DOES IT MATTER WHETHER BLOOD-PRESSURE MEASUREMENTS ARE TAKEN WITH SUBJECTS SITTING OR SUPINE

Background Several guidelines for the management of hypertension do no t give special preference to a specific position of the patient during blood pressure measurement, suggesting that blood pressure readings t aken with patients sitting and with patients supine are interchangeabl e. Objective To test whether there is any difference between the blood pressure readings with patients sitting and supine. Design and method s Blood pressure and heart rate were measured three times each for 245 subjects (171 hypertensives), with subjects both sitting and supine, simultaneously on both arms, with a Hawksley random-zero sphygmomanome ter on the right arm and a semi-automatic oscillometric device (Bosoma t) on the left arm. The sequence of the two positions was randomized. The procedure was repeated on a second occasion for 49 subjects (41 hy pertensives) with the sequence of the positions reversed. Because ther e was no systematic difference among the three readings per position, the averages of the three blood pressure and heart rate readings with subjects sitting and supine were compared and the influences of age, b ody mass index, hypertension and medication on the difference were exa mined. Results We found no influence of the subject's body posture on the systolic blood pressure. We found a higher diastolic blood pressur e [by 5.2 +/- 0.4 mmHg (mean +/- SEM), P < 0.001 with Hawksley random- zero sphygmomanometer] and a greater heart rate [by 1.5 +/- 0.3 beats/ min (mean +/- SEM), P < 0.001] with subjects sitting. The sitting minu s supine differences for diastolic blood pressure and heart rate decre ased significantly with increasing age (P < 0.001). We found no effect of body mass index, hypertension and medication on the sitting-supine differences. Conclusions The subject's body posture influenced especi ally the diastolic blood pressure and heart rate, both of them being s ignificantly higher with patients sitting rather than supine. This eff ect decreased with age. Thus, for indirect blood pressure measurement, diastolic blood pressure values obtained with subjects sitting and su pine cannot automatically be regarded as equivalent. (C) 1998 Rapid Sc ience Ltd.