee's co-pending U. S. application Serial No. 091026,225, filed on February 19,1998, entitled BALLOON CATHETER AND METHOD OF MANUFACTURE, which is incorporated by reference in its entirety. The balloon 14 is attached to the guidewire 16 using any conventional method, such as heat bonding or adhesives. For example, for attachment of a SEBS balloon to a nitinol tube, a primer such as 7701 LOCTITE (TM) by Loctite Corporation is preferably used along with cyanoacrylate adhesive such as LOCTITE 4011.

Low Volume Syringe A preferred embodiment of the low volume syringe 10 is shown schematically in Figure 6. The type or size illustrated is a 0.5 cc tuberculin syringe, although other size syringes having capacity ranging between about 0.02 cc to 1.0 cc may be used. More preferably, the capacity of the low volume syringe is between about 0.25 to 0.50 cc. The resultant displacement required for delivery of about 0.1 cc fluid is about 10 mm for a 0.25 cc syringe. Indicia 42 may be provided along the length of the exterior surface of a cylinder 44 for visual aid of the clinician during use. Nevertheless, as described below in more detail, a stop mechanism is advantageously provided on the syringe 10 in order to accurately limit the inflation fluid intake and expulsion, thereby providing a means for the clinician to safely and accurately perform the desired procedure.

Referring to Figures 6 and 7, the elongate body of the syringe comprises a cylinder 44 having a stop or flange 46 extending radially outward at a proximal end and preferably being attached at a distal end to an injection cap 22. The distal end of the cylinder 44 has a nose portion 48 with a reduced diameter for connection with the injection cap 22. A plunger 50 has a shaft 52 of appropriate length and a resilient piston 54 attached at its distal end. The shaft 52 is

inserted in a central lumen 56 of the cylinder and the piston 54 provides sealing engagement with the inner surface of the cylinder 44. The plunger 50 has a disk 58 at the proximal end of the shaft 52 for operation of the plunger 50. A preferred source for unmodified, conventional syringes is Becton Dickinson & Co. of Franklin Lakes, New Jersey.

The injection cap 22 preferably comprises a modified female member of a luer type connector. A first end 60 of the cap has a proximal wall with an aperture corresponding to the outer diameter of the cylinder 44, and a distal wall having an aperture corresponding to the outer diameter of the nose 48. These apertures are used to mount the injection cap 22 on the syringe 10. A threaded second end 62 of the cap can be screwed onto a male luer member 24, as in the examples of Figures 1 and 4. Alternatively, a tubular segment 64 within the second end 62 of the cap may be directly attached to the control end of the guidewire 16 using a sleeve 66, as described in more detail above in connection with Figure 10. Other suitable cap configurations may also be used to facilitate coupling of the syringe to a guidewire or catheter to provide inflation of the ballon. One preferred source of the cap is Medical Disposables International, Inc. of West Conshohocken, Pennsylvania.

Another preferred embodiment of the low volume syringe is shown in Figures 15-18. The low-volume syringe 310 preferably has a capacity ranging between about 0.05 cc and about 10 cc, and more preferably a capacity between about 0.06 cc and about 2 cc, but the volume of the syringe may vary, for example, depending upon the amount of fluid to be delivered by the syringe. The syringe 310 includes an elongated hollow body 312 which is preferably generally cylindrical, but the body can have any desired shape or cross-section. The body 312 has a distal end 314 with an attachment portion 316 which can be connected to various medical components such as a catheter. The attachment portion 316, for example, may include a nose 318, an injection cap 320 and internal threads 322, but it will be understood that the attachment portion can include any type of known connector to attach the syringe 310 to various types of medical components or instruments. The body 312 also includes a proximal end 324 with a flange or stop 326. The stop 326 includes a radially inwardly extending annular lip 328 which forms an opening 330. The opening 330 is preferably circular and generally aligned with a longitudinal axis 332 extending through the center of the body 312. The stop 326 also includes a radially outwardly extending annular ridge 334. The ridge 334 preferably extends about outwardly about 1116 of an inch from the body 312 and the ridge preferably has a length of about 114 of an inch, but the ridge can have any desired dimensions and configuration. The stop 326 is preferably located at the proximal end 324 of the body 312, but the stop can also be spaced from the end of the body.

The syringe 310 also includes a plunger 336 which is sized and dimensioned to be at least partially positioned within the elongated body 312. The plunger 336 includes an elongated shaft 338 which is generally circular in cross- section and is preferably constructed from a relatively high strength material such as steel, but other types of materials such as plastics, composites and other types of metals may be used. The plunger 336 includes a distal end 340 which is positioned near the distal end 314 of the body 312 and a proximal end 342 which is positioned near the proximal end 324 of the body. The distal end 340 of the plunger 338 includes a piston 344 with a center section 346 and two outwardly extending annular flanges 348 and 350, respectively. The annular flanges 348 and 350 extend outwardly and slidably engage the inner wall of the elongated body 312 to create a fluid-tight seal with the elongated body. The piston 344 is

preferably constructed from a resilient material such as rubber, but it can be constructed from any material which is suitable for its intended purpose. It will be understood that the piston 344 may have any desired size andlor configuration, but the syringe 310 does not require the use of a piston.

