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1. WO2021067630 - DUAL-CHANNEL HEATING AND COOLING APPARATUS AND METHOD

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

DUAL-CHANNEL HEATING AND COOLING APPARATUS AND METHOD

BACKGROUND OF THE INVENTION

[0001] The present invention relates in general to cardiac surgery, and, more specifically, to the heating and cooling of blood or other liquids delivered to a patient during cardiac bypass surgery, transplant procedures, and other cardiac-related procedures.

[0002] Heating and cooling devices are an important part of blood perfusion systems used during cardiac surgery. During surgery, blood is cooled or warmed in a bypass circuit using a blood oxygenator to induce hypothermia to protect the organs. A separate cardioplegia circuit typically provides a dedicated flow of cooled solution directly to the heart, at least periodically. When the surgery has been completed, the blood and/or other liquids flowing in the two circuits is heated prior to the patient waking from anesthesia. During various circumstances that may arise during operation of the blood perfusion system, it becomes desirable not only to heat both circuits or cool both circuits simultaneously, but also to cool one circuit while the other is heating or to deactivate one circuit while the other is either heating or cooling.

[0003] Conduits carrying the blood and/or cardioplegia solution in each circuit pass through respective heat exchangers. Water (or other heat exchange liquid) in the two respective heater/cooler circuits is pumped through passages in the heat exchangers for adding heat to or removing heat from the blood/cardioplegia solution as necessary. An integrated heater/cooler unit having an integrated controller and an integrated power supply usually includes a single ice-bath compartment for selectably cooling the water in both water circuits and a pair of heating devices for selectably heating the water in the two circuits independently.

[0004] In view of electrical safety standards and the desire to power a dual heater/cooler unit from a single conventional outlet in an operating room, it is necessary to ensure that the current drawn from the outlet stays safely within a maximum limit. The significant power consuming elements of the unit are multiple (two, three, or more) water-circulating pumps, and two or more heaters, and the controller electronics (e.g., microcontroller, display, and other related circuitry). One conventional cooling function does not consume power other than that power to operate the controls and pumps since a supply of ice has been used as the source of cooling. The maximum current draw occurs when both heaters operate simultaneously; i.e., both

the blood oxygenator and the cardioplegia circuits are being heated and the multiple pumps are operating. Minor levels of current are used by the system for powering low voltage controllers, sensors and instruments.

[0005] U.S. Pat. No. 6,423,268, issued to King et al., the disclosure of which is incorporated by reference in its entirety, discloses a first heater in heat exchanger relationship with a first fluid circuit and a second heater in heat exchanger relationship with a second fluid circuit, and a power supply connected to the first and second heaters to prevent the first and second heaters from being activated simultaneously. When heating is required in both fluid lines, the logic of the system activates a timer that controls switches to activate or deactivate the AC power supplies for the respective two heaters. The timer causes the power to alternate back and forth between the two heaters, by removing power from one heater before causing power to the other heater.

[0006] U.S. Pat. No. 7,403,704, issued to Eccleston et al., the disclosure of which is incorporated by reference in its entirety, discloses dual channel liquid temperature control apparatus powered by a single electrical mains outlet, having a controller that selectively actuates the first and second channel pumps, and first and second heating elements to selectably heat and cool the heat exchange liquids, such that power draw of all activated pumps and heating elements is maintained within a power limit, to avoid tripping the electrical circuit breaker of the mains outlet circuit. Cooling is provided solely by operator-added ice.

SUMMARY OF THE INVENTION

[0007] The present invention provides an improved dual-channel, heating and cooling apparatus for heating and cooling of two separate liquid circuits. A non-limiting example of two separate liquid circuits includes a cardioplegia solution and a patient’s oxygenated blood during cardiac surgery. The apparatus and a method for using the apparatus for the heating and cooling of two (or more) liquid circuits are using in a variety of surgical procedures, including lung and other organ surgery, and other cardiac surgeries and procedures, including organ transplant procedures.

[0008] In one aspect of the invention, a dual-channel liquid temperature control apparatus controls the temperature of the cardioplegia solution during surgery using electrical power from an electrical convenience outlet having an electrical power limit. A first ” cardioplegia” circulation channel conveys a first heat exchange liquid, usually water, through a cardioplegia heat exchanger. A second “blood oxygenator” circulation channel conveys a second heat exchange liquid, usually water, through a blood oxygenator heat exchanger. A first pump receives and pumps selectively the cardioplegia heat exchange liquid within the cardioplegia circulation channel, to and from the cardioplegia exchanger, and a second pump receives and pumps selectively the blood oxygenator heat exchange liquid within the blood oxygenator circulation channel, to and from the blood oxygenator exchanger. A cardioplegia heater unit is thermally and fluidly coupled to the cardioplegia circulation channel and comprises a first plurality of independently actuatable heating elements, each having a respective power consumption. A blood oxygenator heater unit is thermally and fluidly coupled to the blood oxygenator circulation channel and comprises a second plurality of independently actuatable heating elements, each having a respective power consumption. A cooling reservoir is also thermally and fluidly coupled selectably to the cardioplegia circulation channel and the blood oxygenator circulation channel, the cooling reservoir further comprising a refrigerant system comprising a coolant compressor and a coolant coil.

