Method for noninvasive blood-pressure measurement by evaluation of

Abstract

A microprocessor-controlled, oscillometric method for determining a patient's systolic, diastolic, and mean arterial pressure, practiced in a system comprising an inflatable, occluding cuff, a pump and a valve coupled to the cuff, and monitoring apparatus coupled to the cuff adapted to measure cuff pressure and recurring blood-pressure pulsations occurring in the cuff that are caused by each heart contraction occurring in a measurement cycle. Cuff pressure is raised to a level above the patinet's systolic pressure, and progressively reduced in a stepwise fashion to an ending cuff pressure. A fixed number of pulsations are measured and processed at a first and second cuff-pressure step, and a generally lesser number of oscillations are measured and processed at a third and subsequent cuff-pressure steps. The method includes a first artifact rejection technique used to check for false data relative to the formation of each blood-pressure pulsation. Further, the method includes calculating, for each blood-pressure pulsation, the impulse of a force that is exerted upon the patinet's blood from, and during, each heart contraction that occurs in the measurement cycle. An impulse value is stored relative to each pulsation. A second artifact rejection technique is used, beginning at the second cuff-pressure step, to generate a prediction curve for predicting a next, expected-to-be-stored pulsation impulse value for a next, lower cuff-pressure step. The second artifact rejection technique is also used to repeatedly smooth the prediction curve based on the difference between a pulsation's calculated impulse value and its respective predicted impulse value. A final, smoothed curve is generated reflecting a final impulse value for each cuff-pressure step. From the final curve, the desired blood pressure parameters are derived and displayed in the form of arabic numerals by means of an LCD readout.