Blood Pump and Oxygenator Monitor-Controller and Display Device

This invention relates generally to the art of extracorporeal blood pumping and oxygenation, and more particularly to the art of acquiring, processing, and displaying data for the purposes of providing information to the attending medical personnel of the condition of a patient and the operating characteristics of the blood pumping and oxygenating devices while at the same time automatically using the acquired and calculated data to accurately control the operation of the various sub-systems which make-up the entire extracorporeal blood pumping and oxygenating system.

At present such extracorporeal blood pumping and oxygenating systems are used almost exclusively in open heart surgical procedures where the normal blood flow through the heart and lungs of the patient is interrupted or bypassed. Even a relatively simple system contains several other devices in addition to the basic blood pump and oxygenator. It is essential for the well being of the patient that every device in the system functions perfectly and that any malfunction be detected and corrected as soon as possible. At present the operation of the devices in the system is monitored visually and controlled by the attending personnel. It is not now possible to continuously monitor, display, and use this data to automatically control the devices in the system. The invention makes it possible to continuously monitor, display and to use the acquired and calculated data to automatically optimize the control and operation of the extracorporeal blood pumping and oxygenating system.

At present there is no method or device available for the medical personnel to use to continuously determine the metabolic oxygen consumption of a patient undergoing a total cardio-pulmonary bypass procedure using an extracorporeal blood pumping and oxygenating system. Continuous knowledge of this physiologic parameter would be of great potential value to both the patient and the attending medical personnel. With the use of this invention, it becomes possible, for the first time, to continuously determine and display the metabolic oxygen consumption of a patient undergoing a total cardio-pulmonary bypass procedure.

It is, therefore, a primary object of this invention to provide a blood pump and oxygenator monitor-controller and display device.

It is another object of this invention to provide a blood pump and oxygenator monitor-controller and display device that will accept a plurality of input signals from devices used to monitor the medical conditions of a patient and/or the operating parameters of various devices in an extracorporeal blood pumping and oxygenating system.

It is another object of this invention to provide a blood pump and oxygenator monitor-controller that will display a plurality of measured and calculated input data.

It is another object of this invention to provide a blood pump and oxygenator monitor-controller and display device that utilizes a digital and/or analog computer to control the display of measured data and to use the measured data to calculate and then display additional data useful to the attending medical personnel.

It is another object of this invention to provide a blood pump and oxygenator monitor-controller and display device that will utilize the decision making capabilities of either dedicated circuitry and/or a computer to control and alter the operating characteristics of a plurality of devices attached to the controlling output ports of the computer.

It is yet another object of this invention to provide a blood pump and oxygenator monitor-controller that is economical to manufacture, durable of construction, efficient in use, and is accurate and precise in displaying measured data and controlling the operating parameters of various devices in the extracorporeal blood pumping and oxygenating system.

These objects and others are realized by the provision of a blood pump and oxygenator monitor-controller and display device. The blood pump and oxygenator monitor-controller and display device includes a plurality of input data communication ports and data and output control ports operably connected to decision making or computer circuitry for the purpose of interfacing input data transducers with the decision making or computer circuitry and for interfacing the decision making or computer circuitry through the data and output control ports to the data display units and the sub-systems to be controlled by the blood pump and oxygenator monitor-controller and display device, a plurality of digital and/or analog displays or controlling means responsive thereto for displaying measured and calculated data and/or for controlling the operation of various sub-systems of a blood pumping and oxygenating system.

These objects will become more readily apparent upon reference to the following detailed description, and especially when studied in conjunction with the appended drawings, wherein:

FIG. 1 is a block diagram of the preferred embodiment of the invention as applied to a generalized configuration of a blood pumping and oxygenating system.

With reference to FIG. 1, the preferred embodiment of a generalized blood pumping and oxygenating system similar to those currently used widely in medical practice may be seen as denoted generally by the numeral 10. More specifically, the preferred embodiment 10 includes the patient 11, a patient temperature transducer 12, a hemoglobin content transducer 13, an input oxygen saturation transducer 14, a combination blood oxygenator and heat exchanger 15, an oxygen flow meter with manual flow control valve 16, a 3-way valve 17, a heat exchanger water temperature transducer 18, a blood temperature transducer 19, an output oxygen saturation transducer 20, a blood pump 21, a blood flow rate transducer 22, a free gas bubble trap 23, a blood flow and free gas detector transducer 24, a 3-way flow diversion valve 25, a blood filter 26, a plurality of data communication ports 27, decision making or computer circuitry 28, a plurality of data and output control ports 29, a plurality of manual or external data entry ports 30, an extra fluid supply 31, a valve 32, the fluid transmission conduit or tubing denoted by solid lines connecting the sub-systems, and the monitoring, display, and controlling signal lines for the sub-systems denoted by dashed or broken lines. For the purpose of this disclosure, the preferred embodiment 10 of the apparatus and the operation thereof will be disclosed for accomplishing the teachings of the preferred embodiment 10.

