System for controlling blood oxygenation

Abstract

A system (100, FIG. 1) for controlling blood oxygenation of a patient using an artificial lung 200 having a gas-blood interface 240. The system (100, FIG. 1) includes a controller (150, FIG. 1) configured to receive a measurement of a physiological parameter indicative of oxygenation of the patient's blood and to calculate a difference between the measurement and a target value of the physiological parameter. The controller (150, FIG. 1) is further configured to control the gas supply device (300, FIG. 1) to supply the first oxygenated gas 242a to the first interface area 240a of the gas-blood interface 240 and the second oxygenated gas 242b to the second interface area 240b of the gas-blood interface 240, to reduce the amount of oxygen the blood is exposed to by reducing the flow rate of the second oxygenated gas 242b to reduce the difference in response to the measured value exceeding a target value, and to reduce the oxygen concentration and / or flow rate of the first oxygenated gas 242a in response to the flow rate of the second oxygenated gas 242b being reduced to a threshold value.

Description

[Technical Field]

[0001] The present disclosure relates to systems and methods for controlling blood oxygenation in a patient. In particular, the present disclosure relates to systems and methods for improving blood oxygen control in patients experiencing low metabolic rate, low blood oxygen saturation, and / or elevated blood carbon dioxide levels. [Background technology]

[0002] Cardiac perfusion involves the extracorporeal oxygenation of a patient's blood, for example, when the patient is unable to oxygenate their own blood through breathing. Extracorporeal oxygenation involves an artificial lung functioning in place of the patient's own lungs, for example, during cardiac and / or pulmonary surgery. During extracorporeal oxygenation, the artificial lung is used to control the levels of gases (e.g., oxygen and carbon dioxide) in the patient's blood, a function normally performed by the patient's own lungs. During surgical procedures involving extracorporeal perfusion, patients may experience fluctuations in their demand for the delivery and / or removal of certain gases from their blood.

[0003] For example, a patient may experience fluctuations in metabolic rate. Fluctuations in a patient's metabolic rate lead to fluctuations in the patient's consumption of oxygen from their blood. For example, a patient with a healthy or normal metabolic rate will consume more oxygen from their blood than a patient experiencing a reduced metabolic rate. For example, to perform surgery on the patient's heart, the patient's metabolic rate may be intentionally reduced (e.g., by reducing the patient's body temperature), e.g., before placing the patient in circulatory arrest.

[0004] In another example, a patient may experience fluctuations in blood oxygen saturation. For example, a patient may suffer from low blood oxygen saturation. A cyanotic patient is one who suffers from low blood oxygen saturation, which typically leads to a bluish discoloration of the skin. This condition commonly occurs among infants, especially those with congenital heart disease. Such patients are at risk for adverse effects caused by hyperoxemia (i.e., hyperoxygenation of the blood).

[0005] In another example, a patient may experience fluctuations in blood carbon dioxide levels. For example, during hypothermic circulatory arrest, a patient is cooled to reduce metabolic rate. At lower temperatures, carbon dioxide dissolves more readily in the patient's blood, which can increase carbon dioxide levels in the patient's blood. Following this procedure, carbon dioxide levels must be reduced to avoid the potentially harmful effects of excess carbon dioxide in the patient's blood.

[0006] In conventional approaches, such as those involving single-chamber oxygenators, clinicians may adjust the flow rate of oxygenated gas and / or oxygen concentration throughout the oxygenator. This can have unintended and undesirable consequences for the oxygenator's overall performance. For example, if a clinician reduces the flow rate throughout the oxygenator to reduce oxygen delivery, carbon dioxide and nitrogen removal are also reduced. Thus, clinicians may expose patients to risks associated with inadequate control of blood gases (e.g., too high or too low levels of oxygen, carbon dioxide, and / or nitrogen). Such inadequate control can result in adverse outcomes such as oxidative stress (in the case of hyperoxia), increased risk of gaseous microemboli (in the case of increased nitrogen levels), tissue damage (in the case of hypoxia), or increased risk of cerebral swelling (in the case of increased carbon dioxide levels).

[0007] Even when clinicians can adjust gas flow conditions differently for different portions of the oxygenator, improper operation of such an oxygenator can lead to the same adverse consequences. The wide range of permutations available for controlling oxygenated gases within the oxygenator makes it difficult for clinicians to control the levels of each gas in the patient's blood. In particular, certain clinical scenarios require specific adjustment of each blood gas component to achieve the precise physiological effect desired.

[0008] Therefore, there is a need to provide a system and method for controlling blood oxygenation that has improved versatility and is capable of precisely controlling gases in a patient's blood in specific clinical scenarios.

[0009] It should be noted that for accuracy, and in line with convention in the medical field, pressure values ​​given herein are given in units of mmHg ("millimeters of mercury"). However, these values ​​can be simply converted to atm ("atmospheres") by noting that 1 atm is equal to 760 mmHg, or to Pa ("Pascals") by noting that 1 mmHg is equal to approximately 133.3 Pa. Summary of the Invention

[0010] According to a first aspect, there is provided a system for controlling blood oxygenation of a patient, which is defined in claim 1.

[0011] The system is for controlling blood oxygenation in a patient using an oxygenator having a gas-blood interface. The gas-blood interface is configured to receive blood from a patient and expose the blood to a constant amount of oxygen as the blood passes through the oxygenator to produce oxygenated blood. The gas-blood interface of the oxygenator includes a first interface region and a second interface region. Each of these interface regions is independently configured to be supplied with a respective oxygenated gas. The system includes a controller. The controller is configured to receive a measurement of a physiological parameter indicative of the oxygenation of the patient's blood and calculate a difference between the measurement and a target value of the physiological parameter. The controller is further configured to control the gas delivery device to deliver the first oxygenated gas to the first interface region and the second oxygenated gas to the second interface region. The controller is further configured to control the gas delivery device to reduce the amount of oxygen the blood is exposed to by reducing the flow rate of the second oxygenated gas to reduce the difference in response to the measurement exceeding the target value. The controller is further configured to control the gas supply device to reduce the oxygen concentration and / or flow rate in the first oxygenated gas in response to the flow rate of the second oxygenated gas being reduced to a threshold value.

[0012] Advantageously, supplying oxygenated gas to both the first and second interface regions allows for the oxygenation of the patient's blood to be adjusted while still exposing the blood to a "high" amount of oxygen within the oxygenator. That is, oxygenated gas is supplied across the entire gas-blood interface. Therefore, by exposing the blood to oxygenated gas at both the first and second interface regions, gas can be exchanged across the entire gas-blood interface. This is particularly advantageous when the patient requires a "normal" or "healthy" oxygen saturation (e.g., 98.5%).

[0013] The oxygenated gas (e.g., the first oxygenated gas and / or the second oxygenated gas) may include a mixture of oxygen and nitrogen and / or carbon dioxide. For example, the oxygenated gas may include a mixture of nitrogen and oxygen (but not carbon dioxide). The oxygen concentration in the oxygenated gas may be adjusted by adjusting the relative proportions of nitrogen, carbon dioxide, and / or oxygen in the oxygenated gas. The "oxygen concentration in the oxygenated gas" may equivalently be referred to as the "fraction of inspired oxygen" (abbreviated "FiO2"). The controller may be configured to control one or more valves or actuators controlling the gas supply to the oxygenator to adjust (i.e., increase or decrease) the concentration of any or all components of the oxygenated gas delivered to each gas-blood interface of the oxygenator. Alternatively or additionally, the controller may be configured to control one or more valves or actuators controlling the gas supply to the oxygenator to adjust (i.e., increase or decrease) the flow rate of the oxygenated gas delivered to each gas-blood interface of the oxygenator. In this embodiment, the controller can control the composition and / or flow rate of the oxygenated gas delivered to the first gas-blood interface independently of the composition and / or flow rate of the oxygenated gas delivered to the second gas-blood interface.

[0014] Advantageously, the controller is configured to control the gas supply device in a manner that has physiological benefits during surgery to treat a patient experiencing a low metabolic rate (e.g., a patient undergoing circulatory arrest). Patients experiencing a low metabolic rate have reduced blood oxygenation demands because their bodies do not consume as much oxygen from their blood as part of basic metabolic functions. Thus, during extracorporeal oxygenation, the level of oxygenation in the patient's blood increases because the patient does not consume enough oxygen supplied to the blood by the oxygenator.

[0015] Conventional approaches that do not prevent hyperoxygenation in this situation result in the patient receiving too much oxygen from the oxygenator, leading to hyperoxemia. Alternatively, approaches in which flow rates are indiscriminately reduced across a single- or multi-chamber oxygenator can lead to a complete reduction in oxygenator function, reducing the effectiveness of extracorporeal oxygenation. That is, reducing flow rates and / or concentrations across the oxygenator reduces oxygen delivery to the blood, but also reduces carbon dioxide removal from the patient's blood. This, in turn, can lead to the accumulation of these undesirable gases in the patient's blood.

[0016] In contrast, the controller disclosed herein can avoid hyperoxemia while maintaining other oxygenator functions (e.g., carbon dioxide removal, nitrogen removal) in separate chambers. First, the controller reduces the amount of oxygen to which the blood is exposed by controlling the gas supply device to reduce the flow rate of the second oxygenated gas. During this reduction, independent oxygenated gas supplies are provided to the first and second interface regions. Thus, while the flow rate of the second oxygenated gas is reduced, the oxygenator can still provide gas delivery and / or removal via the first oxygenated gas. In other words, oxygen delivery to the blood can be reduced by reducing the flow rate of the second oxygenated gas, but adequate removal of carbon dioxide and nitrogen can be achieved simultaneously with the first oxygenated gas. In this regard, the first oxygenated gas may be considered a "sweep gas." Similarly, the first interface region may be considered a "sweep chamber" or "sweep region."

[0017] By "independently supplied" it is meant that the composition (e.g., gas concentration) and / or flow conditions (e.g., flow rate) of each oxygenated gas can be independently controlled for each interface region. The controller may be configured to change the number of interface regions to which oxygenated gas is supplied by switching one or more independent gas supplies on or off. For example, the controller may be configured to open or close one or more valves that allow or prevent gas flow from the independent gas supplies to the respective interface regions.

[0018] Additionally, after the flow rate of the second oxygenated gas is reduced to a threshold value, the oxygen concentration and / or flow rate in the first oxygenated gas can be reduced to further reduce oxygen delivery as needed, thereby allowing for lower oxygen delivery to meet oxygenation goals for patients with low metabolic rates.

[0019] For example, the controller may be configured to control the gas supply device to reduce the oxygen concentration and / or flow rate in the first oxygenated gas in response to the flow rate of the second oxygenated gas being reduced to a threshold value and in response to the measured value continuing to exceed a target value.

[0020] The first and second interface regions can be arranged sequentially relative to the direction of blood flow through the oxygenator, i.e., blood passes through each interface region in turn as it passes through the oxygenator. For example, the interface regions can be arranged such that blood passes through the second interface region before passing through the first interface region.

[0021] The first interface area and the second interface area may collectively constitute the entire gas-blood interface. In other words, the gas-blood interface may be divided into only two interface areas. Thus, it is understood that whatever proportion of the gas-blood interface forms the first interface area, the remaining proportion of the gas-blood interface forms the second interface area. The first interface area may be smaller, larger, or equal in size to the second interface area.

