Abstract: Apparatus and methods for noninvasively measuring cardiovascular system parameters. According to a first preferred embodiment, the apparatus generates a time varying electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject, the parameters being modelled by a lumped element electric circuit model analogous to the living subject's cardiovascular system, said circuit model including a systolic capacitor analogous to arterial compliance during systole, said apparatus comprising means for computing the value of said systolic capacitor from a measurement of an elapsed time between two voltage levels within a portion of said voltage waveform corresponding to systole, according to a predetermined criteria; and means for computing at least one said cardiovascular system parameter from said capacitor value. According to a second embodiment, a time-varying systolic arterial compliance is measured by measuring an arterial pulse pressure waveform.

Abstract: Apparatus and methods for noninvasively measuring cardiovascular system parameters. According to a first preferred embodiment, the apparatus generates a time varying electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject, the parameters being modelled by a lumped element electric circuit model analogous to the living subject's cardiovascular system, said circuit model including a systolic capacitor analogous to arterial compliance during systole, said apparatus comprising means for computing the value of said systolic capacitor from a measurement of an elapsed time between two voltage levels within a portion of said voltage waveform corresponding to systole, according to a predetermined criteria; and means for computing at least one said cardiovascular system parameter from said capacitor value. According to a second embodiment, a time-varying systolic arterial compliance is measured by measuring an arterial pulse pressure waveform.

Abstract: An acoustic ranging apparatus directs a burst of acoustic energy toward an acoustically reflective target object. The time it takes for an echo to return to the ranging apparatus is measured to determine the distance between the ranging apparatus and the object. The echo is received, amplified, and compared with a threshold voltage which decays in time in a manner which simulates the attenuation of acoustic energy as a function of distance travelled in the medium. The attenuation function is substantially simulated over the distance range that the ranging apparatus is intended to accurately measure by means of a simple, low cost first order linear circuit. The ranging apparatus responds only to echoes having a magnitude which exceeds the threshold voltage. Suprious or false echoes, such as those due to reflection of acoustic energy in the side lobes produced by an acoustic energy transducer in the ranging apparatus, are ignored.