Circulatory support system

• US 5,965,089 A
• Filed: 10/03/1997
• Issued: 10/12/1999
• Est. Priority Date: 10/04/1996
• Status: Expired due to Term

• Current Assignee: United States Surgical Corporation (Medtronic Plc)
• Original Assignee: United States Surgical Corporation (Medtronic Plc)
• Inventors: Geiste, Robert J., Jarvik, Robert, Stern, Steven J., Alesi, Daniel E., Cashin, Deborah M., Howansky, Mark, Klinger, John F., Day, Steven R., Kaczynski, Francis X., Hammerquist, Kenneth G., Payea, Keith
• Primary Examiner(s): Stright, Ronald
• Assistant Examiner(s): Huseman, Cheryl L.
• Application Number:
  US08/943,504
• Time in Patent Office: 739 Days
• Field of Search: 600/16, 600/504, 623/3, 604/4
• US Class Current: 422/44
• CPC Class Codes: A61M 1/3626 Gas bubble detectors
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 1/3653 Interfaces between patient blood circulation and extra-corporal blood circuit
• CPC Class Codes: A61M 1/3656 Monitoring patency or flow at connection sites; Detecting disconnections
• CPC Class Codes: A61M 1/3659 Cannulae pertaining to extracorporeal circulation
• CPC Class Codes: A61M 1/3666 Cardiac or cardiopulmonary bypass, e.g. heart-lung machines
• CPC Class Codes: A61M 1/3667 with assisted venous return
• CPC Class Codes: A61M 39/281 Automatic tube cut-off devices, e.g. squeezing tube on detection of air
• CPC Class Codes: A61M 60/117 for assisting the heart, e.g. transcutaneous or external ventricular assist devices
• CPC Class Codes: A61M 60/237 the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
• CPC Class Codes: A61M 60/806 Vanes or blades

Abstract

A method for providing at least partial bypass of the heart to supplement the pumping function of the heart to thereby enable the surgeon to perform various surgical procedures thereon includes providing a circulatory assist system having a portable extracorporeal axial flow pump with a pump housing, a rotating pumping member disposed in the pump housing and inlet and outlet cannulated tubes respectively connected to inlet and outlet ports of the pump housing, accessing the patient'"'"'s left atrium of the heart with the inlet cannulated tube, accessing the aorta with the outlet cannulated tube, actuating the rotating pumping member to draw oxygenated blood from the left atrium of the heart through the lumen of the inlet cannulated tube and into the inlet port of the pump housing whereby the pumping member imparts mechanical energy to the oxygenated blood passing through the pump housing and directs the oxygenated blood through the outlet port and through the lumen of the outlet cannulated tube to be transferred by the aorta to the systemic arteries and permitting the right side of the heart to function whereby oxygen-depleted blood returning through the systemic veins to the right atrium is directed through the right ventricle to the patient'"'"'s lungs for oxygenation and subsequent pulmonary circulation.

Claims

1. A circulatory support system to supplement or temporarily replace the pumping function of a patient'"'"'s heart to thereby enable a surgeon to perform surgical procedures thereon, comprising:

an extracorporeal portable axial flow pump having inlet and outlet ports, a motor and a rotating member rotatably mounted in the pump housing to impart mechanical energy to blood entering the inlet port and to direct the blood through the outlet port;

an inlet cannula connected to the inlet port of the pump housing and having an inlet open end portion dimensioned for insertion within the patient'"'"'s heart or blood vessel associated with the heart so that blood is drawn from the patient through a lumen of the inlet cannula and directed into the pump housing;

an outlet cannula connected to the outlet port of the pump housing and having an outlet end portion dimensioned for insertion within the patient so that blood exiting the outlet port of the pump housing is conveyed through a lumen of the outlet cannulated tube into the patient for transfer by the arterial system of the patient;

a control unit having a processor, operatively coupled to the flow pump, for controlling operation thereof,

an air bubble sensor mounted to one of the cannulas for detecting air bubbles in the respective cannula and providing a bubble detect signal indicative of the presence of an air bubble;

a clamping device mounted to one of the cannulas and operative to clamp down on the respective cannula when the bubble detect signal is generated to prevent air from entering the patient'"'"'s bloodstream;

wherein the control unit is operative, responsive to receiving a bubble detect signal, to generate first and second signals, the first signal being an alarm signal to produce an air bubble alarm and the second signal being a motor control signal to shut down the motor to cause rotation of the rotating member of the pump to cease.