The proximal end 342 of the plunger 336 includes a handle 352 comprising a generally circular disk 354 that is mounted to the end of the shaft 338. The disk 354 preferably has a diameter of about 718 of an inch and a thickness of about 118 of an inch so that the clinician can easily grasp the handle 352, but the disk can be larger or smaller and it can have any desired shape such as square, rectangular, triangular, etc. The handle 352 also includes an annular protrusion 356 which extends inwardly along a portion of the shaft 338 of the plunger 336. The protrusion 356 is about 114 of an inch in length and it has an outside diameter of about 114 of an inch, but it can have any desired dimensions depending, for example, upon the amount of fluid to be injected by the syringe 310. The protrusion 356 includes a generally planar inner surface 358 which is configured to contact and abut an outer surface 360 of the stop 326. Thus, when the inner surface 358 of the protrusion 356 contacts and abuts the outer surface 360 of the flange 348, the plunger 336 cannot be pushed further into the body 312. Therefore, the stop 326 and handle 352 limit the movement of the plunger 336 into the body 312.

The shaft 338 of the plunger 336 is preferably generally cylindrical with a generally constant outside diameter, but the shaft also includes at least two sections with decreased or smaller diameters. Specifically, the shaft 338 includes an indented or narrowed section 362 located at the proximal end 342 of the shaft 338. The handle 352 of the plunger 336 is mounted to the distal end of the narrowed section 362 and an abutment surface 364 is formed between this narrowed section and the adjacent central portion 366 of the shaft with its larger diameter. The abutment surface 364 is preferably located generally perpendicular to the longitudinal axis 332 extending through the syringe 310, but the abutment surface can be located at any desired angle and it can have any desired configuration.

The narrowed section 362 of the shaft 338 is sized and configured to be slidably movable within the opening or channel 330 in the flange 326. In particular, the narrowed section 362 of the shaft 338 preferably has an outside diameter of about 0.150 inches, which is slightly smaller than the opening 330 which has an inside diameter of about 0.157 inches. This allows the narrowed section 362 to be slidable within the opening 330. The central portion 366 of the shaft 338, which is located adjacent to the narrowed section 362, however, has a diameter of about 0.171 inches and that is larger than the opening 330. As discussed above, this change in the diameter from the narrowed section 362 to the central portion 366 creates the abutment surface 364. Thus, the narrowed section 362 slides within the opening 330, but the larger diameter portion 366 cannot be inserted through the opening and this prevents the shaft 338 from being pulled back through the opening.

Desirably, the handle 352 and the abutment surface 364 are positioned to limit the range of movement of the shaft 338 within the elongated body 312. Specifically, as seen in Figure 18, when the plunger 336 is fully depressed, the inner surface 358 of the protrusion 356 contacts the outer surface 360 of the flange 326 and this prevents further insertion of the plunger into the body 312. Alternatively, as seen in Figure 16, when the plunger 336 is completely pulled back, the abutment surface 364 contacts the inner surface 358 of the annular lip 328 and this prevents further movement

of the plunger out of the body 12. Thus, the range of movement of the plunger 336 is limited by the handle 352, flange 326 and abutment surface 364. As discussed below, the distance between the inner surface 358 of the protrusion 358 and the abutment surface 364 is preferably about 112 of an inch, but this distance could be larger or smaller. It will be appreciated that the larger the distance between the handle 352 and the abutment surface 364, the larger the range of movement of the shaft 338, and the smaller the distance between the handle and the abutment surface, the smaller the range of movement of the shaft.

The shaft 338 of the plunger 336 also includes an annular groove 370 located between the central portion 366 and distal end 340 of the plunger 336. The annular groove 370 preferably has a depth of about 0.023 of an inch, but it can be larger or smaller. As best seen in Figure 17A, the annular groove 370 has generally radially outwardly extending side walls 372 and 374 that form a generally U-shaped channel. The walls 372 and 372 are preferably positioned at an angle of about 60° from the longitudinal axis 332, but the walls may be positioned at any angle including vertical.

Additionally, all or a portion of the walls 372 and 374 may, for example, be rounded or tapered.

The syringe 310 also includes a housing 380 located between the distal end 314 and proximal 324 end of the elongated body 312. The housing 380 includes an upper surface 382, lower surface 384, front surface 386 and rear surface 386. The upper surface 382 includes a generally rectangular opening 390 and a slot 392 that extends from the upper surface towards the lower surface 384. The upper 382 and lower 384 surfaces of the housing are preferably generally planar and substantially parallel, but the surfaces can have any desired configuration and orientation. The front 386 and rear 388 surfaces of the housing 380 are also preferably generally planar and substantially parallel to facilitate handling of the syringe 310, but these surfaces can have any desired dimensions and configurations.