The embodiment 10 as represented herein is for the realization of a generalized blood pumping and oxygenating system. It will be well understood by those skilled in the art that the principles taught herein may easily be contracted or expanded to produce a blood pump and oxygenator monitor-controller and display device able to monitor, display, and control fewer or more operating parameters and/or sub-systems.

Many of the sub-systems illustrated in the embodiment 10 are commercially available and widely used, therefore, the subject of the following description of the present invention is that of a blood pump and oxygenator monitor-controller and display device only.

For the purpose of describing the operation of the invention refer to embodiment 10 where the flow of blood from the patient through the various sub-systems and then back to the patient will be described. The purpose or operation of each sub-system will be described in sequence as the blood flow is traced from one sub-system to another thereby providing a complete understanding of the operation of the invention.

Blood requiring removal of carbon dioxide and the addition of oxygen flows through a hollow conduit or tube 33 and through the patient temperature transducer 12. The temperature transducer 12 may be of any suitable conventional type. The patient temperature transducer 12 produces an output signal proportional to the temperature of the patient's blood. This signal is then transmitted over the signal line 34 to input 3 of the data communication port 27. The blood then flows through the hemoglobin content transducer 13 which produces an output signal proportional to the total amount of hemoglobin in the blood. This signal is then routed over the signal line 35 to input 4 of the data communication port 27. Next, the blood flows through the input oxygen saturation transducer 14 which produces an output signal proportional to the percent of the total hemoglobin content which is saturated with oxygen. This signal is then routed over the signal line 36 to input 5 of the data communication port 27. The blood then flows through the combination blood oxygenator and heat exchanger 15 where it is oxygenated, has carbon dioxide removed, and is heated or cooled by contact with the heat exchanger unit. The heat exchanger may be built into the blood oxygenator 15 or may be a separate unit preceeding or following the blood oxygenator. Temperature regulated water from an external source enters the system through fluid conduit 70 and flows through the heat exchanger water temperature transducer 18 which produces an output signal proportional to the temperature of the water entering the system. This signal is then transmitted over the signal line 76 to input 7 of the data communication port 27. The water then flows through fluid conduit 37 and 3-way valve 17. The 3-way valve 17 is used to direct the flow of water either through the fluid heat exchanger conduit 38 and through the heat exchanger in the combination blood oxygenator and heat exchanger 15 or causes the water to be shunted or directed away from the combination blood oxygenator and heat exchanger 15 and through fluid conduit 39 which is operably connected to the return line 40 of the external water temperature controller. Oxygen enters the oxygen flow meter with manual flow control valve 16 through fluid conduit 41 and is delivered through fluid conduit 42 to the combination blood oxygenator and heat exchanger 15. Any excess gas delivered to the combination blood oxygenator and heat exchanger 15 is vented to the atmosphere through fluid conduit 43. In the event that extra fluid, which may or may not be blood, is needed for the patient, the valve 32, which is interposed in the fluid conduit 44 connecting the extra fluid supply 31 to the combination blood oxygenator and heat exchanger 15, may be opened to allow the extra fluid supply 31 to flow through fluid conduit 44, and valve 32 into the combination blood oxygenator and heat exchanger 15. Blood and/or fluid leaves the combination blood oxygenator and heat exchanger 15 through fluid conduit 45 and flows through the blood temperature transducer 19 which produces an output signal proportional to the temperature of the blood leaving the combination blood oxygenator and heat exchanger 15. This signal is then transmitted over the signal line 46 to input 6 of the data communication port 27. Blood next flows through fluid conduit 47 into the output oxygen saturation transducer 20 which produces an output signal proportional to the percent of the total hemoglobin content which is saturated with oxygen. This signal is then routed over the signal line 48 to input 8 of the data communication port 27. Blood leaves the output oxygen saturation transducer through fluid conduit 49 and flows into the blood pump 21. A signal representing the operating status of the blood pump 21 is transmitted over signal line 50 to input 9 of the data communication port 27. Operation of the blood pump 21 can be altered by control signals transmitted on the control line 71 which operably connected the blood pump 21 to one of the data and output control ports 29. Blood is pumped through fluid conduit 51 into the blood flow rate transducer 22 which produces a signal proportional to the blood flow rate through the extracorporeal circuit. This is then routed over signal line 52 to input 10 of the data communication port 27. The blood next flows through the fluid conduit 53 to the free gas bubble trap 23 where it is intended that all free gas bubbles which may be entraned in the flowing blood will be trapped and removed from the blood before the flow leaves the free gas bubble trap 23 through fluid conduit 54. The blood flow enters the blood flow and free gas detector transducer 24 which contains two sensing units. The first sensor determines whether the blood is sensed to be flowing or not flowing. If no blood flow is sensed, the blood flow and free gas detector transducer 24 produces a warning signal which is transmitted over the signal line 55 and is delivered to input 11 of the data communication port 27. The warning signal indicates to the system and medical personnel that the second sensing unit in the blood flow and free gas detection transducer 24 most likely would not be able to sense the presence of free gas in the blood flowing through it. If, however, free gas is detected in the blood flowing past the second sensor to the 3-way flow diversion valve 25 through fluid conduit 58, an alarm signal is delivered over signal line 56 to input 12 of the data communication port 27. At the same time, a control signal is delivered over control line 57 to the 3-way flow diversion valve 25 which causes the valve to immediately stop the flow of blood to the patient through fluid conduit 59 and redirects or diverts the blood flow through fluid conduit 60 and back to the output side of the combination blood oxygenator and heat exchanger 15 thereby preventing a life threatening gas embolism. When no more free gas is detected in the blood by the second sensor in the blood flow and free gas detector transducer 24 an appropriate signal is delivered over the signal line 56 to input 12 of the data communication port 27 thereby cancelling the previous alarm condition. At the same time, the control signal on the control line 57 which originated from the blood flow and free gas detector transducer is removed thereby causing the 3-way flow diversion valve 25 to stop the blood flow through fluid conduit 60 and to re-establish the blood flow to the patient through fluid conduit 59. Oxygenated blood is finally returned to the patient through the blood filter 26 and the fluid conduit 61.