2. The system of claim 1 wherein the air bubble sensor is mounted to the inlet cannula and the clamping device is mounted to the outlet cannula.

3. The system of claim 1, wherein the control unit includes a manual switch to permit the pump to be restarted following activation of the bubble alarm, the control unit being responsive to manual operation of the switch to extinguish the bubble alarm and restart rotation of the rotating member.

4. The system of claim 1, further including a flow sensor coupled to one of the inlet or outlet cannulas and providing a flow sense signal to the control unit indicative of blood flow rate within the respective cannula, the control unit operative to generate a low flow rate alarm when the flow rate is determined to be below a predetermined threshold.

5. The system of claim 4 wherein, subsequent to the generation of the low flow rate alarm, the control unit is operative to extinguish the low flow rate alarm when the flow rate is determined to have risen above a predefined threshold.

6. The system of claim 1, further including a pressure transducer for sensing pressure on the inlet side of the pump and providing a pressure sense signal indicative of the pressure sensed, the control unit being operable to command a reduction in motor speed to a non-zero signal when the pressure is determined to be below a predetermined threshold.

7. The system of claim 6 wherein said pressure transducer is disposed in proximity to the inlet open end portion of the inlet cannula, and the system further including a wire running within an outer sheathing of the inlet cannula from the control unit to the pressure transducer, the pressure sense signal being transmitted to the control unit on the wire.

8. The system of claim 6, wherein, following the reduction in motor speed, the control unit is operative to ramp up the motor speed to a speed corresponding to a manually set dial, following a determination based on the pressure sense signal that the pressure has risen to a value above a predefined threshold for at least a specified period of time.

9. The system of claim 1 wherein the control unit includes circuitry for sensing motor current and for generating an alarm when the motor current has risen above a predetermined threshold.

10. The system of claim 1 wherein the blood flow pump is an axial flow pump and includes a pump housing dimensioned for positioning directly on or adjacent to the chest area of a patient.

11. The system of claim 1 wherein the control unit includes a backup motor controller circuit and a manual engage backup switch, the control unit entering a backup mode upon activation of the engage backup switch, the control unit operative in the backup mode to control motor speed based on manual motor speed control independent of alarm conditions.

12. The system of claim 10, wherein the rotating member includes at least one impeller blade extending axially and peripherally with respect to a longitudinal axis of the pump housing, and wherein the motor includes a motor stator disposed in the pump housing, the motor stator and rotatable member having an annular space therebetween defining a blood flow path through the housing.

24. The system of claim 12, wherein the motor stator includes at least one stator blade disposed between the at least one impeller blade and the outlet portion of the pump housing.

13. A control unit for use in a circulatory support system to supplement or temporarily replace the pumping function of a patient'"'"'s heart, the support system including an axial flow pump, having a motor, inlet and outlet cannulas coupled to the flow pump for insertion within the patient, an air bubble detector, and a cannula clamp, each coupled to one of the cannulas, the control unit comprising:

circuitry for supplying power to the flow pump to cause the pump to rotate at a manually selected speed;

circuitry responsive to a bubble sense signal provided by the bubble detector, for generating first and second signals, the first signal being an alarm signal to produce a bubble alarm and the second signal being a motor control signal to control the motor to cause rotation of the pump to cease if the bubble sense signal indicates the presence of an air bubble; and

circuitry responsive to the bubble sense signal indicating the presence of an air bubble for causing the cannula clamp to clamp down on the respective cannula to prevent air from entering the patient'"'"'s bloodstream.

