Apparatus for controlling the supply of oxygenated gas, and cardiac perfusion system

Abstract

An apparatus for controlling the supply of oxygenated gas to an oxygenator (140) includes a mixing chamber (161) having an interior volume (165), multiple inlets (162a, 162b), and multiple outlets (167a, 167b). Each inlet is configured to receive a different supply gas, and each outlet is configured to convey oxygenated gas from the interior volume to the oxygenator (140). The apparatus further includes multiple inlet valves (164a, 164b), each disposed between a corresponding inlet and the interior volume of the mixing chamber, and multiple outlet valves (166a, 166b), each disposed between the interior volume of the mixing chamber and a corresponding outlet. The apparatus further includes a controller (150) configured to open and close each of the inlet valves and each of the outlet valves independently of one another.

Description

[Technical Field]

[0001] The present disclosure relates to a device for controlling the delivery of oxygenated gas to an artificial lung.Embodiments of the device disclosed herein can be used in cardiac perfusion systems. [Background technology]

[0002] Cardiac perfusion is a medical procedure involving extracorporeal oxygenation of a patient's blood. Cardiac perfusion is performed when a patient is unable to oxygenate their own blood by breathing, for example, during cardiac and / or pulmonary surgery. Extracorporeal oxygenation typically uses a pump that acts as a substitute for the patient's own heart and an oxygenator that acts as a substitute for the patient's own lungs. The oxygenator removes carbon dioxide from the patient's blood and adds oxygen. Cardiac perfusion is sometimes known in the art as extracorporeal perfusion or extracorporeal circulation.

[0003] The applicant's patent application, U.S. Pat. No. 6,499,623, discloses an oxygenator for a cardiac system. The oxygenator has a gas inlet zone fluidly connected to a gas-blood interface. The gas inlet zone is separated into two compartments by a partition, thereby dividing the gas-blood interface region into two regions. Each compartment of the gas inlet zone is connected to a respective gas supply, and a flow controller is disposed between each gas supply and its connected inlet zone. The flow controller allows the gas supply for the different interface gas-blood regions to be modulated differently.

[0004] Multiple gas-blood interface regions in an oxygenator, such as that disclosed in U.S. Patent No. 6,277,663, enable advanced ventilation techniques that closely control the patient's blood gas saturation levels. However, implementing such ventilation techniques requires the appropriate gas to be delivered to each gas-blood interface region at the appropriate time. This may require a clinician to manually change connections between the oxygenator and the gas supply, which is time-consuming and introduces the risk of human error. The present disclosure aims to overcome or mitigate these challenges with gas delivery to an oxygenator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Patent Publication No. 2019 / 166823 Summary of the Invention

[0006] A first aspect of the present disclosure relates to an apparatus for controlling the supply of oxygenated gas to an oxygenator. The apparatus includes a mixing chamber having an internal volume, multiple inlets, and multiple outlets, each configured to receive a different supply gas and each configured to deliver oxygenated gas from the internal volume to the oxygenator. The apparatus further includes multiple inlet valves, each disposed between a respective inlet and the internal volume of the mixing chamber. The apparatus further includes multiple outlet valves, each disposed between the internal volume of the mixing chamber and a respective outlet. The apparatus further includes a controller configured to open and close each of the inlet valves and each of the outlet valves independently of one another.

[0007] By independently opening and closing each of the inlet and outlet valves, the devices disclosed herein can automatically operate the oxygenator according to different operating modes without the need for a clinician to change the connections between the oxygenator and the hospital gas supply. Instead of manually changing such connections, the clinician can instruct the device (e.g., by selecting an option from a user interface) to change the oxygenator to a different operating mode. This reduces the risk of human error that can occur when manually changing connections between the oxygenator and the hospital gas supply, thereby improving patient safety. Furthermore, avoiding the need to manually change connections allows the oxygenator's operating mode to be quickly changed when clinical need arises, thereby improving clinical outcomes for patients.

[0008] The devices disclosed herein also allow for different operating modes of the oxygenator to be implemented with a single mixing chamber. That is, the disclosed configuration of the mixing chamber relative to the inlet and outlet valves allows for all operating modes of the oxygenator to be implemented without the need for a second mixing chamber or a direct connection between the oxygenator and the hospital gas supply. Ventilation systems incorporating the disclosed devices are therefore reduced in size and complexity.

[0009] The term "oxygenated gas" refers to the gas provided by the device to the oxygenator. The oxygenated gas is used by the oxygenator to oxygenate the blood. Depending on the composition of the oxygenated gas and / or the composition of the blood, oxygenation can include adding oxygen to the blood, removing carbon dioxide from the blood, or both. The oxygenated gas can be pure oxygen or oxygen mixed with one or more other gases. For example, the oxygenated gas can include a mixture of oxygen with nitrogen and / or carbon dioxide. As another example, the oxygenated gas can include a mixture of nitrogen and oxygen (but not carbon dioxide).

[0010] The term "supply gas" refers to the components of an oxygenated gas. The oxygenated gas may be composed of a single supply gas, or the oxygenated gas may be a mixture of two or more supply gases. The source of the supply gas may be a hospital gas supply. A hospital gas supply (also known as a medical gas supply) is a facility that distributes various gases from a source (e.g., a gas cylinder) to multiple outlets located in a hospital or other medical facility. Oxygen and air are examples of supply gases that a device can receive from a hospital gas supply. Alternatively or additionally, the source of the supply gas may be a gas cylinder co-located with the device disclosed herein.

[0011] As used herein, the term "valve" refers to a component or device that can regulate (i.e., increase, decrease, and / or stop) the flow of gas. Each valve may be of any suitable type, including, but not limited to, a ball valve, a butterfly valve, a diaphragm valve, a gate valve, or a needle valve. In the following disclosure, valves are said to have "positions," but this is not intended to impose any limitations on the type of valve or the manner in which they are actuated.

[0012] Each valve may have or be coupled to an actuator to allow a controller to open or close the valve. For example, a valve may have an electromechanical actuator, such as a motor or solenoid, to which a controller can send an electrical signal (e.g., voltage) to cause the valve to open or close. Other suitable actuators, such as hydraulic or pneumatic actuators, may be used.

[0013] As used herein, the term "open" refers to any position in which the valve allows gas to pass through. The term "fully open" refers to a position in which the valve allows maximum gas to pass through the valve. The term "closed" refers to a position in which the valve does not allow any gas to pass through (in other words, the valve completely prohibits the passage of gas). The term "partially open" refers to an intermediate position between the fully open and closed positions. Thus, a valve is said to be "open" when it is in a fully open position or a partially open position.

[0014] The term "open" refers to moving the position of a valve toward a fully open position, but does not necessarily require that the valve reach the fully open position. The term "fully open" refers to moving the position of a valve so that it reaches the fully open position. The term "close" refers to moving the position of a valve toward a closed position, but does not necessarily require that the valve reach the closed position. The term "closed" refers to moving the position of a valve so that it reaches the closed position. The term "adjust" is used herein to encompass the actions of opening, fully opening, closing, and fully closing a valve.

[0015] The devices disclosed herein can control the composition of the oxygenated gas by opening and / or closing inlet valves to vary the relative proportions of different supply gases entering the mixing chamber. For example, the device can control the oxygen concentration in the oxygenated gas by opening and / or closing inlet valves to adjust the relative proportions of nitrogen, carbon dioxide, and / or oxygen in the oxygenated gas. The devices disclosed herein can also control the flow rate of the oxygenated gas to the oxygenator by opening and / or closing inlet and / or outlet valves.

[0016] Any of the valves mentioned herein may be implemented by a mass flow controller. A mass flow controller is a device including a valve, a sensor, and a control loop configured to adjust the position of the valve to achieve a desired flow rate. The control loop receives the flow rate measured by the sensor and the desired flow rate as its inputs and adjusts the position of the valve to minimize the difference between the measured and desired flow rates. When a valve is implemented by a mass flow controller, the device's controller can open and / or close the valve position by outputting a signal indicative of the desired flow rate to the input of the mass flow controller's control loop.

[0017] In the following examples, it is assumed that a first inlet of the plurality of inlets is connected to a supply of air. For example, the first inlet may be connected to a supply of medical air from a hospital gas supply. The following examples further assume that a second inlet of the plurality of inlets is connected to a supply of oxygen. For example, the second inlet may be connected to a supply of substantially pure oxygen from a hospital gas supply. The following examples further assume that each outlet is connected to a respective inlet of an oxygenator, which may be a multi-zone oxygenator.

[0018] A multi-zone oxygenator is an oxygenator in which the gas-blood interface is separated into two or more gas-blood interface regions, each of which can be independently supplied with oxygenated gas. The presence of multiple gas-blood interface regions allows for precise control of gas exchange within the oxygenator, as blood can be exposed to different oxygenated gas conditions in each region. A dual-zone oxygenator is a multi-zone oxygenator with exactly two gas-blood interface regions.

[0019] The plurality of inlet valves may include a first inlet valve and a second inlet valve, and the controller may be configured to adjust the first inlet valve and the second inlet valve to control the oxygen concentration in the oxygenated gas.

[0020] The first inlet valve is disposed between the first inlet and the internal volume of the mixing chamber. As previously described, the first inlet is connected to an air supply. Adjusting the first inlet valve modulates the proportion of air (mostly nitrogen) in the oxygenated gas. The second inlet valve is disposed between the second inlet and the internal volume of the mixing chamber. As previously described, the second inlet is connected to an oxygen supply. Adjusting the second inlet valve modulates the proportion of oxygen in the oxygenated gas. Thus, by adjusting the first and second inlet valves, the oxygen concentration in the oxygenated gas can be controlled to achieve specific clinical outcomes. For example, increasing the oxygen concentration in the oxygenated gas can enhance oxygen uptake by the patient's blood. As another example, increasing the oxygen concentration in the oxygenated gas can prevent the formation of gas microemboli (gas bubbles in the blood, which often have a high nitrogen content). If gas microemboli are already present in the patient's blood, increasing the oxygen concentration can remove them or reduce their number and / or size. Conversely, decreasing the oxygen concentration in the oxygenated gas can reduce the patient's risk of developing hyperoxia.

