Optical blood flow measurement apparatus and method and implantable defibrillator incorporating same

• US 5,601,611 A
• Filed: 08/05/1994
• Issued: 02/11/1997
• Est. Priority Date: 08/05/1994
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Ventritex Incorporated (Abbott Laboratories Incorporated)
• Inventors: Benedict, George J., Fayram, Timothy A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/286,306
• Time in Patent Office: 921 Days
• Field of Search: 607/6, 607/23, 607/24, 128/634, 128/691, 128/692, 128/673
• US Class Current: 607/6
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A cardiac blood flow sensor includes a light source and a photodetector within a housing. The light source projects a beam through a fiber optic line having a first end optically connected to the housing and a distal tip positioned within the patient'"'"'s heart. Light intermittently reflected off the moving blood cells is transmitted back through the optic line to the detector, which generates a varying signal proportional to the reflected light, and thus proportional to the blood flow rate within the heart. The flow sensor may be contained in a common housing with a defibrillator that is implanted in a patient. The sensor may remain inactive until a potentially unhealthy heart beat rate is detected, upon which the light source is activated. The defibrillator may be activated only if the flow sensor has detected a blood flow rate below a predetermined level.

Claims

1. An optical blood flow measurement apparatus comprising:

a housing having a port for transmitting light between the housing interior and exterior;

a light source within the housing and in optical communication with the port, such that at least a portion of light emitted by the light source is transmitted along a first beam path between the light source and the port;

a photodetector having an electrical output, the photodetector being responsive to the intensity of light impinging on the detector, the photodetector being positioned within the housing and in optical communication with the port, such that at least a portion of light entering the port from outside the housing is transmitted along a second beam path between the port and the detector to impinge on the detector;

a processor connected to the photodetector'"'"'s electrical output for providing a blood flow measurement output; and

a flexible elongated light conduit having a first end optically connected to the housing port, and a light transmissive distal tip for placement at a site of flowing blood, such that light from the light source is transmitted through the conduit, out of the distal tip, and such that at least a portion of any reflected light is received by the distal tip, and transmitted to the detector to generate a signal;

whereby light is directed from the light source to the light transmissive tip and into the blood flow and a portion of the light is reflected back to the distal tip and a portion of the reflected light is transmitted to the detector to generate a signal indicative of the blood flow.

2. The apparatus of claim 1 wherein the conduit comprises a fiber optic line.

3. The apparatus of claim 1 wherein at least a portion of the conduit is enclosed by a biocompatible sheath.

4. The apparatus of claim 1 including a lens connected to the distal tip of the conduit.

5. The apparatus of claim 4 wherein the focus lens is a diverging lens.

6. The apparatus of claim 1 including a beam splitter within the housing and within the first and second beam paths, such that portions of the beam paths are coextensive with each other between the beam splitter and the port, and are separate from each other adjacent the respective light source and photodetector.

7. An optical blood flow measurement apparatus comprising:

a housing having a port for transmitting light between the housing interior and exterior;

a light source within the housing and in optical communication with the port, such that at least a portion of light emitted by the light source is transmitted along a first beam path between the light source and the port;

a photodetector having an electrical output the photodetector being responsive to the intensity of light impinging on the detector, the photodetector being positioned within the housing and in optical communication with the port, such that at least a portion of light entering the port from outside the housing is transmitted along a second beam path between the port and the detector to impinge on the detector;

a processor connected to the photodetector'"'"'s electrical output for providing a blood flow measurement output, wherein the processor includes means for calculating a blood flow rate;

a flexible elongated light conduit having a first end optically connected to the housing port, and a light transmissive distal tip for placement at a site of flowing blood, such that light from the light source is transmitted through the conduit, out of the distal tip, and such that at least a portion of any reflected light is received by the distal tip, and transmitted to the detector to generate a signal;

whereby light is directed from the light source to the light transmissive tip and into the blood flow and a portion of the light is reflected back to the distal tip and a portion of the reflected light is transmitted to the detector to generate a signal indicative of the blood flow.

8. An implantable defibrillator including an optical blood flow measurement apparatus, said measurement apparatus comprising:

a housing having a port for transmitting light between the housing interior and exterior;

a light source within the housing and in optical communication with the port, such that at least a portion of light emitted by the light source is transmitted along a first beam path between the light source and the port;

a photodetector having an electrical output, the photodetector being responsive to the intensity of light impinging on the detector, the photodetector being positioned within the housing and in optical communication with the port, such that at least a portion of light entering the port from outside the housing is transmitted along a second beam path between the port and the detector to impinge on the detector;

a processor connected to the photodetector'"'"'s electrical output for providing a blood flow measurement output;

a flexible elongated light conduit having a first end optically connected to the housing port, and a light transmissive distal tip for placement at a site of flowing blood, such that light from the light source is transmitted through the conduit, out of the distal tip, and such that at least a portion of any reflected light is received by the distal tip, and transmitted to the detector to generate a signal;

whereby light is directed from the light source to the light transmissive tip and into the blood flow and a portion of the light is reflected back to the distal tip and a portion of the reflected light is transmitted to the detector to generate a signal indicative to the blood flow; and

whereby at least a first portion of the defibrillator is contained within the housing and operably connected to the processor, said processor including means to detect a blood flow rate from said reflected light, the defibrillator further including means for detecting a cardiac arrhythmia and means for delivering a therapy in response thereto, the means for detecting a cardiac arrhythmia being responsive to the detected blood flow rate signal from the processor, such that operation of the means for delivering is dependent on the detected blood flow rate.

9. The defibrillator of claim 8 wherein said means for detecting a cardiac arrhythmia includes a heart rate sensor coupled to said processor to provide an indication of said arrhythmia based on a sensed heart rate.

10. A method of measuring blood flow in the blood stream of a patient, the method comprising the steps:

generating light;

transmitting the light through a flexible conduit having a distal tip immersed in the patient'"'"'s blood stream;

projecting the light from the conduit onto blood cells within the blood stream;

receiving at the distal tip of the conduit reflected light from the cells;

transmitting the reflected light through the conduit to a photodetector;

generating an electrical signal in response to the reflected light intensity;

analyzing the electrical signal to determine the blood flow rate whereby the blood flow rate provides an indication of the hemodynamic performance of the patient'"'"'s heart.

12. The method of claim 10 and further including the step of inserting the distal tip into a chamber of the patient'"'"'s heart and wherein the step of projecting the light includes projecting the light within the patient'"'"'s heart.

11. A method of measuring blood flow in the blood stream of a patient, the method comprising the steps:

generating light;

transmitting the light through a flexible conduit having a distal tip immersed in the patient'"'"'s blood stream;

projecting the light from the conduit onto blood cells within the blood stream and diverging the light within the blood stream such that the light may reflect off blood cells;

receiving at the distal tip of the conduit reflected light from the cells;

transmitting the reflected light through the conduit to a photodetector;

generating an electrical signal in response to the reflected light intensity;

analyzing the electrical signal to determine the blood flow rate whereby the blood flow rate provides an indication of the hemodynamic performance of the patient'"'"'s heart.