PRESSURE SENSOR

TECHNICAL FIELD

[0001] The disclosure relates generally to perfusion and autotransfusion systems and more particularly to a blood reservoir having a pressure sensor.

BACKGROUND

[0002] Perfusion entails encouraging physiological solutions, such as blood, through vessels in the body or some portion of the body of a human or other animal. Perfusion can be employed in intracorporeal and extracorporeal circulation, such as during cardiopulmonary bypass surgery and other surgeries and during various therapeutic treatments. Perfusion is useful in maintaining the viability of body parts, such as specific organs or limbs, while the body part remains within the body or while the body part is exterior to the body, such as for transplantation or temporarily removal of a body part to provide access to other body structures. Perfusion can be used for a short period of time, such as less than about six hours, or for extended periods of time, such as greater than about six hours.

[0003] Sometimes, blood perfusion systems include one or more pumps in an extracorporeal circuit that is interconnected with the vascular system of a patient. Typically, cardiopulmonary bypass (CPB) surgery utilizes a perfusion system that allows for the temporary cessation of the heart by replacing the functions of the heart and lungs, which creates a still operating field and allows for the surgical correction of problems, such as vascular stenosis, valvular disorders, and congenital heart and great vessel defects. Perfusion systems for cardiopulmonary bypass surgery include an extracorporeal blood circuit that includes at least one pump and an oxygenation device to replace the functions of the heart and lungs.

[0004] In cardiopulmonary bypass procedures, oxygen-poor blood is gravity- drained or vacuum suctioned from a large vein entering the heart or from other veins (e.g., a femoral vein) in the body and transferred through a venous line in the extracorporeal circuit. The venous blood is pumped to an oxygenator that provides for oxygen transfer to the blood. Oxygen may be introduced into the blood by transfer across a membrane or, less frequently, by bubbling oxygen through the blood. Concurrently, carbon dioxide is removed across the membrane. The oxygenated blood is then returned through an arterial line to the aorta, femoral, or other main artery. Medical personnel configure the perfusion system prior to each bypass procedure, which can be a time consuming process that entails significant manual input of information related to components of the system.

SUMMARY

[0005] Example 1 is a system including a fluid reservoir, a differential pressure sensor, and a controller. The fluid reservoir has a bottom and is to hold a fluid. The differential pressure sensor is coupled to the bottom of the fluid reservoir and to sense a pressure difference between pressure exerted on the differential pressure sensor by the fluid and pressure exerted on the fluid in the fluid reservoir and to provide at least one signal that indicates a fluid level in the fluid reservoir. The controller is to receive the at least one signal and determine a fluid volume in the fluid reservoir based on the at least one signal. The controller is to provide at least one of a fluid level signal that indicates the fluid level in the fluid reservoir and a fluid volume signal that indicates the fluid volume in the fluid reservoir.

[0006] In Example 2, the system of Example 1 in which the differential pressure sensor has a first side to sense the pressure exerted on the differential pressure sensor by the fluid and a second side open to the atmosphere to sense atmospheric pressure.

[0007] In Example 3, the system of any of Examples 1 and 2 in which the differential pressure sensor has a first side to sense the pressure exerted on the differential pressure sensor by the fluid and a second side fluidically coupled to the top of the fluid reservoir to sense the pressure exerted on the fluid in the fluid reservoir.

[0008] In Example 4, the system of any of Examples 1 -3 in which the differential pressure sensor includes a first sensor to sense the pressure exerted on the differential pressure sensor by the fluid and a second sensor to sense the pressure exerted on the fluid in the fluid reservoir. [0009] In Example 5, the system of any of Examples 1 -4 in which the at least one of the fluid level signal that indicates the fluid level in the fluid reservoir and the fluid volume signal that indicates the fluid volume in the fluid reservoir is received by a heart lung machine that adjusts an operating parameter of the heart lung machine based on the at least one of the fluid level signal that indicates the fluid level in the fluid reservoir and the fluid volume signal that indicates the fluid volume in the fluid reservoir.

[0010] In Example 6, the system of any of Examples 1 -5 in which the at least one of the fluid level signal that indicates the fluid level in the fluid reservoir and the fluid volume signal that indicates the fluid volume in the fluid reservoir is received by a display system that displays at least one of the fluid level in the fluid reservoir and the fluid volume in the fluid reservoir.

[0011] In Example 7, the system of any of Examples 1 -6 in which the differential pressure sensor is integrated into the bottom of the fluid reservoir.

[0012] In Example 8, the system of any of Examples 1 -7 in which the differential pressure sensor is one of snap fit and adhesively attached to the bottom of the fluid reservoir.

[0013] In Example 9, the system of any of Examples 1 -8 in which the differential pressure sensor is disposable.

[0014] In Example 10, the system of any of Examples 1 -9 in which the controller is part of a heart lung machine.

[0015] In Example 1 1 , the system of any of Examples 1 -10 in which the controller is part of a display system.

[0016] In Example 12, the system of any of Examples 1 -1 1 in which the controller is part of the differential sensor.

[0017] Example 13 is a sensor system including a first pressure sensor, a second pressure sensor, and a controller. The first pressure sensor is coupled to a fluid reservoir that holds a fluid and has a bottom. The first pressure sensor is coupled to the bottom of the fluid reservoir and is to provide a first signal that indicates hydrostatic pressure exerted by the fluid on the first pressure sensor. The second pressure sensor is to provide a second signal that indicates pressure exerted on the fluid in the fluid reservoir. The controller is to determine at least one of a fluid level in the fluid reservoir and a fluid volume in the fluid reservoir based on the first signal and the second signal.

[0018] In Example 14, the sensor system of Example 13 in which the second pressure sensor is open to the atmosphere to sense atmospheric pressure.

[0019] In Example 15, the sensor system of any of Examples 13 and 14 in which the second pressure sensor is coupled to the top of the fluid reservoir to sense the pressure exerted on the fluid in the fluid reservoir.

[0020] In Example 16, the sensor system of any of Examples 13-15 in which the first pressure sensor and the second pressure sensor are part of a differential pressure sensor.

[0021] Example 17 is a method including providing a fluid reservoir having a bottom and providing a differential pressure sensor coupled to the bottom of the fluid reservoir. The differential pressure sensor sensing a pressure difference between pressure exerted on the differential pressure sensor by fluid in the fluid reservoir and pressure exerted on the fluid in the fluid reservoir, and providing at least one signal that indicates a level of the fluid in the fluid reservoir. A controller receiving the at least one signal and determining a fluid volume in the fluid reservoir based on the at least one signal. The controller providing at least one of a fluid level signal that indicates the fluid level in the fluid reservoir and a fluid volume signal that indicates the fluid volume in the fluid reservoir.

[0022] In Example 18, the method of Example 17 in which sensing a pressure difference includes sensing the pressure exerted on the differential pressure sensor by the fluid on a first side of the differential pressure sensor and sensing atmospheric pressure on a second side of the differential sensor.

[0023] In Example 19, the method of any of Examples 17 and 18 in which sensing a pressure difference includes sensing the pressure exerted on the differential pressure sensor by the fluid on a first side of the differential pressure sensor and sensing through fluidic coupling to the top of the fluid reservoir the pressure exerted on the fluid in the fluid reservoir.

[0024] In Example 20, the method of any of Examples 17-19 in which sensing a pressure difference includes sensing the pressure exerted on the differential pressure sensor by the fluid via a first sensor and sensing the pressure exerted on the fluid in the fluid reservoir via a second sensor.

[0025] Embodiments shown and described herein can be described with reference to a blood level sensor system and/or a blood volume sensor system. As described herein, where the geometry of the blood reservoir is known, it is possible to provide either a fluid level or a fluid volume, as the volume of fluid in the reservoir can be calculated from the detected or sensed blood level and the known geometry of the reservoir.