[0022] For example, the gas-blood interface may be split in half, with the first interface area and the second interface area each constituting 50% of the gas-blood interface (i.e., a "50 / 50 split"). In another example, the first interface area may constitute 40% of the gas-blood interface and the second interface area may constitute 60% of the gas-blood interface (i.e., a "40 / 60 split"), or vice versa (i.e., a "60 / 40 split"). Advantageously, a first interface area constituting 40% of the gas-blood interface provides for appropriate regulation (e.g., addition, removal, and / or maintenance) of carbon dioxide when oxygenated gas is delivered to the first interface area at a standard flow rate commonly used during perfusion procedures (e.g., the oxygenated gas flow rate is approximately the same as the blood flow through the oxygenator, e.g., about 4 to 5 liters per minute). Other possible divisions are also contemplated herein, such as a 30 / 70 split, a 70 / 30 split, a 25 / 75 split, a 75 / 25 split, a 20 / 80 split, an 80 / 20 split, a 10 / 90 split, or a 90 / 10 split.

[0023] The term "gas-blood interface" refers to a component of an oxygenator that allows gas exchange between gas supplied to the gas-blood interface and blood supplied to the gas-blood interface. The gas-blood interface may include one or more hollow fiber groups. Each hollow fiber group may include multiple hollow fibers. Each hollow fiber group may take the form of a hollow fiber bundle, hollow fiber mat, hollow fiber spiral, or other hollow fiber configuration known in the art.

[0024] Each hollow fiber in a hollow fiber group may include an opening for receiving oxygenated gas. Each hollow fiber may include a gas-permeable wall that allows gas exchange between the blood and the oxygenated gas. The hollow fiber groups may be positioned transversely (e.g., vertically) to the blood flow to expose the blood to the oxygenated gas present in the hollow fiber groups as the blood passes through the oxygenator. The gas-blood interface may include multiple hollow fiber groups, each corresponding to a respective one of the interface areas. Alternatively, the gas-blood interface may include a single hollow fiber group, each corresponding to a portion of a single hollow fiber group.

[0025] The gas supply device may include a gas blender configured to receive one or more supply gases, blend the received supply gases, and generate one or more oxygenated gases for supply to the oxygenator. For example, the gas blender may be configured to receive an oxygen gas supply, a nitrogen gas supply, and / or a carbon dioxide gas supply. The oxygen gas supply may include a pure oxygen gas supply (i.e., the oxygen gas supply consists of 100% oxygen). The nitrogen gas supply may include a pure nitrogen gas supply (i.e., the nitrogen gas supply consists of 100% nitrogen). Alternatively, the nitrogen gas supply may include a gas mixture including nitrogen (e.g., the nitrogen gas supply may be air or may include air). The carbon dioxide gas supply may include a pure carbon dioxide gas supply (i.e., the carbon dioxide gas supply consists of 100% carbon dioxide). Alternatively, the carbon dioxide gas supply may include a gas mixture including carbon dioxide (e.g., the carbon dioxide gas supply may be air or may include air). The gas blender may be configured to blend the oxygen gas supply with the nitrogen gas supply and / or the carbon dioxide gas supply to generate one or more oxygenated gases. It should be noted that blending of feed gases may produce an oxygenated gas consisting of only one of the feed gases (e.g., a gas blender may provide an oxygenated gas consisting of 100% oxygen).

[0026] It will be understood that the oxygenated gas may include additional gas components. For example, the oxygenated gas may additionally include one or more anesthetic gases (e.g., isoflurane, sevoflurane, desflurane, and / or nitrous oxide). The oxygenated gas may additionally or alternatively include other gases common in the art (e.g., helium and / or argon).

[0027] Alternatively or additionally, the gas supply device may include one or more valves arranged to control the flow rate and / or composition of the first oxygenated gas and the second oxygenated gas. For example, one or more valves may be present at the gas inlets that supply oxygenated gas to the first and second interface regions. Controlling these valves may control the flow rate of the first and second oxygenated gases. One or more valves may also be connected to gas supplies that supply the constituent gas components of the first and second oxygenated gases. For example, one or more valves may control the flow of gas from an oxygen supply, a nitrogen supply, and / or a carbon dioxide supply. Such valves provide control of gas flow rate and composition. The gas supply device may be integrated with the oxygenator or may be a separate device from the oxygenator.

[0028] Advantageously, the controller adjusts the amount of oxygen based on a measured value of a physiological parameter indicative of the oxygenation of the patient's blood to reduce the difference between the target value and the measured value. This control by the controller may be referred to as "closed loop" control.

[0029] The controller may be configured to perform some or all of these operations continuously. For example, the controller may be configured to continuously receive measurements, continuously calculate the difference, and / or continuously adjust the amount of oxygen. "Continuously" means that the operations may be performed in an ongoing manner without interruption. Alternatively or additionally, the controller may be configured to repeatedly perform some or all of these operations. For example, the controller may be configured to repeatedly receive measurements, repeatedly calculate the difference, and / or repeatedly adjust the amount of oxygen. "Repeatedly" means that the operations may be performed at recurring discrete intervals (e.g., once per millisecond, once per second, once per minute).

[0030] Physiological parameters may generally include any parameter that provides a clinical indication of the level of oxygenation of a patient's blood. "Level of oxygenation" refers to a quantity that indicates how much oxygen is present in a patient's blood. The terms "level of oxygenation of a patient's blood" and "oxygenation of a patient's blood" are used interchangeably herein.

[0031] For example, the physiological parameter may include the oxygen saturation in the patient's blood and / or the partial pressure of oxygen in the patient's blood. The physiological parameter may include a function of the oxygen saturation in the patient's blood and / or the partial pressure of oxygen in the patient's blood.

[0032] As used herein, the term "oxygen saturation" refers to the percentage of oxygenated hemoglobin in a patient's blood relative to the total amount of hemoglobin in the patient's blood. The terms "oxygen saturation" and "blood oxygen saturation" are used interchangeably herein. The term "adjust" refers to increasing or decreasing a parameter.

[0033] The oxygen saturation may include arterial oxygen saturation, venous oxygen saturation, and / or peripheral oxygen saturation.

[0034] Arterial oxygen saturation, abbreviated as "SaO2," is defined as the oxygen saturation in a patient's arterial blood measured directly from the blood. In the field of cardiac perfusion, SaO2 is considered to be the "true" value of oxygen saturation in a patient's arterial blood. This is in contrast to the so-called "peripheral" oxygen saturation in arterial blood, known as SpO2. SpO2 is considered to be an estimate of SaO2 and is measured using pulse oximetry.

[0035] For example, if the measured value is oxygen saturation, the target oxygen saturation may be taken as a typical oxygen saturation in a healthy patient, such as between 95 and 100%, between 98 and 99%, or about 98.5% oxygen saturation. Advantageously, 98.5% oxygen saturation approximates the oxygen saturation in the blood of a healthy patient. Furthermore, selecting an oxygen saturation below 100% allows "headroom" for further increasing saturation if necessary.

[0036] The controller may be configured to receive a target value for the physiological parameter. Specifically, the target value may be received as an input by the controller. For example, the controller may be configured to receive the target value as an input from a user interface. Alternatively or additionally, the controller may be pre-programmed with the target value. Alternatively or additionally, the controller may be configured to retrieve the target value from a look-up table stored on a local or remote server.

[0037] In some embodiments, the controller is further configured to control the gas supply device to decrease the amount of oxygen to which the blood is exposed by decreasing the oxygen concentration in the second oxygenated gas.

[0038] Advantageously, the controller is configured to control the gas supply device to reduce the flow rate and oxygen concentration in the second oxygenated gas, thereby increasing the versatility of the system. In particular, both the oxygen concentration and the flow rate of the oxygenated gas affect the delivery of oxygen and the removal of nitrogen and carbon dioxide from the blood. Therefore, by providing an additional variable (i.e., oxygen concentration) that can be controlled by the controller, the system can more precisely control both the delivery of oxygen (by controlling the oxygen concentration) and the removal of carbon dioxide and nitrogen (by controlling the flow rate).

[0039] The controller may be configured to control the gas supply device to decrease the oxygen concentration in the second oxygenated gas before, after, and / or simultaneously with decreasing the flow rate of the second oxygenated gas.The controller may be configured to control the gas supply device to decrease the oxygen concentration in the second oxygenated gas before, after, and / or simultaneously with decreasing the oxygen concentration and / or flow rate of the first oxygenated gas.

[0040] In an alternative implementation, the controller may be configured to, in response to the measured value exceeding the target value, control the gas supply device to reduce the amount of oxygen to which the blood is exposed by reducing the oxygen concentration in the second oxygenated gas to reduce the difference, instead of reducing the flow rate of the second oxygenated gas to reduce the difference.

[0041] In some embodiments, the controller is configured to control the gas supply device to reduce the flow rate of the second oxygenated gas while maintaining a constant oxygen concentration and / or a constant flow rate of the first oxygenated gas.

[0042] Advantageously, the gas supply device simultaneously maintains a constant oxygen concentration and flow rate of the first oxygenated gas while reducing the flow rate of the second oxygenated gas. This allows the system to reduce oxygen delivery while maintaining a portion of the oxygenator that provides full oxygenation function. That is, despite the reduction in flow rate at the second interface region, the first interface region continues to be supplied with the first oxygenated gas, which is maintained to continue removing undesirable gases from the blood.

[0043] In some embodiments, the constant oxygen concentration in the first oxygenated gas is 100%.

[0044] In other words, the first oxygenated gas may consist of pure oxygen.

[0045] Advantageously, oxygenated gases consisting solely of oxygen are nitrogen-free. Nitrogen is the main component of gaseous microemboli (GMEs), i.e., gas bubbles, in the blood passing through the oxygenator. Essentially, nitrogen does not dissolve in blood, leading to the formation of GMEs. These GMEs can grow in size by accumulating a layer of blood-derived substances (e.g., blood proteins) on their outer surface. GMEs act as obstructions in the blood and can lead to serious complications, such as tissue or organ damage. The nitrogen concentration in the oxygenated gas is too high when the partial pressure of nitrogen in the oxygenated gas is similar to or substantially equal to the partial pressure of nitrogen in blood. This results in reduced (or virtually no) removal of nitrogen from the blood as it passes through the oxygenator due to the lack of a diffusion gradient between the nitrogen in the blood and the nitrogen in the oxygenated gas. As a result, due to the high nitrogen content of blood, there is also a lack of a diffusion gradient between the nitrogen in the GMEs and the nitrogen in the blood itself. Therefore, little or no diffusion of nitrogen from the GME to the blood or from the blood to the oxygenated gas increases the risk that the GME will continue to pass through the bloodstream unaltered by the oxygenator. By providing pure oxygenated gas, a large diffusion gradient is created between the blood and the oxygenated gas, which in turn creates a large diffusion gradient between the GME and the surrounding blood. Thus, more nitrogen moves from the blood to the oxygenated gas and more nitrogen moves from the GME to the blood. This maximizes nitrogen removal, thereby significantly or completely reducing the risk of GME.

