Office blood pressures in supine, sitting, and standing positions: correlation with ambulatory blood pressures

The variability of casual (office) blood pressure according to position at the time of measurement was investigated in 168 untreated patients with a history of mild to moderate essential hypertension. Two measurements were made in the supine, sitting, and standing positions on each of 2 consective days, and 24-hour ambulatory blood pressure monitoring was performed. The mean supine, sitting, and standing blood pressures were 146 ± 15 91 ± 7 , 144 ± 15 96 ± 8 , and 149 ± 17 103 ± 7 mm Hg , respectively. Diastolic blood pressures were significantly different from each other ( P < 0.0001). Supine and sitting systolic blood pressures were not different, but they were different from standing blood pressure ( P < 0.0001). The mean of all three positions (overall blood pressure) was 146 ± 15 96 ± 7 mm Hg . Supine, sitting, standing, and overall diastolic blood pressure means were 90 mm Hg or more in 88, 133, 164, and 133 patients, respectively. The mean awake ambulatory and 24-hour ambulatory blood pressures were 143 ± 16 95 ± 7 and 138 ± 16 92 ± 8 mm Hg , respectively, and diastolic blood pressures were 90 mm Hg or more in 121 and 88 patients, respectively. The correlation of office blood pressure with ambulatory blood pressure varied according to office position and was 0.76 to 0.82 ( P < 0.0001) for systolic blood pressure and 0.60 to 0.69 ( P < 0.0001) for diastolic blood pressure. The study demonstrates that position at measurement significantly influences the estimation of mean blood pressure, blood pressure load (percentage of systolic and diastolic ambulatory readings more than 140 and 90 mm Hg, respectively), and the diagnosis of hypertension and that either the value in the sitting position or the overall value (mean of values in all three positions) may offer a reliable measurement.