[0009] One or more mixing valves are positioned within the cardioplegia circulation channel to direct selectively the first heat exchange liquid from either a heater unit, which can be either a reservoir heater unit or an inline heater unit, or a cooling unit, which can be either a reservoir cooling unit or an inline cooling unit, or a combination or mixture thereof, to the cardioplegia heat exchanger. And one or more mixing valves are positioned within the blood oxygenator circulation channel to direct selectively the blood oxygenator heat exchange liquid from either a blood oxygenator heater unit, which can be either a reservoir heater unit or an inline heater unit, or a cooling unit, which can be either a reservoir cooling unit or an inline cooling unit, or a combination or mixture thereof, to the blood oxygenator heat exchanger.

[0010] A controller can be programmed to selectably actuate the first and second pumps, the one or more mixing valves in the cardioplegia circulation channel, the one or more mixing valves in the blood oxygenator circulation channel, the first plurality of heating elements, the second plurality of heating elements, and the coolant compressor, to selectably and

independently heat or cool the cardioplegia and blood oxygenator heat exchange liquids, while maintaining a power draw of all activated pumps, heating elements, coolant compressor, and control system to a value within a maximum electrical power limit of the electrical convenience (mains) outlet.

[0011] In a further aspect of the invention, the controller can be configured with programming to set a priority of operation by, and therefore of current draw to, the individual powered devices of the system, including as between the cardioplegia heater unit, the blood oxygenator heater unit, and the coolant compressor. In one such aspect, the cardioplegia heating unit of the cardioplegia circulation channel has a top priority, the blood oxygenator heating unit of the blood oxygenator circulation channel has a second priority, and the coolant compressor has a third priority. During operation, whenever the cardioplegia heating unit of the cardioplegia circulation channel is not powered, and there is a demand for cardioplegia heating, then the cardioplegia heating unit will be activated and powered, and the coolant compressor, if presently being powered, will be shut off, and will remain off, and the blood oxygenator heating unit of the blood oxygenator circulation channel, if presently being powered, will shut off as determined by the controller. The determination by the controller is based on programming that determines if the additional current draw that would accompany the activation of the blood oxygenator heater would likely cause an over-drawing of electrical current through the electrical convenience (mains) outlet, resulting in a tripped circuit breaker and loss of power. The current drawn by the cardioplegia heater can include two or more individual heater elements or a single heater element, either or both heaters drawing independently a current draw amount of less than 100%, and up to the maximum current draw.

[0012] In an aspect of the invention, the controller unit is configured to not operate, or to shut off, the coolant compressor unit, whenever both the cardioplegia heater and the blood oxygenator heater are set for “heating”, or when either of the cardioplegia heater or the blood oxygenator heater is set for “heating” at proximate their maximum operating current draw capacity.

[0013] In another aspect of the invention, the controller unit is configured to operate the compressor unit when cooling capacity in the cooling reservoir is needed, provided that the current drawn by the compressor unit will not result in the system exceeding a maximum

electrical current target for the convenience (mains) outlet. Cooling capacity in the cooling reservoir is needed when the amount of ice formed within the cooling reservoir is not at full capacity. When the cooling reservoir at full capacity, then the coolant compressor does not need to operate. The controller unit can also be configured to halt or suspend operation of the compressor unit when a sufficient quantity of ice has formed onto and around the coolant coil, and full capacity is achieved, either by powering off the compressor unit manually, or automatically upon detection of the sufficient quantity of ice in the cooling reservoir, using a temperature sensor.

[0014] In another aspect of the invention, whenever the water within the reservoir of the cardioplegia heater is at an actual temperature (temperature Tactual) below a cardioplegic target temperature or temperature range (temperature Target), typically of about 60°C, the cardioplegia heater elements will be powered with electrical current, in order to heat the water within the reservoir of the cardioplegia heater to or toward the target temperature Ttarget, drawing more or less power depending on the operation settings for the cardioplegia circulation channel and the blood oxygenator circulation channel, and on any power drawn by the blood oxygenator heater and/or the cooling compressor unit.

[0015] The water in the blood oxygenator circulation channel is heated on demand, and the blood oxygenator heater is powered only when heating is required and when the blood oxygenator circulation channel is enabled to flow.

[0016] In an embodiment of the invention, while the water within the reservoir of the cardioplegia heater is at or within the target range temperature Ttar et, the cooling compressor of the refrigerant system is configured to operate when insufficient cooling capacity is available, identified by an insufficient amount of ice in the cooling unit reservoir. However, when electrical current is being drawn, or will need to be drawn, to power the cardioplegia heater, the cooling compressor unit is turned off or disabled for operation if the operation of the coolant compressor unit would result in exceeding the maximum electrical current target for the convenience (mains) outlet.

[0017] The water in the blood oxygenator circulation channel is heated on demand, and the blood oxygenator heater can only be powered with the blood oxygenator circulation channel set for “heating”. The water within the blood oxygenator circulation channel is heated on

demand, and the blood oxygenator heater is powered only when the blood oxygenator circulation channel is “heating”.

[0018] In another aspect of the invention, the controller can be configured and selected to operate the dual channel heating and cooling system in full automatic mode. In an alternative embodiment, the controller can be configured and selected to operate the dual channel heating and cooling system in an automatic mode with a user-selectable override. In an alternative embodiment, the controller can be configured and selected to operate only the blood oxygenator circulation channel in an automatic mode with a user-selectable override. In another alternative embodiment, the controller can be configured and selected to operate one of the dual channels in an automatic mode, with or without a user-selectable override, and the other of the dual channels in a manual mode. For a non-limiting example, the blood oxygenator circulation channel is operated in an automatic mode, while the cardioplegia circulation channel is operated in a manual mode.