[0021] The term "oxygen concentration in an oxygenated gas" is sometimes referred to in the art as "fraction of inspired oxygen" (abbreviated as "FiO2").

[0022] In general, the controller may be configured to control the composition of the oxygenated gas by adjusting the inlet valve.

[0023] For example, the device may include a third inlet and a third inlet valve. The third inlet may be connected to a supply of carbon dioxide from a hospital gas supply. The carbon dioxide supply may be a supply of pure carbon dioxide or a supply of carbogen. The controller may control the composition of carbon dioxide in the oxygenated gas by adjusting the third inlet valve. For example, the composition of carbon dioxide in the oxygenated gas may be increased to reduce the risk of the patient developing hypocapnia. The device may have more than three inlets and inlet valves.

[0024] The controller may be further configured to operate the oxygenator in a first mode by opening all outlet valves. In the first mode, the multi-region oxygenator operates in the same manner as a conventional single-region oxygenator. The device automatically reconfigures how oxygenated gas is delivered to the oxygenator, causing the multi-region oxygenator to operate in the same manner as a conventional single-region oxygenator. This is beneficial for clinicians who do not want to use the advanced ventilation techniques supported by the multi-region oxygenator. Such clinicians simply instruct the device to operate the oxygenator in the first mode (e.g., by selecting an option from a user interface) without having to modify the perfusion system by inserting a single-region oxygenator or changing how the oxygenator is connected to the hospital gas supply. Eliminating the need to modify the perfusion system or the connection to the hospital gas supply reduces the risk of human error, thereby improving patient safety.

[0025] When the oxygenator is operating in the first mode, the oxygenated gas comprises air and, optionally, additional oxygen. The first inlet valve is open (and, optionally, fully open) to allow air to enter the mixing chamber from the hospital gas supply through the first inlet. The second inlet valve is adjusted to control the amount of oxygen entering the mixing chamber from the hospital gas supply through the second inlet. The second inlet valve is closed when the desired oxygen concentration in the oxygenated gas is the same as that in air (i.e., approximately 21%). The second inlet valve can be gradually opened to increase the oxygen concentration in the oxygenated gas above that in air (i.e., 21%). The oxygenated gas is allowed to pass through all outlet valves and enter all gas-blood interface regions of the multi-zone oxygenator. The device may adjust the inlet and / or outlet valves to achieve a desired flow rate of oxygenated gas to the oxygenator.

[0026] Opening all of the outlet valves may include opening each outlet valve to a respective position, each position selected to divide the volumetric flow rate of the oxygenated gas through the multiple outlets according to a predetermined ratio. By accurately dividing the total flow rate of the oxygenated gas among the different outlets, the device can use a multi-region oxygenator to better mimic the function of a single-region oxygenator.

[0027] The predetermined ratio may be selected to be substantially equal to the ratio between the sizes of the respective gas-blood interface areas of the oxygenator. Thus, each gas-blood interface area of ​​the multi-region oxygenator receives an amount of oxygen gas commensurate with its size (i.e., volume and / or surface area). This ensures that all gas-blood interface areas of the oxygenator receive sufficient oxygenated gas to ensure effective blood oxygenation. For example, consider an oxygenator with two gas-blood interface areas. Here, the first gas-blood interface area occupies 40% of the total volume and / or surface area of ​​the oxygenator, and the second gas-blood interface area occupies the remaining 60%. In this case, the device opens the outlet valves so that 40% of the volumetric flow of oxygenated gas is delivered to the first gas-blood interface area (via the first outlet valve and the first outlet) and 60% of the volumetric flow of oxygenated gas is delivered to the second gas-blood interface area (via the second outlet valve and the second outlet).

[0028] The plurality of outlet valves may include a first outlet valve and a second outlet valve, and the controller may be configured to operate the oxygenator in the second mode by modulating the first outlet valve between a partially open position and a fully open position and modulating the second outlet valve between a closed position and an open position.

[0029] In the second mode, the device utilizes the full capacity of the multizone oxygenator by adjusting each outlet valve to deliver a respective oxygenated gas flow rate to each gas-blood interface region of the oxygenator. The oxygenated gas flow rate to each gas-blood interface region of the oxygenator is independent of (and therefore potentially different from) the oxygenated gas flow rates to all other gas-blood interface regions of the oxygenator. This may allow for advanced ventilation techniques that prevent hyperoxia and minimize or eliminate gas microemboli, as described in more detail below.

[0030] The first and second outlets are connected to different gas-blood interface regions of the multi-region oxygenator. Specifically, the first outlet is connected to a first gas-blood interface region of the multi-region oxygenator via a first outlet valve, and the second outlet is connected to a second gas-blood interface region of the multi-region oxygenator via a second outlet valve.

[0031] The controller may configure the oxygenator to regulate the first and second outlet valves by opening the first outlet valve and fully closing the second outlet valve, and by opening the second outlet valve. When the device operates the oxygenator in a second mode, the first outlet valve is at least partially open (and may be fully open) to deliver at least a finite amount of oxygenated gas to the oxygenator, while the second outlet valve remains closed. If a clinical situation requires the delivery of more oxygenated gas to the oxygenator, the second outlet valve may be gradually opened until the required amount of oxygenated gas is delivered. The second outlet valve need not reach a fully open position.

[0032] In this embodiment, the first outlet valve is kept at least partially open to ensure that the first gas-blood interface region of the multi-region oxygenator receives enough oxygenated gas to remove carbon dioxide from the patient's blood. When the patient requires more oxygen, the second outlet valve is opened to allow oxygenated gas to enter the second gas-blood interface region of the multi-region oxygenator. The position of the second outlet valve can be adjusted (e.g., gradually opened and closed) to maintain the patient's blood oxygen saturation at a desired level. Generally, blood oxygen saturation refers to the ratio of oxygenated hemoglobin to the total hemoglobin in the patient's blood.

[0033] The controller may be configured to cause the oxygenator to regulate the second outlet valve by opening the second outlet valve and then fully closing the second outlet valve. The second outlet valve may be closed to prevent hyperoxia, thereby preventing oxygenated gas from entering the second gas-blood interface region of the multi-region oxygenator, thereby reducing oxygen uptake by the patient's blood.

[0034] The plurality of inlet valves may include a first inlet valve and a second inlet valve, and the controller may be further configured to operate the oxygenator in a second mode by adjusting the first inlet valve and the second inlet valve to control the oxygen concentration in the oxygenated gas when the second outlet valve is closed. As described above, adjusting the first inlet valve modulates the proportion of air in the oxygenated gas, and adjusting the second inlet valve modulates the proportion of oxygen in the oxygenated gas. Thus, when the second outlet valve is fully closed, adjusting the first and second inlet valves controls the oxygen concentration in the oxygenated gas supplied to the first gas-blood interface region of the multi-region oxygenator. More specifically, the oxygen concentration in the oxygenated gas supplied to the first gas-blood interface region of the multi-region oxygenator can be modulated between 21% (when the first inlet valve is open and the second inlet valve is closed) and 100% (when the first inlet valve is closed and the second inlet valve is open). This allows for precise control of the oxygen delivered to the first gas-blood interface region of the multi-region oxygenator, preventing hyperoxia.

[0035] The plurality of inlet valves may include a first inlet valve and a second inlet valve, and the controller may be further configured to operate the oxygenator in a second mode by maintaining the first inlet valve in a closed position while the second outlet valve is open and while the first and second outlet valves are open. In this configuration, the device delivers pure oxygen to both the first and second gas-blood interface regions of the multi-zone oxygenator. This configuration may be used to increase blood oxygen saturation when a patient has a high metabolic demand for oxygen.

[0036] The controller may be further configured to operate the oxygenator in a second mode by modulating the second outlet valve between closed and open positions while the first inlet valve is closed, the second inlet valve is closed, and the first outlet valve is open. The flow rate of pure oxygen delivered to the second gas-blood interface region of the multi-region oxygenator is controlled by modulating the second outlet valve while the other valves are in this configuration. This achieves precise control of oxygen uptake by the patient's blood and can prevent hyperoxia.

[0037] A first inlet of the plurality of inlets may be connected (or configured to be connected) to a supply of medical air from a hospital gas supply or a gas cylinder. More specifically, the first inlet may be connected to the supply of medical air. As known to those skilled in the art, medical air is a mixture of nitrogen and oxygen. Medical air typically contains about 79% nitrogen and about 21% oxygen. Medical air may also contain trace amounts of an inert gas (such as argon) and water vapor. Configuring the first inlet to connect to the supply of medical air may include storing a setting that designates the first inlet for connection to the supply of medical air. Thus, the controller recognizes that, in use, the first inlet is to be connected to the supply of medical air. Storing the setting may include setting values ​​of parameters in configuration data stored in the memory of the controller.

[0038] A second inlet of the plurality of inlets may be connected (or configured to be connected) to a supply of oxygen from a hospital gas supply or a gas cylinder. Configuring the second inlet to connect to the supply of oxygen may include storing a setting that designates the second inlet for connection to the supply of oxygen. Thus, the controller recognizes that, in use, the second inlet is to be connected to the supply of oxygen.

[0039] Each outlet may be connected (or configured to be connected) to a respective inlet of the multi-region oxygenator. In other words, each outlet of the mixing chamber may be connected to a different inlet of the multi-region oxygenator. This allows the device to switch between the first and second operating modes of the oxygenator without changing the connections between the hospital gas supply, the mixing chamber, and the oxygenator. Configuring each outlet to connect to a respective inlet of the multi-region oxygenator may include storing a setting that designates the first outlet for connection to a first gas-blood interface region of the oxygenator and the second outlet for connection to a second gas-blood interface region of the oxygenator. Thus, the controller recognizes, in use, that the first outlet is connected to the first gas-blood interface region and the second outlet is connected to the second gas-blood interface region.

