Browse Prior Art Database

Optical Plethysmograph

IP.com Disclosure Number: IPCOM000086181D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Dimmick, RF: AUTHOR [+3]

Abstract

Prior devices for measuring blood flow in a patient have been positioned on ear lobes or around a digit such as a toe to measure the dilation of the capillary bed of tissue. Such devices cause pressure effects tending to squeeze the blood out of the tissue and will provide erroneous signals due to muscle actions.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 71% of the total text.

Page 1 of 2

Optical Plethysmograph

Prior devices for measuring blood flow in a patient have been positioned on ear lobes or around a digit such as a toe to measure the dilation of the capillary bed of tissue. Such devices cause pressure effects tending to squeeze the blood out of the tissue and will provide erroneous signals due to muscle actions.

The plethysmograph 1 and its processor diagrammed utilizes a proximity detector away from the skin to detect the pressure wave of the pulse, and is mounted at the patient's wrist where an artery is close to the surface and the pulse causes a substantial skin movement. The output signal from the plethysmograph 1 is processed in signal conditioner 2. This conditioner comprises AC coupled amplifier stages for the signal and a filter to remove all signal components outside the range of 1 to 4 Hz. The filter is followed by a controlled gain amplifier to provide an output signal having a peak-to-peak difference in the 3 to 9 volt range.

A positive peak detector 3 and a negative peak detector 4 receive the output of conditioner 2, and when a peak is detected will signal an associated sample and hold circuit 5 or 6 to retain the detected peak voltage. A latch 7 is set by the detection of a negative peak and is reset by detection of a positive peak.

The signals in the sample and hold circuits 5 and 6 are combined in a differential amplifier 8 which has an output proportional to the peak-to-peak difference. A comparator 9 controlled by a sin...