[0026] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is an illustration of an integrated perfusion system in accordance with embodiments described in the disclosure.

[0028] Figure 2 is a flow diagram illustrating a method that can be carried out by the integrated perfusion system of Figure 1.

[0029] Figure 3 is a flow diagram illustrating a method that can be carried out by the integrated perfusion system of Figure 1.

[0030] Figure 4 is an illustration of a heart lung machine pack that can be utilized with the integrated perfusion system of Figure 1.

[0031] Figure 5A is an illustration of a perfusion system in accordance with embodiments described in the disclosure.

[0032] Figure 5B is an illustration of an autotransfusion system in accordance with embodiments described in the disclosure.

[0033] Figure 6 is an illustration of a blood reservoir system that includes a differential pressure sensor and a hard shell blood reservoir "open" to the atmosphere.

[0034] Figure 7 is an illustration of a blood reservoir system that includes the differential pressure sensor and the hard shell blood reservoir "closed" and coupled to a vacuum. [0035] Figure 8 is an illustration of a blood reservoir system that includes a differential pressure sensor and a soft shell blood reservoir.

[0036] Figure 9 is an illustration of a blood reservoir system that includes two separate pressure sensors and a hard shell blood reservoir.

[0037] Figure 10 is an illustration of a blood reservoir system that includes two separate pressure sensors and a soft shell blood reservoir.

[0038] Figure 1 1 is an illustration of a method of determining a fluid volume in the blood reservoir systems of Figures 6, 7, and 8.

[0039] Figure 12 is an illustration of a method of determining at least one of a fluid level and a fluid volume in the blood reservoir systems of Figures 9 and 10.

[0040] While the disclosure includes various modifications and alternative forms, embodiments have been shown by way of example in the drawings and are described below. The intention is not to limit the disclosure to the embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.

DETAILED DESCRIPTION

[0041] The disclosure relates to a perfusion system that is easy to set-up, use, and monitor during a bypass procedure, and the disclosure relates to an autotransfusion system. In some embodiments, the disclosure relates to a sensor system that can be used to monitor a blood level or blood volume in a blood reservoir. In some embodiments, the sensor system can be utilized in an integrated perfusion system in which the components are configured to communicate with the perfusion system. In some embodiments, the sensor system can be utilized in a perfusion system lacking communication with components. In some embodiments, the sensor system can be utilized in an autotransfusion system. In some embodiments, the sensor system can be considered a blood level sensor system or a blood volume sensor system, where blood volume is ascertainable from blood level based on a known geometric configuration of the blood reservoir.

[0042] Figure 1 is an illustration of an integrated perfusion system 10 including a heart lung machine (HLM) 12 and a disposable element 14. While a single disposable element 14 is shown, in some embodiments, a plurality of different disposable elements 14 can be utilized with the HLM 12. Also, one example of HLM components is shown in the HLM 12, in some embodiments, the HLM 12 can include other components and/or a different number of components.

[0043] The HLM 12 includes three pump modules 16. Each of the pump modules 16 can be used to provide fluid or gas for delivery to or removal from the heart chambers and/or a surgical field. In one example, one of the pump modules 16 draws blood from the heart, another provides surgical suction, and a third provides cardioplegia fluid (a high potassium solution to arrest the heart). Additional pump modules 16 (not shown) can be added to provide additional fluid transfer. In some embodiments, the HLM 12 includes as few as two pump modules 16 or as many as seven pump modules 16. In some embodiments, the pump modules 16 can be roller or peristaltic pumps. In some embodiments, one or more of the pump modules 16 can be a centrifugal pump.

[0044] Each pump module 16 includes a corresponding control unit 18. In some embodiments, each control unit 18 is configured to operate and monitor the operation of the corresponding pump module 16. In some embodiments, each control unit 18 includes one or more input devices (not illustrated), such as switches, knobs, buttons, and touch screens, so the perfusionist can adjust the operation of the pump module 16. In some embodiments, each pump module 16 includes an alphanumeric display that the control unit 18 uses to display, for example, the value of a setting, the value of a current operating parameter, and/or confirmation that the pump module 16 is operating normally.

[0045] The HLM 12 includes a controller 20 in communication with the control units 18 and configured to operate the HLM 12. In some embodiments, the controller 20 is configured to monitor one or more sensors in the HLM 12 and/or in the disposable element 14 to monitor operation of the HLM 12. Examples of sensors include flow meters, pressure sensors, temperature sensors, and blood gas analyzers.

[0046] While the control units 18 and the controller 20 are illustrated as distinct elements, in some embodiments, these elements can be combined in a single controller. In some embodiments, one or more of the control units 18, in combination, can be configured to operate the HLM 12, thereby negating a need for the controller 20.

[0047] The controller 20 communicates with an input device 22 and an output device 24. The input device 22 can be used by the perfusionist to enter information that is not otherwise entered into the control units 18. The output device 24 can be used by the HLM 12 to display pertinent information to the perfusionist. In some embodiments, the input device 22 can be a key pad, a keyboard, and/or a touch screen. In some embodiments, the output device 24 can be a monitor. In some embodiments, the input device 22 and/or the output device 24 can be a computer, such as a personal computer, a laptop computer, a notebook computer, or a tablet computer. In some embodiments, the input device 22 and the output device 24 can be in a single computer.

[0048] The HLM 12 includes an RF sensor 26. In some embodiments, the RF sensor 26 can be configured to receive information from an active RFID tag placed on the disposable element 14. In some embodiments, the RF sensor 26 can be a hand held device that is used to scan a passive RFID tag on the disposable element 14. In some embodiments, the RF sensor 26 can be replaced with any suitable wireless communication receiver.

[0049] The disposable element 14 includes an RFID tag 28. In some embodiments, the disposable element 14 includes an active RFID tag and/or a passive RFID tag configured to communicate with the RF sensor 26. In some embodiments, the RFID tag 28 can be replaced with any suitable wireless communication transmitter. In some embodiments, the system includes one or more of the RFID configurations disclosed in U.S. patent application 12/763,561 , filed on April 20, 2010, which is hereby incorporated by reference in its entirety.

[0050] Passive RFID tags lack a power supply and, in some embodiments, are powered by an induced current caused by an incoming radio-frequency scan. Since passive RFID tags lack a power supply, they are smaller and less expensive than active RFID tags. Active RFID tags include an onboard power supply, such as a battery. While this increases the size and expense of the RFID tag, the active RFID tag can store more information and transmit further. RFID tags, whether active or passive, can be selected to transmit at a variety of frequencies depending on need. Options include low frequency (about 100 to 500 kilohertz), high frequency (about 10 to 15 megahertz), ultra high frequency (about 860 to 960 megahertz), and microwave frequency (about 2.45 gigahertz) RFID tags.

[0051] The disposable element 14 can be one, two, or a plurality of different disposable elements that can be used in conjunction with the HLM 12. Examples of disposable elements 14 include tubing sets, blood reservoirs, oxygenators, heat exchangers, and arterial filters. In some embodiments, a tubing set includes a number of different tubes, potentially of different lengths and/or sizes, for providing fluid flow between components of the HLM 12 as well as providing fluid flow between the HLM 12 and a patient.

[0052] In some embodiments, the disposable element 14 can be a blood reservoir such as a venous blood reservoir, a vent blood reservoir, or a cardiotomy or suction blood reservoir. In some embodiments, the disposable element 14 can be a blood reservoir that combines one or more of a venous blood reservoir, a vent reservoir, and a suction reservoir in a single structure. In some embodiments, one or more of the aforementioned sensors can be disposable elements that include an RFID tag 28 to provide information identifying the sensor and/or for transmitting sensed values to the controller 20.