[0040] The multiple inlets and multiple outlets may be in fluid communication with the interior volume of the mixing chamber. In this embodiment, multiple feed gases can enter the interior volume of the mixing chamber, where the feed gases mix to form an oxygenated gas of substantially uniform composition throughout the interior volume. The oxygenated gas can exit the interior volume of the mixing chamber through the multiple outlets. Because the composition of the oxygenated gas is substantially uniform throughout the interior volume of the mixing chamber, the oxygenated gas exiting each outlet has substantially the same composition.

[0041] The device may further include a pressure sensor configured to measure the pressure within the internal volume of the mixing chamber. Measurements of the pressure within the internal volume of the mixing chamber may be used to ensure effective operation and / or safety of the oxygenator, as described below.

[0042] The controller may be configured to receive a first pressure measurement from the pressure sensor. The controller may be further configured to open or close one of the inlet valves and / or one of the outlet valves to minimize the difference between the pressure measurement and the target pressure. The target pressure may be selected to be higher than the pressure at the gas outlet of the oxygenator. More specifically, the target pressure may be higher than the pressure at the gas outlet of the oxygenator sufficiently to ensure there is a pressure differential across the oxygenator, thereby ensuring that oxygenated gas flows through the oxygenator and allowing gas exchange to occur within the oxygenator.

[0043] The controller may be configured to receive a second pressure measurement from the pressure sensor. The controller may be further configured to close at least one of the inlet valves when the second pressure measurement exceeds a safety threshold. The ability to automatically close any or all of the inlet valves may be beneficial if the device closes the outlet valves via a safety mechanism when an abnormal event occurs. The abnormal event may be, for example, a malfunction of the perfusion system, a clinician error, or a clinical problem with the patient. The controller may be configured to detect the abnormal event and automatically close the outlet valve to protect patient safety. However, closing the outlet valve may increase pressure within the internal volume of the mixing chamber, which may pose a danger to people working near the mixing chamber. Therefore, the controller may be configured to close at least one of the inlet valves when the pressure inside the mixture in the internal volume of the mixing chamber exceeds a safety threshold to prevent the pressure from increasing to a dangerous level.

[0044] The device may include other types of sensors. For example, without limitation, the device may include one or more flow sensors each configured to measure the flow rate of the oxygenated gas through a corresponding outlet, a thermometer configured to measure the temperature of the oxygenated gas in the mixing chamber, an oxygen concentration sensor configured to measure the oxygen concentration in the oxygenated gas, a carbon dioxide concentration sensor configured to measure the carbon dioxide concentration in the oxygenated gas, or any combination thereof.

[0045] The controller may be configured to control the flow rate of oxygenated gas through the at least one outlet valve by adjusting the inlet valve and / or adjusting the at least one outlet valve.

[0046] The mixing chamber, multiple inlet valves, and multiple outlet valves may be integrated into the gas blender. In other words, the mixing chamber, inlet valve, and outlet valve are provided as an integrated device, referred to herein as a gas blender. This simplifies the task of connecting the mixing chamber, inlet valves, and outlet valves between the gas supply and the oxygenator. The clinician simply connects tubing between each gas blender inlet and the correct gas supply and between each gas blender outlet and the correct oxygenator inlet. The clinician does not need to make any other connections between the gas supply and the oxygenator, nor does the clinician need to change connections during the course of the cardiac perfusion procedure.

[0047] The controller may be configured to open the first outlet valve to maintain a flow of oxygenated gas through the first outlet to a first gas-blood interface area of ​​the oxygenator, while modulating the second outlet valve between a fully closed position and an open position to control a flow of oxygenated gas through the second outlet to a second gas-blood interface area of ​​the oxygenator, wherein the first gas-blood interface area of ​​the oxygenator is smaller than the second gas-blood interface area of ​​the oxygenator. The controller may be further configured, in response to determining that the flow of oxygenated gas through the first outlet exceeds a first threshold, to open the second outlet valve to maintain a flow of oxygenated gas through the second outlet to the first gas-blood interface area, while modulating the first outlet valve between a fully closed position and an open position to control a flow of oxygenated gas through the first outlet to the first gas-blood interface area.

[0048] Initially, the first (i.e., smaller) gas-blood interface area is used to remove carbon dioxide from the blood, while the second (i.e., larger) gas-blood interface area is used to regulate blood oxygen saturation. If the first gas-blood interface area is not large enough to effectively remove carbon dioxide from the patient's blood, as indicated by a high flow rate of oxygenated gas through the first outlet, the controller automatically switches to use the second (i.e., larger) gas-blood interface area to remove carbon dioxide from the blood. This ensures effective removal of carbon dioxide from the patient's blood.

[0049] The controller may be further configured, in response to determining that the flow of oxygenated gas through the second outlet is below a second threshold, to open the first outlet valve to maintain the flow of oxygenated gas through the first outlet to the first gas-blood interface region, while modulating the second outlet valve between a fully closed position and an open position to control the flow of oxygenated gas through the second outlet to the second gas-blood interface region.

[0050] The controller may store settings indicating the size of each of the first and second gas-blood interface areas. As described above, the controller may store settings that designate the first outlet for connection to the first gas-blood interface area of ​​the oxygenator and the second outlet for connection to the second gas-blood interface area of ​​the oxygenator. These settings inform the controller which outlet valve controls the flow of oxygenated gas to the larger gas-blood interface area and which outlet valve controls the flow of oxygenated gas to the smaller gas-blood interface area.

[0051] According to a further aspect of the present disclosure, a cardiac perfusion system includes an apparatus for controlling the supply of oxygenated gas to an oxygenator as described above. The cardiac perfusion system may further include an oxygenator having a plurality of gas-blood interface regions and a plurality of oxygenator gas inlets. Each oxygenator gas inlet may be configured to receive oxygenated gas and deliver the oxygenated gas to a respective one of the plurality of gas-blood interface regions. Each outlet of the mixing chamber may be connected to a respective oxygenator gas inlet.

[0052] As used herein, "cardiac perfusion" refers to a medical procedure in which blood is withdrawn from a patient, oxygenated, and returned to the patient. Cardiac perfusion encompasses extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass (CPB).

[0053] A first inlet of the mixing chamber's multiple inlets may be connected to a hospital gas supply or a supply of medical air from a gas cylinder, and a second inlet of the mixing chamber's multiple inlets may be connected to a hospital gas supply or a supply of oxygen from a gas cylinder.

[0054] According to a further aspect of the present disclosure, there is provided a method of controlling an oxygenator, the method being performed by a controller coupled to the mixing chamber, the controller opening and closing a plurality of inlet valves and a plurality of outlet valves of the mixing chamber to operate the oxygenator according to the first and / or second operating modes disclosed herein.

[0055] According to a further aspect of the present disclosure, a processor-readable medium is provided that includes processor-executable instructions that, when executed by a processor, cause a controller including the processor to perform any of the methods of controlling an oxygenator disclosed herein. The processor-readable medium may be non-transitory (e.g., a disk or memory device) or transitory (e.g., a signal).

[0056] According to a further aspect of the present disclosure, there is provided a computer program comprising processor-executable instructions that, when executed by a processor, cause a controller comprising the processor to perform any of the methods of controlling an oxygenator disclosed herein. [Brief explanation of the drawings]

[0057] Embodiments will now be described, purely by way of example, with reference to the accompanying drawings, in which like features are indicated with like reference numerals and in which:

[0058] [Figure 1] FIG. 1 is a schematic diagram of a cardiac perfusion system including a gas blender and controller according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of the gas blender and oxygenator shown in FIG. [Figure 3] FIG. 3 is a schematic diagram of the controller shown in FIGS. [Figure 4] FIG. 4 is a schematic diagram showing the oxygenator of FIG. 2 when operating in a first mode. [Figure 5] FIG. 5 is a flow chart of a method of operating the oxygenator in the first mode shown in FIG. [Figure 6] FIG. 6 is a schematic diagram illustrating the oxygenator of FIG. 2 when operating in a second mode. [Figure 7] FIG. 7 is a flow chart of a method of operating the oxygenator in the second mode shown in FIG. [Figure 8] FIG. 8 is a flow chart of a method for using different gas-blood interface regions of an oxygenator as sweep chambers. DETAILED DESCRIPTION OF THE INVENTION

[0059] 1 is a schematic diagram of an example cardiac perfusion system 100 incorporating a gas blender 160 and a controller 150 according to the present disclosure. In addition to the gas blender 160 and the controller 150, the cardiac perfusion system 100 includes one or more sensors 110, a venous reservoir 120, a pump 130, and an oxygenator 140. In use, the cardiac perfusion system 100 receives deoxygenated blood from a patient via a venous line 122 and stores the deoxygenated blood in the venous reservoir 120. The pump 130 pumps the deoxygenated blood from the venous reservoir 120, passes it through the oxygenator 140, and returns the oxygenated blood to the patient via an arterial line 132 (indicated by arrow "A").

[0060] Venous reservoir 120 receives deoxygenated blood from the patient via venous line 122. Venous reservoir 120 may additionally be configured to receive blood from the patient via one or more salvage lines, one or more purge lines, and / or one or more lines configured to carry surgical fluids (e.g., priming solution, volume expander, blood, and / or medications), as represented by line 124 in FIG. 1 . Venous reservoir 120 is positioned upstream of oxygenator 140, between the patient and oxygenator 140. It will be appreciated that in other implementations, the exact location of venous reservoir 120 and pump 130 may vary. Indeed, system 100 need not necessarily include venous reservoir 120 and pump 130. In such cases, oxygenator 140 may be configured to receive blood directly from the patient.

[0061] Pump 130 drives blood through cardiac perfusion system 100. As shown in Figure 1, pump 130 is located downstream of venous reservoir 120 and upstream of oxygenator 140. In the depicted embodiment, pump 130 is a roller (or peristaltic) pump. However, it is understood that other types of pumps, such as centrifugal pumps, may be used in some circumstances.