[0046] For similar reasons, because the first oxygenated gas does not contain carbon dioxide, carbon dioxide removal is also maximized. Thus, advantageously, removal of undesirable gases (e.g., carbon dioxide and nitrogen) is maximized even while the flow rate of the second oxygenated gas is reduced to reduce the amount of oxygen to which the blood is exposed.

[0047] In some embodiments, the controller is further configured to control the gas delivery device to maintain the flow rate of the second oxygenated gas at a threshold value. The controller may be further configured to increase the amount of oxygen to which the blood is exposed by increasing the oxygen concentration and / or flow rate of the first oxygenated gas.

[0048] The controller may be configured to decrease the oxygen concentration and / or flow rate in the first oxygenated gas, and then maintain the flow rate of the second oxygenated gas and increase the oxygen concentration and / or flow rate in the first oxygenated gas. That is, the controller may decrease the oxygen concentration and / or flow rate in the first oxygenated gas until a target value is reached, and then increase these variables. For example, this may be performed in response to a change (e.g., an increase) in the target value or in response to a change in a measured value (e.g., due to a physiological change in the patient that results in a change in metabolic rate).

[0049] The controller may generally be configured to adjust (e.g., increase and / or decrease) the oxygen concentration and / or flow rate in the first oxygenated gas while maintaining the flow rate of the second oxygenated gas at a threshold value. Generally, the controller may be configured to adjust the oxygen concentration and / or flow rate in the first oxygenated gas and / or the second oxygenated gas in response to changes in the measured and / or target value of the physiological parameter. That is, the controller may be configured to maintain or adjust the oxygen concentration in the patient's blood during a clinical intervention.

[0050] In some embodiments, the threshold is a zero flow rate.

[0051] That is, the controller first reduces the flow rate of the second oxygenated gas until the flow rate reaches zero (i.e., there is no longer any flow of the second oxygenated gas at the second interface region). In this case, the controller has reduced the flow rate of the second oxygenated gas until it cannot be reduced any further. Thus, at this stage, the amount of oxygen to which the blood is exposed is at the minimum level achievable by controlling only the flow rate of the second oxygenated gas. At this stage, the oxygen concentration in the first oxygenated gas is reduced to continue to reduce the amount of oxygen to which the blood is exposed. The threshold flow rate need not be zero, but may instead be another value appropriate for the particular clinical situation.

[0052] Preferably, the controller may be configured to control the gas supply device to supply a first oxygenated gas to the first interface region and a second oxygenated gas to the second interface region, the first oxygenated gas consisting of pure oxygen; to reduce the amount of oxygen to which the blood is exposed by reducing the flow rate of the second oxygenated gas to zero in response to the measured value exceeding a target value (e.g., due to a decrease in the patient's metabolic rate) to reduce the difference; and to reduce the oxygen concentration in the first oxygenated gas in response to the flow rate of the second oxygenated gas being reduced to zero and in response to the measured value continuing to exceed the target value to reduce the difference.

[0053] In some embodiments, the controller is further configured to control the gas supply device to initially supply the first oxygenated gas solely to the first interface region without supplying the second oxygenated gas to the second interface region. The controller may be further configured to control the gas supply device to adjust the amount of oxygen to which the blood is exposed by adjusting the oxygen concentration and / or flow rate in the first oxygenated gas. The controller may then be further configured to control the gas supply device to begin supplying the second oxygenated gas to the second interface region of the gas-blood interface to increase the amount of oxygen to which the blood is exposed.

[0054] It will be understood that the term "initially" in this context refers to the sole delivery of the first oxygenated gas occurring before the delivery of both the first oxygenated gas and the second oxygenated gas, however, it will also be understood that the sole delivery of the first oxygenated gas may occur after the delivery of both the first and second oxygenated gases, since the controller may be configured to stop the delivery of the second oxygenated gas.

[0055] The controller may be configured to increase and / or decrease the amount of oxygen to which the blood is exposed by increasing and / or decreasing the oxygen concentration and / or flow rate in the first oxygenated gas.

[0056] Advantageously, this feature allows blood to be initially exposed to a small amount of oxygen by delivering only a portion of the gas-blood interface (rather than delivering the entire gas-blood interface). That is, blood is exposed to oxygenated gas only at the first interface region, and thus can only exchange gas while at the first interface region of the gas-blood interface. This is particularly advantageous when treating a patient currently experiencing a reduced metabolic rate (e.g., a patient undergoing circulatory arrest) and / or reduced oxygen saturation (e.g., a cyanotic patient). This feature allows, for example, the patient's current oxygen saturation (or other physiological parameter indicative of the patient's blood oxygenation) to be selected as a target saturation (e.g., to initially tailor treatment to the patient's current clinical condition), even if the patient's oxygen saturation is very low.

[0057] Initially, supplying the first oxygenated gas solely to the first interface region may include supplying the first oxygenated gas consisting of pure oxygen. Advantageously, supplying pure oxygen solely to the first interface region (e.g., 40% of the gas-blood interface) provides a sufficiently high diffusion gradient for carbon dioxide between the blood passing through the oxygenator and the first oxygenated gas to ensure adequate removal of carbon dioxide from the blood.

[0058] In particular, this feature allows the system to expose the blood to less oxygen (and thus operate at a lower oxygen saturation) than if oxygenated gas were delivered to the entire gas-blood interface. As an example, delivering oxygenated gas containing 20% ​​oxygen to the entire gas-blood interface will expose the blood to more oxygen than delivering oxygenated gas containing 20% ​​oxygen to only 40% of the gas-blood interface.

[0059] Advantageously, this feature further allows the system to gradually increase the oxygenation of the patient's blood by gradually increasing the oxygen concentration and / or flow rate in the first oxygenated gas. That is, the controller may be configured to increase the amount of oxygen to which the blood is exposed by adjusting the oxygen concentration and / or flow rate in the first oxygenated gas. This allows the amount of oxygen to which the blood is exposed to gradually increase, thereby increasing the oxygenation of the patient's blood.

[0060] At a certain point, the system can begin supplying a second oxygenated gas to the second interface region to further increase the amount of oxygen the blood is exposed to, thus further increasing the oxygenation of the patient's blood.

[0061] In general, the first oxygenated gas may be the same as or different from the second oxygenated gas. For example, the first oxygenated gas may be supplied from a first gas supply that is independent of the second gas supply that supplies the second oxygenated gas. This allows the flow rates and / or compositions of the first oxygenated gas and the second oxygenated gas to be independently adjusted. Alternatively, the first oxygenated gas and the second oxygenated gas may be supplied from a single gas supply. In this case, the controller may be configured to independently adjust the flow rates of the first oxygenated gas and the second oxygenated gas by controlling which interface area is supplied by the single gas supply. However, in such an example, it may be impossible to change the composition of the first oxygenated gas independently from the second oxygenated gas.

[0062] In some embodiments, the controller is configured to control the gas supply device to adjust the amount of oxygen to which the blood is exposed in response to the measured value being below the target value by increasing the oxygen concentration and / or flow rate in the first oxygenated gas to increase the amount of oxygen to which the blood is exposed.

[0063] In some embodiments, the controller is configured to control the gas supply device to begin supplying the second oxygenated gas in response to the oxygen concentration in the first oxygenated gas being increased to a threshold concentration.

[0064] That is, the controller first increases the oxygen concentration in the first oxygenated gas until the oxygen concentration reaches a threshold concentration, at which point the controller begins supplying a second oxygenated gas to the second interface region. For example, the threshold concentration may be 100%. In this case, the controller increases the oxygen concentration in the first oxygenated gas until it cannot be increased any further. That is, at this stage, the amount of oxygen to which the blood is exposed is at its maximum while gas is being supplied only to the first interface region. At this stage, a second oxygenated gas is supplied to the second interface region to continue increasing the amount of oxygen to which the blood is exposed. The threshold concentration need not be 100% but may instead be another value appropriate for a particular clinical situation.

[0065] Alternatively or additionally, the controller may be configured to control the gas supply device to start supplying the second oxygenated gas in response to the flow rate of the first oxygenated gas being increased to a threshold flow rate. For example, the threshold flow rate may be a maximum safe flow rate (e.g., 5 liters per minute) that can be supplied through the oxygenator during extracorporeal oxygenation. The maximum safe flow rate of the oxygenated gas may be determined based on the pressure of the patient's blood in the oxygenator. For example, the maximum safe flow rate of the oxygenated gas may be selected so that the pressure of the oxygenated gas is lower than the pressure of the patient's blood in the oxygenator.

[0066] In some embodiments, the controller is further configured to increase the oxygen concentration and / or flow rate in the second oxygenated gas after starting the supply of the second oxygenated gas to further increase the amount of oxygen to which the blood is exposed.

[0067] In some embodiments, the controller is further configured to receive a second measurement value of a second physiological parameter indicative of a carbon dioxide level in the patient's blood, and to calculate a difference between the second measurement value and a second target value of the second physiological parameter.

[0068] Advantageously, the controller is configured to monitor the removal of carbon dioxide by the oxygenator. This is advantageous in that the controller ensures adequate carbon dioxide removal while adjusting the oxygenation gas in the oxygenator. As described above, adjusting the oxygen concentration and / or flow rate in the first and second oxygenation gases affects the removal of carbon dioxide. Thus, by monitoring the carbon dioxide level and comparing it to a target value, the controller can ensure that the carbon dioxide level remains within a safe range during clinical intervention. For example, the second physiological parameter may be the partial pressure of carbon dioxide, abbreviated as "PaCO2."

[0069] In some embodiments, the controller is further configured to control the gas supply device to increase the flow rate of the second oxygenated gas while simultaneously reducing the oxygen concentration in the second oxygenated gas in response to the second measured value exceeding the second target value.

[0070] Advantageously, this feature allows the controller to respond to insufficient carbon dioxide removal. That is, if the second measurement value exceeds the second target value, the carbon dioxide level is higher than desired and, therefore, carbon dioxide removal is insufficient. Carbon dioxide removal can be increased by increasing the flow rate of oxygenated gas through the oxygenator. However, increasing the flow rate of oxygenated gas alone increases the volume of oxygen within the oxygenator, leading to increased oxygen delivery to the patient's blood and the risk of hyperoxemia. Therefore, to adjust oxygen delivery while increasing carbon dioxide removal, the controller is configured to reduce the oxygen concentration in the second oxygenated gas.

[0071] This is particularly advantageous in various clinical scenarios that increase carbon dioxide in a patient's blood, such as during hypothermic circulatory arrest, during intravascular venous harvesting in coronary artery bypass graft surgery, or during resuscitation after a prolonged period of inadequate perfusion (e.g., during cardiopulmonary resuscitation).

[0072] In some embodiments, the controller is configured to control the gas supply device to increase the flow rate of the second oxygenated gas while simultaneously reducing the oxygen concentration in the second oxygenated gas to maintain a constant oxygen volume within the second interface region.

[0073] Advantageously, the controller thereby offsets the increase in flow rate by reducing the oxygen concentration, so that the volume of oxygen in the second interface region remains constant. This leads to increased carbon dioxide removal (due to increased flow rate) without increasing the supply of oxygen. More specifically, maintaining a constant volume of oxygen means that the diffusion gradient between the second oxygenated gas and the patient's blood remains unchanged, resulting in little or no change in the transfer of oxygen across the gas-blood interface. Thus, carbon dioxide removal can be increased without affecting the supply of oxygen.