[0019] In another embodiment of the present invention, a water heating device includes a UV lamp, and a system and method for disinfecting a supply of water contained within a water circulation channel during a non-surgical time period. The water heating device includes a closed elongated container having an inlet end having a water inlet port, and an outlet end having a water outlet port, a flow pathway for a supply of water flowing from the water inlet port to the water outlet port, and a UV lamp contained within the water heating device and configured to emit UV light along the flow pathway. The UV lamp is positioned so that the emissions from the lamp illuminate the mass of water contained within the water heating device. Reflectors and other means for directing and focusing the light output of the UV lamp within the water heating device can be employed. The UV lamp and socket can be isolated electrically from the liquid volume of the water heating device by well-known means. The UV lamp and socket are also configured for control by the controller and its programming. In one non-limiting example, the controller can require a user of the dual-channel heating and cooling apparatus to make a manual selection acknowledging that the UV-connected water heating device is not connected to a water heating and cooling system that is connected to a patient, and until the acknowledgement is made, the UV lamp is incapable of being electrically energized. In an alternative embodiment, the controller can operate in an automatic mode that electrically energizes the UV lamp when the UV-connected water heating device is in fact connected to a water heating and cooling system that is connected to a patient, or may permit a user of the dual-channel heating and cooling apparatus to make a manual selection acknowledging that the UV-connected water heating device is in fact connected to a water heating and cooling system that is connected to a patient, and the UV lamp is capable of being electrically energized. The UV lamp and socket can also include a breaker switch to mechanically isolate them from an electrical supply, to completely prevent any electrical interaction between the UV lamp and socket, and a patient.

[0020] In various embodiments, an additional safety feature can include a water leakage detector device for detecting a water leak in the housing of the UV lamp. In various embodiments, when a water leak occurs and the water leakage detector is activated, the power to the UV lamp is shut off and an alarm signal is activated. In other embodiments, when a water leak occurs and the water leakage detector is activated, the power to the entire dual-channel, heating and cooling apparatus is shut off.

[0021] The present invention also provides a method for sanitizing the water in the water system of a dual-channel, heating and cooling apparatus, while the apparatus is not connected to a patient during a surgical procedure, comprising the steps of: 1) re-circulating a supply of water in a first circulation channel including a water heating device and at least one of a cardioplegia heat exchanger circuit and a patient heat exchanger circuit; 2) heating the re-circulating supply of water with the water heating device to an elevated temperature to facilitate optimum sanitization of the at least one circuit, 3) irradiating the supply of water at the elevated temperature with UV light from a UV lamp positioned in a portion of the first circulation channel within a flow pathway of the mass of water being re-circulated through the first circulation channel, and 4) re circulating the UV irradiated supply of water through the first circulation channel, for a period of time sufficient to reduce or destroy bacteria within the re-circulating supply of water. The irradiating with UV light is typically provided within the cardioplegia heating reservoir. The method further includes re-circulating the supply of water through a cooling water reservoir in fluid communication with the first circulation channel. In an aspect of the invention, an elevated temperature of the water that facilitates optimum sanitization is up to and including 41°C, such as about 41°C.

[0022] The present invention includes a cooling water reservoir that includes a container having a floor and a sidewall, a series of coolant coils secured within the reservoir and in coolant communication with a refrigerant system comprising a coolant compressor. In an embodiment of the invention, the cooling unit comprises a cooling tank having an insulated wall and a floor, and a refrigerant coil. In a non-limiting embodiment, the refrigerant coil comprises a plurality of tubing segments connected in fluid communication in series, including a plurality of spaced-apart vertically-orients straight tube segments connected in series to an adjacent straight tube segment by a connecting tube segment, where the plurality of straight tube segments are spaced in plan view along the floor to optimize uniform spacing of the straight tube segments from one another and within the reservoir space. The refrigerant coil includes an inlet end connected to the output of the refrigerant system, and an outlet end that connects to the inlet of the refrigerant system. Preferably also the straight tube segments and connecting tube segments are placed away from the sidewalls by a distance sufficient to allow water to flow along the sidewall. The uniform spacing of the straight tube segments maximizes the transfer of heat between the recirculating refrigerant water contained within the tank to a layer of ice that builds-up on the outer surface of, and between, the plurality of straight tube segments.

[0023] In alternative embodiments, the refrigerant coil can comprise a plurality of horizontally-oriented or diagonally-oriented straight tube segments, joined in series by a plurality of connecting tube segments. In other alternative embodiments, the refrigerant coil can include a combination of straight or curved segments, in various combinations of vertical or horizontal orientations. In other alternative embodiments, the colling coil can include one or more helical coils, with a first outer helical coil of a first diameter, and one or more inner helical coils of a second smaller diameter.

[0024] A preferred arrangements of refrigerant coil segments provides substantially equal spacing between segments to optimize liquid flow across all surfaces of the refrigerant coil, or across a layer of ice that has built up on the outside surface of the refrigerant coil, and avoids dead pools of water which may allow for the buildup of excessively-thick layers of ice on the coil segments within the pool.

[0025] In a further aspect of the invention, the cooling unit further includes a thermometer probe, extending from the insulated wall into the volume of the cooling tank, and into a space proximate a center of a gap between at least two adjacent straight tube segments of the refrigerant coil, the thermometer probe including a sensor configured to detect both a

temperature of the water within the cooling reservoir, and a temperature of a thickened layer of ice formed on each of said outside surfaces of, and temperatures therebetween, for determining when the thickened layers of ice are proximate to bridging the gap, and optionally configured to provide a control signal to unpower the coolant compressor to stop the further formation and thickening of the layers of ice.

