An Experimental Study on the Blood Pressure Cuff as a Transducer for Oscillometric Blood Pressure Measurements

Noninvasive blood pressure (BP) measurements still rely on empirical interpretation of arterial oscillations recorded via cuff-based oscillometric methods. Extensive effort has dedicated to establishing a theoretical basis for oscillometry, aiming at more accurate BP estimations and measurement of additional hemodynamic parameters. However, oscillometry is still a heuristic method for BP inference. Goal: This study is focused on improving our understanding of the expression of arm volume pulsations in oscillometric signals. The aim is to identify the main factors that determine the transfer function of arm volume to cuff pressure oscillations for existing cuff devices this being an essential step in establishing a theoretical basis for oscillometry. Methods: The effects of air compression within the cuff and the influence of viscoelastic cuff material properties on the transfer function are studied by an experimental setup. Mechanical numerical modeling is used to interpret the results. Results: Air compression is found to be of adiabatic nature in the frequency range of interest. The cuff material exhibits viscous characteristics which is the cause of cuff response dependence on inflation speed, tightness of wrapping, time passed since previous measurement, and heart rate. Conclusion: It was found that typical cuffs used in clinical practice exhibit complex behavior. Cuff hardware needs to be improved to enable practical translation of pressure to arm volume oscillations. The presented characterization method contributes to standardized development of new cuff prototypes and to identification of designs, techniques, and materials with improved properties for enabling BP measurement accuracy and extraction of additional hemodynamic information.