Signals from the patient temperature transducer 12, hemoglobin content transducer 13, input oxygen saturation transducer 14, heat exchanger water temperature transducer 18, blood temperature transducer 19, output oxygen saturation transducer 20, blood pump 21, blood flow rate transducer 22, and the blood flow and free gas detector transducer 24 are all routed into the data communication ports 27. In addition, manual or external data entry unit 30 allows the operator to enter data and/or operating parameters through inputs 1 and 2 of the data communication port 27 over signal lines 62 and 63 respectively. The inputs directed through the data communication ports 27 are routed to the decision making or computer circuitry 28 where appropriate display and control signals are generated and delivered to the data and output control ports 29. The data and output control ports 29 provide the appropriate interfacing circuitry to implement the display and control functions desired.

The type of signal, analog and/or digital, provided by the data and output control ports 29 will depend upon what element or device is to be driven or caused to operate. To illustrate this point, examples will now be given of the types of signals which would be generated by the data and output control ports 29 and carried by output control lines 64, 65, 66 and 67 to each element or device being driven or caused to operate. It should be noted that the input data lines 34, 35, 36, 46, 76, 48, 50, 52, 55, and 56 as well as the output control lines 64, 65, 66, and 67 are depicted in schematic form in the preferred embodiment 10, and therefore, each of these input and output lines may be made up of a plurality of signal carrying lines. Consequently, the output control line 64 could drive a plurality of either digital and/or analog type display units. For illustration of the preferred embodiment 10, the output control line 64 would drive display units indicating the temperature of the patient as measured by the patient temperature transducer 12, the total hemoglobin content of the blood as measured by the hemoglobin content transducer 13, the percent of the total hemoglobin saturated with oxygen as measured by the input oxygen saturation transducer 14, the temperature of the water flowing into the heat exchanger as measured by the heat exchanger water temperature transducer 18, the temperature of the blood leaving the combination blood oxygenator and heat exchanger 15 as measured by the blood temperature transducer 19, the percent of the total hemoglobin content of the blood saturated with oxygen after the blood has been oxygenated as measured by the output oxygen saturation transducer 20, the volume flow of blood per unit of time as measured by the blood flow rate transducer 22, and the output status of the blood flow and free gas detector transducer 24 indicating whether or not blood flow was being detected and whether or not free gas in the flowing blood was detected. In addition to displaying the various detected and measured parameters, the blood pump and oxygenator monitor-controller and display device would also be able to derive and display such operating parameters as speed of the blood pump 21, and therefore, blood flow rate for comparison to the measured blood flow rate as detected by the blood flow rate transducer 22. Such comparisons would be made by the decision making or computer circuitry 28. This circuitry, when provided with all of the input data described previously, can calculate and display many other useful relationships such as the difference between the percent of the total hemoglobin in the blood which is saturated with oxygen from the blood entering and leaving the combination blood oxygenator and heat exchanger 15.