[0074] It will be appreciated that these operations can be reversed to achieve the opposite physiological effect. That is, the controller may be further configured to control the gas delivery device to reduce the flow rate of the second oxygenated gas while simultaneously increasing the oxygen concentration in the second oxygenated gas in response to the second measured value being below the second target value. The controller may be configured to reduce the flow rate of the second oxygenated gas while simultaneously increasing the oxygen concentration in the second oxygenated gas so as to maintain a constant oxygen volume within the second interface area.

[0075] This may be particularly advantageous in the case of, for example, brain injury.Reducing blood carbon dioxide level can reduce blood flow to the patient's brain, which is particularly advantageous for reducing swelling in the case of brain injury.In contrast, reducing the flow rate of the second oxygenated gas can reduce carbon dioxide removal, thereby increasing the carbon dioxide level in the patient's blood.If desired, both the flow rate and oxygen concentration in the second oxygenated gas can be reduced to limit oxygenation and carbon dioxide removal, thereby reducing the risk of brain swelling and also reducing the risk of brain tissue damage caused by hyperoxia.Therefore, both the flow rate and oxygen concentration in the second oxygenated gas can be changed to address brain swelling caused by high carbon dioxide level and reduce the risk of brain tissue damage related to hyperoxia.

[0076] In some embodiments, the controller is configured to control the gas supply device to simultaneously maintain a constant oxygen concentration and constant flow rate of the first oxygenated gas while increasing the flow rate of the second oxygenated gas and simultaneously decreasing the oxygen concentration in the second oxygenated gas.

[0077] The benefits of maintaining gas flow conditions (i.e., oxygen concentration and flow rate) in the first oxygenated gas are discussed above. As previously mentioned, this allows the controller to maintain other oxygenator functions (e.g., carbon dioxide removal, nitrogen removal) at the first interface region.

[0078] According to a second aspect, there is provided a system for controlling blood oxygenation of a patient, as defined in claim 15.

[0079] The system is for controlling blood oxygenation in a patient using an oxygenator having a gas-blood interface configured to receive blood from a patient and expose the blood to a constant amount of oxygen as the blood passes through the oxygenator to produce oxygenated blood. The gas-blood interface of the oxygenator includes a first interface region and a second interface region. Each of these interface regions is configured to be independently supplied with a respective oxygenated gas. The system includes a controller. The controller is configured to receive a measurement of a physiological parameter indicative of the level of carbon dioxide in the patient's blood and calculate a difference between the measurement and a target value for the physiological parameter. The controller is further configured to control the gas delivery device to deliver a first oxygenated gas to the first interface region and a second oxygenated gas to the second interface region. The controller is further configured to control the gas delivery device to increase the flow rate of the second oxygenated gas while simultaneously reducing the oxygen concentration in the second oxygenated gas in response to the measurement exceeding the target value.

[0080] It will be understood that the process of blood oxygenation (as compared to the parameters of oxygenation) involves the addition and / or removal of multiple blood gases (e.g., oxygen, carbon dioxide, and nitrogen) and does not simply refer to the addition of oxygen to the blood. In this regard, the system may be considered a system for controlling a patient's blood carbon dioxide levels using an artificial lung.

[0081] Advantageously, the controller is thereby configured to monitor the removal of carbon dioxide by the oxygenator, as described above. Advantageously, this feature allows the controller to respond to insufficient removal of carbon dioxide, as described above.

[0082] In some embodiments, the controller is configured to control the gas supply device to increase the flow rate of the second oxygenated gas while simultaneously reducing the oxygen concentration in the second oxygenated gas to maintain a constant oxygen volume within the second interface region.

[0083] In some embodiments, the controller is configured to control the gas supply device to simultaneously maintain a constant flow rate and / or a constant concentration of the first oxygenated gas while increasing the flow rate of the second oxygenated gas and simultaneously decreasing the oxygen concentration in the second oxygenated gas.

[0084] In some embodiments, the system further includes a gas supply, which may be configured to control the flow rate and / or concentration of oxygen in the first oxygenated gas and the second oxygenated gas.

[0085] In some embodiments, the system further comprises an oxygenator.

[0086] The system may be supplied independently of the oxygenator and / or gas supply. For example, the system may include a control module or control unit configured for connection to the oxygenator and / or gas supply. The system may include the oxygenator and / or gas supply already connected to and / or integrated with the controller.

[0087] While the systems described herein generally include a single oxygenator, in some implementations, they may include multiple oxygenators. Multiple oxygenators may be arranged in series, such that blood received from a patient passes through a first oxygenator, followed by a second oxygenator, and so on. Alternatively, multiple oxygenators may be arranged in parallel and / or in any combination of series and parallel. In such examples, each oxygenator in the system may be connected to a separate gas supply and / or a separate, independent gas supply. That is, each oxygenator may be configured to expose blood to one or more oxygenated gases that are controllable independently from one or more oxygenated gases in another oxygenator in the system. Any or all oxygenators in the system may include the features and characteristics of the oxygenators described herein. For example, one or more (e.g., all) oxygenators in the system may include a gas-blood interface divided into multiple interface areas. For example, a system may include multiple oxygenators, each including a gas-blood interface including a first interface area and a second interface area. Alternatively, a single oxygenator in the system may include multiple interface areas, and any additional oxygenators in the system may include a gas-blood interface with a single interface area (i.e., an undivided gas-blood interface). In this regard, it is understood that the controllers described herein may be configured to control systems including multiple oxygenators.

[0088] In some embodiments, the oxygenator includes a gas inlet zone for receiving an oxygenated gas to the gas-blood interface. The gas inlet zone may include a partition dividing the gas inlet zone into a first gas inlet region and a second gas inlet region. The first gas inlet region may be configured to receive a first oxygenated gas. The first gas inlet region may be configured to provide the first oxygenated gas to the first interface region. The second gas inlet region may be configured to receive a second oxygenated gas. The second gas inlet region may be configured to provide the second oxygenated gas to the second interface region.

[0089] The gas-blood interface of the oxygenator may include multiple hollow fiber groups, each hollow fiber group corresponding to one of the interface regions, i.e., one of the gas inlet regions. Alternatively, the gas-blood interface may include a single hollow fiber group, each interface region (i.e., each gas inlet zone) corresponding to a portion of a single hollow fiber group.

[0090] One or more partitions may separate the gas-blood interfaces. For example, a partition may extend from the gas inlet zone into and through the gas-blood interface. If the gas-blood interface includes multiple hollow fiber groups, the hollow fiber groups may be separated from each other by gaps in which the partitions are located.

[0091] At least one of the one or more partitions may be movable. For example, the one or more partitions may be movable to adjust the relative size of each gas inlet area. The controller may be configured to adjust the position of the one or more partitions (e.g., by activating a motor coupled to the one or more partitions). For example, the controller may be configured to receive an input representing a desired value of a physiological parameter and / or a desired position of the one or more partitions. The controller may be further configured to adjust the position of the one or more partitions in response to the input. The controller may be further configured to translate the desired value of the physiological parameter into the position of the one or more partitions. For example, adjusting one or more partitions to increase the size of the interface area through which oxygenated gas is delivered may increase the exposure of blood to the oxygenated gas, which in turn may increase the oxygenation level in the blood.

[0092] In some embodiments, the system further includes a sensor configured to measure a physiological parameter, and the controller may be configured to receive the measurement from the sensor.

[0093] The sensor may be configured to measure physiological parameters (e.g., oxygen saturation present in oxygenated blood) via spectrophotometry performed in the bloodline. Advantageously, spectrophotometry provides an accurate means of measuring physiological parameters related to blood oxygenation. Furthermore, spectrophotometry is a non-invasive method (e.g., to measure pH or temperature) that can be performed intraoperatively without contacting the patient's blood.

[0094] Spectrophotometry for measuring oxygen saturation involves a white light source being shone onto blood in a blood line. The white light is at least partially reflected by the blood, and the reflected light is detected by a receiver. The receiver detects only wavelengths reflected by the blood, not wavelengths absorbed by the blood. Some wavelengths of the white light are strongly absorbed by oxygenated hemoglobin, and other wavelengths are strongly absorbed by deoxygenated hemoglobin. By measuring the absorption of each wavelength and comparing the relative absorption, the ratio of deoxygenated to oxygenated hemoglobin can be determined, which can then be used to determine the oxygen saturation in the blood.

[0095] To aid in spectrophotometry, the blood line may be transparent, for example, the blood line may be transparent to each wavelength of light used in spectrophotometry.

[0096] In some embodiments, the sensor is disposed on a blood line. The blood line may be connected to an oxygenator. The blood line may be configured to carry oxygenated blood from the oxygenator to the patient.

[0097] Advantageously, the sensor measures the physiological parameter after oxygenation by the oxygenator. The sensor may be considered to be "located downstream of the oxygenator." That is, blood flow passes the sensor after passing through the oxygenator. In other words, the sensor is located downstream relative to the direction of blood flow. In this regard, the physiological parameter measured by the sensor may be considered to constitute an "arterial" measurement. This is in contrast to an "venous" measurement, which is made upstream of the oxygenator (e.g., immediately after blood leaves the patient or between the venous reservoir and the oxygenator).

[0098] Venous measurements of physiological parameters are significantly affected by patient physiological factors. For example, venous oxygen saturation and venous partial pressure are functions of the patient's metabolic rate, blood flow, hemoglobin level, and other physiological parameters. Therefore, performing venous measurements inherently builds uncertainty and a lack of precision into any subsequent control of the patient's blood oxygen level based thereon. To control oxygenation based on venous measurements, clinicians need to understand anesthetic factors, the patient's degree of paralysis, the patient's body temperature, the state of the patient's capillary bed, autonomic responses (e.g., immune or inflammatory responses), and various other factors. Therefore, using sensors to measure physiological parameters after oxygenation by an artificial lung improves the accuracy and safety of systems for controlling blood oxygenation.

[0099] In some embodiments, the system further includes a venous reservoir configured to receive blood from the patient. The system may further include a pump configured to drive blood flow from the venous reservoir through the oxygenator.

[0100] The venous reservoir may be located upstream of the oxygenator. The venous reservoir may be configured to be located between the oxygenator and the patient. That is, the venous reservoir may receive deoxygenated blood from the patient. The pump may be configured to withdraw deoxygenated blood from the venous reservoir and to infuse the deoxygenated blood into the oxygenator. The pump may be located upstream of the oxygenator. The pump may be located downstream of the venous reservoir. The pump may be located between the venous reservoir and the oxygenator. The pump may be a centrifugal pump or a roller (peristaltic) pump.

[0101] It will be understood that any feature, function, characteristic, or advantage described with respect to the first aspect may also apply to the second aspect, and vice versa. Similarly, any feature, function, characteristic, or advantage described with respect to the system may also apply to the corresponding method, and vice versa. [Brief explanation of the drawings]

[0102] Examples will now be described with reference to the accompanying drawings.