[0026] In an aspect of the invention, a booster pump recirculates the cooling water within the cooling tank around the outside surfaces of the lengths of the refrigerated refrigerant coil and across the surface of ice formed on the coils, to maximize cooling of the cooling water that is being pumped out of the cooling tank to the cooling exchangers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic/block diagram of the dual-channel heating and cooling system of the present invention in conjunction with a perfusion system.

[0028] FIG. 2 illustrates a partially cut-away view of the cooling water reservoir showing an arrangement of refrigerant coils within the cooling water reservoir.

[0029] FIG. 3 illustrates a plan view of the refrigerant coils arranged within the cooling water reservoir.

[0030] FIG. 4 illustrates a decision chart for determining when the cardioplegia heating elements and the cooling unit compressor are programmed to operate or to not operate

DETAILED DESCRIPTION OF THE INVENTION

[0031] The dual-channel heating and cooling apparatus of the invention provides both heating and cooling, including ice-making, for two distinct circulation channels: a cardioplegia (heart) liquid circulation channel and a blood oxygenator (whole body) liquid circulation channel.

[0032] The entire system is portably mounted and configured to be powered by a single mains power outlet. The system is controlled to provide refrigeration and/or ice making using available electrical current available beyond any instant electrical current supplied for heating, and up to a maximum electrical current available. As an example, for a typical 120 volt, 20 amp mains circuit, the maximum continuous electrical current draw is typically about 16 amps, while a short-term or “instantaneous” draw can be up to 18 amps.

[0033] Each circulating system is heated using separate blood heating units, including a cardioplegia heating unit and a blood oxygenator heating unit, and are cooled using a common cooling unit. Each system also uses controllable three-way flow valves to bypass a portion of the recirculating heat exchange liquid through either (or both) the respective heating unit or the cooling unit.

Cardioplegia Heating and Cooling

[0034] On the cardioplegia side, a pump 22 circulates water, as a heat exchange liquid, in through the water-side of a cardioplegia heat exchanger 20, with the cardioplegia solution and/or blood of the patient passing into and out from the cardio-side of the exchanger 20. The water exiting the exchanger 20 through line 21 passes through at least one or both of a cardioplegia heating reservoir 24 having one or more variably-controllable heating elements 25, and a common cooling unit 60, employing a first 3-way mixing valve 28, a second 3-way mixing valve 32, and various by-pass and connection piping lines as described below, and back to the inlet end of the pump 22. All flow to the inlet side of the pump 22 is delivered through a first 3-way mixing valve 28. In this example Pump 22 draws a current amount denoted II. In this example, a typical maximum current II is about 1 amp.

[0035] The first 3-way mixing valve 28 is also referred to as the cooling selection valve. The mixing valve 28 has a first inlet port 29 and second inlet port 30. A control unit has a setting position of “X” having a position value between 0 and 100, representing the proportion or percentage of flow through first inlet port 29, and provides for 100% flow through first inlet port 29, 100% flow through second inlet port 30, or a mixture of flows through both the first inlet port 29 and the second inlet port 30 that sum to 100%. The first inlet port 29 is fluidly connected directly to the common cooling unit 60 through feed line 27, where cooling water is typically at 0-4°C. The second inlet port 30 of the first 3 -way mixing valve 28 receives flow through line 31 from the outflow of a second 3-way mixing valve 32. The drawing of liquid into the pump 22 draws the liquid upstream into the 3 -way mixing valve 28, and as applicable into the second 3-way mixing valve 32.

[0036] The second 3-way mixing valve 32 is referred to as the heating selection valve. The second 3-way mixing valve 32 has a first inlet port 33 is fluidly connected directly to the cardioplegia heat exchanger 20 through feed line 35, and a second inlet port 34 that receives flow through bypass line 36 from the return 26. The control unit of second 3 -way mixing valve 28 has a setting position of “Y” having a position value between 0 and 100, representing the proportion or percentage of flow through first inlet port 33, and provides for 100% flow through first inlet port 33, 100% flow through second inlet port 34, and a mixture of flows through both the first inlet port 33 and the second inlet port 34 that sum to 100%.

[0037] In one aspect of the invention, either first inlet port 29 of mixing valve 28 is completely closed (0% flow, X=0), or first inlet port 33 of mixing valve 32 is completely closed (0% flow, Y=0), or both are closed, since it will rarely, if ever, require that returning water from the cardioplegia heat exchanger 20 will require both heated liquid from heater reservoir 24 and cooling liquid from in common cooling unit 60. The inflow to pump 22 consists of the sum of flow (1) through line 27 from the cooling unit 60, (2) through line 35 from cardioplegia heater reservoir 24, and (3) through by-pass line 36.

[0038] If the required temperature T1 of the water to be pumped to the cardioplegia heat exchange 20 is higher than the temperature T2 of the water being returned from the cardioplegia heat exchanger 20, such that heating of the water is required, then the settings are X=0, and Y= up to 100, and the flow through pump 22 is up to 100% through heat line 35 at a liquid temperature of T3, and the remainder through by-pass line 36 at a liquid temperature of T2. In an aspect of the invention, 100% of the flow passes through the cardioplegia heating reservoir 24 and heat line 35, and control of the amount of heat to achieve the target water temperature T1 is the electrical current passing 16 passing through the cardioplegia heating element(s) 25. In this feature of the invention, the cardioplegia heat exchanger 20 provides complete, on-demand heating requirements for the cardioplegia circulation channel. To provide maximum heating of the water returned to the exchanger 20, X=0 and Y=100, directing 100% of the water flow through cardioplegia heat exchanger 20.