[0062] The oxygenator 140 receives deoxygenated blood via the blood inlet 144. The oxygenator also receives oxygenated gas from the gas blender 160 via two or more (in this case, two) oxygenator gas inlets 142a, 142b. The oxygenated gas may include air, oxygen, and / or a mixture of air and oxygen, as described in more detail below. The blood passes through the oxygenator 140, where gases dissolved in the blood are exchanged with gases received via the oxygenator gas inlets 142a, 142b. Gas exchange within the oxygenator 140 generally involves the removal of carbon dioxide from the blood and the addition of oxygen to the blood. In this embodiment, the oxygenator 140 converts deoxygenated blood into oxygenated blood. The oxygenated blood exits the oxygenator 140 via the blood outlet 148 and is returned to the patient via the arterial line 132. Waste gases exit the oxygenator 140 via the gas exhaust 146.

[0063] Gas blender 160 receives one or more supply gases and produces an oxygenated gas for delivery to oxygenator 140. Gas blender 160 includes two or more (in this case, two) inlets 162a, 162b and two or more (in this case, two) outlets 167a, 167b. In use, first inlet 162a is connected to a first source 174a of a first supply gas via tubing 170a. Similarly, in use, second inlet 162b is connected to a second source 174b of a second supply gas via tubing 170b. Either of first and second sources 174a, 174b may be a hospital gas supply or a gas cylinder that is not part of the hospital gas supply. Generally, the first supply gas is different from the second supply gas. For example, the first supply gas may be medical air and the second supply gas may be pure oxygen. Gas blender 160 may include additional inlets (not shown) for receiving additional supply gases. For example, gas blender 160 may include another inlet that, during use, is connected to a source of carbon dioxide. Alternatively or additionally, gas blender 160 may include another inlet that, during use, is connected to a source of anesthetic gas (e.g., nitrous oxide). The supply gas may additionally or alternatively include other gases common in the art (e.g., helium and / or argon). Gas blender 160 is configured to blend (i.e., mix) the supply gases received via inlets 162a, 162b to produce an oxygenated gas. Controller 150 controls gas blender 160 to adjust the composition of the oxygenated gas, as described in more detail below. Sometimes, the oxygenated gas may consist of only one of the supply gases (e.g., gas blender 160 may produce an oxygenated gas consisting solely of oxygen or medical air). Oxygenated gas may exit gas blender 160 via outlets 167a, 167b. In use, a first outlet 167a of gas blender 160 is connected to a first inlet 142a of oxygenator 140 via tubing 172a. Similarly, a second outlet 167b of gas blender 160 is connected to a second inlet 142b of oxygenator 140 via tubing 172b.Inlets 162a, 162b and outlets 167a, 167b may be ports to which tubes 170a, 170b, 172a, 172b can be connected. Gas blender 160 may include additional outlets (not shown) to allow connection to an oxygenator 140 having more than two inlets. That is, gas blender 160 may have a number of outlets 167a, 167b equal to the number of inlets 142a, 142b on oxygenator 140.

[0064] It is advantageous for the number of outlets 167a, 167b from the gas blender 160 to be equal to the number of inlets 142a, 142b to the oxygenator 140, as this allows the supply of oxygenated gas to each gas-blood interface region of the oxygenator 140 to be independent from the supply to the other gas-blood interface regions. However, in some embodiments, the number of outlets 167a, 167b from the gas blender 160 may be different from the number of inlets 142a, 142b to the oxygenator 140. In such embodiments, a "Y" connector may be used to split and / or combine gas lines. In the example herein, the number of inlets 162a, 162b to the gas blender 160 is equal to the number of outlets 167a, 167b from the gas blender 160, but it should be understood that the number of inlets 162a, 162b to the gas blender 160 may be different from the number of outlets 167a, 167b from the gas blender 160.

[0065] Controller 150 controls gas blender 160. More specifically, controller 150 controls the composition of the oxygenated gas produced by gas blender 160, controls outlets 167 a, 167 b of gas blender 160 that are used to deliver the oxygenated gas to oxygenator 140, and controls the flow rate of oxygenated gas to oxygenator 140.

[0066] Controller 150 may be a dedicated controller solely for the purpose of controlling gas blender 160. Alternatively, controller 150 may control other components of perfusion system 100. For example, controller 150 may control the pumping of blood by pump 130, the operation of oxygenator 140, and / or various valves and / or actuators not shown in Figures 1 and 2. Controller 150 may also monitor physiological parameters of the patient and / or parameters of cardiac perfusion system 100 to ensure that the cardiac perfusion procedure is performed safely and effectively.

[0067] The controller 150 is communicatively connected to the gas blender 160 and one or more sensors 110, as shown by the dashed-dotted lines in FIG. 1 . That is, the controller 150 may be configured to communicate with the gas blender 160 and one or more sensors 110. This communication may occur via a hard connection (e.g., a wired connection) or wireless communication. In this regard, it is understood that the dashed-dotted lines depicted in FIG. 1 are merely exemplary and do not necessarily represent physical connections between components. Furthermore, it is understood that the controller 150 may be communicatively connected to more or fewer components in the system 100. For example, the controller 150 need not communicate directly with one or more sensors 110, but instead may be configured to communicate with an intermediate transceiver that relays measurements from the sensors 110 to the controller 150. As used herein, “communication” with the controller 150 refers to both the receipt of data (e.g., measurements) by the controller 150 and the transmission of data (e.g., instructions or commands) by the controller 150.

[0068] One or more sensors 110 are configured to measure parameters related to the cardiac perfusion system 100 and / or parameters related to the patient. While FIG. 1 shows a single sensor 110 located on the arterial line 132, it should be understood that this is merely exemplary. The sensor 110 may be located in any or all of the following: the venous reservoir 120, the pump 130, the oxygenator 140, the gas blender 160, the blood line (e.g., the venous line 122, the arterial line 132, and / or any intermediate blood line between the venous reservoir 120 and the oxygenator 140), or the gas line (e.g., any tubing providing gas supply to or gas removal from the gas blender 160 and / or the oxygenator 140). Alternatively or additionally, the sensor 110 may be located in or on the patient. The location of the sensor 110 is selected according to the parameter to be measured. The sensor 110 may be configured to measure, for example, gas pressure, gas flow, gas composition (e.g., partial pressure of oxygen, carbon dioxide, or other gases), blood pressure, blood flow, blood composition (e.g., oxygen or carbon dioxide saturation in the blood), or blood volume (e.g., blood volume in the venous reservoir 120).

[0069] Cardiac perfusion system 100 may optionally further include other components not shown in Figure 1. For example, cardiac perfusion system 100 may include any or all of: a cardioplegia device for stopping the patient's heart; a heating and cooling device for regulating the temperature of the blood; one or more additional pumps for flowing blood from, through, and / or to the patient; and one or more valves for controlling the flow of blood.

[0070] FIG. 2 shows gas blender 160 and oxygenator 140 in detail. Gas blender 160 includes a mixing chamber 161 having an internal volume 165. Internal volume 165 of mixing chamber 161 is fluidly connected to inlets 162a, 162b and outlets 167a, 167b. Inlet valves 164a, 164b are disposed between each inlet 162a, 162b and internal volume 165 of mixing chamber 161. Opening first inlet valve 164a allows a first supply gas to enter mixing chamber 161 via first inlet 162a. Similarly, opening second inlet valve 164b allows a second supply gas to enter mixing chamber 161 via second inlet 162b. Once in internal volume 165 of mixing chamber 161, the first and second supply gases mix to produce oxygenated gas. Outlet valves 166a, 166b are disposed between the interior volume 165 of the mixing chamber 161 and each of the outlets 167a, 167b. Opening the first outlet valve 166a allows oxygenated gas to exit the interior volume 165 of the mixing chamber 161 through the first outlet 167a. Similarly, opening the second outlet valve 166b allows oxygenated gas to exit the interior volume 165 of the mixing chamber 161 through the second outlet 167b. Because the composition of the oxygenated gas is substantially uniform throughout the mixing chamber 161, the composition of the oxygenated gas exiting the mixing chamber 161 through the first outlet 167a is substantially the same as the composition of the oxygenated gas exiting the mixing chamber 161 through the second outlet 167b.

[0071] Controller 150 is configured to communicate a respective control signal to each of inlet valves 164a, 164b and each of outlet valves 166a, 166b. Each control signal is configured to open or close a respective valve 164a, 164b, 166a, 166b. Controller 150 can open or close each of inlet valves 164a, 164b and each of outlet valves 166a, 166b independently of one another. By independently controlling each valve 164a, 164b, 166a, 166b, controller 150 can perform various tasks, including switching between operating modes of multi-region oxygenator 140, controlling the composition of the oxygenated gas, and controlling the flow rate of oxygenated gas to oxygenator 140. More specifically, controller 150 can control the composition of the oxygenated gas by opening or closing each inlet valve 164a, 164b to allow the supply gas to enter mixing chamber 161 in a desired ratio. The controller can control the flow of oxygenated gas to the oxygenator 140 by opening or closing each valve 164a, 164b, 166a, 166b to produce a desired gas throughput from the inlets 162a, 162b to the outlets 167a, 167b.

[0072] The mixing chamber 161 may include a pressure sensor 163 within its interior volume 165. The pressure sensor 163 is configured to measure the pressure of the oxygenated gas within the interior volume 165 of the mixing chamber 161. The controller 150 is configured to receive the pressure measurement from the pressure sensor 163 and to control the pressure of the oxygenated gas within the mixing chamber 161 based on the pressure measurement.

[0073] For example, controller 150 may be configured to maintain the pressure in mixing chamber 161 at a target pressure that ensures that mixing chamber 161 is at a positive pressure relative to gas outlet 146 of oxygenator 140. In other words, the target pressure may be higher than the pressure at gas outlet 146 of oxygenator 140 sufficiently to ensure that there is a pressure differential across oxygenator 140, thereby ensuring that oxygenated gas flows through oxygenator 140 and gas exchange occurs within oxygenator 140. If the pressure measurement made by pressure sensor 163 is lower than the target pressure, controller 150 may increase the pressure in interior volume 165 of mixing chamber 161 by opening any or all of inlet valves 164a, 164b and / or closing any or all of outlet valves 166a, 166b. Conversely, if the pressure measurement is higher than the target pressure, the controller 150 may reduce the pressure in the internal volume 165 of the mixing chamber 161 by closing any or all of the inlet valves 164a, 164b and / or by opening any or all of the outlet valves 166a, 166b.