[0053] The RFID tag 28 can be attached to the disposable element 14 and programmed with or otherwise configured to include a variety of information pertaining to the disposable element 14. In some embodiments, the RFID tag 28 can be adhesively secured to the disposable element 14. In some embodiments, the RFID tag 28 can be molded into the disposable element 14. In some embodiments the RFID tag 28 can be a standalone card, similar in size and shape to a credit card, which can be packed with the disposable element 14 in such a way that it can be removed by the user and swiped by the RF sensor 26.

[0054] In some embodiments, the RFID tag 28 can include data or identifying information for the disposable element 14, such as the name of the particular disposable element 14, a reference code, a serial number, a lot number, and/or an expiration date. In some embodiments, this information may be communicated to the controller 20 and used to confirm that the proper disposable elements 14 are being used for a particular setting or patient. For example, the controller 20 may recognize that a pediatric tubing set is being used in combination with an adult-sized blood reservoir or the controller 20 may recognize that an expected component is missing. The controller 20 can recognize potential mismatches in equipment as a result of the information provided by the RFID tag 28 attached to each of the one or more disposable elements 14.

[0055] In some embodiments, the RFID tag 28 can include descriptive or design information for the disposable element 14, such as materials, a list of components, priming volume of a component or tubing circuit, tubing size, tubing length, minimum and maximum working pressures, minimum and maximum working volume, and blood reservoir sizing information, such as blood reservoir dimensions. In some embodiments, this information can be communicated to the controller 20 and used by the controller 20 to at least partially configure and/or operate the HLM 12. For example, the controller 20 can use the sizing information provided from each of the disposable elements 14 to determine a working blood volume for the HLM 12.

[0056] In some embodiments, information obtained from the RFID tag 28 can be provided to the perfusionist. In some embodiments, the output device 24 can be configured to provide alphanumeric or graphical representations of the obtained information. In some embodiments, the RFID tag 28 can include instructional information displayed by the output device 24 to instruct the perfusionist in optimal setup and/or operation of a disposable element 14. In some embodiments, the output device 24 can be a computer such as a personal computer, a laptop computer, a notebook computer, or a tablet computer. In some embodiments, the RFID tag 28 can include displayable information that, for example, suggests an optimal circuit design based upon the components being used or provides updated use instructions. In some embodiments, information from the RFID tag 28 is displayed on an integrated data management system (DMS).

[0057] In some embodiments, the RFID tag 28 can include information provided by a manufacturer of the disposable element 14, such as technical features of the disposable element 14 that have changed from a previous version or batch and/or information that can be displayed by the output device 24 that requires the user to acknowledge receipt of the information before the controller 20 proceeds with a procedure. In some embodiments, the RFID tag 28 can receive error messages from the controller 20 and the RFID tag 28 can be returned to the manufacturer, thereby providing the manufacturer with feedback regarding the performance of the disposable element 14 as well as other components.

[0058] Figure 2 is a flow diagram illustrating a method that can be carried out using the perfusion system 10 of Figure 1. At 30, a disposable element 14 having an RFID tag 28 is attached to the HLM 12. At 32, the RFID tag 28 is read, where the RFID tag 28 can be an active RFID tag or a passive RFID tag. At 34, the HLM 12 is configured based at least in part upon information that was read from the RFID tag 28. In some embodiments, the controller 20 automatically configures the HLM 12 in response to the information. In some embodiments, the RFID tag 28 can be read before the disposable element 14 is attached to the HLM 12. In some embodiments, the RFID tag 28 can be read after the disposable element 14 is attached to the HLM 12.

[0059] Figure 3 is a flow diagram illustrating a method that can be carried out using the perfusion system 10 of Figure 1. The method of Figure 3 is the same as the method of Figure 2, with the addition that, at 36, at least some of the information read from the RFID tag 28 can be displayed on the output device 24.

[0060] Figure 4 is an illustration of a heart lung machine pack 38 that can be utilized with the perfusion system 10 of Figure 1. In some embodiments, the heart lung machine pack 38 can include all of the disposable elements 14 that will be used together for a patient and can be customized for the patient. In some embodiments, the heart lung machine pack 38 can include a housing 40 that, once filled, can be sealed to keep the contents clean and sterile.

[0061] The heart lung machine pack 38 includes a tubing set 42 and a disposable component 44. The tubing set 42 can include a plurality of different tubes. The disposable component 44 can be any of the disposable components discussed above with respect to the disposable element 14. In some embodiments, the heart lung machine pack 38 will include a plurality of different disposable components 44.

[0062] The tubing set 42 includes a first RFID tag 46 while the disposable component 44 includes a second RFID tag 48. As described above, each of the first RFID tag 46 and the second RFID tag 48 can be either an active or a passive RFID tag and include readable information pertaining to the component to which it is attached. In some embodiments, the housing 40 can include a third RFID tag 50 that, for example, identifies the contents of the heart lung machine pack 38. In some embodiments, the first RFID tag 46 and the second RFID tag 48 will not be included and the third RFID tag 50 can be encoded with all of the information for the tubing set 42 and the disposable component 44.

[0063] Figure 5A is an illustration of a perfusion system 52. In some embodiments, the perfusion system 52 can be similar to the perfusion system 10 of Figure 1.

[0064] The perfusion system 52 includes an HLM 54, a blood reservoir 56, a fluid sensor 58, and a controller 60. In some embodiments, the HLM 54 can be similar to the HLM 12 (shown in Figure 1 ). In some embodiments, the blood reservoir 56 can be a venous blood reservoir, a vent blood reservoir, or a cardiotomy or suction blood reservoir. In some embodiments, the blood reservoir 56 can be a blood reservoir that combines one or more of a venous blood reservoir, a vent reservoir, and/or a suction reservoir in a single structure.

[0065] The fluid sensor 58 can be configured to continuously monitor a variable blood level in the blood reservoir 56. The fluid sensor 58 provides one or more electrical signals that are proportional to the blood level in the blood reservoir 56. In some embodiments, as will be subsequently described, the fluid sensor 58 can be one or more pressure sensors for detecting the blood level in the blood reservoir 56. In some embodiments, the fluid sensor 58 can be one or more pressure sensors that provide voltage signals that correlate to pressure signals for detecting the blood level in the blood reservoir 56. In some embodiments, the fluid sensor 58 can be a differential pressure sensor that senses the difference between the hydrostatic pressure exerted on one side of the differential pressure sensor by the fluid in the blood reservoir and the pressure exerted on the fluid in the blood reservoir at, for example, the top of the blood reservoir and above the fluid. In some embodiments, the fluid sensor 58 can be two pressure sensors, where a first pressure sensor senses the hydrostatic pressure exerted on the first pressure sensor by the fluid in the blood reservoir and a second pressure sensor senses the pressure exerted on the fluid in the blood reservoir at, for example, the top of the blood reservoir and above the fluid.

[0066] The controller 60 can receive the one or more electrical signals from the fluid sensor 58 and determine or calculate the blood level and/or the blood volume in the blood reservoir 56. The controller 60 can determine or calculate the blood volume in the blood reservoir based on the one or more electrical signals as well as a known shape or geometry of the blood reservoir 56. In some embodiments, the blood reservoir 56 can include an RFID tag (not illustrated) that provides the controller 60 with information pertaining to the known geometry of the blood reservoir 56. In some embodiments, the volume of the blood reservoir is calculated according to one or more of the techniques described in U.S. patent application 12/763,561 , filed on April 20, 2010, previously incorporated by reference herein. In some embodiments, the volume of the blood reservoir 56 is calculated by integrating the level of blood in the reservoir against the known cross-sectional area of the blood reservoir 56 at various heights throughout the blood reservoir 56.

[0067] If the blood reservoir 56 is a hard shell blood reservoir, the known geometry of the blood reservoir 56 can include the cross-sectional area of the blood reservoir 56, or a width and depth of the blood reservoir 56 as well as details on how the cross-sectional area varies relative to height within the blood reservoir 56. If the blood reservoir 56 is a soft shell reservoir, the known geometry can be based at least in part upon a known lateral expansion rate of the soft shell reservoir relative to the blood level within the blood reservoir 56.