[0103] [Figure 1] 1 is a schematic diagram of a system for controlling blood oxygenation of a patient. [Figure 2] 1 is a schematic diagram of an example of an oxygenator of a system for controlling blood oxygenation of a patient. [Figure 3A] 3 is a schematic diagram of the oxygenator of FIG. 2 having a first interface region to which a first oxygenated gas is delivered. [Figure 3B] 3 is a schematic diagram of the oxygenator of FIG. 2 having a first interface region to which a first oxygenated gas is delivered and a second interface region to which a second oxygenated gas is delivered. [Figure 4] 1 is a flowchart of a first example of a method for controlling blood oxygenation of a patient using an artificial lung. [Figure 5] 1 is a flowchart of a second example of a method for controlling blood oxygenation in a patient using an artificial lung. [Figure 6]10 is a flowchart of a third example of a method for controlling blood oxygenation in a patient using an artificial lung. [Figure 7] FIG. 3 is a schematic diagram showing the operating state of the oxygenator of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0104] FIG. 1 depicts a system 100 for controlling a patient's blood oxygenation. The patient's position relative to system 100 is indicated by arrow P, which indicates which blood lines (see below) lead to the patient. System 100 includes an oxygenator 200. Oxygenator 200 includes a gas-blood interface 240 (see FIG. 2) configured to receive blood from the patient and expose the blood to a quantity of oxygen as the blood passes through oxygenator 200 to produce oxygenated blood. The structure of oxygenator 200 is described in detail with reference to FIG. 2.

[0105] System 100 further includes a gas supply device 300. Gas supply device 300 is configured to control the flow rates and / or oxygen concentrations of first oxygenated gas 242a and second oxygenated gas 242b (shown in FIGS. 3A and 3B). First oxygenated gas 242a may be supplied to oxygenator 200 via first gas inlet 222a. Second oxygenated gas 242b may be supplied to oxygenator 200 via second gas inlet 222b.

[0106] Gas supply apparatus 300 is depicted as a single component receiving first gas supply 302a and second gas supply 302b. For example, gas supply apparatus 300 may include a gas blender configured to receive one or more supply gases and blend the supply gases to produce one or more oxygenated gases for delivery to oxygenator 200. However, it is understood that gas supply apparatus 300 may include multiple components. For example, in addition to or instead of a gas blender, gas supply apparatus 300 may include one or more valves that control the flow rate of one or more supply gases such that gas supply apparatus 300 can control the flow rate and / or oxygen concentration in one or more oxygenated gases delivered to oxygenator 200. Gas supply apparatus 300 may include valves, actuators, and / or other gas flow control mechanisms that control gas flow to and / or from oxygenator 200.

[0107] System 100 further includes sensor 110. Sensor 110 is positioned downstream of oxygenator 200. In the illustrated example, sensor 110 is positioned upstream of the patient on the blood line (in this case, arterial line 132) exiting oxygenator 200. Sensor 110 may be configured to measure a physiological parameter indicative of the oxygenation of the patient's blood. For example, sensor 110 may be configured to measure the oxygen saturation present in oxygenated blood (i.e., in the blood after oxygenation by oxygenator 200). For example, sensor 110 may be configured to measure the oxygen saturation present in oxygenated blood via spectrophotometry performed in arterial line 132. In this case, sensor 110 is considered to measure "arterial oxygen saturation" (SaO2). It is understood that other techniques for measuring oxygen saturation may be used in sensor 110. Furthermore, sensor 110 may be positioned downstream of oxygenator 200 but not upstream of the patient. For example, sensor 110 may include a pulse oximeter attached to the patient. In this case, sensor 110 is considered to measure "peripheral oxygen saturation" (SpO2), which is understood in the art to represent an estimate of SaO2, which is considered to be the "true" value of oxygen saturation in a patient's arterial blood.

[0108] Alternatively or additionally, sensor 110 may be configured to measure a physiological parameter indicative of the level of carbon dioxide in the patient's blood. For example, sensor 110 may be configured to measure the partial pressure of carbon dioxide present in oxygenated blood (i.e., in blood after oxygenation by oxygenator 200). For example, sensor 110 may be configured to measure the partial pressure of carbon dioxide via a blood gas analysis, such as an arterial blood gas (ABG) test. In such a case, sensor 110 may be an invasive blood gas sensor. It is understood that other technologies for measuring the partial pressure of carbon dioxide may be used with sensor 110. System 100 may include an additional sensor (not shown) for measuring the partial pressure of carbon dioxide. That is, the system may include a first sensor 110 for measuring a physiological parameter indicative of the oxygenation of the patient's blood and a second sensor (not shown) for measuring a physiological parameter indicative of the level of carbon dioxide in the patient's blood.

[0109] System 100 further includes a controller 150. Controller 150 is configured to receive measurements from sensor 110 (or any other sensors present in system 100). Controller 150 is further configured to calculate a difference between the measurements and a target value for the physiological parameter. The functionality of controller 150 is described in detail below with reference to Figures 3A-5.

[0110] Controller 150 is communicatively connected to oxygenator 200, gas supply 300, and sensor 110, as shown by the dashed lines in FIG. 1 . That is, controller 150 may be configured to communicate with oxygenator 200, gas supply 300, and sensor 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 lines depicted in FIG. 1 are merely exemplary and do not necessarily represent physical connections between components. Furthermore, it is understood that controller 150 may be communicatively connected to more or fewer components in system 100. For example, controller 150 need not necessarily communicate directly with oxygenator 200, but instead may be configured to communicate only with gas supply 300. Similarly, controller 150 need not necessarily communicate directly with sensor 110, but instead may be configured to communicate with an intermediate transceiver that relays measurements from sensor 110 to controller 150. The controller 150 may further be configured to communicate with the pump 130 and / or other components present in the system 100. Other arrangements of communication connections between components will be readily appreciated by those skilled in the art.

[0111] It should be noted that "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.

[0112] The controller 150 may include any suitable type of data processing device, such as a microprocessor, microcontroller, or application specific integrated circuit (ASIC), which may be communicatively coupled to memory (e.g., volatile memory, non-volatile memory, or both volatile and non-volatile memory) that stores processor-executable instructions that cause the controller to perform any of the methods disclosed herein.

[0113] As shown in FIG. 1 , system 100 is configured to receive blood from a patient via venous line 122 and return blood to the patient via arterial line 132. The connection of system 100 to the patient is indicated by arrow P in FIG. 1 . System 100 further includes a venous reservoir 120 configured to receive 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 between the patient and oxygenator 200, upstream of oxygenator 200. It will be understood that the exact location of venous reservoir 120 and pump 130 may vary in other implementations. Indeed, system 100 need not necessarily include venous reservoir 120 and pump 130. In such cases, the oxygenator 200 may be configured to receive blood directly from the patient.

[0114] Blood is collected in venous reservoir 120 and driven through oxygenator 200 by pump 130. Pump 130 is positioned downstream of venous reservoir 120 and upstream of oxygenator 200. 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 depending on the circumstances. Blood exits pump 130 and is received by oxygenator 200 via blood inlet 210. The blood is oxygenated by oxygenator 200, then exits the oxygenator via blood outlet 212, passes sensor 110, and is returned to the patient via arterial line 132. The blood flow path through system 100 is indicated in FIG. 1 by arrow A.

[0115] Although system 100 is depicted as including various components (e.g., sensor 110, oxygenator 200, gas supply 300, venous reservoir 120, pump 130), it is understood that system 100 may include only controller 150. That is, it is not required that system 100 include sensor 110, oxygenator 200, or any of the other components depicted in FIG. 1 . System 100 may instead be provided with controller 150 configured to communicate with and / or control any of the aforementioned components. The additional components in FIG. 1 are included in system 100 for illustrative purposes only to illustrate a context in which controller 150 may operate. However, system 100 may include any or all of the additional components in FIG. 1 .

[0116] FIG. 2 depicts an example of the structure of an oxygenator 200. As described above, oxygenator 200 includes a blood inlet 210 for receiving blood from a patient and a blood outlet 212 for returning blood to the patient. Oxygenator 200 further includes two gas inlets, depicted by arrow G, for accepting two oxygenated gases into oxygenator 200. Oxygenator 200 includes a first gas inlet 222a and a second gas inlet 222b. First gas inlet 222a and second gas inlet 222b are each fluidly connected to a gas inlet zone 230. Oxygenator 200 further includes a gas outlet 226 (which may be referred to as a gas exhaust port 226) for releasing waste gas from oxygenator 200. The oxygenated gas exits oxygenator 200 from gas outlet 226 through gas outlet zone 231.

[0117] The gas inlet zone 230 includes a partition 232 that divides the gas inlet zone 230 into multiple (in this case, two) gas inlet regions 234 a, 234 b. Each gas inlet region 234 a, 234 b is configured to receive a different one of the oxygenated gases. More specifically, the first gas inlet region 234 a is configured to receive the oxygenated gas from the first gas inlet 222 a, and the second gas inlet region 234 b is configured to receive the oxygenated gas from the second gas inlet 222 b.

[0118] Oxygenator 200 further includes a gas-blood interface 240. Gas inlet zone 230 is fluidly connected to gas-blood interface 240. Gas outlet zone 231 is also fluidly connected to gas-blood interface 240. That is, oxygenated gas enters gas-blood interface 240 from gas inlet zone 230 and exits gas-blood interface 240 via gas outlet zone 231.

[0119] The gas-blood interface 240 may include one or more hollow fiber groups, each of which may include multiple hollow fibers. Each hollow fiber group includes an inlet potting fluidly connected to the gas inlet zone 230. Each hollow fiber group includes an outlet potting fluidly connected to the gas outlet zone 231.

[0120] Gas-blood interface 240 is configured to receive oxygenated gases to expose blood to a constant amount of oxygen. For example, one or more oxygenated gases may enter the hollow fiber group from gas inlet zone 230 through the inlet potting. Blood enters oxygenator 200 through blood inlet 210. As the blood and one or more oxygenated gases pass through gas-blood interface 240 as they pass through oxygenator 200, gas-blood interface 240 is configured to allow gaseous exchange between the blood and the oxygenated gases supplied to gas-blood interface 240. This includes the transfer of gases (e.g., oxygen, carbon dioxide, nitrogen) from the blood into the oxygenated gases, as well as the transfer of gases (e.g., oxygen, carbon dioxide) into the blood and out of the oxygenated gases. After gaseous exchange, the (now oxygenated) blood exits oxygenator 200 through blood outlet 212 to the patient, and the oxygenated gases (now waste gases) exit oxygenator 200 through gas outlet 226.

[0121] 2, the presence of multiple gas inlet regions 234a, 234b allows for effective delivery of respective oxygenated gases to different proportions of the gas-blood interface 240. In this regard, the gas-blood interface 240 includes multiple (in this case, two) interface regions 240a, 240b, each configured to be independently delivered with a respective oxygenated gas.

[0122] 2 divides the gas inlet zone 230 into equal-sized first and second gas inlet regions 234a and 234b. That is, the partition 232 divides the gas inlet zone 230 (and thus the gas-blood interface 240) in half, such that the first and second gas inlet regions 234a and 234b each comprise 50% of the gas inlet zone 230. Furthermore, the partition 232 functions to divide the gas-blood interface 240 in half, such that the first and second interface regions 240a and 240b each comprise 50% of the gas-blood interface 240. However, it will be understood that this division is merely one example, and that the partition 232 (and / or multiple partitions) may be positioned in various locations to create different divisions of the gas inlet zone 230 and the gas-blood interface 240. For example, the partitions 232 may be positioned such that the first gas inlet area 234a comprises 40% of the gas inlet zone 230 and the second gas inlet area 234b comprises 60% of the gas inlet zone 230. That is, the gas-blood interface 240 may be divided such that the first interface area 240a comprises 40% of the gas-blood interface 240 and the second interface area 240b comprises 60% of the gas-blood interface 240.