[0039] In another aspect of the invention, control of the temperature T1 of the water to be pumped to the cardioplegia heat exchange 20 can be provided by mixing less than 100% of the water flow passing through the cardioplegia heat exchanger 20 and through first port 33 of

mixing valve 32, and the remaining water flow passing through the bypass line 26 and through the second port 34. The controller can maintain the required temperature T1 of the water by adjusting the mixture of the hotter water from the cardioplegia heat exchanger 20, with the less-hot water returning through bypass line 36 from the return line 26 at temperature T2.

[0040] Controller 10 adjusts the positions of the 3 -way valves 28 and 32, and the electrical current passed to the cardioplegia heating element(s) 25, based on feedback signals from the temperature sensors, using well-known temperature control principles.

[0041] When cooling water is required in the cardioplegia heat exchanger 20 for reducing the heating temperature of, or cooling the temperature of, the cardio blood, then the settings are X is up to 100, and Y=0. The water flow through pump 22 is up to 100% through cooling supply line 27 at a liquid temperature of T4 and the remaining through by-pass line 36 at a liquid temperature of T2. To provide maximum cooling of the water returned to the exchanger 20, X=100, and all the flow through pump 22 is supplied through cooling supply line 27 at a liquid temperature of T4.

[0042] A non-limiting example of a water pump is a centrifugal pump that delivers up to 15 L/min of water towards its fully loaded condition, to maintain a constant flow rate under normal use conditions, typically drawing a maximum of about 1 amp.

Blood oxygenator-side Heating and Cooling

[0043] On the blood oxygenator side, a pump 42 circulates water in through the water side of a blood oxygenator heat exchanger 40, with the blood of the patient passing into and out from the blood-side of the exchanger 40. A portion of the pump 42 output can also pass through a heating blanket in contact with the patient’s skin. The water exiting the exchanger 40 through line 41 passes selectively through a blood oxygenator heating unit 44 having one or more variably controlled heating elements 45, and/or the common cooling unit 60, via a blood oxygenator -side 3 -way mixing valve 48, with various by-pass and connection piping lines as described below, and back to the inlet end of the pump 42. All flow to the inlet side of the pump 42 is delivered through the 3-way mixing valve 48. Pump 42 draws a current amount denoted 12. In this example, the typical maximum current 12 is about 1 amp.

[0044] The blood oxygenator-side mixing valve 48 has a first inlet port 49 and second inlet port 50. The control unit provides for either 100% flow through first inlet port 49 from line 47 connected directly to the common cooling unit 60 at a liquid temperature of T4, 100% flow through second inlet port 50 from lines 43 and 46 connected to the blood oxygenator heating unit 44 at a liquid temperature of T7, or a mixture of flow through both the first inlet port 49 and the second inlet port 50 that sums to 100% at a liquid temperature between T4 and T7. The liquid flow rate through the line 47 and first inlet port 49 draws a liquid flow through line 46 that bypasses the blood oxygenator heating elements 45, and through line 43 of heated water from the blood oxygenator heater unit 44. The 3-way mixing valve 48 has a setting position of Z having a value between 0 and 100, representing the flow amount or portion through first inlet port 49.

[0045] To provide maximum heating of the water returned to the blood oxygenator heat exchanger 40, Z=0 (no flow through the cooling unit 60), and all of the flow through pump 42 is brought from the blood oxygenator heating unit 44 through line 43,46 at a liquid temperature of T7, through second inlet port 50 of the 3-way mixing valve 48. The blood oxygenator heating unit 44 is an in-line, on-demand heating unit, which provides very little reservoir capacity for heated water. Essentially 100% of the heating of the water being used to heat the water pumped to and circulated through blood oxygenator heat exchanger 40 is provided instantaneously by the blood oxygenator heating unit 44.

[0046] To provide cooling of the water coming from and being returned to the blood oxygenator heat exchanger 40, the mixing valve 48 is positioned with Z up to 100, and the flow through pump 42 is brought from the common cooling unit 60 through line 47 at a liquid temperature of T4, and through first inlet port 49 of the 3-way mixing valve 48. When providing cooling, all of the return water flow passes through the un-powered blood oxygenator heater unit 44 with the on-demand heater elements 44 are turned or powered off. The inflow to pump 42 is the water flow drawn through the 3-way mixing valve 48 at a setting Z of up to 100, and consists of the sum of flow (1) through line 47 from the cooling unit 60 consisting of cold water at a liquid temperature of T4, and (2) through line 46 from return line 43 at liquid temperature of T7. As needed, a mixture of the cold water from the cooling unit 60 and the return water from the blood oxygenator heater unit 44 can be used to achieve the required temperature T5 of the water to be pumped to the blood oxygenator heat exchange 40.

[0047] In various embodiments of the invention, the control system can provide for gradient control of the temperature of the liquid passing through the blood-oxygenator heat exchanger, which will allows or enables only a maximum temperature differential of the liquid relative to the patient temperature. A gradient control feature warms or cools at a rate less than standard maximum. For example, if the patient temperature is 24°C and water at 41°C is provided, there is significant temperature difference (about 17°C) between the patient temperature and the warming temperature. In various embodiments, the temperature of the warming water passing into the blood-oxygenator heat exchanger is controlled to provide a smaller temperature differential with the patient temperature. In an example, a controlled or gradient temperature differential is used, and the warming liquid passing through the blood-oxygenator heat exchanger would be to 32°C (8°C above the patient temperature of 24°C. As the patient’s temperature warms, the temperature of the warming liquid is increased to maintain the gradient temperature difference, up to the maximum water temperature, for example, 41°C. In a similar manner, a gradient temperature differential can be used when cooling a patient, such that the cooling water passing into the blood-oxygenator heat exchanger is no greater than, for example, 8°C below the patient temperature. For example, cooling a patient with a patient temperature of 37 °C blood temperature would control the cooling water temperature to no less than 29°C (the gradient temperature difference of 8°C below the patient temperature. The gradient temperature differential can be a selectable range of from FC to 15°C, in temperature increments between about 0.5°C to 2°C, for example 0.5°C or 1°C.