[0068] Figure 5B is an illustration of an autotransfusion system 300, according to some embodiments described in the disclosure. The autotransfusion system 300 includes a centrifuge 302, a pump 304, a sensor 306, and a controller 308. The controller 308 is operatively connected to the centrifuge 302, the pump 304, and the sensor 306 to provide the autotransfusion system 300. The controller 308 is communicatively coupled to the centrifuge 302 through a first communications path 310, to the pump 304 through a second communications path 312, and to the sensor 306 through a third communications path 314. [0069] The autotransfusion system 300 further includes: a salvaged blood reservoir 316, a salvaged blood fluid sensor 318, and a salvaged blood valve 320; a wash solution container 322, a wash solution fluid sensor 324, and a wash solution valve 326; a collection bag 328, a collection fluid sensor 330, and a collection valve 332; and a waste container 334 and a waste fluid sensor 336. In some embodiments, the autotransfusion system 300 includes at least one but not all of the fluid sensors 318, 324, 330, and 336.

[0070] The controller 308 is operatively connected to each of the salvaged blood fluid sensor 318, the salvaged blood valve 320, the wash solution fluid sensor 324, the wash solution valve 326, the collection fluid sensor 330, the collection valve 332, and the waste fluid sensor 336. In some embodiments, the controller 308 is communicatively coupled (not shown for clarity) to each of the salvaged blood fluid sensor 318, the salvaged blood valve 320, the wash solution fluid sensor 324, the wash solution valve 326, the collection fluid sensor 330, the collection valve 332, and the waste fluid sensor 336.

[0071] In the autotransfusion system 300, an inlet line 338 suctions salvaged blood from an operation field of a patient or from another blood source and carries the suctioned blood to the salvaged blood reservoir 316. In a fill phase, the salvaged blood in the salvaged blood reservoir 316 is pumped through a salvaged blood line 340 and the salvaged blood valve 320 into a system line 342 by the pump 304. The salvaged blood is further pumped through a bowl inlet line 344 into a centrifuge bowl 346 in the centrifuge 302 by the pump 304. As the salvaged blood is pumped into the centrifuge bowl 346, the salvaged blood valve 320 is open and the other valves, including the wash solution valve 326 and the collection valve 332, are closed. In some embodiments, the centrifuge bowl 346 receives the shed or salvaged blood directly from the operation field or directly from the other source.

[0072] In the fill phase, the centrifuge bowl 346 is filled with the salvaged blood as the centrifuge 302 rotates or spins the centrifuge bowl 346. The spinning centrifuge bowl 346 separates the blood into components according to the relative densities of the components. The red blood cells, which are the densest components of the blood, are propelled outward, against the circumferential wall of the centrifuge bowl 346. Other components, such as white blood cells and platelets, are arranged in a thin layer, referred to as the buffy coat, directly adjacent the concentrated mass of red blood cells. A plasma layer that includes undesirable components is situated above the buffy coat. As filling the centrifuge bowl 346 continues, more of the red blood cells are pushed upward along the circumferential wall of the centrifuge bowl 346, which pushes the plasma layer out of an outlet at the top of the centrifuge bowl 346. The plasma flows through a first waste line 348 connected to the outlet of the centrifuge bowl 346, past the sensor 306, and through a second waste line 350 into the waste container 334. The sensor 306 senses when the buffy coat begins to come out of the outlet or when the buffy coat is at or near the top of the centrifuge bowl 346 and the sensor 306 provides a corresponding signal to the controller 308. In response to the signal from the sensor 306, the controller 308 stops the fill phase.

[0073] After the fill phase, the autotransfusion system 300 washes the blood in the centrifuge bowl 346 in a wash phase. Wash solution contained in the wash solution container 322 is pumped into the centrifuge bowl 346 by the pump 304. The wash solution is pumped through a wash solution line 352 and the wash solution valve 326 into the system line 342 by the pump 304. The wash solution is further pumped through the bowl inlet line 344 and into the centrifuge bowl 346 by the pump 304. As the wash solution is pumped into the centrifuge bowl 346, the wash solution valve 326 is open and the other valves, including the salvaged blood valve 320 and the collection valve 332, are closed. In some embodiments, the wash solution is a saline solution.

[0074] In the wash phase, the controller 308 controls the centrifuge bowl 346 and the pump 304 to wash the blood in the centrifuge bowl 346. In the wash phase, more of the plasma or supernatant that includes the undesirable components is removed and flows through the first waste line 348 connected to the outlet of the centrifuge bowl 346, past the sensor 306, and through the second waste line 350 and into the waste container 334.

[0075] After washing the concentrated red blood cells in the centrifuge bowl 346, the final product is pumped out of the centrifuge bowl 346 through the bowl inlet line 344 and into the system line 342 by the pump 304. The final product is further pumped through the collection valve 332 and the collection line 354 into the collection bag 328. In this emptying phase, the controller 308 opens the collection valve 332 and closes the other valves, including the salvaged blood valve 320 and the wash solution valve 326.

[0076] The final product of concentrated red blood cells in the collection bag 328 can be used for reinfusion back into the patient via outlet line 356.

[0077] Each of the fluid sensors 318, 324, 330, and 336 can be configured to continuously monitor a variable fluid level in its corresponding container or bag 316, 322, 328, and 334. Each of the fluid sensors 318, 324, 330, and 336 provides one or more electrical signals that are proportional to the fluid level in its corresponding container or bag 316, 322, 328, and 334. In some embodiments, as will be subsequently described, each of the fluid sensors 318, 324, 330, and 336 can be one or more pressure sensors for detecting the fluid level in its corresponding container or bag 316, 322, 328, and 334. In some embodiments, each of the fluid sensors 318, 324, 330, and 336 can be one or more pressure sensors that provide voltage signals that correlate to pressure signals for detecting the fluid level in its corresponding container or bag 316, 322, 328, and 334. In some embodiments, each of the fluid sensors 318, 324, 330, and 336 can be a differential pressure sensor that senses the difference between the hydrostatic pressure exerted on one side of the differential pressure sensor by the fluid in its corresponding container or bag 316, 322, 328, and 334 and the pressure exerted on the fluid at, for example, the top of its corresponding container or bag 316, 322, 328, and 334 and above the fluid. In some embodiments, each of the fluid sensors 318, 324, 330, and 336 can be two pressure sensors, where a first pressure sensor senses the hydrostatic pressure exerted on the first pressure sensor by the fluid in its corresponding container or bag 316, 322, 328, and 334 and a second pressure sensor senses the pressure exerted on the fluid at, for example, the top of its corresponding container or bag 316, 322, 328, and 334 and above the fluid.

[0078] The controller 308 can receive the one or more electrical signals from each of the fluid sensors 318, 324, 330, and 336 and determine or calculate the fluid level and/or the fluid volume in its corresponding container or bag 316, 322, 328, and 334. The controller 308 can determine or calculate the fluid volume based on the one or more electrical signals as well as a known shape or geometry of the corresponding container or bag 316, 322, 328, and 334. In some embodiments, one or more of the containers or bags 316, 322, 328, and 334 includes an RFID tag (not illustrated) that provides the controller 308 with information pertaining to the known geometry of the container or bag. In some embodiments, the volume of the container or bag 316, 322, 328, and 334 is calculated according to one or more of the techniques described in U.S. patent application 12/763,561 , filed on April 20, 2010, previously incorporated by reference herein. In some embodiments, the volume of the container or bag 316, 322, 328, and 334 is calculated by integrating the level of fluid against the known cross- sectional area of the container or bag 316, 322, 328, and 334 at various heights throughout the container or bag 316, 322, 328, and 334.