[0074] As another example, controller 150 may be configured to prevent the pressure in mixing chamber 161 from exceeding a safe operating pressure (referred to herein as a "safety threshold"). If the value of a pressure measurement made by pressure sensor 163 exceeds the safety threshold, controller 150 may close some or all of inlet valves 164a, 164b to prevent further pressure buildup in mixing chamber 161. Alternatively or additionally, if the value of a pressure measurement made by pressure sensor 163 exceeds the safety threshold, controller 150 may open an exhaust valve (not shown) to release oxygenated gas from mixing chamber 161 to the atmosphere or to a gas collection device, thereby reducing the pressure in mixing chamber 161.

[0075] Oxygenator 140 is a dual-zone oxygenator. That is, oxygenator 140 has a gas-blood interface 147 separated into two gas-blood interface regions 147a, 147b, each of which can be independently supplied with oxygenated gas via a respective oxygenator gas inlet 142a, 142b. Gas-blood interface 147 is the medium through which gas exchange between oxygenated gas and blood occurs. As described above, oxygenator 140 includes a blood inlet 144 for receiving blood from the patient and a blood outlet 148 for returning blood to the patient. Oxygenator 140 includes a first oxygenator gas inlet 142a and a second oxygenator gas inlet 142b. First oxygenator gas inlet 142a and second oxygenator gas inlet 142b are each fluidly connected to a gas inlet zone 143. Oxygenator 140 further includes a gas outlet 146 for releasing waste gas from oxygenator 140. Waste gases exit oxygenator 140 through gas outlet zone 180 and gas outlet 146. Gas outlet 146 may be coupled to a vacuum pump to facilitate the flow of oxygenated gas through oxygenator 140 and / or to help extract waste gases from oxygenator 140.

[0076] Gas inlet zone 143 includes a partition 149 that divides gas inlet zone 143 into multiple (in this case, two) gas inlet regions 145a, 145b. Each gas inlet region 145a, 145b is configured to receive oxygenated gas from a respective oxygenator gas inlet 142a, 142b. More specifically, first gas inlet region 145a is configured to receive oxygenated gas from first oxygenator gas inlet 142a, and second gas inlet region 145b is configured to receive oxygenated gas from second oxygenator gas inlet 142b. Furthermore, first gas inlet region 145a is configured to receive oxygenated gas from first outlet 167a of gas blender 160 via tube 172a and first oxygenator gas inlet 142a. Second gas inlet region 145b is configured to receive oxygenated gas from second outlet 167b of gas blender 160 via tube 172b and second oxygenator gas inlet 142b.

[0077] The gas inlet zone 143 is fluidly connected to the gas-blood interface 147. The gas outlet zone 180 is fluidly connected to the gas-blood interface 147. Thus, oxygenated gas enters the gas-blood interface 147 from the gas inlet zone 143 and exits the gas-blood interface 147 via the gas outlet zone 180. The gas-blood interface 147 may include one or more hollow fiber groups, and each hollow fiber group may include multiple hollow fibers. Each hollow fiber group may include an inlet potting in fluid communication with the gas inlet zone 143. Each hollow fiber group may include an outlet potting in fluid communication with the gas outlet zone 180.

[0078] Gas-blood interface 140 is configured to allow oxygenated gas to be supplied to expose the blood to oxygen. For example, oxygenated gas may enter the hollow fiber group from gas inlet zone 143 through the inlet potting. Blood enters oxygenator 140 through blood inlet 144. As the blood and oxygenated gas pass through gas-blood interface 147 as they pass through oxygenator 140, gas-blood interface 147 is configured to allow gas exchange between the blood and the oxygenated gas. This includes the transfer of gases (e.g., oxygen, carbon dioxide, nitrogen) from the blood into the oxygenated gas, as well as the transfer of gases (e.g., oxygen, carbon dioxide) from the oxygenated gas into the blood. After gas exchange, the blood (now oxygenated) exits oxygenator 140 toward the patient through blood outlet 148, and the oxygenated gas (now waste gas) exits oxygenator 140 through gas outlet 146.

[0079] As previously described, the partition 149 divides the gas inlet zone 143 into a first gas inlet region 145a and a second gas inlet region 145b. This divides the gas-blood interface 147 into two gas-blood interface regions 147a, 147b, allowing each region to be independently supplied with oxygenated gas via its respective gas inlet region 145a, 145b. This allows different volumetric flow rates of oxygenated gas to be supplied to each region 147a, 147b of the gas-blood interface 147.

[0080] 2 penetrates gas inlet zone 143 but does not penetrate gas-blood interface 147. In this case, partition 149 may abut the inlet potting of the hollow fiber group to prevent gas flow between gas-blood interface regions 147a, 147b. Alternatively, if some gas leakage is allowed between gas inlet regions 145a, 145b, partition 149 need not abut the inlet potting. In other examples, partition 149 may penetrate gas inlet zone 143 and at least partially penetrate gas-blood interface 147, physically separating gas-blood interface 147 into gas-blood interface regions 147a, 147b.

[0081] 2, partition 149 divides gas inlet zone 143 into equal-sized first and second gas inlet regions 145a and 145b. That is, partition 149 divides gas inlet zone 143 (and thus gas-blood interface 147) in half, with first gas inlet region 145a and second gas inlet region 145b each constituting 50% of gas inlet zone 143. Partition 149 therefore functions to divide gas-blood interface 147 in half, with first gas-blood interface region 147a and second gas-blood interface region 147b each constituting 50% of gas-blood interface 147. However, it will be understood that this division is merely an example, and partition 149 (and / or multiple partitions) may be positioned in various locations to create different divisions of gas inlet zone 143 and gas-blood interface 147. For example, partition 149 may be positioned such that first gas inlet area 145a constitutes 40% of gas inlet zone 143 and second gas inlet area 145b constitutes 60% of gas inlet zone 143. That is, gas-blood interface 147 may be divided such that first gas-blood interface area 147a constitutes 40% of gas-blood interface 147 and second gas-blood interface area 147b constitutes 60% of gas-blood interface 147.

[0082] Figure 3 is a schematic diagram of the controller 150 shown in Figures 1 and 2. The controller includes a processor 202, a memory 204, an input / output (I / O) interface 208, and a user interface 210.

[0083] The processor 202 may be any suitable type of data processing device, such as a microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC). The processor 202 is communicatively coupled to a memory 204. The memory 204 may include volatile memory, non-volatile memory, or both volatile and non-volatile memory. The memory 204 stores a control program 206. The control program 206 includes processor-executable instructions that, when executed by the processor 202, cause the controller 150 to perform any of the methods described below with reference to FIGS. 5, 7, and 8.

[0084] I / O interface 208 receives data from one or more sensors 110 and outputs control signals. More specifically, I / O interface 208 communicates control signals to gas blender 160, which cause gas blender 160 to operate in the manner disclosed herein. In embodiments in which controller 150 controls other components of perfusion system 100 in addition to gas blender 160, I / O interface 208 may also communicate control signals to pump 130, oxygenator 140, and / or other valves and / or actuators not shown in FIGS. 1 and 2 . I / O interface 208 may be configured to receive analog and / or digital data from one or more sensors 110. Similarly, I / O interface 208 may be configured to send analog and / or digital control signals to gas blender 160 and / or other components of perfusion system 100.

[0085] The user interface 210 includes a display 212, a keyboard 214, and optionally, a speaker 216. The display 212 is configured to output a visual representation of information related to the cardiac perfusion procedure, such as a visual alarm signal and / or a visual representation of particular data collected by the control program 206. The display 212 may be any suitable type of output device. For example, the display 212 may be a liquid crystal display (LCD) screen or an organic light emitting diode (OLED) screen. The keyboard 214 includes a plurality of buttons that a user can use to input information for use by the control program 206. For example, a clinician (e.g., a perfusionist) can use keyboard 214 to select a particular operating mode of oxygenator 140, a target blood oxygen saturation to be achieved by oxygenator 140, a target blood carbon dioxide pressure to be achieved by oxygenator 140, the composition of the oxygenated gas to be produced by gas blender 160 (e.g., by setting the desired ratio of oxygen, nitrogen, and / or carbon dioxide in the oxygenated gas), and / or the flow rate of the oxygenated gas through any or all of outlets 167a, 167b of gas blender 160. Display 212 and keyboard 214 may be integrated with each other in the form of a touchscreen. Speaker 216 can output audio information, such as audible alarm signals and / or audio display of certain data collected by the monitoring program.

[0086] The operation of the gas blender 160 is described with reference to Figures 4 through 8. The gas blender 160 described herein allows a multiregion oxygenator 140 (such as the dual-chamber oxygenator described above) to automatically switch between different operating modes without a clinician having to change the connections between the oxygenator and a supply gas source (e.g., a hospital gas supply).

[0087] A first operating mode of the oxygenator 140 is shown in FIG. 4. In this first operating mode, the gas blender 160 causes the multi-zone oxygenator 140 to operate as if it were a conventional single-zone oxygenator. That is, the gas blender 160 delivers oxygenated gas to all gas-blood interface regions 147a, 147b simultaneously. The hatched lines in FIG. 4 indicate that oxygenated gas is delivered to both the first gas-blood interface region 147a and the second gas-blood interface region 147b. Because the oxygenated gas is mixed in the mixing chamber 161 before delivery to the oxygenator 140, all gas-blood interface regions 147a, 147b receive oxygenated gas of substantially the same composition.

[0088] A method 500 for operating an oxygenator in a first mode is shown in Figure 5. Method 500 may begin with operation 502, in which controller 150 opens all outlet valves 166a, 166b of gas blender 160. Opening all outlet valves 166a, 166b allows oxygenated gas to flow from gas blender 160 to all gas-blood interface regions 147a, 147b of oxygenator 140.