Heating Units

[0048] Heating provided in the cardioplegia heating unit 24 uses one or more electrical resistance heating coils powered by the current delivered from the mains outlet, drawing a current amount denoted 13. The cardioplegia heating unit 24 includes a reservoir of heated water, and heating of the water in the reservoir is performed, and current consumed, in order to maintain the water in the respective reservoir at an elevated temperature. Typically the temperature of the liquid in the cardio heating reservoir 24 is maintained at the elevated temperature range, between 45-60°C. The reservoir volume of the cardioplegia heating unit 24 is typically between about 1 liter and 10 liters. The cardio heating unit 24 draws a current amount denoted 13, which can include two heating elements 25 having variable control, with a maximum current draw in this example of 5.2 amps each (10.4 amps total).

[0049] The blood oxygenator heating unit 44 includes a small-volume reservoir for water and one or more heating elements 45 for heating the returning water sufficiently to raise the water temperature to a target temperature, typically up to about 41 °C. The reservoir volume of the blood oxygenator heating unit 44 is typically less than about 0.7 liters. The blood oxygenator heating unit 44 draws a current amount denoted 14, which can include two or more heating elements having variable control, with a maximum current draw in this example of 5.2 amps each (10.4 amps total).

[0050] Typically, the blood oxygenator heating unit 44 is not powered in order to achieve specific temperature for the blood oxygenator liquid passing into the blood oxygenator heat exchanger 40. Rather, the target to which the heating by the blood oxygenator heating unit 44 is controlled is the patient temperature, and more specifically the patient blood temperature that flows on the blood-side of the oxygenator heat exchanger 40. The exception is the use of gradient heating control, discussed hereinabove, wherein a maximum temperature differential of the liquid relative to the patient temperature is maintained and controlled.

Cooling Unit

[0051] Cooling from the cooling unit 60 can be provided by a combination of an initial charge of ice into the reservoir 62, and an internal refrigerant coil 68 that is cooled by an on board refrigerant system comprising a compressor unit 66. The compressor unit 66 draws a current amount denoted 15, which is typically a consistent 6 amps.

[0052] Figures 2 and 3 illustrate a cooling unit 60 comprising a tank 160 having an insulated wall 161 and a floor 162. The refrigerant coil 68 is attached to the floor 162 through an inlet fitting 163 and an outlet fitting 164. The refrigerant coil 68 comprises a plurality of tube segments 165, vertically-oriented straight tube segments 166 connected in a series alternately by a plurality of bottom connector tube segments 168, which connect the bottom ends of a first and second successive straight tube segments 166, and by a plurality of top connector tube segments 169, which connect the top ends of the second straight tube segment 166 and a third successive straight tube segment 166. The plurality of tube segments 165, and particularly the series of vertically-oriented straight tube segments 166, are spaced across the area of the floor 162 to provide substantially uniform spacing of the straight tube segments 166 from one another. The uniform spacing of the straight tube segments 166, and the corresponding bottom connector tube segments 168 and top connector tube segments 169, optimizes and maximizes the exposure of the circulating cooling water contained within the cooling tank 160 to the outside surface area of the tube segments, and to the thick layer of ice that builds up on the outer surface of, and between, the tube segments 165, to maximize the transfer of heat from and cooling of the circulating cooling water to the refrigerant system.

[0053] Circulating water from either the cardioplegia circulation channel or the blood oxygenator circulation channel passes independently into the cooling tank 160, from the blood oxygenator circulation channel through a water inlet port 172 extending through the tank wall 161, vertically above the refrigerant coil 68 and near the top end of the cooling tank 160 and from the cardioplegia circulation channel through a water inlet port 174 extending through the tank wall 161, vertically above the refrigerant coil 68 and near the top end of the cooling tank 160. Chilled or cooled circulating water passes out of the cooling tank 160, to the blood oxygenator circulation channel through a water outlet port 173, vertically at the level of the refrigerant coil 68 and near the floor 162 of the tank cooling 160, and to the cardioplegia circulation channel through a water outlet port 175, vertically at the level of the refrigerant coil 68 and near the floor 162 of the tank cooling 160. The inlet ports 172 and 174 are oriented to provide entry of the respective circulating water in a tangential direction along the inside surface of the wall 161, while water outlet ports 173 and 175 are oriented to provide an exit for the cooled recirculating water. In various embodiments, the cooled recirculating water exits in the same tangential direction, causing movement of the cooling water in a swirling pattern (clockwise or counterclockwise direction) around and through the refrigerant coil 68, to optimize cooling.

