Some effects of alteration of posture on arterial blood pressure

Abstract On changing from the recumbent to standing position the systolic pressure is from 5 to 40 mm. Hg below the recumbent level about ten seconds after the change. There is a rapid recovery after this initial drop and after about thirty seconds many have regained or passed the recumbent level. In some few cases the recovery is slower. Diastolic pressure usually rises slightly on standing. The same type of reaction is seen when the subjects are tilted into the vertical posture but the drop is greater and the recovery less. Prolonged quiet standing is a severe strain on the circulation as shown by the frequency of fainting. Reflexes from the carotid sinuses and arch of aorta are responsible (in part at least) for the reactions leading to the recovery of the pressure.