[0089] Optionally, operation 502 may include controller 150 opening outlet valves 166a, 166b to divide the volumetric flow of oxygenated gas through each outlet 167a, 167b according to a predetermined ratio. For example, consider an oxygenator 140 in which a first gas-blood interface area 147a constitutes 40% of the gas-blood interface 147 and a second gas-blood interface area 147b constitutes 60% of the gas-blood interface 147. Controller 150 may open first outlet valve 166a less than second outlet valve 166b so that 40% of the volumetric flow of oxygenated gas exiting gas blender 160 enters first gas-blood interface area 147a through first outlet 167a, while 60% of the volumetric flow of oxygenated gas exiting gas blender 160 enters second gas-blood interface area 147b through second outlet 167b. In this embodiment, each gas-blood interface region 147a, 147b receives an amount of oxygenated gas commensurate with its size (e.g., volume or surface area), thereby improving the ability of the multi-region oxygenator 140 to operate as if it were a traditional single-region oxygenator. Dividing the flow of oxygenated gas through the outlets 167a, 167b according to the size of the gas-blood interface regions 147a, 147b also helps control the rate at which carbon dioxide is removed from the patient's blood. As another example, if the first and second gas-blood interface regions 147a, 147b are the same size, the controller 150 may open each outlet valve 166a, 166b equally to divide the volumetric flow of oxygenated gas equally among all of the gas-blood interface regions 147a, 147b. It should be understood that these are merely examples of how the controller 150 may divide the flow of oxygenated gas between the gas-blood interface regions 147a, 147b, and that the controller 150 may divide the volumetric flow rate of oxygenated gas through each outlet 167a, 167b according to other predetermined ratios to achieve a particular clinical outcome.

[0090] To appropriately divide the volumetric flow rates, controller 150 may access a stored mapping (e.g., a look-up table) of the positions of each outlet valve 166a, 166b that causes the volumetric flow rate of oxygenated gas through each outlet 167a, 167b to follow a predetermined ratio. Alternatively, controller 150 may receive measurements of the volumetric flow rate of oxygenated gas through each outlet 167a, 167b from one or more gas flow sensors and implement a feedback loop to ensure that the volumetric flow rate through each outlet 167a, 167b follows the predetermined ratio. The gas flow sensors may be located in any suitable location, such as in or adjacent to outlet valves 166a, 166b, in or adjacent to outlets 167a, 167b of gas blender 160, in line with tubing 172a, 172b, and / or in or adjacent to inlets 142a, 142b of oxygenator 140.

[0091] In operation 504, the controller 150 adjusts the inlet valves 164a, 164b of the gas blender 160 to control the oxygen concentration in the oxygenated gas. The oxygen concentration in the oxygenated gas is sometimes known in the art as the "fraction of inspired oxygen" (abbreviated as FiO2). For example, if the first inlet 162a of the gas blender 160 is connected to a source of medical-grade air and the second inlet 162b of the gas blender 160 is connected to a source of pure oxygen, the controller 150 may increase the oxygen concentration in the oxygenated gas by closing the first inlet valve 164a and / or opening the second inlet valve 164b. Conversely, the controller 150 may decrease the oxygen concentration in the oxygenated gas by opening the first inlet valve 164a and / or closing the second inlet valve 164b.

[0092] As part of operations 502 and 504, controller 150 may adjust any or all of inlet valves 164a, 164b and outlet valves 166a, 166b to control the total volumetric flow rate of oxygenated gas delivered from gas blender 160 to oxygenator 140. For example, controller 150 may increase the total volumetric flow rate of oxygenated gas delivered from gas blender 160 to oxygenator 140 by opening any or all of inlet valves 164a, 164b and outlet valves 166a, 166b. Conversely, controller 150 may decrease the total volumetric flow rate of oxygenated gas delivered from gas blender 160 to oxygenator 140 by closing any or all of inlet valves 164a, 164b and outlet valves 166a, 166b.

[0093] It should be noted that operation 502 does not have to occur before operation 504. Substantially the same result can be achieved by performing operation 504 before operation 502, or by performing operations 502 and 504 simultaneously.

[0094] A second operating mode of the oxygenator 140 is shown in FIG. 6. In the second operating mode, the gas blender 160 utilizes the full functionality of the multizone oxygenator 140. That is, the gas blender 160 selects whether to deliver oxygenated gas to only a subset of the gas-blood interface regions 147a, 147b (e.g., only the first gas-blood interface region 147a), or to simultaneously deliver oxygenated gas to all gas-blood interface regions 147a, 147b. The second operating mode allows for precise control of gas exchange within the oxygenator 140, which in turn can be used to achieve precise control of oxygen, carbon dioxide, and / or nitrogen saturations in the patient's blood.

[0095] As shown in Figure 6, the oxygenator 140 may have any of several "states" when operating in the second mode. In particular, Figure 6 illustrates a series of states that may occur during treatment of a patient experiencing a low metabolic rate, inadequate carbon dioxide removal, or low oxygen saturation (e.g., cyanosis).

[0096] Figure 6 is divided into a series of four states (a) through (d), which are described sequentially below. The transitions between states are indicated by arrows 661, 663, 665, and 667. In each state, oxygenator 140 is depicted. The following description begins with state (a), but because the process is cyclical, any state can be considered a "start."

[0097] In state (a), oxygenated gas is supplied to the first gas-blood interface region 147a of the oxygenator 140 by the gas blender 160. This is indicated by the hatched lines in the first gas-blood interface region 147a. No oxygenated gas is supplied to the second gas-blood interface region 147b. This is indicated by the absence of hatched lines from the second gas-blood interface region 147b. As shown in FIG. 6, oxygenated gas is supplied at 100% FiO2. That is, in state (a), the oxygenated gas consists solely of oxygen. The oxygenator 140 may be operated in this state to supply oxygen to the patient's blood and remove carbon dioxide from the patient's blood. However, given that the first gas-blood interface region 147a occupies only a percentage (e.g., 40%) of the total gas-blood interface, the supply of oxygen gas may not be sufficient to bring the patient's blood oxygen saturation to a desired value (referred to herein as a "target value"). The target blood oxygen saturation may be selected by a clinician based on the patient's clinical needs. Sensor 110 may measure blood oxygen saturation and provide the measurement to controller 150. Controller 150 may compare the measured blood oxygen saturation to a target value, and if the measured blood oxygen saturation is lower than the target value, controller 150 and gas blender 160 may transition oxygenator 140 to state (b), as indicated by arrow 661.

[0098] In state (b), the first gas-blood interface region 147a continues to receive a supply of oxygenated gas at 100% FiO2. However, the second gas-blood interface region 147b now begins to receive a supply of oxygenated gas, as indicated by the hatched lines in the second gas-blood interface region 147b. That is, the flow rate of oxygenated gas to the second gas-blood interface region 147b may be increased from zero. The flow rate of oxygenated gas to the second gas-blood interface region 147b may continue to increase until a target value is reached (e.g., until the sensor 110 measures a blood oxygen saturation level equal to the target value). Supplying oxygenated gas to the second gas-blood interface region 147b increases the amount of oxygen the blood is exposed to beyond the amount possible by supplying only the first gas-blood interface region 147a. Therefore, by supplying both interface regions 147a, 147b, higher oxygen saturation levels can be achieved. Both gas-blood interface regions 147a, 147b receive oxygenated gas of substantially the same composition because the oxygenated gas is mixed in mixing chamber 161 before being delivered to oxygenator 140. The oxygenator may operate in state (b) to increase the oxygen saturation in the patient's blood to a healthy level (e.g., 98.5%). However, the patient's metabolic rate may decrease during a surgical procedure. This, in turn, means that the blood needs to be exposed to a lower amount of oxygen in oxygenator 140 to achieve the same oxygen saturation in the patient's blood. This decrease in metabolic rate may be detected in the form of an increase in oxygen saturation in the patient's blood caused by the continued supply of oxygenated gas at the same oxygen concentration and flow rate despite the decreased metabolic rate. This may be detected, for example, by sensor 110. In such a case, controller 150 and gas blender 160 may transition oxygenator 140 to state (c), as indicated by arrow 663.

[0099] In state (c), the flow rate of oxygenated gas to the second gas-blood interface region 147b is reduced. Thus, the amount of oxygen the blood is exposed to is reduced, causing the patient's blood oxygen saturation to decrease. The measured blood oxygen saturation may be reduced to the target value with a low, but non-zero, flow rate of oxygenated gas to the second gas-blood interface region 147b. Alternatively, it may be necessary to reduce the flow rate of oxygenated gas to the second gas-blood interface region 147b to zero (ensuring no oxygenated gas is present in the second gas-blood interface region 147b) before the target blood oxygen saturation is achieved. In some cases, this reduction to zero may not be sufficient to achieve the target value. Therefore, to continue reducing the amount of oxygen the blood is exposed to (e.g., in response to the flow rate of the second gas-blood interface region 147b being reduced to zero), the controller 150 and gas blender 160 may transition the oxygenator 140 to state (d), as indicated by arrow 665.

[0100] In state (d), there is no supply of oxygenated gas to the second gas-blood interface region 147b, as indicated by the absence of hatching from the second gas-blood interface region 147b. To further reduce the amount of oxygen to which the blood is exposed, the oxygen concentration and / or flow rate of the oxygenated gas delivered to the first gas-blood interface region 147a may be reduced. This further reduces the amount of oxygen in the oxygenator 140, thereby allowing the patient's blood oxygen saturation to further decrease until the measured value reaches a target value. Advantageously, this allows the controller 150 to effectively manage blood oxygen saturation in patients experiencing a low metabolic rate (e.g., a patient whose body temperature has been intentionally lowered during a cardiac perfusion procedure). As the patient returns to a high (e.g., normal) metabolic rate, the FiO2 and / or flow rate of the oxygenated gas delivered to the first gas-blood interface region 147a can be increased again to increase the amount of oxygen present in the oxygenator 140. The FiO2 may continue to increase until it reaches 100%. Controller 150 and gas blender 160 therefore return oxygenator 140 to state (a), as indicated by arrow 667.

