Implantable tissue perfusion sensing system and method

• US 8,886,465 B2
• Filed: 02/28/2008
• Issued: 11/11/2014
• Est. Priority Date: 02/28/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Cinbis, Can, Carney, James K.
• Primary Examiner(s): Moran, Marjorie
• Assistant Examiner(s): Skibinsky, Anna
• Application Number:
  US12/039,263
• Publication Number:
  US 20080208020A1
• Time in Patent Office: 2,448 Days
• Field of Search: None
• US Class Current: 702/19
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

A medical device for sensing cardiac events that includes a plurality of light sources capable of emitting light at a plurality of wavelengths, and a detector to detect the emitted light. A processor determines a plurality of light measurements in response to the emitted light detected by the detector, updates, for each of the plurality of wavelengths, a first normalization coefficient and a second normalization coefficient in response to the detected emitted light, and adjusts the determined plurality of light measurements in response to the first normalization coefficient and the second normalization coefficient.

Claims

1. A method of adjusting sensing in a medical device, comprising:

determining light emitted by a plurality of light sources at a plurality of wavelengths received at a detector;

determining a plurality of light measurements in response to the emitted light detected by the detector;

updating, for each of the plurality of wavelengths, a first normalization coefficient and a second normalization coefficient in response to the detected emitted light,

wherein the first normalization coefficient corresponds to peak-to-peak changes in the plurality of light measurements and the second normalization coefficient corresponds to average amplitudes of the plurality of light measurements; and

adjusting the determined plurality of light measurements in response to the first normalization coefficient and the second normalization coefficient,

the method further comprising;

determining a first baseline associated with the first normalization coefficient and a second baseline associated with the second normalization coefficient;

updating the first normalization coefficient by calculating a ratio of the first baseline and an average of the peak-to-peak changes in the plurality of light measurements; and

updating the second normalization coefficient by calculating a difference between a second baseline and a product of the previously updated first normalization coefficient and a current average amplitude.

2. The method of claim 1, further comprising adjusting a current light measurement of the plurality of light measurements in response to a difference between a product of the current updated first normalization coefficient and the current light measurement and the current updated second normalization coefficient.