A locking member 394 is configured to slidably fit within the slot 392 and the upper portion of the locking member is configured to extend through the opening 390 in the housing 380. As best seen in Figure 15, the locking member 394 has a generally rectangular configuration with a lower surface 396, upper surface 398, front surface 400 and rear surface 402. The lower surface 396 includes two cylindrical openings 404 which extend toward the upper surface 398 and a resilient member such as a spring 406 which is placed in each opening. The springs 406 are used to create a spring force which pushes the locking member 396 away from the lower surface 384 of the housing 380.

The locking member 394 also includes an opening 410 through which the shaft 338 of the plunger 336 extends.

As best seen in Figure 17, the lower portion 412 of the opening 410 is sized and dimensioned to fit within the annular groove 370 in the plunger 336. More preferably, as seen in Figure 17A, the lower portion 412 of the opening 410 includes inwardly tapered walls 414 and 416 to securely engage the annular groove. The walls 414 and 416 are preferably tapered at about the same angles as the side walls 372 and 374 of the annular groove 370 so that the locking member 394 securely engages the plunger shaft 338, but the walls can be tapered at any desired angle.

In a preferred embodiment of the syringe 310 for inflating an occlusion balloon having a diameter of about 4.5 to 5.0 mm, for example, the body 312 has an overall length of about 4.71 inches and the stop 326 has a length of about 0.20 inches. The rear surface 388 of the housing 380 is about 1.38 inches from the proximal end 324 of the body 312 and the housing has a length of about 0.28 inches. In particular, the rear wall of the housing 380 has a length of about 0.9 inches,

the slot 392 has a length of about 0.10 inches, and the front wall of the housing has a length of about 0.9 inches. The corresponding plunger 336 has a shaft 338 with an overall length of about 4.43 inches with a narrowed proximal section 362 having a length of about 0.50 inches and a central portion 366 having a length of about 0.21 inches. The annular groove 370 preferably has a length of about 0.21 inches which is slightly larger than the corresponding length of the locking member 394. It will be appreciated that the syringe 310 can have any desired sizes and dimensions depending, for example, upon the size of the balloon to be inflated or the intended use of the syringe.

In operation, the syringe 310 is filled with fluid and the plunger 338 is in the retracted or open position as shown in Figure 16. In this open position, the abutment surface 364 contacts and abuts the inner surface 329 of the annular lip 328, and this prevents the plunger 336 from being pulled out of the body 312 of the syringe 310. The plunger 338 is then pushed forward until the locking member 394 is aligned with the annular groove in the plunger shaft 338 and the springs 406 force the lower portion 412 of the locking member 394 into the annular groove 370 to prevent additional movement of the shaft. Thus, as shown in Figure 17, the plunger 336 is held in the locked position by the locking member 394. This causes the syringe 310 to deliver a predetermined amount of fluid depending, for example, upon the internal volume of the body 312 and the distance traveled by the plunger 336. Thus, the clinician does not have to guess or estimate how much fluid has been delivered by the syringe 310.

The locking member 394 can be released by pushing down on the upper surface 398 of the locking member, which extends through the opening 390 in the housing 380, with sufficient force to overcome the springs 406. This allows the plunger 336 to once again be moved within the elongated body 312. For example, as shown in Figure 18, the plunger 336 can be further inserted into the elongated body until the inner surface 358 of the protrusion 356 contacts the outer surface 360 of the flange 326. This allows a second predetermined volume of fluid to be inserted by the syringe 310.

Thus, the syringe 310 delivers two different predetermined amounts of fluid: a first amount of fluid is delivered until the locking member 394 locks the plunger 336 into position, and a second amount of fluid is delivered after the locking member is released and the plunger is fully depressed. Alternatively, instead of pushing the plunger 336 forward, the locking member 394 may be released and the plunger may be pulled into a retracted position.

Another preferred embodiment of the low volume syringe is shown in Figure 19-21. The syringe shown in Figures 19-21 has generally the same configuration as that shown and described above in connection with Figures 15-19, but the syringe includes a spring 420 positioned between the distal end 340 of the shaft 338 and the piston 344. The spring 420 is preferably about 0.5 inches in length and it is constructed from coiled steel, but the spring may comprise any compressible material with suitable characteristics. Additionally, the spring 420 may be placed in other locations along the length of the plunger 336 including, for example, but without limitation, between the handle 352 and the proximal end 342 of the shaft, and the spring may have any desired length and spring constant. The spring 420 preferably has a spring constant which is selected to prevent overinflation or excessive pressurization of the balloon. Specifically, the spring constant is selected so that once the balloon is inflated to a predetermined pressure, the spring will compress if any additional pressure is provided. That is, if the balloon is inflated to a desired predetermined pressure and the plunger 336 is

depressed further, the spring 420 compresses to absorb this force and additional fluid is not delivered to the ballon. Thus, the balloon is not overinflated or over pressurized.

The embodiment shown in Figures 19-21 may be particularly useful to prevent damage to a vessel if the balloon has a larger diameter than the vessel. For example, if the vessel to be occluded by the balloon is estimated to have an inside diameter of 6.0 mm but the vessel actually has an inside diameter of 4.0 mm, the spring 420 may prevent over pressurization of the balloon and damage to the vessel. In particular, the balloon will be inflated until the predetermined pressure is reached and then the spring 420 will compress. Advantageously, the spring rate may be selected so that the spring 420 compresses before damage to the surrounding healthy tissue occurs. Thus, the spring 420 allows the same balloon to cover a wide range of vessels with various sizes because it prevents over pressurization of the balloon and damage to the surrounding tissue.

Stop Member In the embodiment of Figures 6 and 7, the limiting of the fluid intake and expulsion is accomplished by a tube 70 on the plunger 50 both of which are contained within the lumen 56 of the cylinder 44. The tube 70 has a length shorter than the lengths of the cylinder 44 and the shaft 52 and this length determines the volumetric intake and expulsion of the fluid from the syringe. The inner diameter of the tube 70 is preferably sized to be approximately the same as the outer diameter of the plunger shaft 52. The tube 70 is circumferentially attached to the plunger shaft 52, as shown in Figure 7.

Preferably, an adhesive, such as LOCTITE (TM) 4011 is used to secure the tube 70 to the shaft 52; although, attachment of the tube 70 to the plunger shaft 52 is not required to achieve the benefits of the present invention.

In use, for intake of the inflation fluid, a proximal end of the tube 70 contacts a distal face 72 of an insert within the barrel 74, as shown in more detail in Figure 6A, thus providing a stop mechanism for limiting the intake of inflation fluid (and thereby limiting the amount of fluid which is available for inflation). The barrel 74 is attached to a proximal face 76 of the flange 46 and thereby limits the plunger's outward or proximal travel with respect to the cylinder 44. The barrel 74 has a central channel 78 sized to allow the plunger shaft 52 to slide through, but not the plunger shaft 52 having the tube 70 surrounding it. Preferably, the distal end of the barrel 74 is secured to the face 76 of the flange 46 using adhesive.

Alternatively, the tube 70 and barrel 74 may be integrally formed with the plunger 50 and flange 46, respectively, of the syringe 10.

It will be noted from Figure 6 that the proximal face 73 of the barrel 74 can be positioned a predetermined distance from the disk 58. In other words, the length of the barrel 74 can be varied so that the proximal surface 73 thereof may also serve as a stop mechanism, alone or in combination with action of the tube 70.

For the 0.5 cc syringe shown, preferred dimensions of the tube 70 include an OD of about 0.135" and an ID of about 0.127", with a tube length of about 45 mm. The preferred tube material is nylon 12. The corresponding preferred dimensions of the barrel 74 are an OD of about 0.288" and an ID of about 0.128", with a barrel length of about 0.260".

The preferred barrel material is a polycarbonate.

An alternative embodiment of the low volume syringe is shown in Figure 8, wherein a conventional syringe 88 is retro-fit with a stop member 80 that is attached over the proximal end of the syringe. The member 80 includes an

attachment portion 82 and two limiting portions 84,86. The attachment portion 82 is at the distal end of the member 80 and may be secured to the distal face 77 of the cylinder flange 46 using adhesive, or it may be attached to the outer surface of the cylinder 44. The limiting portion 86 at the proximal end of the member extends proximally past the plunger disk 58, or in a direction away from the plunger shaft 52. At least this portion 86 should be limited to two segments of an annular disk of no more than about 45 degrees each, for example, to allow a proximal opening sufficient for a thumb or the like to access the plunger disk 58. The other limiting portion 84, intermediate the other portions 82,86, is positioned between the cylinder flange 46 and the plunger disk 58. Thus, the limiting portions 84,86 form the intake and delivery stops for the modified syringe 88; although, in alternative embodiments, the portion 84 may be omitted without loss of benefit of the present invention.

Another embodiment of a retro-fit stop member 90 for a conventional syringe is shown in Figures 9A and 9B. A preferably C-shaped attachment disk 92 has an arm 94 extending transverse to its diameter and parallel to the length of the syringe cylinder 44. A smaller disk 96 is provided at right angles to the arm 94 and is substantially parallel to and aligned over the C-shaped disk 92. The opening of the C-shaped disk 92 allows the member 90 to be snapped into place over the distal end of the syringe cylinder 44 and is preferably left free to slide thereover. The smaller disk 96 is preferably glued to the outer face of the plunger disk 58. Alternatively, the C-shaped disk 92 could be glued into place on the cylinder 44, and the smaller disk 96 could be left free to engage and disengage the plunger disk 58 during use. Thus, the intake or travel of the plunger 50 in this modified syringe is limited by the length of the arm 94 of the stop member 90.

Another arm (not shown) comprising a member extending parallel to the C-shaped disk 92 and smaller disk 96 and provided along the longitudinal arm 94 between the two disks 92,96 may be provided to limit the amount delivered by the syringe, in a manner similar to Figure 8. Although, if the predetermined amount of fluid to be drawn into the inflation syringe is to be the same as the predetermined amount of fluid to be delivered or injected by the syringe, then the construction shown in Figures 9A and 9B accomplishes this goal.

The stop member 20,80,90 is preferably made of a resilient material and manufactured in various lengths. The member may be integrally formed, as a retro-fit mechanism or directly on the syringe, or assemble from smaller components. As a retro-fit, the stop member may have alternative configurations that can be hinged, snapped or clipped into place, for example, over the proximal end of the syringe. The retro-fitting is also suitable for providing advantages of the low volume syringe of the present invention to syringes comprising larger diameter plunger barrels that preclude the use of a tube 70 in the cylinder lumen 56.

Inflation Syringe Assemble In the embodiment of Figure 4, the inflation syringe 10 is used in an assembly 100 including a conventional high capacity or reservoir syringe 110, coupled therewith by a connector or valve 112. The reservoir syringe 110 provides the desirable power and volume for quickly priming the balloon 14, guidewire 16 and valve 112, as well as for quickly deflating the balloon 14 for withdrawal from the patient. However, it will be noted that the inflation syringe 10 can be utilized in combination with other reservoir systems, of which the assembly 100 is only one example.

Thus, in the embodiment of Figure 4, a syringe assembly 100 is shown attached to a proximal end of a short tube section 216 using a stopcock or three-way valve 112. The tube section 216 is in turn attached to the fitting 24 of the inflation adapter 30, as shown in Figure 1. Alternatively, as discussed below in more detail, the syringe assembly 100 may be directly coupled, without the adapter 30, to the proximal end of the guidewire catheter 12 using the valve 112.

The assembly 100 is operably coupled using the valve 112 to allow fluid to flow in one of three paths provided by lumens in three fittings 114,116,118 of the valve 112. Figures 5A-5C show various positions of the valve 112 during operation and are described in detail below. It is understood that other valves may be used for allowing directional control of the inflation fluid. Thus, referring again to Figure 4, the end of the tube 216 is attached to one of the fittings 114, a large capacity or reservoir syringe 110 is attached at a second fitting 116, and a low volume or inflation syringe 10 constructed in accordance with the present invention is attached to the third fitting 118. The reservoir syringe 110 is any conventional type having a capacity of between about 10-30 cc, for example. In the example shown, the inflation syringe 10 of Figure 6 is used; although, it is readily apparent that any other syringe having a stop member constructed in accordance with the present invention may also be used.

The end of the tube section 216 is preferably attached to the valve fitting 114 using a sleeve 120. The remaining two valve fittings 116,118 preferably comprise male luers, and a distal end of the reservoir syringe 110 is preferably threaded for engagement to one fitting 116. The distal end 62 of the injection cap 22 is also threadably engaged with the remaining valve fitting 118. Although the reservoir syringe 110 is shown attached to the intermediate fitting 116, the inflation syringe 10 could alternatively be attached at that location with the reservoir syringe 110 attached at the side fitting 118 of the valve 112.

As noted above, Figures 5A 5C illustrate the operation, various schematic side views, of the valve 112 which is utilized in connection with the syringe assembly 100 of the present invention. These figures illustrate the valve 112 in partial cross-section with the reservoir syringe 110 removed such that its position would be coming out of the page toward the reader, as illustrated in the top view of Figure 4. Likewise, the inflation syringe 10 and its connection via injection cap 22 are shown to the left and the short tubing 216 leading to the inflation lumen 15 of the balloon catheter 14 is illustrated leading to the right, in a manner consistent with Figure 4.

Referring in detail to Figure 5A, a central member 122 of the valve 112 is operated to allow flow between the inflation lumen 15 of the guidewire 16 (via the tubing 216), the reservoir syringe 110, and the inflation syringe 10. The central member 122 has a cylindrical body 124 contained in a housing 126 of the valve, with the fittings 114,116,118 integrally formed on the housing. Apertures 128-130 are provided circumferentially about the body 124 at three locations.

The aperture locations correspond to the lumens of the fittings 114,116,118. The body 124 protrudes out of an upper end of the housing 126 and terminates in a lever 132 for positioning by a clinician for the appropriate flow path.

Preferably, the portion of the central member body 124 below the lever 132 does not have an aperture (e. g., there is no aperture in the vertical wall of the housing 126 which is aligned beneath the lever 132), such that the position of the lever 132 indicates which lumen is closed.

Thus, in the lever position of Figure 5A, with the inflation syringe 10 to the left, the reservoir syringe 110 toward the reader, and the tubing 216 to the right, the fluid path is through the lumens of the inflation syringe 10 and the guidewire 16. That is, the aperture 130 is aligned with the fitting 118 leading to the inflation syringe 10, and the aperture 128 is aligned with the fitting 114 leading to the guidewire tubing 216, such that fluid flow from left to right is facilitated.

