BACKGROUND

Field of the Invention

The present invention relates to a device and method for extracting venous blood from a body by making an incision on a superficial vein. Particularly, the present invention relates to a spring-operated incisor to rapidly penetrate the superficial veins for extraction of venous blood for subsequent blood analysis.

Background of the Invention

Blood samples are often required for various medical purposes such as for blood donation, screening or diagnosing various illnesses at the point-of-care. The most common blood extraction process is called venipuncture, wherein venous blood is extracted from superficial veins by inserting a cannula into a vein's lumen. When small quantity of blood is required, i.e. 5ul - 50ul, other techniques such as finger-stick or heel-stick (for infants) can be performed to draw capillary whole blood. For these techniques, the 'injury' and the bleeding caused can create discomfort or fear on the individuals or the care takers.

For venipuncture procedure, first a superficial vein usually on the forearm is chosen and fixated, then a hypodermic needle or a catheter is inserted into the vein's lumen and venous blood is sucked out using an evacuated tube, which provides the vacuum pressure and the container for the blood suction. The insertion of the needle in a vein's lumen requires specific skill that can only be acquired via formal training and frequent practice. The pain and discomfort caused by venipuncture are unbearable by most adults and this procedure is avoided as much as possible except when vast blood sample (e.g. 50- 100ml) is needed. It is impossible to perform venipuncture alone without any help.

When smaller blood sample is needed, normally finger-stick is chosen. For current point-of- care diagnostic devices, such as a normal rapid test using lateral-flow immunosorbent test strip, a capillary blood sample of 5ul - 50ul is needed. This minute blood sample can be obtained by using a lancet to make an incision of 0.5mm - 3mm deep on finger tips so that whole blood from the capillaries can flow out of the incision and can be collected. For infants, a heel-stick procedure is involved, in which a blade is used to cut a shallow incision for blood collection purpose. Both methods do not rely on vacuum pressure to obtain blood, but squeezing or massaging the incision site is normally performed to enhance the blood flow. The finger-stick procedure can be performed by a patient alone, but normally the medical personnel will perform it on the patient due to the discomfort or fear of injuring own-self.

Venous blood is preferable to capillary blood for some diagnostic tests because of the following reasons: (1) capillary blood is normally contaminated with interstitial and intercellular fluids due to its way of extraction, the contamination will affect the test results, and that (2) venous blood is abundant due to its extraction method (extracted from vein's lumen), causing most available blood test validations are based on venous blood; as a result, venous blood is highly preferable when availability of samples and validated results for comparison are brought into consideration, and lastly (3) capillary blood resembles arterial blood more than venous blood in terms of major characteristics of blood samples, so test results obtained from capillary blood cannot be used for or against the test results obtained from venous blood.

Currently there is not any simple device which allows a novice end user to extract venous blood sample by himself at home. The existence of such device will tremendously improve the accuracy of the test results and expand the variety of blood tests that can be made available over-the-counter. There is a need for a simple method and device for obtaining venous blood for various point-of-care diagnostics, wherein only one or a few tests are required and therefore the volume of the blood sample required is relatively low, for instance 50-100ul.

Closest Prior Arts

US patent 4,154,229 awarded to Becton, Dickinson and Company reported a vacuum blood collection tube with a needle attached to the tube for collecting venous blood from the vein. This venipuncture method is a common practice for the medical industry, wherein a needle is inserted into the vein's lumen and venous blood is sucked out from a vein by vacuum pressure. This practice remains a common practice for venous blood withdrawal. The disadvantages of this method are that (1) inserting a needle into a vein's lumen requires high level of skill, therefore common people are not able to perform this method; and that (2) maintaining vacuum pressure in the tube requires extra components and processes which make the device bulky and expensive.

US patent 4,703, 76 land 4,703,762 awarded to Rathbone et. al. reported a blood collection tube attached with a needle for extracting venous blood without applying vacuum pressure. The device was designed to be inserted into a test tube for centrifugation at a later stage. Although eliminating the need for vacuum pressure, this prior art still required insertion of needle into the vein's lumen for venous blood extraction, just relying merely on the venous pressure.

