How long shall the patient rest before clinic blood pressure measurement?

The optimal time at rest before clinic blood pressure (BP) measurement is still undefined. In this study in patients with essential hypertension, the time course of the hemodynamic changes during a 16-min rest in the chair-seated position was evaluated and compared with that observed in a stabilized postural condition, such as after a prolonged supine rest.

In 55 untreated essential hypertensive patients, BP, heart rate, stroke volume (impedance cardiography), and systemic vascular resistances were measured every other minute during a 16-min rest in the chair-seated position and, in random sequence, in the last 16 min of a 60-min supine rest.

Overall, systolic BP (SBP) and diastolic BP (DBP) decreased by 11.6 and 4.3 mm Hg, respectively, during the chair-seated rest; only a 1.8-mm Hg decrease in SBP was observed in the control supine study. The chair-seated fall in BP was associated with a decrease in systemic vascular resistances, in the absence of significant changes in cardiac index. From the logarithmic curve of SBP and DBP decrements, a half-time of 5.8 and 5.5 min respectively, was calculated. Decrements in SBP, but not DBP, were inversely related to the corresponding baseline values.

In untreated essential hypertensive patients a significant decrease in SBP and DBP associated with a systemic vasodilation was observed during a 16-min rest in the chair-seated position. Because approximately 75% of the spontaneous fall in BP occurred within 10 min, it appears that this time at rest before clinic BP evaluation could improve the precision and accuracy of the measurement.