It will be noted that the aperture 129, in this lever position of Figure 5A, is the back of the body 124 which is a closed position. This aperture is closed by means of the house 126, it being understood that Figure 5A-5C schematically represent the flow of fluid in the valve 112. Thus, the lever position of Figure 5B corresponds to flow between the inflation and reservoir syringes (e. g., the aperture 129 is in fluid communication with aperture 130 leading to the reservoir syringe 110, the aperture 130 not being visible in Figure 5B because of the partial cross-section), and the position of Figure 5C corresponds to flow between the reservoir syringe and guidewire lumens (e. g., aperture 128, which is not shown in Figure 5C due to the partial cross-section, leading from the reservoir syringe 110 is in fluid communication with aperture 129 leading to the guidewire tubing 216). It will be noted from Figures 5B and 5C that the lever 132 in each case is directed toward the device which is closed from fluid communication, e. g., the guidewire tubing 216 in the case of Figure 5B and the inflation syringe 10 in the case of Figure 5C.

An alternative syringe assembly is shown in Figure 12, wherein a conventional four-way manifold 200 is attached to the reservoir syringe 110 and a y-connection 210 attached to the proximal end of catheter 212. The manifold 200 provides a pressure monitoring line 202, a dye supply line 204, a saline supply line 206, and a waste removal line 208.

Proximal this first connection 210, another y-connection 210 couples the low volume syringe 10 with the guidewire 16 and, thus, with the manifold 200 and reservoir syringe 110. the syringe 10 is used to inflate the distal balloon 14 on guidewire 16. Although the use of a manifold 200 is typically reserved for procedures using larger or therapeutic balloons, those skilled in the art will appreciate that the present invention is readily adapted for use with this more elaborate system.

As understood by those skilled in the art, the assembly in the present invention is not limited to the embodiments discussed herein, and may be included with other adapters, manifolds, andlor connectors, as desired. That is, advantages realized from the use of the low volume syringe with the higher volume syringe for deflation and inflation of a balloon during various procedures is not limited to their particular connections or additional apparatus.

Methods of inflating a Medical Balloon One method of inflating a medical balloon using an inflation syringe 10 having features of the present invention may be described with reference to Figure 1. The balloon catheter 12 may have already been primed or evacuated, and the balloon 14 may have already been inserted to its desired position within the patient, as desired. Alternatively, these steps may be performed after the syringe assembly 100 has been secured at the proximal end of the catheter 12. In addition, the inflation adapter 30 may be used to perform additional procedures requiring access to the inflation lumen 15 of the catheter, as known to those skilled in the art, prior to use of the syringe assembly 100 of the present invention, it being noted that the present method is not limited to the use of an inflation adapter 30 or the like.

In the present method, a proximal end of the balloon catheter 12 having a low profile valve 32 is arranged to lie within the inflation adapter 30 such that a side-access inflation port 17 of the catheter is located within a sealed inflation

area contained in the adapter housing. The low profile valve 32 is closed (Figure 3A) and an actuator 40 on the adapter 30 is in a first position, such that any flow through the inflation lumen 15 of the catheter 12 is prevented. Next, the adapter 30 is closed and secured using a locking clip 38.

It should be noted that more than one reservoir or high volume syringe 110 may be used, as necessary or desirable according to the procedure andlor clinician. That is, a first reservoir syringe may be used in the assembly 100 to prime the catheter's inflation lumen 15 and the balloon 14, with the valve lever 132 in the position of Figure 5C (the inflation syringe 10 to the left of the figure). The inflation syringe 10 may be pre-fi ! ! ed or empty, or, alternatively, a plug (not shown) may be temporarily used in place of the syringe 10. The lever 132 could then be positioned as in Figure 5A so that the first reservoir syringe can be removed and a second reservoir syringe containing dye or other inflation fluid can be connected to the valve 112.

The lever 132 is then positioned as in Figure 5B to allow the fluid to flow from the reservoir syringe 110, through the fitting 118 where the inflation syringe 10 has been attached, and into the inflation syringe 10, the intake of the syringe 10 being limited by its tube 70. The lever 132 is then positioned as in Figure 5A to allow injection of the pressurized fluid into the catheter 12.

If an inflation adapter 30 is being used, the actuator 40 is moved from the first position to a second position, thereby moving the panels 291 to cause the opening of the low profile valve 32 (Figure 3B) and to allow flow into the inflation port 17 of the catheter 12. Delivery of the inflation fluid is complete upon the depression or pushing of the syringe plunger 50. The actuator 40 is moved back to the first position to reposition the panels 291 and close the valve 32 to maintain the balloon 14 in its inflated state. The low volume syringe 10 may then be removed, andlor the necessary medical procedures continued. A third large capacity syringe 110 may be substituted at the fitting 116 with the lever 132 in the position of Figure 5C for quick deflation of the balloon 24 and removal of the catheter 12 from the patient.

