Effect of body position on circulatory adaptation to exercise in patients with essential hypertension

Abstract

The effect of body position on the central circulatory adaptation to exercise has been studied in ten patients, seven men and three women, with essential hypertension. The subjects were studied at rest and during exercise in sitting and recumbent body positions. With exercise of increasing intensity, the rise of systolic pressure in relation to that of cardiac output was steeper than in a group of normal subjects both in supine and in sitting body position. However, the rise of systemic arterial pressure in relation to cardiac output showed no correlation with resting blood pressure, duration of hypertension, or age. