Ambulatory blood pressure variation in normotensive subjects in relation to the sitting or standing position

OBJECTIVE: To evaluate the physiological variations in arterial blood pressure in normotensive subjects during activity and in relation to the sitting or lying position. METHODS: The subjects were 30 healthy volunteers who were normotensive and receiving no treatment. Blood pressure was measured using the validated monitor Diasys Integra (NOVACOR SA, Rueil-Malmaison, France) with an integral position sensor. Blood pressure was recorded every 15min over a 24h period, additional measurements being made in the first, third and sixth minutes after standing up. RESULTS: During the active period (1000-2000h), 53% of the measures were made in the standing position. Over this period, the values of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were significantly elevated in the standing position in comparison to the sitting position. The difference was of the order of 5mmHg for the SBP, 3.5mmHg for the DBP and 9beats/min for the heart rate. The SBP, DBP and heart rate measured in the first, third and sixth minutes after standing up were not significantly different. CONCLUSION: When measuring the blood pressure and heart rate in ambulatory patients, it seems justified to evaluate the patient's position during monitoring in order to achieve a better reproducibility and also to uncover any problems of blood pressure control with positional change, as could exist in patients with autonomic dysfunction. This might also aid in evaluating antihypertensive treatment and also any deleterious hypotensive effects.