An alternative method of inflating a low volume balloon utilizes the system shown in Figure 12, and is more typically used with larger balloons. The steps of this method are similar to those described for use of the three-way valve 112 wherein the various flow paths are achieved by use of the manifold 200. Additional steps, as desired or required, may be included for the removal of airifluid waste, arterial pressure monitoring, and the injection (s) of dye andlor inflation fluid as accommodated by the lines 208,202,204,206, respectively, of the manifold 200. In this method, however, the low volume syringe 10 is preferably filled, according to the limits of its stop member 20, prior to attachment to the y-connector 210.

Thus, the stop mechanism comprising either integral or retro-fit members of the present invention provides built- in control during the use of the syringe. The stop member can be provided for a predetermined intake displacement and also, preferably, for a predetermined fluid delivery displacement. The combination of the initial syringe capacity and the specific plunger displacement limits provided by the stop member determine the effective capacity of the low volume syringe. The elongate nature of the cylinder lumen preferably allows travel, for example, of about 10 mm by the piston in the lumen for the delivery of about 0.1 cc of fluid. This relatively large amount of travel for a small amount of fluid provides enhanced tactile feedback to the clinician that the fluid delivery was achieved.

Hich Pressure Capacity Syringe Svstem During the inflation of the occlusion balloon 14, the pressure in the system adjacent to the syringe 10 can reach pressures up to 200 psi. This pressure build up is caused by the sudden volume change caused by the influx of fluid into the valve 112 and lines 216 and 16 leading to the occlusion balloon 14. The build up pressure will peak initial and then dissipate as the pressure disperses through the lines 216,16 toward the occlusion balloon 14. Eventually, the build up pressure will dissipate when the occlusion balloon 14 inflates. Typically, the build up pressure peaks and then stabilizes within 5 seconds. Therefore, the syringe system 100 must be able to withstand the peak pressure for at least 5 seconds.

Figure 13 illustrates a system that can withstand the initial build up pressure. The system is similar to the dual syringe system 100 of Figures 1 and 4. To avoid confusion, reference numerals of identical parts will remain the same whereas new parts will receive new numbers. Although this figure illustrates a dual syringe system, this by no means limits the invention to this configuration. For example, the high pressure capability syringe system can be incorporated in conjunction with a single syringe system.

In Figure 13, the large volume syringe 110 is attached and in fluid communication with a three-way high-pressure stop cock valve 322. A preferred provider of the high pressure valve is Merit Medical Systems part number M3SNP.

Preferably, the valve is rated to handle pressures of 250 psi. Even more preferably, the valve 322 should be rated to withstand a pressure of 500 psi. Luer type couplings extend from all sides of the valve 322. Preferably the coupling 262 includes an extended engagement area, namely a greater number of threads, to ensure the positive sealing between the low volume syringe 10 and the valve 322. Likewise, the syringe 10 includes a mating, engagement area to complete the connection between the syringe 10 and the fitting 362. Although not illustrated, an 0-ring could be incorporated between the mating surfaces of the syringe 10 and the fitting 362 to insure a leak-free seal.

A similar high pressure fitting 364 is located on the opposing side of the high pressure stop cock valve 322. As before, this fitting 364 has an extended engagement area, i. e. more threads, to lessen the load caused by the high build up pressure. Attached to the high pressure fitting 364 is a high pressure line 316 leading either to an inflation device or directly to the occlusion balloon (both not shown in this figure). Preferably, the high pressure line 316 is rated to withstand a pressure of 250 psi. Even more preferably, the line 316 is rated to withstand a pressure of 500 psi. An example of the line is part number 70078 manufactured by Mallinkrodt.

Still referring to Figure 13, a similar high pressure fitting 366 is located on the remaining side of the high pressure stop cock valve 322. As before, this fitting 366 preferably is a luer type connector with an extended engagement area, i. e. more threads, to lessen the toad caused by the high build up pressure. Attached to the high pressure fitting 366 is a large volume reservoir syringe 110 which has a mating connector at a distal end which mates with the high pressure fitting 366 to insure a fluid tight seal.

Connectivitv of the Valve The connectivity of the valve 322 is the same as illustrated in Figures 5A-5B. The valve 322 can be set in a first position providing fluid communication between the low volume 10 syringe and the high volume syringe 110. The valve 322 can also be set in a second position providing fluid communication between the low volume syringe 10 and the high

pressure line 316. Finally, the valve 322 can be set in a third position in which fluid communication is provided between the high volume syringe 110 and the high pressure line 316.

Through the use of a high pressure valve 322 and a high pressure fittings 362,364 and 366 leaks in the system are prevented. Further, even though the figure illustrates a dual syringe system with a three position valve, the high pressure system can be comprised of a single syringe system with or without a valve.

Removable Plunger Stop Mechanism As previously discussed, the large volume syringe 110 can be used to create a vacuum. The vacuum is created by pulling the plunger 374 toward a proximal portion of the housing 370. In order to maintain the negative pressure the plunger 374 must be held in place. Typically, this is achieved by pulling the plunger 374 toward the proximal end of the housing 370 until the plate 376, mounted on the end of the plunger 374 is snapped into position proximal of a ring 372 extending radially inward into to the housing 370. The ring 372 holds the plunger 374 in place and maintains a vacuum within the system.