[0123] 2 penetrates gas inlet zone 230 but not gas-blood interface 240. In such cases, partition 232 may abut the inlet potting of the hollow fiber group to prevent gas flow between interface regions 240a, 240b. Alternatively, partition 232 may not abut the inlet potting, since leakage of gas flow between gas inlet regions 234a, 234b may be tolerated. In other examples, partition 232 may penetrate gas inlet zone 230 and at least partially penetrate gas-blood interface 240, physically separating gas-blood interface 240 into interface regions 240a, 240b.

[0124] It is noted that, in general, the oxygenated gas supplied to each of the gas inlet regions 234a, 234b may come from the same or different gas sources. The oxygenated gases may have the same composition or different compositions.

[0125] As described above, the gas supply apparatus 300 may include one or more valves arranged to control the flow rate and / or composition of the first oxygenated gas and the second oxygenated gas. For example, as shown in FIG. 2, the gas supply apparatus may include a first valve 304a configured to control the flow of oxygenated gas to the first gas inlet 222a and a second valve 304b configured to control the flow of oxygenated gas to the second gas inlet 222b. The controller 150 may be configured to control (e.g., open or close) the first valve 304a and the second valve 304b independently of each other to adjust (e.g., increase or decrease) the flow rate through each interface region 240a, 240b. Alternatively or additionally, the gas supply apparatus 300 may include a gas blender for controlling the gas flow and / or composition, as described above. It will be understood that other examples of valves, actuators, blenders, gas flow controllers, or other components for controlling the flow rate and / or composition of gases may be used in place of and / or in addition to the valves or gas blenders described herein.

[0126] 3A and 3B, the general function of the oxygenator 200 (and system 100) will be described. As previously described, the partition 232 allows the gas inlet regions 234a, 234b to be independently supplied with oxygenated gas. Starting with FIG. 3A, the first gas inlet 222a may be supplied with a first oxygenated gas 242a. The first gas inlet 222a may be supplied with the first oxygenated gas 242a without supplying oxygenated gas to the second gas inlet 222b (i.e., oxygenated gas is supplied only to the first gas inlet 222a). This allows the first oxygenated gas 242a to be supplied to the first gas inlet region 234a and, therefore, to the first interface region 240a.

[0127] In this situation, blood passing through the oxygenator 200 is exposed to the first oxygenated gas 242a through only a portion (50% in this case) of the gas-blood interface 240. That is, the blood is not substantially exposed to the oxygenated gas while passing through the second interface region 240b. The blood is exposed to the first oxygenated gas 242a only as it passes through the first interface region 240a. Thus, the amount of oxygen to which the blood is exposed within the oxygenator 200 can be kept low. To further adjust (e.g., increase and / or decrease) the amount of oxygen to which the blood is exposed, the concentration and / or flow rate of the first oxygenated gas 242a can be adjusted as described above. It will be appreciated that, depending on the relative sizes of the first and second interface regions 240a and 240b, a similar effect can be achieved by supplying oxygenated gas only to the second interface region 240b via the second gas inlet 222b.

[0128] 3B, a first oxygenated gas 242a is provided to the first gas inlet 222a as in FIG. 3A, and a second oxygenated gas 242b is provided to the second gas inlet 222b, thereby providing the second oxygenated gas 242b to the second gas inlet region 234b and thus to the second interface region 240b.

[0129] In this situation, blood passing through oxygenator 200 is exposed to second oxygenated gas 242b as it passes through second interface region 240b, and then to first oxygenated gas 242a as it passes through first interface region 240a. Thus, the amount of oxygen to which blood is exposed within oxygenator 200 is increased relative to the situation shown in FIG. 3A. To further adjust (e.g., increase and / or decrease) the amount of oxygen to which blood is exposed, the concentration and / or flow rate of first oxygenated gas 242a and / or second oxygenated gas 242b can be adjusted as described above. It will be understood that the flow rate and / or composition of first oxygenated gas 242a can be adjusted independently of the flow rate and / or composition of second oxygenated gas 242b.

[0130] In this manner, the controller 150 can use the oxygenator 200 and the gas supply 300 to control the amount of oxygen the blood is exposed to within the oxygenator 200 .

[0131] The first oxygenated gas 242a and / or the second oxygenated gas 242b may consist of pure oxygen. The first oxygenated gas 242a and / or the second oxygenated gas 242b may include a mixture of oxygen and nitrogen.

[0132] While specific examples of oxygenators that can be used in system 100 have been described, it is understood that other oxygenators that achieve the same or similar functions may be used. For example, an oxygenator may include multiple gas inlet zones, each connecting to a separate gas inlet. Alternatively, one or more gas inlets may be directly connected to a gas-blood interface, which may be separated into multiple interface regions within the oxygenator. It is understood that other oxygenator configurations exist that allow multiple interface regions to be independently supplied with respective oxygenated gases. Furthermore, while the oxygenator is shown as including two gas inlet regions and two interface regions, it is understood that virtually any number of gas inlet regions and interface regions may be present. The more gas inlet regions and interface regions there are, the more independent oxygenated gases can be supplied to the gas-blood interface.

[0133] The overall functionality of system 100 will now be described with reference to Figures 4 to 7. It will be understood that controller 150 may be configured to control gas supply apparatus 300 to perform any of the methods described herein.

[0134] 4 depicts a first example method 400 of controlling a patient's blood oxygenation as contemplated herein. The controller 150 may be configured to perform any or all of the operations of the method 400. The method 400 includes receiving 402 a measurement value of a physiological parameter indicative of the oxygenation of the patient's blood. The measurement value may be measured by the sensor 110 and received by the controller 150 from the sensor 110, for example. The method 400 further includes calculating 404 a difference between the measurement value and a target value of the physiological parameter. The method 400 further includes supplying 406 a first oxygenated gas 242 a to the first interface region 240 a of the gas-blood interface 240 and a second oxygenated gas 242 b to the second interface region 240 b of the gas-blood interface 240. The method 400 further includes, in response to the measurement value exceeding the target value, decreasing 408 the flow rate of the second oxygenated gas 242 b to reduce the difference, thereby decreasing the amount of oxygen the blood is exposed to. Method 400 further includes reducing 410 the oxygen concentration and / or flow rate in the first oxygenated gas 242a in response to the flow rate of the second oxygenated gas 242b being reduced to the threshold value (and the measured physiological parameter still exceeding the target value). After reducing 408 the flow rate of the second oxygenated gas 242b and / or after reducing 410 the oxygen concentration and / or flow rate in the first oxygenated gas 242a, the method may include recalculating the difference between the measured value and the target value, as indicated by the return arrows in FIG. 4. It will be understood that various operations within method 400, and method 400 as a whole, may be performed repeatedly and / or continuously. For example, method 400 may include receiving updated measurements and repeating method 400 in response to the updated measurements.

[0135] It will be appreciated that the delivery of the first and second oxygenated gases may occur at different times within the method 400. For example, the first and second oxygenated gases may be delivered before measurements are received.

[0136] Advantageously, method 400 is particularly useful for treating patients experiencing a low metabolic rate. A patient's metabolic rate may decrease during surgery involving extracorporeal oxygenation. For example, a patient's metabolic rate may be intentionally decreased by a clinician lowering the patient's body temperature. Following the decrease in metabolic rate, the patient's body consumes less oxygen from the blood, which in turn increases a physiological parameter indicative of blood oxygenation. Following this increase, controller 150 configured to execute method 400 responds by decreasing the flow rate of second oxygenated gas 242b within second interface region 240b. A constant concentration and / or flow rate of first oxygenated gas 242a may be maintained while the flow rate of second oxygenated gas 242b is decreased.

[0137] Advantageously, the continuous supply of first oxygenated gas 242a allows system 100 to continue providing a "sweep" function. That is, first interface area 240a still provides adequate carbon dioxide and nitrogen removal and a basal level of oxygenation while reducing the flow rate of second interface area 240b to reduce oxygen delivery. Only after the flow rate of second oxygenated gas 242b is reduced to a threshold value (e.g., zero) does controller 150 reduce the oxygen concentration and / or flow rate in first oxygenated gas 242a. This allows the amount of oxygen the blood is exposed to to be further reduced to reach a target value.

[0138] Optionally, method 400 may further include increasing the amount of oxygen to which the blood is exposed by maintaining the flow rate of second oxygenated gas 242b at the threshold value and increasing 412 the oxygen concentration and / or flow rate in first oxygenated gas 242a. For example, the oxygen concentration and / or flow rate of first oxygenated gas 242a may be increased back to an original level (i.e., the level before it was reduced in operation 410 in response to reducing the flow rate of second oxygenated gas 242b to the threshold value). For example, the oxygen concentration in first oxygenated gas 242a may be increased to 100%.

[0139] As indicated by feature 401, method 400 may be preceded by method 500, which will be described below with reference to Figure 5. As indicated by feature 414, method 400 may be followed by method 600, which will be described below with reference to Figure 6. Alternatively, method 600 may be performed independently of method 400.

[0140] 5 depicts a second example method 500 of controlling a patient's blood oxygenation as contemplated herein. The controller 150 may be configured to perform any or all of the operations of the method 500. The method 500 initially includes supplying 502 a first oxygenated gas 242 a only to the first interface region 240 a of the gas-blood interface 240 without supplying 504 a second oxygenated gas 242 b to the second interface region 240 b. The method 500 may further include adjusting 504 the amount of oxygen to which the blood is exposed by adjusting the oxygen concentration and / or flow rate in the first oxygenated gas 242 a. The method 500 further includes subsequently starting 506 the supply of the second oxygenated gas 242 b to the second interface region 240 b of the gas-blood interface 240 to increase the amount of oxygen to which the blood is exposed. Initiating 506 the supply of the second oxygenated gas 242b may be in response to the oxygen concentration in the first oxygenated gas 242a being increased to a threshold concentration (eg, 100% oxygen).

[0141] In one example scenario, oxygenated gas (in the form of first oxygenated gas 242a) may initially be supplied only to the first interface region 242a. At this stage, the first oxygenated gas 242a may include a mixture of nitrogen and oxygen. In this regard, the blood is exposed to a "low" amount of oxygen (and thus a "low" oxygen saturation may be achieved in the patient's blood). The oxygen concentration in the first oxygenated gas 242a may be gradually increased to increase the amount of oxygen to which the blood is exposed (and thus increase blood oxygen saturation). When the oxygen concentration in the first oxygenated gas 242a reaches 100%, it is no longer possible to increase the amount of oxygen to which the blood is exposed by increasing the oxygen concentration in the first oxygenated gas 242a. Therefore, the supply of the second oxygenated gas 242b is initiated to further increase the amount of oxygen to which the blood is exposed. The oxygen concentration and / or flow rate of the second oxygenated gas 242b can then be further adjusted to adjust the amount of oxygen the blood is exposed to.