14. The control unit of claim 13, further comprising a manual switch to permit the pump to be restarted following activation of the bubble alarm, the control unit being responsive to manual operation of the switch to extinguish the bubble alarm, restart the pump and cease actuation of the cannula clamp.

15. The control unit of claim 14, wherein the system further includes a pressure transducer coupled to the inlet cannula and a flow rate sensor coupled to one of the cannulas, the control unit operative to receive a pressure sense signal from the pressure transducer and to command a reduction in motor speed to a non-zero speed and generate a low pressure alarm when the pressure is determined to be below a predetermined pressure threshold, and to generate a low flow rate alarm when the flow rate is determined to be below a predetermined flow threshold based on a flow rate signal received from the flow sensor.

16. The control unit of claim 15, wherein, following the reduction in motor speed, the control unit is operative to ramp up the motor speed to a speed corresponding to a manually set dial, following a determination based on the pressure sense signal that the pressure has risen to a value above a predefined threshold for at least a specified period of time.

17. The control unit of claim 16, further including circuitry for sensing motor current and for generating an alarm when the motor current has risen above a predetermined threshold.

18. The control unit of claim 13, further including a backup motor controller circuit and a manual engage backup switch, the control unit entering a backup mode upon activation of the engage backup switch, the control unit operative in the backup mode to control motor speed based on manual motor speed control independent of alarm conditions.

19. The control unit of claim 13, having a housing of a generally elongated, solid rectangular shape to facilitate use within an operating room.

20. The control unit of claim 19 wherein the control unit housing is about four feet in height, about one foot in width and 3-7 inches in thickness.

22. The control unit of claim 13, further including circuitry for receiving a flow rate signal from a flow rate sensor coupled to one of the cannulas, means for generating, responsive to the flow rate signal, a low flow rate alarm if flow rate is determined to be below a predetermined threshold, and a flow blockage alarm if the flow rate has dropped by more than a predefined amount or percent.

21. A control unit for use in a circulatory support system to supplement or temporarily replace the pumping function of a patient'"'"'s heart, the support system including an axial flow pump, having a motor, inlet and outlet cannulas coupled to the flow pump for insertion within the patient, an air bubble detector, and a cannula clamp, each coupled to one of the cannulas, the control unit comprising:

circuitry for supplying power to the flow pump to cause the pump to rotate at a manually selected speed;

circuitry responsive to a bubble sense signal provided by the bubble detector, for generating first and second signal,the first signal being an alarm signal to produce a bubble alarm and the second signal being a motor control signal to control the motor to cause rotation of the pump to cease if the bubble sense signal indicates the presence of an air bubble;

circuitry responsive to the bubble sense signal indicating the presence of an air bubble for causing the cannula clamp to clamp down on the respective cannula to prevent air from entering the patient'"'"'s bloodstream;

a front portion with a front display that displays motor speed and flow rate and visible alarm indicators corresponding to particular alarm conditions; and

a rear portion with a rear display that displays motor speed and flow rate and generally the same visible alarm indicators as the front display.

23. A control unit for use in a circulatory support system to supplement or temporarily replace the pumping function of a patient'"'"'s heart, the support system including a blood flow pump, inlet and outlet cannulas coupled to the flow pump for insertion within the patient, an air bubble and flow rate detector, and a cannula clamp, each coupled to one of the cannulas, the control unit comprising:

circuitry for supplying power to the flow pump to cause the pump to rotate;

a sensor for sensing an air bubble condition and for sensing the blood flow rate;

circuitry responsive to a bubble sense signal provided by the bubble detector, for generating a bubble alarm and for causing rotation of the pump to cease if the bubble sense signal indicates the presence of an air bubble, the circuitry further responsive to a flow rate signal to generate a low flow alarm signal if the flow rate does not exceed a threshold value; and

circuitry responsive to the bubble sense signal indicating the presence of an air bubble for causing the cannula clamp to clamp down on the respective cannula to prevent air from entering the patient'"'"'s bloodstream.