In order to prevent the complete withdrawal of the plunger 374 from the housing 370, a plunger stop mechanism 380 is incorporated with the high volume syringe 110. The plunger stop mechanism 380, in the embodiment shown in Figure 13, Figure 14A and Figure 14B is comprised of two removable clips 382. Preferably, the clips 382 are slid onto the finger stops 384 of the housing 370. Although not illustrated, the clips 382 include snap fit means to positively engage either the finger stops 384 or the cylinder housing 370.

The clips 382 are shown in detail in Figures 14A and 14B. Preferably, the clips 382 are made of a polycarbonate or nylon material. The shape of the clip 382, as shown in side view in Figure 14B is a U-section with uneven surfaces 386, 388. As best seen in Figure 14A the shape of the surface 386 is arcuate in shape to mate with the outside of the cylindrical housing 370 distal of the finger tab 384.

The surface 388 extends into the chamber created by the housing 370 and is positioned proximal of the finger stop 384. The shape of the surface 388 must be designed not to interfere with the shaft 390 of the plunger 374.

Nevertheless, the surface 388 must extend into the cylinder so as to abut the disk 376 of the plunger 374 when the distal end of the plunger 374 is pulled toward the proximal end of the housing 370. To assemble the stopper mechanism 380 the clinical technician would simply push the clip 382 onto the finger tab 384 thereby locking the clips 382 in place.

The clips 382 as shown in Figure 13, Figure 14A and 14B are removable from the finger stops 384. In an alternative embodiment (not shown) the clips 382 could be formed integrally with the finger stops 384 of the syringe 110.

In this embodiment, the plunger 374 would be inserted into the housing at an angle to clear the surface extending into the cylinder of the housing.

Yet another embodiment (also not illustrated) would include a system with one clip formed integrally with the cylinder housing and the other clip snapped onto the finger stop. This arrangement would allow for improved ease of assembly of the plunger into the syringe housing. For example, the clinical technician would remove the clip from the finger stop, place the plunger within the syringe housing and then replace the clip onto the finger stop effectively locking the plunger within the housing.

Clips Aiding in the Vacuum Creation As mentioned earlier, the clinical technicians use the syringes as a vacuum source for aspiration or removal of air bubbles in a preparation setting. In order to provide a vacuum the plunger 374 must be pulled toward the proximal end of the housing 370 thereby creating a vacuum within the system. To maintain the vacuum the plunger 374 must be held into place. As illustrated above, a ring 372 extending into the cylinder of the housing 370 of the syringe 110 is used to hold the plunger 374 in place.

The clips 382, however, could also be used to hold the plunger 374 in place. For instance, in the embodiment where the clips are removable, the plunger 374 could be locked in place by the clips 382. In this configuration, the plate 376 would be located proximal of the surface 388.

Alternative Uses for the Dual Svrinae Svstem In addition to providing a highly responsive inflation system for an occlusion balloon the dual syringe system also has a variety of other uses. For instance, the system could be used to deliver precise amounts of therapeutic drugs or medicine to the patient. The system may also be used to irrigation or aspiration. Additionally, the system can be used to infuse whole blood as is described below.

Typically, whole blood is infused into patients with roller type pumps. One problem associated with this type of pump is that roller mechanisms apply a shear stress that often damages the blood cells with the crushing force of the rollers. The dual syringe system could overcome the problem of damaging the blood by providing a hydrostatic pressure that would provide pressure for the transfusion without causing the damaging forces on the cells. The blood cells, because of their circular shape, can withstand great hydrostatic pressure and therefore would not be damaged. Preferably, the large volume syringe will be used to infuse blood.

An inflation syringe constructed in accordance with the present invention is preferably used in an assembly further comprising a reservoir syringe and a three-way valve. This assembly is preferably coupled to an inflation adapter used to open and close a catheter valve at the proximal end of the catheter. In a preferred method of the present invention, the three-way valve and catheter valve are used to communicate the reservoir syringe with the inflation lumen of the catheter to prime the balloon catheter prior to insertion into the patient's vasculature. The valves are then appropriately set by the clinician to allow the inflation syringe to easily and precisely deliver the proper amount of fluid through the catheter's inflation lumen to the ballon. In one application, the inflation fluid injected by the syringe may be dye for a fluoroscopy procedure. The valves are further set and the reservoir syringe used to deflate the balloon for withdrawal from the patient.

A low volume syringe, and an assembly comprising the low volume syringe and a reservoir syringe, having features in accordance with the present invention are not limited to use with the inflation adapter or three way valve as presented herein. Other arrangements or assemblies may include this combination of syringes of the present invention.

Similarly, the method of the present invention may omit the use of an inflation adapter andlor three-way valve, etc., without loss of benefit from the present invention.

The embodiments of the apparatus and method as described above are provided merely to illustrate the present invention. Changes and modifications may be made from the embodiments presented herein by those skilled in the art without departure from the spirit and scope of the invention, as defined by the appended claims.