A Basis for Use of Long Cuff Bladders in Oscillometric Blood Pressure Measurement

Oscillometric blood pressures (BPs) are determined from the pressure pulses (oscillometric pulses) generated in the BP cuff during cuff inflation or deflation. Because of its reliance on pressure pulses in the cuff, oscillometric BP determination is directly affected by cuff-arm compliance, which can be characterized by the relationship between the mass of air and baseline cuff pressure in the cuff-arm system. In this study, cuff-arm compliance data were obtained from eight young healthy subjects using two cuffs that have the same bladder width but different bladder lengths. The data show that the rate of change of cuff pressure with mass of air in the cuff-arm system increases with cuff pressure, and that at any given cuff pressure the rate of change of cuff pressure with mass of air for a longer bladder is always smaller than that for a shorter bladder. The results of an analysis of the cuff-arm system and cuff-arm compliance data show that the use of cuff bladders that completely encircle the arm [(bladder length L)/(arm circumference C) ≥ 1] will help reduce oscillometric BP measurement variations caused by the nonlinear characteristics of cuff-arm compliance and those variations caused by the use of different bladder lengths. This finding provides a basis for the use of such long bladders in oscillometric BP measurement. Additionally, the results suggest that the use of such bladders will make feasible the standardization of oscillometric and auscultatory BP determination criteria, as well as facilitate the evaluation of oscillometric and auscultatory BP monitors using noninvasive blood pressure (NIBP) simulators.