Patent ID: 8419649

Claim:
A system for monitoring a patient's vital signs, the system comprising: a pressure-delivery system for applying a variable pressure to the patient's arm; a pressure sensor for measuring a time-dependent pressure waveform representing the pressure applied to the patient's arm; an optical sensor configured to attach to the patient and generate a time-dependent optical waveform representing a flow of blood within the patient; an electrode system configured to attach to the patient and generate a time-dependent electrical waveform representing activity of the patient's heart; and a processing component programmed to: i) determine a pulse transit time when pressure is applied to the patient's arm by the pressure system, wherein pulse transit time is a measure of a separation in time of a first feature of the time-dependent electrical waveform and a second feature of the time-dependent optical waveform; ii) determine a variation in an amplitude of the optical waveform versus the pressure applied to the patient's arm; iii) fit a function to the variation in the amplitude of the optical waveform; iv) use the calibration value for the blood pressure parameter and a subsequently measured pulse transit time obtained for the patient when no pressure is applied to the patient's arm to determine the patient's blood pressure at that subsequent time.