Abstract: A non-invasive optical sensor which uses the motion signal to calculate the physiological characteristic being measured. For pulse oximetry, a least squares or a ratio-of-ratios technique can be applied to the motion signal itself. This is made possible by selecting a site on the patient where variations in motion produce signals of two wavelengths which are sufficiently correlated. In particular, it has been determined that a sensor placed on a nail, in particular a thumbnail, exhibits the characteristics of having the red and infrared signals correlated when used for pulse oximetry, and the resulting signals correlate to arterial oxygen saturation.
Type:
Grant
Filed:
July 7, 1999
Date of Patent:
April 16, 2002
Assignee:
Nellocr Puritan Bennett Incorporated
Inventors:
Rodney Chin, Paul Mannheimer, Ross Flewelling