Optical sensor and method for detecting a patient condition

• US 8,512,254 B2
• Filed: 08/03/2012
• Issued: 08/20/2013
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Donofrio, William T.
• Primary Examiner(s): Holmes, Rex R
• Application Number:
  US13/566,057
• Publication Number:
  US 20120303081A1
• Time in Patent Office: 382 Days
• Field of Search: 607/3, 607/6, 607 17- 22, 600/301, 600322-324, 600/333, 600/500, 600507-508
• US Class Current: 600/507
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

An implantable medical device for monitoring tissue perfusion that includes a light source emitting a light signal and a light detector receiving emitted light scattered by a volume of body tissue. The light detector emits a signal having an alternating current component corresponding to the pulsatility of blood flow in the body tissue volume. A processor receives the current signal and determines a patient condition in response to the alternating component of the current signal.

Claims

1. An implantable medical device for monitoring blood flow pulsatility in a volume of body tissue in a patient, the device comprising:

at least two electrodes for sensing a cardiac electrical signal;

a light source for emitting a modulated light signal;

a filter for filtering the wavelengths of the modulated light signal scattered by the volume of body tissue;

a light detector for receiving the filtered modulated light signal and emitting a current signal having an alternating current component correlated to pulsatility of blood flow within the volume of body tissue;

a processor for receiving the cardiac electrical signal, detecting an arrhythmia in response to the cardiac electrical signal, receiving the light detector signal, determining a pulsatility metric in response to the alternating current component of the light detector signal, comparing the pulsatility metric to a heart rate determined from the cardiac electrical signal, confirming the arrhythmia in response to the comparison, and detecting T-wave oversensing in response to the cardiac electrical signal being greater than the pulsatility metric, wherein the pulsatility metric is a frequency of the alternating current component and; and

a therapy control module coupled to the processor and delivering an anti-arrhythmia therapy in response to the arrhythmia confirmation.

2. The device of claim 1, wherein the processor is further configured to detect T-wave undersensing in response to the pulsatility metric being greater than the cardiac electrical signal.

3. The device of claim 1, wherein the processor confirms the arrhythmia in response to the pulsatility metric being approximately equal to the cardiac electrical signal.

4. The device of claim 1, further comprising a signal modulator modulating the emitted light signal wherein the processor demodulates light detector signal.

5. The device of claim 4 wherein the emitted light signal is modulated at a carrier frequency of approximately 100 to 10,000 Hz.

6. The device of claim 1, wherein the light detector is a photo darlington device.

7. The device of claim 1, wherein the processor determines one of a frequency of the alternating current component and a peak-to-peak amplitude difference of the alternating current component.

8. The device of claim 7 wherein the processor determines a heart rate from the cardiac electrical signals and compares the determined heart rate to the frequency of the alternating current component.

9. The device of claim 1, wherein the processor further determines the presence of a motion artifact in the light detector signal.