[0101] When controller 150 and gas blender 160 operate oxygenator 140 according to the second mode, as described above, each of gas-blood interface regions 147a, 147b has a different primary purpose. The primary purpose of first gas-blood interface region 147a is to remove (or "sweep") carbon dioxide from the blood, and therefore first gas-blood interface region 147a is described as a "sweep chamber." The oxygenated gas supplied to first gas-blood interface region 147a is described as a "sweep gas." The primary purpose of second gas-blood interface region 147b is to control blood oxygen saturation, and therefore second gas-blood interface region 147b is described as an "oxygen regulation chamber." The different primary purposes of the gas-blood interface regions 147a, 147b are achieved not by fundamental differences in the structure of the gas-blood interface regions 147a, 147b themselves, but by the manner in which the gas blender 160 delivers oxygenated gas to the gas-blood interface regions 147a, 147b. It should be understood that, even though this is not the primary purpose of the regions, the first gas-blood interface region 147a may contribute to controlling blood oxygen saturation, and the second gas-blood interface region 147b may contribute to removing carbon dioxide from the blood. That is, the first and second gas-blood interface regions 147a, 147b control both blood oxygen saturation and the partial pressure of carbon dioxide in the blood. Adjusting the total gas flow and gas composition (FiO2) between these gas-blood interface regions affects the partial pressure of carbon dioxide in the blood and blood oxygen saturation, and the controller 150 manages both oxygen saturation and carbon dioxide pressure by automatically adjusting the gas flow between the different gas-blood interface regions 147a, 147b.

[0102] Figure 6 illustrates a specific example of the operation of the oxygenator 140 in a patient who initially has a normal metabolic rate and then has a low metabolic rate. In practice, the patient's metabolic rate may increase or decrease during a surgical procedure, so the oxygenator 140 may move freely between all of the states in Figure 6. That is, the sequence of states is not simply limited to the sequence illustrated, but instead may increase and / or decrease the oxygen concentration and / or flow rate of oxygenated gas to the first and / or second gas-blood interface regions 147a, 147b as needed to achieve target blood oxygen saturation values.

[0103] A method 700 for operating the oxygenator 140 in a second mode is shown in Figure 7. Method 700 may begin with operation 702, in which the controller 150 opens the first outlet valve 166a of the gas blender 160 and fully closes the second outlet valve 166b of the gas blender 160. Opening the first outlet valve 166a allows oxygenated gas to flow from the gas blender 160 to the first gas-blood interface region 147a of the oxygenator 140. Fully closing the second outlet valve 166b prevents oxygenated gas from flowing from the gas blender 160 to the second gas-blood interface region 147b of the oxygenator 140.

[0104] In operation 704, the controller 150 fully closes the first inlet valve 164a of the gas blender 160 and opens the second inlet valve 164b of the gas blender 160. If the first inlet 162a of the gas blender 160 is connected to a source of medical air and the second inlet 162b of the gas blender 160 is connected to a source of pure oxygen, then fully closing the first inlet valve 164a and opening the second inlet valve 164b ensures that the oxygenated gas consists solely of oxygen.

[0105] During the performance of operations 702 and 704, oxygenator 140 is in state (a) shown in Figure 6. It should be noted that operation 702 does not have to occur before operation 704. Substantially the same result can be achieved by performing operation 704 before operation 702, or by performing operations 702 and 704 simultaneously. After performing operations 702 and 704, method 700 may proceed to operation 706, or to operations 710 and 712.

[0106] In operation 706, controller 150 opens second outlet valve 166b of gas blender 160. Opening second outlet valve 166b allows oxygenated gas to flow from gas blender 160 into second gas-blood interface region 147b of oxygenator 140. During operation 706, controller 150 leaves first outlet valve 166a open, allowing oxygenated gas to continue flowing into first gas-blood interface region 147a of oxygenator 140. Controller 150 also keeps first inlet valve 164a fully closed and leaves second inlet valve 164b open, allowing the oxygenated gas to consist solely of oxygen. During operation 706, oxygenator 140 is in state (b) shown in FIG. 6 . After performing operation 706, method 700 may proceed to operation 702, operation 708, or operations 710 and 712.

[0107] In operation 708, controller 150 closes second outlet valve 166b of gas blender 160. Closing second outlet valve 166b reduces the flow of oxygenated gas from gas blender 160 to second gas-blood interface region 147b of oxygenator 140. During operation 708, controller 150 leaves first outlet valve 166a open, allowing oxygenated gas to continue flowing into first gas-blood interface region 147a of oxygenator 140. Controller 150 also keeps first inlet valve 164a fully closed and second inlet valve 164b open, allowing the oxygenated gas to consist solely of oxygen. During operation 708, oxygenator 140 is in state (c) shown in FIG. 6 . After performing operation 708, method 700 may proceed to operation 702, operation 706, or operations 710 and 712. In particular, method 700 may alternate between operations 706 and 708, in which second outlet valve 166b is opened or closed to regulate the amount of oxygen entering second gas-blood interface region 147b, thereby maintaining the patient's blood oxygen saturation at a desired level.

[0108] In operation 710, controller 150 fully closes second outlet valve 166b of gas blender 160. Fully closing second outlet valve 166b prevents oxygenated gas from flowing from gas blender 160 to second gas-blood interface region 147b of oxygenator 140. During operation 710, controller 150 leaves first outlet valve 166a open, allowing oxygenated gas to continue flowing into first gas-blood interface region 147a of oxygenator 140.

[0109] In operation 712, the controller 150 adjusts the inlet valves 164a, 164b of the gas blender 160 to control the oxygen concentration in the oxygenated gas. For example, if the first inlet 162a of the gas blender 160 is connected to a source of medical-grade air and the second inlet 162b of the gas blender 160 is connected to a source of pure oxygen, the controller 150 may increase the oxygen concentration in the oxygenated gas by closing the first inlet valve 164a and / or opening the second inlet valve 164b. Conversely, the controller 150 may decrease the oxygen concentration in the oxygenated gas by opening the first inlet valve 164a and / or closing the second inlet valve 164b. Thus, in operation 712, the controller 150 opens and closes the inlet valves 164a, 164b to regulate the amount of oxygen entering the first gas-blood interface region 147a, thereby maintaining the patient's blood oxygen saturation at a desired level.

[0110] During the performance of operations 710 and 712, oxygenator 140 is in state (d) shown in Figure 6. It should be noted that operation 710 does not have to occur before operation 712. Substantially the same result can be achieved by performing operation 712 before operation 710, or by performing operations 710 and 712 simultaneously. After performing operations 710 and 712, method 700 typically proceeds to operation 704.

[0111] During operations 702 through 712, the controller 150 may adjust either the inlet valves 164a, 164b or the outlet valves 166a, 166b to control the total volumetric flow rate of oxygenated gas delivered from the gas blender 160 to the oxygenator 140, depending on the particular condition of the oxygenator 140.

[0112] As previously mentioned, depending on the particular clinical scenario, any of states (a) through (d) in Figure 6 can be treated as a starting state. Thus, method 700 may begin with any of operations 702 through 712, depending on the current state of gas blender 160 and the patient's clinical requirements.

[0113] The combination of controller 150 and gas blender 160 allows a clinician (e.g., a perfusionist) to easily and quickly switch between the various operating modes supported by the multiregion oxygenator. For example, the clinician can select a particular operating mode via user interface 210 (see FIG. 3 ) without manually changing the connections between supply gas sources 174 a, 174 b, gas blender 160, and oxygenator 140.

[0114] Additionally, the controller 150 can automatically transition between various states of the second operating mode, as shown in FIG. 6, without the need for manual intervention by a clinician. For example, the controller 150 may automatically adjust the inlet valves 164a, 164b and the outlet valves 166a, 166b based on a measured physiological parameter indicative of the oxygenation of the patient's blood. The controller 150 may automatically adjust the inlet valves 164a, 164b and the outlet valves 166a, 166b to minimize the difference between the measured physiological parameter and a target value for the physiological parameter. The physiological parameter may be arterial oxygen saturation (abbreviated as "SaO2"), which is defined as the oxygen saturation in the arterial blood measured directly from the patient's arterial blood. The arterial oxygen saturation may be measured by a sensor 110 located downstream of the oxygenator 140 (i.e., the blood passes through the sensor 110 after passing through the oxygenator 140). Alternatively, the physiological parameter may be peripheral oxygen saturation (abbreviated as "SpO2"). Arterial oxygen saturation may be measured by a pulse oximetry sensor placed on the patient. Alternatively or additionally, the physiological parameter may be carbon dioxide partial pressure (abbreviated as "PaCO2"). Carbon dioxide partial pressure may be measured by a sensor 110 placed downstream of the oxygenator 140. Accordingly, the controller 150 may automatically adjust the inlet valves 164a, 164b and the outlet valves 166a, 166b to maintain the patient's blood oxygen and / or carbon dioxide levels at target values.

[0115] FIG. 8 is a flowchart of a method 800 by which the controller 150 can automatically switch between different gas-blood interface areas 147a, 147b of the oxygenator 140 for use as sweep chambers. As previously described, each gas-blood interface area 147a, 147b can have a different size (e.g., volume or surface area). For example, the first gas-blood interface area 147a may constitute 40% of the gas-blood interface 147, and the second gas-blood interface area 147b may constitute 60% of the gas-blood interface 147. Typically, the smaller gas-blood interface area 147a functions as the sweep chamber (i.e., the gas-blood interface area whose primary purpose is to remove carbon dioxide from the blood), and the larger gas-blood interface area 147b functions as the oxygen regulation chamber (i.e., the gas-blood interface area whose primary purpose is to control oxygen saturation in the blood). However, sometimes the smaller gas-blood interface area 147a may not be large enough to effectively remove carbon dioxide from the patient's blood. For example, the smaller gas-blood interface area 147a may not have enough surface area to remove a sufficient amount of carbon dioxide produced by a larger patient. To ensure the effectiveness of the cardiac perfusion process performed on such a patient, the controller 150 can automatically switch to using the larger gas-blood interface area 147b as a sweep chamber by performing a method 800 shown in FIG.