[0142] Advantageously, method 500 is particularly useful for treating patients experiencing low oxygen saturation. Due to the patient's current low oxygen saturation in their blood, oxygenator 200 should be operated to expose the blood to a reduced amount of oxygen to reduce the risk of hyperoxemia. Thus, by initially delivering oxygen only to first interface region 240a, oxygenator 200 exposes the blood to a reduced amount of oxygen, thus reducing the risk of overoxygenating the patient. The patient's oxygenation can then be adjusted by adjusting the oxygen concentration and / or flow rate of first oxygenated gas 242a. Then, when it is desired to increase the patient's oxygen saturation (e.g., at the end of a clinical intervention, such as after surgery to repair congenital heart disease), delivery of second oxygenated gas 242b can be initiated to increase the amount of oxygen the blood is exposed to.

[0143] Optionally, the method 500 (e.g., adjusting 504) may further include increasing the amount of oxygen to which the blood is exposed by increasing 508 the oxygen concentration and / or flow rate in the first oxygenated gas 242a in response to the measured value being below the target value.

[0144] Optionally, the method 500 may further include increasing 510 the oxygen concentration and / or flow rate of the second oxygenated gas 242b after starting the delivery of the first oxygenated gas 242a to further increase the amount of oxygen to which the blood is exposed.

[0145] 6 illustrates a third example method 600 of controlling blood oxygenation of a patient as contemplated herein. Controller 150 may be configured to perform any or all of the operations of method 600. Method 600 may be performed subsequent to method 400 of FIG. 4 or may be performed independently. That is, controller 150 may be configured to perform method 400 and / or to perform method 600.

[0146] The method 600 includes receiving 602 a measurement value of a physiological parameter indicative of the level of carbon dioxide in the patient's blood. The measurement value may be measured by the sensor 110 and received by the controller 150 from the sensor 110, for example. The method 600 further includes calculating 604 a difference between the measurement value and a target value of the physiological parameter. The method 600 further includes delivering 606 a first oxygenated gas 242 a to the first interface region 240 a of the gas-blood interface 240 and a second oxygenated gas 242 b to the second interface region 240 b of the gas-blood interface 240. The method 600 further includes increasing 608 the flow rate of the second oxygenated gas 242 b while simultaneously reducing the oxygen concentration in the second oxygenated gas 242 b in response to the measurement value exceeding the target value. After increasing 608 the flow rate of the second oxygenated gas 242 b, the method may include recalculating the difference between the measurement value and the target value, as indicated by the return arrow in FIG. 6 . It will be understood that various operations within method 600, and method 600 as a whole, may be performed repeatedly and / or continuously. For example, method 600 may include receiving updated measurements and repeating method 600 in response to the updated measurements.

[0147] It will be appreciated that the delivery of the first and second oxygenated gases may occur at different times within method 600. For example, the first and second oxygenated gases may be delivered before measurements are received.

[0148] Advantageously, method 600 is particularly useful for treating patients experiencing elevated levels of carbon dioxide in their blood. For example, patients may experience elevated levels of carbon dioxide in their blood during intravascular venous harvesting in coronary artery bypass graft surgery, during resuscitation after prolonged perfusion, or during hypothermic circulatory arrest (when the patient's metabolic rate is reduced). Following these increases in carbon dioxide, controller 150 configured to execute method 600 responds by increasing the flow rate of second oxygenated gas 242b while simultaneously reducing the oxygen concentration in second oxygenated gas 242b. The increased flow rate results in an increased rate of carbon dioxide removal from the blood, and reducing the oxygen concentration prevents or reduces increased oxygen delivery. Thus, oxygen delivery can be maintained while increasing carbon dioxide removal from the patient's blood.

[0149] Turning now to Figure 7, an example of the operation of the system described herein will be described. Figure 7 shows a schematic representation of several "states" that may exist during the operation of the system described herein. In particular, Figure 7 illustrates a range of states that may arise during the treatment of a patient experiencing low metabolic rate, inadequate carbon dioxide removal, or low oxygen saturation (e.g., cyanosis).

[0150] FIG. 7 is divided into a series of four states, (a) through (d), which are described sequentially below. Transitions between states are indicated by arrows 760, 762, 764, and 766. In each state, oxygenator 700 is depicted. For clarity, details of oxygenator 700 are not described or labeled in FIG. 7 . However, it is understood that oxygenator 700 may share any or all of the features of oxygenator 200 described above. The only features labeled in FIG. 7 are first interface region 740a, second interface region 740b, first oxygenated gas 742a, and second oxygenated gas 742b. While the following description begins with state (a), it is understood that any state can be considered "start" because the process is cyclical.

[0151] In state (a), a first oxygenated gas 742a is supplied to the first interface area 740a. No oxygenated gas is supplied to the second interface area 740b. As shown in FIG. 7, the first oxygenated gas 742a is supplied at 100% FiO2. That is, in state (a), the first oxygenated gas 742a consists solely of oxygen. The oxygenator 700 may be operated in this state to both oxygenate the patient's blood and remove carbon dioxide from the patient's blood. In this regard, the first oxygenated gas 742a may be considered a "sweep gas." However, given that the first interface area 740a represents only a percentage (e.g., 40%) of the total gas-blood interface, the supply of the first oxygenated gas 742a may not be sufficient to reach a target value for a physiological parameter indicative of oxygenation in the patient's blood (e.g., oxygen saturation). For example, a sensor may measure a physiological parameter value that is below the target value. The system may then transition to state (b), as indicated by arrow 760.

[0152] In state (b), the first interface region 740a continues to be supplied with the first oxygenated gas 742a at 100% FiO2. However, the second interface region 740b now begins to be supplied with the second oxygenated gas 742b. That is, the flow rate of the second oxygenated gas 742b may be increased from zero. The flow rate of the second oxygenated gas 742b may continue to be increased until a target value is reached (e.g., until a sensor measures a value equal to the target value). It will be appreciated that by supplying the second oxygenated gas 242b to the second interface region 740b, the amount of oxygen to which the blood is exposed increases beyond the amount possible by supplying only the first interface region 740a. Thus, high oxygen saturation may be achieved by supplying both interface regions 740a, 740b. The second oxygenated gas 742b may be provided at 100% FiO2 (i.e., pure oxygen). The oxygen concentration in the second oxygenated gas 742b may be adjusted in addition to, or instead of, adjusting the flow rate of the second oxygenated gas 742b. The system may operate in this state to increase the oxygen saturation in the patient's blood to a healthy level (e.g., 98.5%). However, during a surgical procedure, the patient's metabolic rate may decrease. This, in turn, means that the blood needs to be exposed to less oxygen in the oxygenator to achieve the same blood oxygen saturation. This decrease in metabolic rate may be detected in the form of an increase in the patient's blood oxygen saturation caused by the continued supply of the first and second oxygenated gases 742a, 742b at the same oxygen concentration and flow rate despite the decreased metabolic rate. This may be detected, for example, by a sensor. In such a case, the system may transition to state (c), as indicated by arrow 762.

[0153] In embodiments in which the system is controlling carbon dioxide levels in the patient's blood (in addition to or instead of oxygenating the patient's blood), the oxygen concentration in the second oxygenated gas 742b may be reduced while in state (b) simultaneously with an increase in the flow rate in the second oxygenated gas 742b.

[0154] In state (c), the flow rate of the second oxygenated gas 742b is reduced (e.g., to a threshold value (e.g., zero)). This reduces the volume of second oxygenated gas 742b present at the second interface region 740b at a given time. Therefore, the amount of oxygen to which the blood is exposed is reduced, resulting in a decrease in oxygenation of the patient's blood. The measurement may be reduced to the target value at a lower flow rate of the second oxygenated gas 742b. Alternatively, the flow rate of the second oxygenated gas 742b may need to be reduced to zero (so that no oxygenated gas is present at the second interface region 640b) before the target oxygen saturation can be achieved. In some instances, this reduction to zero may not be sufficient to achieve the target oxygen saturation. Therefore, the system may transition to state (d), as indicated by arrow 764, to continue reducing the amount of oxygen to which the blood is exposed (e.g., in response to the flow rate of the second oxygenated gas 742b being reduced to zero).

[0155] In state (d), there is no oxygenated gas supply to the second interface region 740b. The oxygen concentration and / or flow rate of the first oxygenated gas 742a may be reduced to further reduce the amount of oxygen to which the blood is exposed. This further reduces the amount of oxygen in the oxygenator 700, allowing a physiological parameter indicative of oxygenation in the patient's blood to be further reduced until the measured value reaches a target value. Advantageously, this allows the system to effectively manage the oxygenation level of a patient experiencing a low metabolic rate (e.g., a patient undergoing circulatory arrest). As the patient returns to a high (e.g., normal) metabolic rate, the FiO2 and / or flow rate of the first oxygenated gas 742a can again be increased to increase the amount of oxygen present in the oxygenator 700. The FiO2 may continue to be increased until it reaches 100%. The system thereby returns to state (a), as indicated by arrow 766.

[0156] It will be appreciated that Figure 7 represents a specific example of the operation of the system described herein in a patient who initially has a normal metabolic rate and then has a low metabolic rate. In practice, as the patient's metabolic rate may increase or decrease during a surgical procedure, the system may freely move between all of the states in Figure 7. That is, the system is not limited to the sequence described, but may instead increase and / or decrease the concentration and / or flow rate of the first and / or second oxygenated gases as needed to achieve a target value for a physiological parameter indicative of the oxygenation of the patient's blood.

[0157] As previously mentioned, any of states (a) through (d) in FIG. 7 may be treated as a starting state depending on the particular clinical scenario.

[0158] For example, in method 400, the system may begin in state (c) with both oxygenated gases being delivered and the flow rate of the second oxygenated gas 642b reduced to a threshold value (e.g., zero). In this case, in state (d), the oxygen concentration and / or flow rate of the first oxygenated gas 742a may be reduced and then increased, as described above.

[0159] In another example, for method 500, the system may initially start in state (a) where only the first oxygenated gas 242a is supplied and the oxygen concentration and / or flow rate of the first oxygenated gas 242a is adjusted.

[0160] In another example, for method 600, the system may begin in state (b) with both oxygenated gases being supplied and the flow rate of second oxygenated gas 642b being increased, where the oxygen concentration in second oxygenated gas 242b is simultaneously reduced in state (b).

[0161] It will be understood that any features, functions, characteristics, or advantages described with respect to the system example above may also apply to the method example above, and vice versa.

[0162] According to the present disclosure, the following aspects are also contemplated.

[0163] Aspect 1. A method of controlling blood oxygenation in a patient using an oxygenator, the oxygenator having a gas-blood interface configured to receive blood from the patient and expose the blood to a quantity of oxygen as the blood passes through the oxygenator to produce oxygenated blood, the gas-blood interface including a first interface region and a second interface region each configured to be independently supplied with a respective oxygenating gas, the method comprising: receiving a measurement of a physiological parameter indicative of blood oxygenation of the patient; calculating a difference between the measured value and a target value for the physiological parameter; delivering a first oxygenated gas to the first interface region of the gas-blood interface; delivering a second oxygenated gas to the second interface region of the gas-blood interface; In response to the measured value exceeding the target value, decreasing the amount of oxygen to which the blood is exposed by decreasing the flow rate of the second oxygenated gas to reduce the difference; reducing the oxygen concentration and / or flow rate of the first oxygenated gas in response to the flow rate of the second oxygenated gas being reduced to a threshold value; A method comprising:

[0164] Embodiment 2. The method of embodiment 1, further comprising decreasing the amount of oxygen to which said blood is exposed by reducing the oxygen concentration of said second oxygenated gas.

