A comparative study of the measurement of mean arterial blood pressure using automatic oscillometers, arterial cannulation and auscultation.

Mean brachial artery pressures determined by five different non-invasive automatic oscillometric and one auscultatory preferred (oscillometric back-up) blood pressure (BP) monitors were compared with mean arterial pressures (MAP) obtained by cannulation of the radial artery of the same arm. The devices tested all performed similarly, showing a wide range of variation (+40% to -29%) compared with the directly measured MAP, and all tended to over-read at low values and under-read at high values. Trend information was generally acceptable, but occasionally was misleading. In addition, using one of the devices, systolic and diastolic blood pressure measurements were compared with those obtained by auscultation. This gives a range of differences from +22 to -25 mmHg for systolic and +20 to -12 mmHg for diastolic BP measurements. (The average fell within 1.0 mmHg of the auscultatory measurement, with a standard deviation of 10 mmHg.) Thus, the automatic oscillometric BP monitors tested were comparable in accuracy to auscultatory BP measurement, and are satisfactory for routine use in the appropriate clinical context. However, in settings where significance is to be attached to individual BP readings rather than to trends, or where a high degree of accuracy is required, automatic oscillometric machines cannot be regarded as satisfactory alternatives to arterial cannulation.