Blood pressure level changes caused by posture change and physical exercise: can they be determined accurately using a standard cuff method?

The accuracy of the indirect standard cuff method of measurement was tested against intra-arterial blood pressure readings (Oxford method) in a series of simple clinical tests: in the sitting, supine and standing positions, during bicycle ergometer test and during recovery. The mean discrepancy between methods varied in tests from -2.3 to 12.9 mmHg for systolic blood pressure level and from -4.3 to 18.2 mmHg for diastolic blood pressure level. Blood pressure responses to other tests were analysed using the value measured in the sitting position as the reference. The mean discrepancy between the methods in test responses varied from -6.3 to 8.9 mmHg for systolic responses and from -2.3 to 20.3 mmHg for diastolic responses. The data analysis indicates that the accuracy of the indirect method varies considerably between tests and also between subjects. We conclude that at present the standard cuff method cannot replace the direct method for determining blood pressure responses and reactivity.