[0165] Embodiment 3. The method of embodiment 1 or embodiment 2, further comprising reducing the flow rate of said second oxygenated gas while maintaining a constant oxygen concentration and / or a constant flow rate of said first oxygenated gas.

[0166] Aspect 4. The method of Aspect 3, wherein said constant oxygen concentration in said first oxygenated gas is 100%.

[0167] Embodiment 5. The method of any of embodiments 1 to 4, further comprising maintaining a flow rate of the second oxygenated gas at the threshold value and increasing the amount of oxygen to which the blood is exposed by increasing the oxygen concentration and / or flow rate of the first oxygenated gas.

[0168] Embodiment 6. The method of any one of embodiments 1 to 5, wherein the threshold is a zero flow rate.

[0169] Aspect 7. First, supplying the first oxygenated gas only to the first interface region without supplying the second oxygenated gas to the second interface region; adjusting the amount of oxygen to which the blood is exposed by adjusting the oxygen concentration and / or flow rate of the first oxygenated gas; thereafter, commencing delivery of the second oxygenated gas to the second interface region of the gas-blood interface to increase the amount of oxygen to which the blood is exposed. The method of any of embodiments 1 to 6, further comprising:

[0170] Embodiment 8. The method of embodiment 7, wherein adjusting the amount of oxygen to which the blood is exposed comprises, in response to the measured value being below the target value, increasing the amount of oxygen to which the blood is exposed by increasing the oxygen concentration and / or flow rate of the first oxygenated gas.

[0171] Embodiment 9 The method of embodiment 7 or embodiment 8, wherein initiating the supply of said second oxygenated gas is in response to the oxygen concentration of said first oxygenated gas being increased to a threshold concentration.

[0172] Embodiment 10. The method of any of embodiments 7 to 9, further comprising, after initiating delivery of the second oxygenated gas, increasing the oxygen concentration and / or flow rate of the second oxygenated gas so as to further increase the amount of oxygen to which the blood is exposed.

[0173] Aspect 11. Receiving a second measurement of a second physiological parameter indicative of a level of carbon dioxide in the patient's blood; calculating a difference between the second measured value and a second target value for the second physiological parameter; The method of any one of embodiments 1 to 10, further comprising:

[0174] Embodiment 12. The method of embodiment 11, further comprising, in response to said second measured value exceeding said second target value, increasing the flow rate of said second oxygenated gas while simultaneously decreasing the oxygen concentration of said second oxygenated gas.

[0175] Embodiment 13. The method of embodiment 12, wherein a constant oxygen volume within the second interface region is maintained by simultaneously increasing the flow rate of the second oxygenated gas and decreasing the oxygen concentration in the second oxygenated gas.

[0176] Embodiment 14 The method of embodiment 12 or embodiment 13, further comprising simultaneously maintaining a constant oxygen concentration and constant flow rate of said first oxygenated gas while simultaneously increasing the flow rate of said second oxygenated gas and decreasing the oxygen concentration of said second oxygenated gas.

[0177] Aspect 15. A method of controlling blood oxygenation in a patient using an oxygenator, the oxygenator having a gas-blood interface configured to receive blood from the patient and expose the blood to a quantity of oxygen as the blood passes through the oxygenator to produce oxygenated blood, the gas-blood interface including a first interface region and a second interface region each configured to receive a respective oxygenated gas independently, the method comprising: receiving a measurement of a physiological parameter indicative of a level of carbon dioxide in the patient's blood; calculating a difference between the measured value and a target value for the physiological parameter; delivering a first oxygenated gas to the first interface region of the gas-blood interface; delivering a second oxygenated gas to the second interface region of the gas-blood interface; increasing the flow rate of the second oxygenated gas while simultaneously decreasing the oxygen concentration of the second oxygenated gas in response to the measured value exceeding the target value; A method comprising:

[0178] Embodiment 16 The method of embodiment 15, comprising increasing the flow rate of the second oxygenated gas while simultaneously decreasing the oxygen concentration in the second oxygenated gas to maintain a constant oxygen volume in the second interface region.

[0179] Embodiment 17 The method of embodiment 15 or embodiment 16, further comprising maintaining the flow rate and / or concentration of the first oxygenated gas while increasing the flow rate of the second oxygenated gas and simultaneously decreasing the oxygen concentration of the second oxygenated gas.

Claims

1. 1. A system for controlling blood oxygenation in a patient using an artificial lung, comprising: the oxygenator has a gas-blood interface configured to receive blood from the patient and expose the blood to a quantity of oxygen as the blood passes through the oxygenator to produce oxygenated blood, the gas-blood interface including a first interface region and a second interface region each configured to receive an independent supply of a respective oxygenated gas; The system comprises: receiving a measured value of a physiological parameter indicative of blood oxygenation of the patient and calculating a difference between the measured value and a target value of the physiological parameter; Control the gas supply device supplying the first oxygenated gas to the first interface region and the second oxygenated gas to the second interface region; In response to the measured value exceeding the target value, decreasing the amount of oxygen to which the blood is exposed by decreasing the flow rate of the second oxygenated gas to reduce the difference; reducing the oxygen concentration and / or flow rate of the first oxygenated gas in response to the flow rate of the second oxygenated gas being reduced to a threshold value; a controller configured to:

2. 10. The system of claim 1, wherein the controller is further configured to control the gas supply device to reduce the amount of oxygen to which the blood is exposed by reducing the oxygen concentration in the second oxygenated gas.

3. 3. The system of claim 1 or claim 2, wherein the controller is configured to control the gas supply device to reduce the flow rate of the second oxygenated gas while maintaining a constant oxygen concentration of the first oxygenated gas and / or a constant flow rate of the first oxygenated gas.

4. 4. The system of claim 3, wherein the constant oxygen concentration in the first oxygenated gas is 100%.

5. The controller further comprises: maintaining the flow rate of the second oxygenated gas at the threshold; increasing the amount of oxygen to which the blood is exposed by increasing the oxygen concentration and / or flow rate of the first oxygenated gas; The system of claim 1 , configured to control the gas supply device to:

6. The system of claim 1 , wherein the threshold is zero flow rate.

7. The controller further comprises: first supplying the first oxygenated gas only to the first interface region without supplying the second oxygenated gas to the second interface region; adjusting the amount of oxygen to which the blood is exposed by adjusting the oxygen concentration and / or flow rate of the first oxygenated gas; thereafter, commencing delivery of the second oxygenated gas to the second interface region of the gas-blood interface to increase the amount of oxygen to which the blood is exposed; The system of claim 1 , configured to control the gas supply device to:

8. 8. The system of claim 7, wherein the controller is configured to control the gas supply device to adjust the amount of oxygen to which the blood is exposed by increasing the oxygen concentration and / or flow rate of the first oxygenated gas in response to the measured value being below the target value.

9. 9. The system of claim 7 or claim 8, wherein the controller is configured to control the gas supply device to start supplying the second oxygenated gas in response to the oxygen concentration of the first oxygenated gas being increased to a threshold concentration.

10. 10. The system of claim 7, wherein the controller is further configured to increase the oxygen concentration and / or flow rate of the second oxygenated gas after starting the supply of the second oxygenated gas to further increase the amount of oxygen to which the blood is exposed.

11. The controller further comprises: receiving a second measurement of a second physiological parameter indicative of a level of carbon dioxide in the patient's blood; calculating a difference between the second measured value and a second target value of the second physiological parameter; The system of any one of claims 1 to 10, configured to:

12. 12. The system of claim 11, wherein the controller is further configured to control the gas delivery device to increase the flow rate of the second oxygenated gas while simultaneously decreasing the oxygen concentration of the second oxygenated gas in response to the second measured value exceeding the second target value.

13. 13. The system of claim 12, wherein the controller is configured to control the gas supply device to increase the flow rate of the second oxygenated gas while simultaneously decreasing the oxygen concentration of the second oxygenated gas to maintain a constant oxygen volume within the second interface area.

14. 14. The system of claim 12 or claim 13, wherein the controller is configured to control the gas delivery device to simultaneously maintain a constant oxygen concentration and constant flow rate of the first oxygenated gas while increasing the flow rate of the second oxygenated gas and simultaneously decreasing the oxygen concentration of the second oxygenated gas.

15. 1. A system for controlling blood oxygenation in a patient using an artificial lung, comprising: the oxygenator has a gas-blood interface configured to receive blood from the patient and expose the blood to a quantity of oxygen as the blood passes through the oxygenator to produce oxygenated blood, the gas-blood interface including a first interface region and a second interface region each configured to receive an independent supply of a respective oxygenated gas; The system comprises: receiving a measured value of a physiological parameter indicative of a level of carbon dioxide in the patient's blood and calculating a difference between the measured value and a target value of the physiological parameter; Control the gas supply device supplying the first oxygenated gas to the first interface region and the second oxygenated gas to the second interface region; increasing the flow rate of the second oxygenated gas while simultaneously decreasing the oxygen concentration of the second oxygenated gas in response to the measured value exceeding the target value; a controller configured to:

16. 16. The system of claim 15, wherein the controller is configured to control the gas supply device to increase the flow rate of the second oxygenated gas while simultaneously decreasing the oxygen concentration of the second oxygenated gas to maintain a constant oxygen volume within the second interface area.

17. 17. The system of claim 15 or claim 16, wherein the controller is configured to control the gas delivery device to simultaneously maintain a constant flow rate and / or constant concentration of the first oxygenated gas while increasing the flow rate of the second oxygenated gas and simultaneously decreasing the oxygen concentration of the second oxygenated gas.

18. 18. The system of any one of claims 1 to 17, wherein the system further comprises the gas supply device, the gas supply device configured to control the flow rate and / or oxygen concentration of the first oxygenated gas and the second oxygenated gas.

19. 19. The system of any one of claims 1 to 18, wherein the controller further comprises an oxygenator.

20. the oxygenator includes a gas inlet zone for receiving oxygenated gas to a gas-blood interface; The gas inlet zone comprises: a first gas inlet region configured to receive the first oxygenated gas and provide the first oxygenated gas to the first interface region; a second gas inlet region configured to receive the second oxygenated gas and provide the second oxygenated gas to the second interface region; 20. The system of claim 19, further comprising a partition that divides the data into:

21. 21. The system of claim 1, further comprising a sensor configured to measure the physiological parameter, and wherein the controller is configured to receive the measurement from the sensor.

22. 22. The system of claim 21 when dependent on claim 19 or claim 20, wherein the sensor is disposed on a blood line, the blood line being configured to be connected to the oxygenator and to carry the oxygenated blood from the oxygenator to the patient.

23. The system further comprises: a venous reservoir configured to receive blood from the patient; a pump configured to drive blood flow from the venous reservoir through the oxygenator; and 23. The system of any one of claims 19 to 22, comprising:

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