Errors of oscillometric blood pressure measurement as predicted by simulation

To study factors affecting the accuracy of oscillometric measurement.

By means of a computer-based simulator, a variety of arterial pressure pulses of different shapes and amplitudes were composed as an input signal of the model, whereas cuff volume oscillations were obtained as an output signal. The shape of the artery-cuff pressure/volume relationship was modified. Thereafter, oscillation envelopes were drawn and an estimation of systolic and diastolic pressures was performed by implementing fixed characteristic ratios. The mean arterial pressure was estimated using the maximum oscillation criterion. Altogether, 32 combinations of four affecting factors were studied.

For the studied range of affecting factors, the induced errors in systolic pressure, diastolic pressure, and mean arterial pressures were 15, 14, and 27 mmHg, respectively. Systolic readings moved toward underestimation and diastolic readings moved toward overestimation if pulse pressure increased. Arterial stiffening induced systematic overestimation of the systolic pressure and overestimation or underestimation of the diastolic pressure compared with a normal artery, with errors depending on the interaction of the symmetry and steepness indices of the artery-cuff pressure/volume curve. Errors of mean arterial pressure were proportional to pulse pressure, showing overestimation if stiffness increased and/or arterial pressure pulses became steeper.

Oscillometric readings of systolic and diastolic pressures are strongly influenced by pulse pressure and the shape of the artery-cuff pressure/volume curve, whereas those of the mean arterial pressure are affected by pulse pressure and both the shape of the artery-cuff pressure/volume curve and the shape of the arterial pulse.