Patent ID: 7544168

Claim:
An automatic cuff-based blood-pressure measuring device for measuring the systolic blood pressure (SBP) of a subject, the device comprising: a pressure cuff for wrapping around an arm of the subject; a photoplethysmographic (PPG) sensor for generating an output signal indicative of arterial blood volume change induced by heart beat of the subject, said PPG sensor being adapted for attachment to skin of the subject in a first peripheral site distal to the middle of the pressure cuff; an electrically controlled pump for inflating and deflating the cuff; and a second sensor for attachment to the skin in a second peripheral site which is not distal to the middle of the pressure cuff and which produces an output indicative of a second hemodynamic parameter related to the heart beat; wherein the device is configured to: (a) activate said pump to inflate said cuff, automatically detect the disappearance of a pulse from said PPG signal, and activate said pump to slowly deflate said cuff; (b) derive from the second hemodynamic parameter signal the arrival time of each pulse; and (c) during said deflation, automatically detect the reappearance of the PPG signal, wherein the automatic detection of reappearance of the PPG signal during the deflation periods includes defining time segments, based upon said arrival time of each pulse as derived from said second sensor, during which a full PPG pulse of a reappearing PPG pulse in the output of said PPG sensor would be expected to occur, and applying a decision algorithm which determines whether a PPG pulse appears in time segments of the output of said PPG sensor, where said decision algorithm includes calculation of at least one of the following two parameters characterizing PPG pulses in each segment: a pulse pattern parameter and the correlation of the signal in each segment with the signal in the neighboring segments.