[0054] The cooling unit 60 can further include a sensor for detecting the temperature of the cooling liquid within the cooling tank 160. One or more thermometer probe 176 (one is illustrated in Figure 2), which includes a temperature sensor, can be disposed to extend from the insulated wall into the volume of the cooling tank, for example, into a space proximate a center of a gap between at least two adjacent tube segments, for example, vertical straight tube 166,167 of the refrigerant coil 68. In various embodiments, the thermometer probe 176 includes a sensor having multiple temperature detection points (not shown) along its length, The sensor of the thermometer probe 176 can detect the temperature at multiple positions along the length, of the contents within the reservoir of the cooling tank 160 and between the tube segments of the

refrigerant coil 68, the contents consisting of either the circulating cooling water and the ice formed by the refrigerant unit. The sensitivity of the sensor can detect, at any of the detection points, the temperature change between just above 0°C, before water turns to ice or after ice has melted to water, and at or just below 0°C, after the ice has formed. If the ice forming on the tube segments, for example, the straight tube segments 166,167, bridges across and forms a solid block of ice, the sensor in the thermometer probe 176 can detect a temperature of the block of ice at one or more of the detection points. A plurality of thermometer probes can be used to detect the temperature of the contents at various points in space, between the tube segments of the refrigerant coil, within the reservoir of the cooling tank 160. The controller can also be configured to detect the temperature signals of each of the temperature detection points along the length of the thermometer probe 176. When all of the detection points in the thermometer probe 176 detect a temperature at or below freezing (0°C), an indication is made of the formation of a block of ice around the coil segments of the cooling coil, indicating that a sufficient quantity of ice has been formed, and can provide a control signal to unpower the coolant compressor 66, to stop or prevent operation of the coolant compressor unit when a block of ice has formed around the coolant coil 68.

[0055] A booster flow pump 64 (Figure 1) is also provided to recirculate the cooling liquid from within the cooling tank 160 through port 183, through the booster flow pump 64, and back into the cooling tank 160 through port 182. The inflow of cooling water circulates around the outside of and through the refrigerant coil 68 to maximize cooling of the cooling water that is being pumped out of the cooling tank to the cooling exchangers 20,40. The booster flow pump 64 draws a current amount denoted 16. The booster flow pump 64 can rapidly decrease the temperature T4 of the liquid within the cooling unit 60 by intimately circulating the water around the ice and chilled refrigerant coil 68 within the reservoir 62 (Fig. 1).

Current Control Unit

[0056] The system also includes an electrical power control system including a controller with programming for executing one or more priority rules for controlling and limiting power, and thereby the drawing of current, to either the refrigeration/ice making unit and/or to the heating units, depending upon the surgical and patient needs. The control unit monitors the temperature of the liquid pumped through the cardioplegia and blood oxygenator heat

exchangers, and controls the operation of the heaters and refrigerant system, as well as the positioning of the three-way valves within the circulating system, to maintain the actual current draw from the mains outlet to less than the maximum allowable.

[0057] The powered units that draw current from the mains outlet include the cardioplegia pump 22 (current II), the blood oxygenator pump 42 (current 12), the cardioplegia heater 25 (current 13), the blood oxygenator heater unit 44 (current 14), the compressor unit 66 (current 15), and the booster flow pump 64 (current 16) and the controls systems. The units drawing the most current are the cardioplegia heater 24 (current 13), the blood oxygenator heater unit 44 (current 14), the compressor unit 66 (current 15), and therefore the controller and the priority rules are directed to limiting at least one, or two, of the three powered units in order to prevent the system from drawing more than a maximum continuous current draw, and a maximum in rush current draw, which would result in the tripping of the circuit breaker protecting the mains unit into which the system has been plugged.

[0058] In one aspect of the invention, the cardioplegia heater 24 has current drawing priority over both the blood oxygenator heater unit 44 and the compressor unit 66. The compressor unit 66 is configured to not operate, and will not refrigerate and/or form ice in situ within the cooling reservoir, whenever both the cardioplegia heater 24 and the blood oxygenator heater unit 44 are “Heating”, or when either of the cardioplegia heater 24 or the blood oxygenator heater unit 44 is “Heating” at near maximum current capacity. The cardioplegia heater 24 or the blood oxygenator heater unit 44 are each configured to draw about 10.4 amps at maximum power draw. Consequently, when both the cardioplegia heater 24 or the blood oxygenator heater unit 44 are “heating”, their respective current draws are within a range of about 15-60%, and together do not exceed 100% combined, or not more than 10.4 amps combined.

[0059] Nevertheless, in another aspect of the invention, the controller is configured to cause the compressor unit 66 to operate (drawing about a steady 6 amps) to refrigerate and/or form ice in situ within the cooling reservoir, provided that the current 16 drawn by the compressor unit 66 will not result in all units exceeding a maximum electrical current.

[0060] In some embodiments of the present invention, simultaneous operation of all of the heating elements, compressor unit, pumps, instruments and controller will draw a total

operating current that is in excess of the maximum amperage capacity of a mains power supply available to the dual-channel, heating and cooling apparatus.

[0061] Figure 4 illustrates a decision chart for determining when the cardioplegia heating elements, the blood oxygenator heating elements, and the cooling unit compressor are programmed to operate or to not operate. For the cardioplegia heater unit 24, the temperature T3 of the cardioplegia liquid within the cardioplegia heater unit 24 is monitored continuously and a determination is made of whether the temperature T3 is either (i) within the target range (cardioplegic target temperature range B), or (ii) below the target range. If the temperature T3 of the cardioplegia liquid within the cardioplegia heater unit is within the target range, the cardioplegia heating element(s) 25 are not powered on. If the temperature T3 of the cardioplegia liquid within the cardioplegia heater unit is below the target range, the cardioplegia heating element(s) 25 are powered on. Depending upon the difference between the monitored temperature T3 and the cardioplegic target temperature range B, either or both of the cardioplegia heating element(s) 25 are powered on to a power level up to full power. The powering of the cardioplegia heating element(s) 25 to heat and raise the temperature of the cardioplegia liquid within the cardioplegia heater unit 24 is typically given top priority.