The stoichiometric oxygen capacity of hemoglobin may be computed from its molecular weight and the molar volume of oxygen. As one mole of oxygen at STP is equivalent to 22,414 milliliters and as human hemoglobin has a typical molecular weight of 64,458 grams per mole and an equivalent weight one-fourth this, one gram of hemoglobin can combine with 1.39 milliliters of oxygen (from the Annual Meeting International Committee for Standardization in Hematology, 1966). Therefore, by entering this data into the decision making or computer circuitry 28 by way of a program element in the computer or from the manual or external data entry unit 30 which is operably connected to the decision making or computer circuitry 28 through the data communication ports 27, the oxygen content of the blood may be determined or calculated and this displayed from the data and output control ports 29 by using the following mathematical relationship: ##EQU1## where hemoglobin and the percent hemoglobin saturated with oxygen are expressed to a common base. That is, both the hemoglobin concentration and the percent of the hemoglobin saturated with oxygen must relate either to the total amount of hemoglobin or to the hemoglobin available for oxygenation. Both approaches are equivalent.

At present there is no method or device available for the medical presonnel to use to be able to continuously determine the metobolic oxygen consumption of a patient undergoing a total cardio-pulmonary bypass procedure using an extracorporeal blood pumping and oxygenating system. Continuous knowledge of this physiologic parameter would be of great potential value to both the patient and the attending medical personnel. When all of the input data described previously is available, it becomes possible, for the first time, to continuously determine and display the metabolic oxygen consumption of a patient undergoing a total cardio-pulmonary bypass procedure. The mathematical relationship required to make this calculation is: ##EQU2##

It should be obvious from the above to anyone skilled in the art that the number of operating parameters which can be monitored, determined, or calculated and displayed by the system is limited only by the form and the number of data inputs supplied to the system's data communication ports 27.

Other illustrations of the preferred embodiment 10 follow. The output control line 65 would deliver an analog and/or digital control signal to the input of the external water temperature controller. Output control line 66 would deliver a control signal to the 3-way valve 17 which would either allow the temperature regulated water from the external temperature controller to flow through the heat exchanger contained in the combination blood exygenator and heat exchanger 15, or to direct the flow of water through fluid conduits 39 and 40 to return the water to the external temperature controller without passing through the heat exchanger. The output control line 67 would deliver an analog and/or digital control signal to the controlling sub-system of the blood pump 21 for the purpose of controlling the blood flow rate through the extracorporeal blood circuit.

It is obvious from the above to anyone skilled in the art that the number of operating parameters which can be controlled by the data and output control ports 29 is limited only by the number of data inputs provided in the system's data communication ports 27 and/or by the number of data and output control ports 29 which are provided.

The types of data communication ports 27 and data and output control ports 29 which would be used to construct the blood pump and oxygenator monitor-controller and display device will be mandated by the type of decision making or computer circuitry 28 which is used. Such decisions and their implementation would be accomplished easily by all who are ordinarily skilled in the art.

Many variations of the embodiment disclosed here will be obvious to those skilled in the art. Some examples of such variations could include the use of only analog type circuitry, the use of only digital type circuitry, the use of a combination of analog and digital circuitry, and the use of hydraulic or other type signals separately or in combination with those listed previously. It is to be understood that these and other variations are not to be taken as outside the intent and scope of the appended claims.