Hypotension associated with prone body position: a possible overlooked postural hypotension.

Conditions related to the dysregulation of blood pressure (BP), such as orthostatic hypotension, have been shown to be significantly associated with cardiovascular disease. Recently, the prone body position has been recognized as a possible postural factor leading to BP dysregulation. We conducted a cross-sectional study to investigate the BP response to a change in body position from supine to prone. The study subjects consisted of 271 middle-aged healthy males, randomly selected from the employees of a large manufacturing enterprise in Ehime Prefecture, Japan. Brachial BP and heart rate were measured in a sitting, supine and prone position, in that order, and each difference was defined as a postural change. The postural changes in aortic hemodynamics were also assessed using a SphygmoCor system. The basal BP measured in the sitting position was significantly decreased in the supine position (132+/-18 to 130+/-17 mmHg, p<0.001). A further reduction was observed after the postural change from supine to prone (130+/-17 to 125+/-16 mmHg, p<0.001). The heart rate was increased with the supine-to-prone postural change (4.1+/-5.8 beats/min, p<0.001), while it showed a significant decrease with the sitting-to-supine postural change (-7.6+/-5.6 beats/ min, p<0.05). The impact of BP reduction was more prominent in the aortic artery (-3.3+/-6.7%) than the brachial artery (-3.0+/-6.3%, p=0.020). Multiple regression analysis showed that basal systolic BP was a solely significant determinant of the prone-hypotension (beta=-0.309, p<0.001). In conclusion, these results indicate that lying in a prone posture could lead to unregulated postural hypotension, which has the possibility of being a novel predictor of cardiovascular frailty.