Determination of Blood Pressure and Hemodynamics from Oscillometric Waveforms

Abstract: An experimental system (Carditor) for noninvasive determination of blood pressures and hemodynamics is presented. The system consists of a wrist cuff, a battery powered module with pneumatic and electronic circuits, and a notebook computer. The computer controls cuff inflation, deflation and data acquisition functions during gradual cuff deflation. Proprietary software is used to analyze oscillometric waveforms obtained from radial artery. Systolic, mean and diastolic blood pressures and stroke volume are computed first. Stroke volume is then adjusted for body area and the adjusted value is used to compute cardiac output. Total peripheral resistance and systemic arterial compliance are computed from arterial pressures, cardiac output and stroke volume. The computed hemodynamic variables are displayed on the computer screen in a “quadrant ” graphic form. Preliminary hemodynamic data from from a group of 41 men and women (age 17-76) were used for qualitative comparison with published data (deSimone, n=544). Carditor results: stroke volume=76 ml, heart rate=70 bpm, cardiac output=5.3 l/min. DeSimone results: stroke volume=81 ml, heart rate=68 bpm, cardiac output=5.5 l/min. Examples of test results and clinical applications of the system are discussed. Key-Words: Bioimpedance, blood pressure, hemodynamic, microcontroller, oscillometric waveforms, sensor