[0079] If the container or bag 316, 322, 328, and 334 is a hard shell reservoir, the known geometry can include the cross-sectional area of the container or bag 316, 322, 328, and 334, or a width and depth of the container or bag 316, 322, 328, and 334 as well as details on how the cross-sectional area varies relative to height within the container or bag 316, 322, 328, and 334. If the container or bag 316, 322, 328, and 334 is a soft shell reservoir, the known geometry can be based at least in part upon a known lateral expansion rate of the soft shell reservoir relative to the fluid level within the container or bag 316, 322, 328, and 334.

[0080] The auto transfusion system 300 can include one or more of the blood reservoir systems 70, 1 10, 150, and 190, described herein, to take the place of one or more of the fluid sensors 318, 324, 330, and 336 and the corresponding containers or bags 316, 322, 328, and 334. As used herein, the term blood reservoir can include one or more of the salvaged blood reservoir 316, the wash solution container 322, the collection bag 328, and the waste container 334. Also, as used herein, the term fluid reservoir can include one or more of the blood reservoirs 72, 1 12, 156, and 196 in the blood reservoir systems 70, 1 10, 150, and 190 and the salvaged blood reservoir 316, the wash solution container 322, the collection bag 328, and the waste container 334.

[0081] Figures 6 and 7 are illustrations of a blood reservoir system 70 that can be used in a perfusion system, such as the perfusion system 10 of Figure 1 and the perfusion system 52 of Figure 5A. The blood reservoir system 70 can also be used in an autotransfusion system, such as autotransfusion system 300 of Figure 5B. The blood reservoir system 70 includes a blood reservoir 72 and a sensor system 74 that includes a differential pressure sensor 76 and a controller 78. In some embodiments, the blood reservoir 72 can be similar to the blood reservoir 56. In some embodiments, the differential pressure sensor 76 can be similar to the fluid sensor 58. In some embodiments, the controller 78 can be similar to the controller 60.

[0082] Figure 6 is an illustration of the blood reservoir system 70 with the blood reservoir 72 "open" to the atmosphere, such as when draining a patient by gravity. Figure 7 is an illustration of the blood reservoir system 70 with the blood reservoir 72 "closed" and fluidically coupled to a vacuum, such as when draining a patient with vacuum.

[0083] The blood reservoir 72 is a rigid, hard shell blood reservoir. The blood reservoir 72 is illustrated containing a volume of fluid 80, such as blood, that defines an interface 82 between the volume of fluid 80 and the air or other gas 84 in the space above the volume of fluid 80 in the blood reservoir 72. The blood reservoir 72 can include a first opening 86 that can be left open to the atmosphere, as shown in Figure 6, or fluidically coupled to a vacuum, as shown in Figure 7, a second opening 88 that can be an inlet for the fluid, and a third opening 90 that can be an outlet for the fluid. In some embodiments, the blood reservoir 72 can be a rigid, hard shell blood reservoir with a known geometry that can include the cross-sectional area of the blood reservoir 72, or a width and depth of the blood reservoir 72, as well as details on how the cross- sectional area varies relative to height within the blood reservoir 72.

[0084] The differential pressure sensor 76 can be located at the bottom 92 of the blood reservoir 72 to sense the pressure difference between the pressure exerted on the differential pressure sensor 76 by the fluid in the blood reservoir 72 and the pressure exerted on the volume of fluid 80 from the air or other gas 84 above the volume of fluid 80 in the blood reservoir 72. The differential pressure sensor 76 provides a signal that indicates the fluid level in the blood reservoir 72 and the controller 78 determines or calculates the fluid volume based on the fluid level and the known geometric configuration of the blood reservoir 72.

[0085] To sense the pressure difference, a first side 94 of the differential pressure sensor 76 can be in contact with the volume of fluid 80 in the blood reservoir 72 to sense the hydrostatic pressure exerted on the first side 94 of the differential pressure sensor 76 by the volume of fluid 80. As shown in Figure 6, a second side 96 of the differential pressure sensor 76 can be left open to the atmosphere to sense the atmospheric pressure, which is the pressure exerted on the volume of fluid 80 from above the volume of fluid 80 in the blood reservoir 72 with the first opening 86 left open to the atmosphere. Alternatively, as shown in Figure 7, the second side 96 of the differential pressure sensor 76 can be fluidically coupled with a tube 98 to the top 100 of the blood reservoir 72, such that the second side 96 of the differential pressure sensor 76 is fluidically coupled to the air or other gas 84 above the volume of fluid 80 in the blood reservoir 72, to sense the pressure exerted on the volume of fluid 80 from above the volume of fluid 80 in the blood reservoir 72.

[0086] The differential pressure sensor 76 can provide at least one electrical signal that correlates to the pressure difference and the pressures exerted on the first and second sides 94 and 96 of the differential pressure sensor 76, where the at least one electrical signal indicates the fluid level in the blood reservoir 72. In some embodiments, the differential pressure sensor 76 can provide at least one voltage signal that indicates the fluid level in the blood reservoir 72. In some embodiments, the differential pressure sensor 76 can provide the at least one electrical signal as a wired electrical signal(s). In some embodiments, the differential pressure sensor 76 can provide the at least one electrical signal as a wireless signal(s).

[0087] The differential pressure sensor 76 can be integrated into the blood reservoir 72. In some embodiments, the differential pressure sensor 76 can be snap fit into the bottom of the blood reservoir 72. In some embodiments, the differential pressure sensor 76 can be adhesively attached to the bottom of the blood reservoir 72. In some embodiments, the differential pressure sensor 76 can be molded into the blood reservoir 72, such that the differential pressure sensor 76 can be at least partially protected by the plastic material of the blood reservoir 72.

[0088] In some embodiments, the differential pressure sensor 76 can include a single pressure sensing transducer or diaphragm that receives a first pressure on the first side 94 and a second pressure on the second side 96, and can provide an electrical signal that indicates the fluid level in the blood reservoir 72. In some embodiments, the differential pressure sensor 76 includes a first pressure sensing transducer or diaphragm at first side 94 and a second pressure sensing transducer or diaphragm at second side 96 and can provide one or more electrical signals that indicate the fluid level in the blood reservoir 72. In some embodiments, the differential pressure sensor 76 includes two pressure sensors in a package.

[0089] In some embodiments, the differential pressure sensor 76 can be disposable. In some embodiments, the differential pressure sensor 76 can be modeled after a disposable pressure sensor, such as Measurement Specialties 1620 model, which is a fully piezoresistive silicon pressure sensor for use in invasive blood pressure monitoring. The model 1620 can be used with automated assembly equipment and dropped directly into a disposable unit. Also, the model 1620 includes a dielectric gel placed over the sensor to provide electric and fluidic isolation and the model 1620 can be sterilized. In addition, the model 1620 has an operating product life of 168 hours and a shelf life of 5 years. In some embodiments, the differential pressure sensor 76 can be provided based on a micro-electromechanical system (MEMS) component, such as Measurement Specialties MS763 die.

[0090] The controller 78 can receive the at least one electrical signal from the differential pressure sensor 76 via communications path 102 and determine or calculate the fluid volume in the blood reservoir 72 based on the at least one electrical signal and the known geometric configuration of the blood reservoir 72. The controller 78 can provide at least one signal indicating at least one of: the fluid level in the blood reservoir 72 (a fluid level signal); and the fluid volume in the blood reservoir 72 (a fluid volume signal). In some embodiments, an HLM, such as the HLM 12 (shown in Figure 1 ) or the HLM 54 (shown in Figure 5A), can receive the at least one signal from the controller 78 and adjust an operating parameter of the HLM based on the at least one of the fluid level signal and the fluid volume signal. In some embodiments, a system, such as the DMS, can receive the at least one signal from the controller 78 and display at least one of the fluid level and the fluid volume in the blood reservoir 72.

