Patent ID: 6733461
Filing Date: 2004-05-11
Classification: A61B,Y10S

Abstract:
A method for computerized calculation of a variable physiological parameter of a patient, the method comprising:(a) identifying the physiological parameter to be quantitatively monitored and estimated; (b) measuring an oscillometric blood-pressure signal and a tonometric blood-pressure signal, which signals are quantitatively dependent on a particular value for the physiological parameter; (c) obtaining a sequence of values that are based on the oscillometric signal and the tonometric signal; (d) receiving the sequence of values as input signals to a computer system; (e) processing the input signals within the computer system to convert the sequence of values to an output signal corresponding to the particular value of the physiological parameter; and (f) using the oscillometric signal to calibrate the tonometric signal; wherein a calibrated radial pressure waveform Pr(t) is derived from the tonometric signal Sr(t) as follows: Pr(t)=(1/ar)(Sr(t)âˆ’br)+p where ar=(Sr(tD)âˆ’Sr(tM))/(DBPâˆ’MBP), br=Sr(tM)âˆ’ar MBP, and p=&rgr; gh are calibration factors, and where &rgr;=density of blood, g=acceleration to gravity, h=height difference between the oscillometric and the tonometric measurement sites, and is zero if the patient is supine, MBP is oscillometric mean arterial blood pressure measured near time tM, and DBP is oscillometric diastolic blood pressure measured near time tD.