Plethysmometry: an automated cuff-based method for estimating ranges of systolic, diastolic and mean arterial pressures

Abstract Background: Conventional cuff based methods report single systolic and diastolic pressure values and depend either on Korotkoff sounds or on empirical oscillometric algorithms. Methods: We developed a patented cuff based method, termed plethysmometry, that simultaneously records cuff pressure and finger photoplethysmograms from the cuffed and contralateral arms. The contralateral photoplethysmogram serves as an internal physiological reference for pulse amplitude. Following an initial pressure ramp, 16 cuff pressure plateaus are applied. Absolute and normalized pulse amplitudes in the cuffed arm are related to cuff pressure to estimate lower and upper systolic and diastolic pressures. Mean arterial pressure is estimated independently from cuff pressure oscillation amplitude. The estimations are done by automated algorithms developed in MATLAB. Results: The method reports lower and upper systolic, diastolic and mean arterial pressure ranges (during the recording period), together with their average values. Average pulse pressure is also reported. Graphs are provided for reference to check the accuracy of reported pressures. Conclusion: Plethysmometry provides an objective digital record of the cuff pressure and pulse traces and estimates systolic and diastolic pressure ranges from the pulse response of the individual subject to graded cuff pressure. It also reports mean arterial pressure. Comparison of plethysmometric systolic and diastolic pressures with sphygmomanometrically derived pressures and diagnostic agreement are reported in a companion paper.