[0091] While the controller 78 is shown as a distinct element and can be a standalone controller, in some embodiments, the controller 78 can be part of an HLM or part of a controller (similar to the controller 20) operating an HLM. Also, in some embodiments, the controller 78 can be part of the differential pressure sensor 76 or part of a display system, such as the DMS.

[0092] In operation of the blood reservoir system 70 with the blood reservoir 72 "open" as shown in Figure 6, the first opening 86 is open to the atmosphere and the differential pressure sensor 76 can sense the hydrostatic pressure exerted on the first side 94 of the differential pressure sensor 76 by the fluid in the blood reservoir 72 and the atmospheric pressure exerted on the second side 96 of the differential pressure sensor 76, where the atmospheric pressure is the pressure exerted on the volume of fluid 80 from the air or atmosphere at 84 above the volume of fluid 80 in the blood reservoir 72. The differential pressure sensor 76 provides at least one electrical signal that indicates the fluid level in the blood reservoir 72. The controller 78 receives the at least one electrical signal from the differential pressure sensor 76 and determines the fluid volume in the blood reservoir 72 based on the at least one electrical signal and the known geometric configuration of the blood reservoir 72. The controller 78 provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir 72 and a fluid volume signal that indicates the fluid volume in the blood reservoir 72.

[0093] In operation of the blood reservoir system 70 with the blood reservoir 72 "closed" as shown in Figure 7, the first opening 86 is fluidically coupled to a vacuum and the second side 96 of the differential pressure sensor 76 is fluidically coupled to the air or other gas 84 above the volume of fluid 80 in the blood reservoir 72. The differential pressure sensor 76 can sense the hydrostatic pressure exerted on the first side 94 of the differential pressure sensor 76 by the fluid in the blood reservoir 72 and the pressure exerted on the volume of fluid 80 from the air or other gas 84 above the volume of fluid 80 via the tube 98 and the second side 96 of the differential pressure sensor 76. The differential pressure sensor 76 provides at least one electrical signal that indicates the fluid level in the blood reservoir 72. The controller 78 receives the at least one electrical signal from the differential pressure sensor 76 and determines the fluid volume in the blood reservoir 72 based on the at least one electrical signal and the known geometric configuration of the blood reservoir 72. The controller 78 provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir 72 and a fluid volume signal that indicates the fluid volume in the blood reservoir 72. [0094] Figure 8 is an illustration of a blood reservoir system 110 that includes a soft shell blood reservoir 1 12 and a sensor system 1 14 that can be used in a perfusion system, such as the perfusion system 10 of Figure 1 and the perfusion system 52 of Figure 5A. The blood reservoir system 1 10 can also be used in an autotransfusion system, such as autotransfusion system 300 of Figure 5B. The sensor system 1 14 includes a differential pressure sensor 1 16 and a controller 1 18. In some embodiments, the blood reservoir 1 12 can be similar to the blood reservoir 56. In some embodiments, the differential pressure sensor 1 16 can be similar to the fluid sensor 58. In some embodiments, the controller 1 18 can be similar to the controller 60.

[0095] The soft shell blood reservoir 1 12 is illustrated containing a volume of fluid 120, such as blood, that defines an interface 122 between the volume of fluid 120 and the air or other gas 124 in the space above the volume of fluid 120 in the blood reservoir 1 12. The blood reservoir 1 12 can include a first opening 126 that can be an inlet for the fluid and a second opening 128 that can be an outlet for the fluid. In some embodiments, the blood reservoir 1 12 can be a soft shell blood reservoir with a known geometry that can be based at least in part upon a known lateral expansion rate of the soft shell blood reservoir relative to the blood or fluid level within the blood reservoir 1 12.

[0096] The differential pressure sensor 1 16 can be located at the bottom 130 of the blood reservoir 1 12 to sense the pressure difference between the pressure exerted on the differential pressure sensor 1 16 by the fluid in the blood reservoir 1 12 and the pressure exerted on the soft shell blood reservoir 1 12, which is the atmospheric pressure. The differential pressure sensor 1 16 provides a signal that indicates the fluid level in the soft shell blood reservoir 1 12 and the controller 1 18 determines or calculates the fluid volume based on the fluid level and the known geometric configuration of the soft shell blood reservoir 1 12.

[0097] To sense the pressure difference, a first side 132 of the differential pressure sensor 1 16 can be in contact with the volume of fluid 120 in the blood reservoir 1 12 to sense the hydrostatic pressure exerted on the first side 132 of the differential pressure sensor 1 16 by the volume of fluid 120. A second side 134 of the differential pressure sensor 1 16 can be left open to the atmosphere to sense the atmospheric pressure.

[0098] The differential pressure sensor 1 16 can provide at least one electrical signal that correlates to the pressure difference and the pressures exerted on the first and second sides 132 and 134 of the differential pressure sensor 1 16, where the at least one electrical signal indicates the fluid level in the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 can provide at least one voltage signal that indicates the fluid level in the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 can provide the at least one electrical signal as a wired electrical signal(s). In some embodiments, the differential pressure sensor 1 16 can provide the at least one electrical signal as a wireless signal(s).

[0099] The differential pressure sensor 1 16 can be integrated into the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 can be snap fit into the bottom of the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 can be adhesively attached to the bottom of the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 can be molded into the blood reservoir 1 12, such that the differential pressure sensor 1 16 can be at least partially protected by the plastic material of the blood reservoir 1 12.

[00100] In some embodiments, the differential pressure sensor 1 16 can include a single pressure sensing transducer or diaphragm that receives a first pressure on the first side 132 and a second pressure on the second side 134, and can provide an electrical signal that indicates the fluid level in the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 includes a first pressure sensing transducer or diaphragm at first side 132 and a second pressure sensing transducer or diaphragm at second side 134 and can provide one or more electrical signals that indicate the fluid level in the blood reservoir 1 12. In some embodiments, the differential pressure sensor 1 16 includes two pressure sensors in a package.

[00101] In some embodiments, the differential pressure sensor 1 16 can be disposable. In some embodiments, the differential pressure sensor 1 16 can be modeled after a disposable pressure sensor, such as Measurement Specialties 1620 model, which is a fully piezoresistive silicon pressure sensor for use in invasive blood pressure monitoring. The model 1620 can be used with automated assembly equipment and dropped directly into a disposable unit. Also, the model 1620 includes a dielectric gel placed over the sensor to provide electric and fluidic isolation and the model 1620 can be sterilized. In addition, the model 1620 has an operating product life of 168 hours and a shelf life of 5 years. In some embodiments, the differential pressure sensor 1 16 can be provided based on a micro-electromechanical system (MEMS) component, such as Measurement Specialties MS763 die.

[00102] The controller 1 18 can receive the at least one electrical signal from the differential pressure sensor 1 16 via communications path 136 and determine or calculate the fluid volume in the blood reservoir 1 12 based on the at least one electrical signal and the known geometric configuration of the blood reservoir 1 12. The controller 1 18 can provide at least one signal indicating at least one of: the fluid level in the blood reservoir 1 12 (a fluid level signal); and the fluid volume in the blood reservoir 1 12 (a fluid volume signal). In some embodiments, an HLM, such as the HLM 12 (shown in Figure 1 ) or the HLM 54 (shown in Figure 5A), can receive the at least one signal from the controller 1 18 and adjust an operating parameter of the HLM based on the at least one of the fluid level signal and the fluid volume signal. In some embodiments, a system, such as the DMS, can receive the at least one signal from the controller 1 18 and display at least one of the fluid level and the fluid volume in the blood reservoir 1 12.

[00103] While the controller 1 18 is shown as a distinct element and can be a standalone controller, in some embodiments, the controller 1 18 can be part of an HLM or part of a controller (similar to the controller 20) operating an HLM. Also, in some embodiments, the controller 1 18 can be part of the differential pressure sensor 1 16 or part of a display system, such as the DMS.