With the advancement of diagnostics technologies, the volume of blood sample required for performing a meaningful blood test has significantly reduced to 0.3ul to lOOul. Therefore, there is a need for easy and rapid venous blood extraction to be used in point-of-care setting, wherein roughly lOOul of venous blood is obtained for in-vitro diagnostic purposes.

SUMMARY OF THE INVENTION

The preferred embodiment of the present invention involves a spring-operated superficial vein incisor 100 comprising an elongated body 110 having a distal opening 112; a trigger system 120, further comprising an annular button 122 and a button spring 124; an actuation system 130, further comprising a cocking sleeve 132, a cocking bush 134, an actuation spring 136 a needle seat 138 and a stopper ring 140; and a detachable cannula module 150, further comprising a cannula holder 152 and a cannula 154. In operation, first a disposable cannula module 150 is inserted into the needle seat 138 by tight-fitting. Next, the cocking sleeve 132 is pulled backward to cock the incisor 100. Subsequently, a skin site 200 having a viable superficial vein 300 thereunder, preferably on the forearm, is chosen and the incisor 100 is placed over the identified skin site with the distal opening 112 resting on the viable superficial vein 300 for fixating the vein. Then, the annular button 122 is depressed releasing the compressed actuation spring 136. As a result, the cannula 154 is propelled forward at high speed to penetrate the skin site 200 and the vein 300. Lastly, the cannula 154 is removed from the vein completely after a few seconds, and venous blood will flow out from the incision due to venous pressure. BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows a perspective view of the present invention FIG. 2 shows an exploded view of the present invention

FIG. 3 shows a section view of the present invention without the detachable cannula

module 150.

FIG. 4 (a) - (c) shows the cocking mechanism of the present invention

FIG. 5 (a) - (c) shows the superficial vein incision process by the present invention

FIG. 6 shows the venous blood flowing out from the incision made by the cannula.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to extraction of venous blood using a spring-operated superficial vein incisor. The present invention provides a simple and economical solution to enable small venous blood sample to be extracted by a patient at home or by a doctor at his clinic. The present invention involves inserting a cannula rapidly and perpendicularly into the skin for making an incision on the superficial vein so that the venous blood will flow out to the skin surface due to the venous blood pressure.

This is quite different to the current venipuncture method, in which a cannula or a catheter is inserted into a superficial vein's lumen to withdraw venous blood under vacuum pressure. The cannula is normally inserted at an acute angle (-15 degrees) to the skin such that the beveled tip is able to slice open the skin and cut through the skin tissue and then to reach the vein. Finally, the bevel opening of the cannula has to be fully immersed into the vein's lumen so that the venous blood will be diverted out into the cannula due to the venous blood pressure. This procedure is not something that a normal person is able and willing to perform particularly on himself. However, if the procedure is simplified into a spring-loaded device which rapidly inserts a cannula into the skin perpendicularly (because this is much easier to do than inserting a cannula at an acute angle to the skin) to just make an incision on the superficial vein (rather than inserting a cannula into the vein's lumen), the venous blood extraction procedure becomes 'user-friendly' and most novice people are able and willing to perform it on themselves. The preferred embodiment of the present invention is shown in FIGS. 1-3. The preferred embodiment is a spring-operated superficial vein incisor 100, which comprises an elongated body 110 having a distal opening 112; a trigger system 120, which further comprises an annular button 122, a button spring 124 and a male latch 126a; an actuation system 130, which further comprises a cocking sleeve 132, a cocking bush 134, an actuation spring 136, a needle seat 138 and a stopper ring 140; and a detachable cannula module 150, which further comprises a cannula holder 152 and a cannula 154. The elongated body 110 houses the actuation spring 136 and the distal opening 112 will be rested on a skin site 200 having a viable superficial vein 300 thereunder to (1) stabilize the incisor 100, (2) maintain a largely perpendicular orientation for the incision to take place later, and (3) fixate the viable superficial vein 300 for incision. The distal opening 112 may take the form of an oval shape or any other convenient shapes to provide a good fixating grip onto the bulging superficial vein. The distal opening 112 is also preferably transparent to allow provide visual access to the vein for aiming the cannula 154 at the vein. The actuation spring 136 is held within the elongated body 110 between the cocking bush 134 and the stopper ring 140, cocking of the spring can be achieved by pulling backward the cocking sleeve 132 thereby reducing the length between the cocking bush 134 and the stopper ring 140, compressing the actuation spring 136. When the cocking sleeve 132 is fully retracted and the actuation spring 136 is fully compressed, the button spring 124 will push the male latch 126a to engage with the female latch 126b on the cocking bush 134. To trigger the device 100, the annular button 122 is depressed causing the male latch 126a to disengage from the latch hole 126b, thereby releasing the actuation spring 136 to extend forward.