[0062] Figure 4 also illustrates, for the blood oxygenator heater unit 44, the temperature T5 of the blood oxygenator liquid entering the blood oxygenator heater exchanger 40 is monitored continuously and a determination is made of whether the temperature T5 is either (i) within a blood oxygenator target temperature range for heating, or (ii) below the blood oxygenator target temperature range for heating. If the temperature T5 of the blood oxygenator liquid entering the blood oxygenator heater exchanger 40 is within the target range for heating, or if the blood oxygenator heater unit 44 is not heating, the blood oxygenator heating element(s) 45 are powered off. If the temperature T5 of the blood oxygenator liquid entering the blood oxygenator heater exchanger 40 is below the blood oxygenator target temperature range for heating, the blood oxygenator heating element(s) 45 are powered on, either at full power or at a partial power. Depending upon the difference between the monitored temperature T5 and the blood oxygenator target temperature range, one or both of the blood oxygenator heating element(s) 45 are powered on to a power level, up to full power. The powering of the blood oxygenator heating element(s) 45 to heat and raise the temperature of the liquid entering the blood oxygenator heater exchanger 40 to the blood oxygenator target temperature range for

heating is typically given second priority, below the cardioplegia heater unit 24 and above the cooling compressor.

[0063] Figure 4 also illustrates, for the cooling unit 60, the temperature T4 within the cooling unit 60 is monitored continuously and a determination is made, based on the temperature(s) T3, of the ice quantity capacity of the cooling reservoir 62. The temperature(s) T3 detected within the cooling reservoir 62 can determine whether the quantity of ice or of an ice block with the reservoir 62 is full (at full capacity), or low, which can be a quantity of ice less than a full quantity. If the quantity of ice or of an ice block within the reservoir 62 is full or at full capacity, the cooling unit compressor unit 66 is off, i.e., not powered on. If the quantity of ice or of an ice block within the reservoir 62 is low or below full capacity, a determination is made to power-on the compressor unit 66, or not.

[0064] Before the compressor unit 66 is powered on, a determination is made whether or not the cardioplegia heating element(s) 25 and/or blood oxygenator heating element(s) 45 are powered on; if the cardioplegia heating element(s) 25 and the blood oxygenator heating element(s) 45 are off, a determination is made that total amperage drawn by the system after the compressor unit 66 is powered will be below the maximum amperage rating; if the cardioplegia heating element(s) 25 and/or the blood oxygenator heating element(s) 45 are powered on, a determination is made, whether or not, that total amperage drawn by the system after the compressor unit 66, including the current drawn by the cardioplegia heating element(s) 25 and/or the blood oxygenator heating element(s) 45 exceeds the maximum amperage rating. If the maximum amperage rating of the system will be exceeded, then the cooling unit compressor unit 66 will not be powered on, and remains off. If the maximum amperage rating of the system will not be exceeded, then the cooling unit compressor unit 66 will be powered on and the making of ice around the refrigerant coils is resumed. In this latter scenario, either or both the cardioplegia heating element(s) 25 and the blood oxygenator heating element(s) 45 may be operating at a lower current draw level based on the heating requirements of the cardioplegia heater unit and the blood oxygenator heater unit.

[0065] In various embodiments, cardioplegia heating elements 25 can be controlled wherein if the cardioplegia heat exchanger circuit is not used for a prolonged period of time (by non-limiting example, over a weekend or even overnight), the cardioplegia heating elements 25

are controlled to off, until the cardioplegia heat exchanger circuit become active again. This feature minimizes wasted heating energy to maintain the system target temperature, and wear on the heater elements.

[0066] Finally, the control system can include a means for operating and controlling the compressor unit automatically, or to manually shut off or shut down the compressor unit. If the compressor unit 66 is operating to make ice, the operator or user of the system can manually shutoff the compressor unit, despite the control system having determined that the compressor unit may operate in the automatic mode. The means for operating and controlling the compressor unit can includes switch that can operate between an automatic position and an off position. In another embodiment, a dedicated shutoff button can be provided to override the automatic operation and control of, and shut off, the compressor unit.

[0067] It is understood that if the cooling unit compressor unit 66 is ever operating with the cardioplegia heating elements 25 off, and then powering will be required of the cardioplegia heating elements 25, either at full power or at partial power, a determination is made whether the resulting total amperage drawn by the entire system, with the heating elements 25 operating at full power or at partial power, will exceed the maximum amperage rating. In various embodiments, when the heating elements 25 are operated at partial power, the maximum amperage rating of the system may not be exceeded. If the maximum amperage rating will be exceeded, the compressor unit 66 is immediately shut off, before the cardioplegia heating elements 25 are powered on.

[0068] In one example typical component maximum current draw, in amps, are

[0069] 1. Cardioplegia heater(s) 25 - up to 10.4 amps (two elements of 5.2 amps each, variably controlled);

[0070] 2. Oxygenator heater(s) 45 - up to 10.4 amps (two elements of 5.2 amps each, variably controlled);

[0071] 3. Cooling compressor 66 - 6 amps;

[0072] 4. Cardioplegia pump 22 - 1-1.5 amp;

[0073] 5. Oxygenator pump 42 - 1-1.5 amp;

[0074] 6. Booster pump 64 - 1-1.5 amp; and

[0075] 7. Miscellaneous: controllers, relays, sensor, instruments, and display - 0-3 amps.