[00104] In operation of the blood reservoir system 1 10 with the soft shell blood reservoir 1 12, the differential pressure sensor 1 16 can sense the hydrostatic pressure exerted on the first side 132 of the differential pressure sensor 1 16 by the fluid in the blood reservoir 1 12 and the atmospheric pressure exerted on the second side 134 of the differential pressure sensor 1 16, where the atmospheric pressure is the pressure exerted on the soft shell blood reservoir 1 12. The differential pressure sensor 1 16 provides at least one electrical signal that indicates the fluid level in the blood reservoir 1 12. The controller 1 18 receives the at least one electrical signal from the differential pressure sensor 1 16 and determines the fluid volume in the blood reservoir 1 12 based on the at least one electrical signal and the known geometric configuration of the blood reservoir 1 12. The controller 1 18 provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir 1 12 and a fluid volume signal that indicates the fluid volume in the blood reservoir 1 12.

[00105] Figure 9 is an illustration of a blood reservoir system 150 that includes two separate pressure sensors, a first pressure sensor 152 and a second pressure sensor 154. The blood reservoir system 150 can be used in a perfusion system, such as the perfusion system 10 of Figure 1 and the perfusion system 52 of Figure 5A. The blood reservoir system 150 can also be used in an autotransfusion system, such as autotransfusion system 300 of Figure 5B. The blood reservoir system 150 includes a blood reservoir 156 and a sensor system 158 that includes the first pressure sensor 152, the second pressure sensor 154, and a controller 160. The blood reservoir system 150 can be used with the blood reservoir 156 "open" to the atmosphere, such as when draining a patient by gravity, and with the blood reservoir 156 "closed" and fluidically coupled to a vacuum, such as when draining a patient with vacuum. In some embodiments, the blood reservoir 156 can be similar to the blood reservoir 56. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be similar to the fluid sensor 58. In some embodiments, the controller 160 can be similar to the controller 60.

[00106] The blood reservoir 156 is a rigid, hard shell blood reservoir illustrated containing a volume of fluid 162, such as blood, that defines an interface 164 between the volume of fluid 162 and the air or other gas 166 in the space above the volume of fluid 162 in the blood reservoir 156. The blood reservoir 156 can include a first opening 168 that can be left open to the atmosphere or fluidically coupled to a vacuum, a second opening 170 that can be an inlet for the fluid, and a third opening 172 that can be an outlet for the fluid. In some embodiments, the blood reservoir 156 can be a rigid, hard shell blood reservoir with a known geometry that can include the cross-sectional area of the blood reservoir 156, or a width and depth of the blood reservoir 156, as well as details on how the cross-sectional area varies relative to height within the blood reservoir 156.

[00107] The first pressure sensor 152 can be located at the bottom 174 of the blood reservoir 156 and in contact with the volume of fluid 162 to sense the hydrostatic pressure exerted on the first pressure sensor 152 by the fluid in the blood reservoir 156. The second pressure sensor 154 can be located at the top 176 of the blood reservoir 156 and in contact with the air or other gas 166 to sense the pressure exerted on the volume of fluid 162 above the fluid in the blood reservoir 156. In some embodiments, if the first opening 168 is open to the atmosphere, the second pressure sensor 154 can be left unattached to the blood reservoir 156 and open to the atmosphere to sense the atmospheric pressure, which is the pressure exerted on the volume of fluid 162 in the blood reservoir 156.

[00108] The fluid level in the blood reservoir 156 can be determined from the pressure difference between the pressure sensed by the first pressure sensor 152 and the pressure sensed by the second pressure sensor 154, and the fluid volume can be determined based on the fluid level and the known geometric configuration of the blood reservoir 156.

[00109] Each of the first and second pressure sensors 152 and 154 can provide at least one electrical signal, such as a voltage signal, that correlates to the pressure sensed by the pressure sensor, where the at least one electrical signal is proportional to or at least related to the fluid level and the fluid volume in the blood reservoir 156. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can provide the at least one electrical signal as a wired electrical signal(s). In some embodiments, one or both of the first and second pressure sensors 152 and 154 can provide the at least one electrical signal as a wireless signal(s).

[00110] Also, each of the first and second pressure sensors 152 and 154 can be integrated into the blood reservoir 156. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be snap fit into the blood reservoir 156. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be adhesively attached to the blood reservoir 156. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be molded into the blood reservoir 156, such that only a connector may be accessible outside the blood reservoir 156 and the pressure sensor can be at least partially protected by the plastic material of the blood reservoir 156.

[00111] In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be disposable. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be modeled after a disposable pressure sensor, such as Measurement Specialties 1620 model, which is a fully piezoresistive silicon pressure sensor for use in invasive blood pressure monitoring. The model 1620 can be used with automated assembly equipment and dropped directly into a disposable unit. Also, the model 1620 includes a dielectric gel placed over the sensor to provide electric and fluidic isolation and the model 1620 can be sterilized. In addition, the model 1620 has an operating product life of 168 hours and a shelf life of 5 years. In some embodiments, one or both of the first and second pressure sensors 152 and 154 can be provided based on a micro-electromechanical system (MEMS) component, such as Measurement Specialties MS763 die.

[00112] The controller 160 can receive the at least one electrical signal from each of the first and second pressure sensors 152 and 154 via communication paths 178 and 180, respectively. The controller 160 can determine or calculate at least one of a fluid level in the blood reservoir 156 and a fluid volume in the blood reservoir 156 based on the signals and the known geometry of the rigid, hard shell blood reservoir 156. The controller 160 can provide at least one signal indicating at least one of: the fluid level in the blood reservoir 156 (a fluid level signal); and the fluid volume in the blood reservoir 156 (a fluid volume signal). In some embodiments, an HLM, such as the HLM 12 (shown in Figure 1 ) or the HLM 54 (shown in Figure 5A), can receive the at least one signal from the controller 160 and adjust an operating parameter of the HLM based on the at least one of the fluid level signal and the fluid volume signal. In some embodiments, a system, such as the DMS, can receive the at least one signal from the controller 160 and display at least one of the fluid level and the fluid volume in the blood reservoir 156.

[00113] While the controller 160 is shown as a distinct element and can be a standalone controller, in some embodiments, the controller 160 can be part of an HLM or part of a controller (similar to the controller 20) operating an HLM. Also, in some embodiments, the controller 160 can be part of one or both of the first and second pressure sensors 152 and 154 or part of a display system, such as the DMS.

[00114] In operation of the blood reservoir system 150, with the blood reservoir 156 "open" and the first opening 158 open to the atmosphere, the first pressure sensor 152 can sense the hydrostatic pressure exerted on the first pressure sensor 152 by the fluid in the blood reservoir 156 and the second pressure sensor 154 can sense the atmospheric pressure exerted on the volume of fluid 152 in the blood reservoir 156. Next, each of the first and second pressure sensors 152 and 154 provides at least one electrical signal that indicates the pressure sensed by the pressure sensor. The controller 160 receives the signals from the first and second pressure sensors 152 and 154 and determines at least one of a fluid level in the blood reservoir 156 and a fluid volume in the blood reservoir 156 based on the received signals and the known geometry of the rigid, hard shell blood reservoir 156. The controller 160 provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir 156 and a fluid volume signal that indicates the fluid volume in the blood reservoir 156.

[00115] In operation of the blood reservoir system 150, with the blood reservoir 156 "closed" and the first opening 168 fluidically coupled to a vacuum, the first pressure sensor 152 can sense the hydrostatic pressure exerted on the first pressure sensor 152 by the fluid in the blood reservoir 156 and the second pressure sensor 154 can sense the pressure exerted on the volume of fluid 162 above the volume of fluid 162 under vacuum. Next, each of the first and second pressure sensors 152 and 154 provides at least one electrical signal that indicates the pressure sensed by the pressure sensor. The controller 160 receives the signals from the first and second pressure sensors 152 and 154 and determines at least one of a fluid level in the blood reservoir 156 and a fluid volume in the blood reservoir 156 based on the received signals. The controller 160 provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir 156 and a fluid volume signal that indicates the fluid volume in the blood reservoir 156.