[0116] Method 800 begins with operation 802, in which controller 150 configures gas blender 160 to use the smaller gas-blood interface area (i.e., first gas-blood interface area 147a) as a sweep chamber. More specifically, controller 150 leaves first outlet valve 166a of gas blender 160 open to ensure oxygenated gas flows through first gas-blood interface area 147a to remove carbon dioxide from the blood. Controller 150 adjusts (e.g., opens, closes, and / or fully closes) second outlet valve 166b to control the supply of oxygenated gas to second gas-blood interface area 147b, thereby regulating the patient's blood oxygen saturation. Operation 802 may include executing method 700 of FIG. 7 to transition oxygenator 140 between the various states shown in FIG. 6.

[0117] During operation 802, the controller 150 monitors the gas flow rate to the sweep chamber. For example, the controller 150 may receive a volumetric flow rate measurement made by a sensor located between the mixing chamber 161 and the first outlet 167a of the gas blender 160.

[0118] In operation 804, the controller 150 compares the measured gas flow rate to a first threshold value. The first threshold value is a predetermined value that indicates an "excessive" oxygenated gas flow rate to the sweep chamber. If the measured gas flow rate is equal to or less than the first threshold value, the controller 150 continues to use the smaller gas-blood interface area as the sweep chamber, and the method returns to operation 802. Alternatively, if the measured gas flow rate is greater than the first threshold value, a larger gas-blood interface area should be used as the sweep chamber to ensure sufficient carbon dioxide removal, and the method then proceeds to operation 806.

[0119] In operation 806, the controller 150 configures the gas blender 160 to use the larger gas-blood interface area (i.e., the second gas-blood interface area 147b) as a sweep chamber. To do this, the controller 150 effectively switches the roles of the first and second outlet valves 166a, 166b, so that the first outlet valve 166a functions as if it were the second outlet valve 166b when performing method 700 of FIG. 7, and the second outlet valve 166b functions as if it were the first outlet valve 166a when performing method 700. More specifically, the controller 150 leaves the second outlet valve 166b of the gas blender 160 open to ensure that oxygenated gas flows through the second gas-blood interface area 147b to remove carbon dioxide from the blood. The controller 150 adjusts (e.g., opens, closes, and / or fully closes) the first outlet valve 166a to control the supply of oxygenated gas to the first gas-blood interface area 147a, thereby regulating the patient's blood oxygen saturation. Operation 804 may transition the oxygenator 140 between the various states shown in FIG. 6, but rather than performing the method 700 exactly as shown in FIG. 7, the roles of the first and second outlet valves 166a, 166b are switched. In this embodiment, using the larger gas-blood interface area as a sweep chamber increases the rate at which carbon dioxide is removed from the patient's blood.

[0120] During operation 806, the controller 150 monitors the gas flow rate to the sweep chamber. For example, the controller 150 may receive a volumetric flow rate measurement made by a sensor located between the mixing chamber 161 and the second outlet 167b of the gas blender 160.

[0121] In operation 808, the controller 150 compares the measured gas flow rate to a second threshold value. The second threshold value is a predetermined value that indicates a "low" oxygenated gas flow rate to the sweep chamber. If the measured gas flow rate is less than the second threshold value, the controller 150 reverts to using the small gas-blood interface area as the sweep chamber, and the method returns to operation 802. Alternatively, if the measured gas flow rate is equal to or greater than the second threshold value, the controller 150 continues to use the large gas-blood interface area as the sweep chamber, and the method then returns to operation 806.

[0122] By performing the method 800 shown in FIG. 8, the controller 150 can automatically switch between using different gas-blood interface regions 147a, 147b of the oxygenator 140 as sweep chambers without the need for a clinician to manually change connections between the supply gas sources 174a, 174b, the gas blender 160, and the oxygenator 140.

[0123] It will be understood that the invention has been described above purely by way of example and that modifications in detail are possible within the scope of the claims. In particular, the order of operations shown in Figures 5, 7, and 8 is merely exemplary. Any of the operations shown in methods 500, 700, and 800 may be performed in a different order that achieves substantially the same result.

Claims

1. 1. An apparatus for controlling the supply of oxygenated gas to an artificial lung, comprising: a mixing chamber having an internal volume, a plurality of inlets, and a plurality of outlets, each inlet configured to receive a different supply gas and each outlet configured to convey oxygenated gas from the internal volume to the oxygenator; a plurality of inlet valves, each inlet valve disposed between a corresponding inlet and the interior volume of the mixing chamber; a plurality of outlet valves, each outlet valve disposed between the interior volume of the mixing chamber and a corresponding outlet; a controller configured to open and close each of the inlet valves and each of the outlet valves independently of one another; 1. An apparatus comprising:

2. 2. The apparatus of claim 1, wherein the plurality of inlet valves includes a first inlet valve and a second inlet valve, and the controller is configured to adjust the first inlet valve and the second inlet valve to control the oxygen concentration in the oxygenated gas.

3. 3. The apparatus of claim 1 or 2, wherein the controller is further configured to operate the oxygenator in a first mode by opening all of the outlet valves.

4. 4. The apparatus of claim 3, wherein opening all of the outlet valves comprises opening each outlet valve to a corresponding position, each position selected to divide the volumetric flow rate of the oxygenated gas through the multiple outlets according to a predetermined ratio.

5. 5. The apparatus of claim 4, wherein the predetermined ratio is selected to be substantially equal to the ratio between the sizes of the respective gas-blood interface areas of the oxygenators.

6. 6. The apparatus of claim 1, wherein the plurality of outlet valves includes a first outlet valve and a second outlet valve, and the controller is configured to operate the oxygenator in a second mode by modulating the first outlet valve between a partially open position and a fully open position and modulating the second outlet valve between a closed position and an open position.

7. The controller opening the first outlet valve and fully closing the second outlet valve; fully closing the second outlet valve and then opening the second outlet valve; 7. The apparatus of claim 6, wherein the oxygenator is configured to adjust the first and second outlet valves by

8. 8. The apparatus of claim 7, wherein the controller is configured to cause the oxygenator to regulate the second outlet valve by opening the second outlet valve and then fully closing the second outlet valve.

9. 9. The apparatus of claim 6, wherein the plurality of inlet valves includes a first inlet valve and a second inlet valve, and the controller is further configured to operate the oxygenator in the second mode by adjusting the first inlet valve and the second inlet valve to control the oxygen concentration in the oxygenated gas when the second outlet valve is closed.

10. 10. The apparatus of any one of claims 6 to 9, wherein the plurality of inlet valves includes a first inlet valve and a second inlet valve, and the controller is further configured to operate the oxygenator in the second mode by maintaining the first inlet valve in a closed position while the second outlet valve is open and while the first and second outlet valves are open.

11. 11. The apparatus of claim 10, wherein the controller is further configured to operate the oxygenator in the second mode by modulating the second outlet valve between a closed position and an open position while the first inlet valve is closed, while the second inlet valve is closed, and while the first outlet valve is open.

12. 12. The apparatus of claim 1, wherein a first inlet of the plurality of inlets is configured to be connected to a hospital gas supply or a supply of medical air from a gas cylinder.

13. 13. The apparatus of any one of claims 1 to 12, wherein a second inlet of the plurality of inlets is configured to be connected to a hospital gas supply or a supply of oxygen from a gas cylinder.

14. 14. The device of any one of claims 1 to 13, wherein each outlet is configured to be connected to a respective inlet of a multiregion oxygenator.

15. 15. The apparatus of claim 1, wherein the plurality of inlets and the plurality of outlets are in fluid communication with the interior volume of the mixing chamber.

16. 16. The apparatus of claim 1, further comprising a pressure sensor configured to measure a pressure within the internal volume of the mixing chamber.

17. The controller receiving a first pressure measurement from the pressure sensor; opening and closing any of the inlet valves and / or any of the outlet valves to minimize the difference between the pressure measurements and a target pressure; 17. The apparatus of claim 16, configured to:

18. The controller receiving a second pressure measurement from the pressure sensor; closing at least one of the inlet valves when the second pressure measurement exceeds a safety threshold; 18. The apparatus of claim 16 or 17, configured to:

19. 19. The apparatus of any one of claims 1 to 18, wherein the controller is further configured to control the flow rate of the oxygenated gas through at least one of the outlet valves by adjusting an inlet valve and / or adjusting the at least one outlet valve.

20. 20. The apparatus of claim 1, wherein the mixing chamber, the plurality of inlet valves, and the plurality of outlet valves are integrated into a gas blender.

21. The controller further comprises: opening the first outlet valve to maintain a flow of oxygenated gas through a first outlet to a first gas-blood interface area of ​​the oxygenator, while modulating the second outlet valve between a fully closed position and an open position to control a flow of oxygenated gas through a second outlet to a second gas-blood interface area of ​​the oxygenator, wherein the first gas-blood interface area of ​​the oxygenator is smaller than the second gas-blood interface area of ​​the oxygenator; in response to determining that the flow of oxygenated gas through the first outlet exceeds a first threshold, opening the second outlet valve to maintain the flow of oxygenated gas through the second outlet to the first gas-blood interface area, while modulating the first outlet valve between a fully closed position and an open position to control the flow of oxygenated gas through the first outlet to the first gas-blood interface area; 21. The apparatus of claim 1, configured to:

22. The controller further comprises:

22. The apparatus of claim 21, configured to, in response to determining that the flow of oxygenated gas through the second outlet is below a second threshold, open the first outlet valve to maintain the flow of oxygenated gas through the first outlet to the first gas-blood interface region, while modulating the second outlet valve between the fully closed position and the open position to control the flow of oxygenated gas through the second outlet to the second gas-blood interface region.

23. 1. A cardiac perfusion system comprising: An apparatus according to any one of claims 1 to 22; an oxygenator having multiple gas-blood interface regions and multiple oxygenator gas inlets; Including, each oxygenator gas inlet configured to receive an oxygenated gas and deliver the oxygenated gas to a respective gas-blood interface region of the plurality of gas-blood interface regions; A cardiac perfusion system wherein each outlet of said mixing chamber is connected to a respective oxygenator gas inlet.

24. a first inlet of the plurality of inlets of the mixing chamber connected to a hospital gas supply or a supply of medical air from a gas cylinder; 24. The cardiac perfusion system of claim 23, wherein a second inlet of the plurality of inlets of the mixing chamber is connected to a supply of oxygen from a hospital gas supply or a gas cylinder.

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