Image Number 4 for United States Patent #5551438.
A transducer assembly (12) is applied to the surface of the body beneath an inflatable cuff (10). Transducers (12c) are disposed upon a substrate (12a) and may include from one to some large number of transducers suitable for detecting an oscillation resulting from arterial blood flow within a partially occluded artery. Each transducer (12c) can be of large size, relative to an artery (16), to eliminate a requirement that the transducer be accurately placed over and maintained upon the artery. The substrate can be provided to have a surface with a radius of curvature selected to approximate a curvature of the extremity to which the transducer array is applied. The cuff pressure is increased to a level above the systolic pressure of the individual and then gradually reduced. Oscillations are sensed by one or more of the transducers as the cuff pressure is decreased. When the systolic pressure is reached, the sensed oscillations begin to increase in amplitude until they reach a maximum amplitude. The cuff pressure at the point of maximum amplitude is correlated with the Mean Arterial Pressure of the subject. Methods for accomplishing a sub-diastolic continuous measurement cycle and a Mean Arterial Pressure monitoring cycle are also provided.