[00116] Figure 10 is an illustration of a blood reservoir system 190 that includes two separate pressure sensors, a first pressure sensor 192 and a second pressure sensor 194, and a soft shell blood reservoir 196. The blood reservoir system 190 can be used in a perfusion system, such as the perfusion system 10 of Figure 1 and the perfusion system 52 of Figure 5A. The blood reservoir system 190 can also be used in an autotransfusion system, such as autotransfusion system 300 of Figure 5B. The blood reservoir system 190 includes the soft shell blood reservoir 196 and a sensor system 198 that includes the first pressure sensor 192, the second pressure sensor 194, and a controller 200. In some embodiments, the soft shell blood reservoir 196 can be similar to the blood reservoir 56. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be similar to the fluid sensor 58. In some embodiments, the controller 200 can be similar to the controller 60.

[00117] The soft shell blood reservoir 196 is illustrated containing a volume of fluid 202, such as blood, that defines an interface 204 between the volume of fluid 202 and the air or other gas 206 in the space above the volume of fluid 202 in the blood reservoir 196. The blood reservoir 196 can include a first opening 208 that can be an inlet for the fluid and a second opening 210 that can be an outlet for the fluid. In some embodiments, the blood reservoir 196 can be a soft shell blood reservoir with a known geometry that can be based at least in part upon a known lateral expansion rate of the soft shell blood reservoir relative to the blood or fluid level within the blood reservoir 196.

[00118] The first pressure sensor 192 can be located at the bottom 212 of the blood reservoir 196 and in contact with the volume of fluid 202 to sense the hydrostatic pressure exerted on the first pressure sensor 192 by the fluid in the blood reservoir 196. The second pressure sensor 194 can be left unattached to the blood reservoir 196 and open to the atmosphere to sense the atmospheric pressure, which is the pressure exerted on the soft shell blood reservoir 196.

[00119] The fluid level in the blood reservoir 196 can be determined from the pressure difference between the pressure sensed by the first pressure sensor 192 and the pressure sensed by the second pressure sensor 194, and the fluid volume can be determined based on the fluid level and the known geometric configuration of the blood reservoir 196. [00120] Each of the first and second pressure sensors 192 and 194 can provide at least one electrical signal, such as a voltage signal, that correlates to the pressure sensed by the pressure sensor, where the at least one electrical signal is proportional to or at least related to the fluid level and the fluid volume in the blood reservoir 196. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can provide the at least one electrical signal as a wired electrical signal(s). In some embodiments, one or both of the first and second pressure sensors 192 and 194 can provide the at least one electrical signal as a wireless signal(s).

[00121] Also, each of the first and second pressure sensors 192 and 194 can be integrated into the blood reservoir 196, with the second pressure sensor exposed to atmospheric pressure. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be snap fit into the blood reservoir 196. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be adhesively attached to the blood reservoir 196. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be molded into the blood reservoir 196.

[00122] In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be disposable. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be modeled after a disposable pressure sensor, such as Measurement Specialties 1620 model, which is a fully piezoresistive silicon pressure sensor for use in invasive blood pressure monitoring. The model 1620 can be used with automated assembly equipment and dropped directly into a disposable unit. Also, the model 1620 includes a dielectric gel placed over the sensor to provide electric and fluidic isolation and the model 1620 can be sterilized. In addition, the model 1620 has an operating product life of 168 hours and a shelf life of 5 years. In some embodiments, one or both of the first and second pressure sensors 192 and 194 can be provided based on a micro-electromechanical system (MEMS) component, such as Measurement Specialties MS763 die.

[00123] The controller 200 can receive the at least one electrical signal from each of the first and second pressure sensors 192 and 194 via communication paths 214 and 216, respectively. The controller 200 can determine or calculate at least one of a fluid level in the blood reservoir 196 and a fluid volume in the blood reservoir 196 based on the signals and the known geometry of the soft shell blood reservoir 196. The controller 200 can provide at least one signal indicating at least one of: the fluid level in the blood reservoir 196 (a fluid level signal); and the fluid volume in the blood reservoir 196 (a fluid volume signal). In some embodiments, an HLM, such as the HLM 12 (shown in Figure 1 ) or the HLM 54 (shown in Figure 5A), can receive the at least one signal from the controller 200 and adjust an operating parameter of the HLM based on the at least one of the fluid level signal and the fluid volume signal. In some embodiments, a system, such as the DMS, can receive the at least one signal from the controller 200 and display at least one of the fluid level and the fluid volume in the blood reservoir 196.

[00124] While the controller 200 is shown as a distinct element and can be a standalone controller, in some embodiments, the controller 200 can be part of an HLM or part of a controller (similar to the controller 20) operating an HLM. Also, in some embodiments, the controller 200 can be part of one or both of the first and second pressure sensors 192 and 194 or part of a display system, such as the DMS.

[00125] In operation of the blood reservoir system 190, the first pressure sensor 192 can sense the hydrostatic pressure exerted on the first pressure sensor 192 by the fluid in the blood reservoir 196 and the second pressure sensor 194 can sense the atmospheric pressure exerted on the volume of fluid 192 in the soft shell blood reservoir 196. Next, each of the first and second pressure sensors 192 and 194 provides at least one electrical signal that indicates the pressure sensed by the pressure sensor. The controller 200 receives the signals from the first and second pressure sensors 192 and 194 and determines at least one of a fluid level in the blood reservoir 196 and a fluid volume in the blood reservoir 196 based on the received signals and the known geometry of the soft shell blood reservoir 196. The controller 200 provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir 196 and a fluid volume signal that indicates the fluid volume in the blood reservoir 196.

[00126] Figure 1 1 is an illustration of a method of determining the fluid volume in the blood reservoir system 70 of Figures 6 and 7 and in the blood reservoir system 1 10 of Figure 8. [00127] At 230, the differential pressure sensor senses the pressure difference between pressures on the first and second sides of the differential pressure sensor. The differential pressure sensor senses the pressure difference between the pressure exerted on the differential pressure sensor by fluid in the blood reservoir and the pressure exerted on the fluid in the blood reservoir.

[00128] At 232, the differential pressure sensor provides at least one signal that indicates the fluid level in the blood reservoir.

[00129] At 234, a controller receives the at least one signal from the differential pressure sensor and, at 236, the controller determines the fluid volume in the blood reservoir based on the at least one signal. At 238, the controller provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir and a fluid volume signal that indicates the fluid volume in the blood reservoir.

[00130] Figure 12 is an illustration of a method of determining at least one of a fluid level and a fluid volume in the blood reservoir system 150 of Figure 9 and in the blood reservoir system 190 of Figure 10.

[00131] At 250, the first pressure sensor located at the bottom of the blood reservoir and in contact with the volume of fluid senses the hydrostatic pressure exerted on the first pressure sensor by the fluid in the blood reservoir. At 252, the second pressure sensor senses the pressure exerted on the volume of fluid in the blood reservoir.

[00132] At 254, each of the first and second pressure sensors provides at least one electrical signal that indicates or correlates to the pressure sensed by the pressure sensor.

[00133] At 256, the controller receives the signals from the first and second pressure sensors and, at 258, the controller determines at least one of a fluid level in the blood reservoir and a fluid volume in the blood reservoir based on the received signals. At 260, the controller provides at least one of a fluid level signal that indicates the fluid level in the blood reservoir and a fluid volume signal that indicates the fluid volume in the blood reservoir.

[00134] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.