FIG. 3 shows the incisor 100 at its original state. As shown, the incisor 100 does not contain any detachable cannula module 150. This allows new cannulas to be used in every new venous blood extraction. The detachable cannula module 150 may be a standard hypodermic cannula hub. The main function of the cannula is to make an incision on the superficial vein deep enough to reach the lumen of the vein such that venous blood will flow out from the lumen to the skin upon removal of the cannula. The size of the cannula determines how big the incision is and therefore how much venous blood can be extracted. The typical size of the cannulas varies from 19G to 31G, or 1mm to 0.26mm outer diameter (OD), and the venous blood samples ranges from lOOul to lOul. For effective extraction of venous blood, the cannula needs to reach the lumen of the superficial vein, which is located < 5mm below the skin. Hence, the penetration depth required is roughly 5mm deep. Thus, the length of the cannula is 5mm or longer.

FIG. 4 shows the cocking mechanism of the spring-operated superficial vein incisor 100. As shown in FIG. 4A, a detachable cannula module 150 is tight-fitted into the needle seat 138, which is fastened to the cocking sleeve 132. Next, as shown in FIG. 4B, the cocking sleeve 132 is pulled backward so that the latch hole 126b on the needle seat 138 is pulled backward to meet the male latch 126a. During this cocking process, the actuation spring 136 is compressed by the backward-moving stopper ring 140. The latching step is shown in FIG. 4C, in which the button spring 124 extends and the male latch 126a is pushed inward to engage the latch hole 126b. Once the male latch 126a is engaged with the latch hole 126b, the cocking process is complete.

Prior to using the incisor 100, a viable superficial vein should be identified. The preferable body part is the inner upper arm. Normally a superficial vein is bulging on the skin and it can be identified quite easily. Alternatively, when a superficial vein is not obvious, a tourniquet is used to restrict the blood flow thereby dilating the superficial veins, making them easily identifiable.

FIGS. 5A-5C show the operation of the spring-operated superficial vein incisor 100. In Figure 5A, the incisor 100 is placed on a skin site 200 having a viable superficial vein 300 thereunder, with the distal opening 112 compressing the skin site 200 and fixating the viable superficial vein 300 thereunder. The distal opening 112 is preferably made of transparent material to allow the user to aim the cannula 154 at the viable superficial vein 300. The distal opening 112, apart from fixating the vein 300, helps orientate the incisor 100 to be largely perpendicular (90 degrees) to the skin site 200. Hence, the distal opening 112 plays a vital role in providing a repeatable and reliable penetration of the cannula 154 into the skin site 200 and the viable superficial vein 300 thereunder.

Next, as shown in FIGS. 5B and 5C, the annular button 122 is depressed, thereby disengaging the male latch 126a from the latch hole 126b. Once the latch is unlocked, the actuation spring 136 is released, pushing the stopper ring 140 forward rapidly. As a result, the detachable cannula module 150 is actuated forward at high speed and the cannula 154 is inserted into the skin site 200 and the viable superficial vein 300 thereunder. The actuation speed is in the range of lm/s to 6 m/s and the typical penetration depth of the cannula 154 is roughly 5mm. It is advisable that once the cannula 154 is inserted into the lumen of the viable superficial vein 300, the cannula 154 is left in the vein 300 for at least 1 second, or more commonly a few seconds to form a viable incision so that meaningful venous blood sample can be collected. Lastly, the venous blood from the lumen of the viable superficial vein 300 flows to the skin site 200 via the incision made by the cannula 154. The venous blood 400 can be collected using a capillary tube, a pipette or a fibrous membrane for further analysis.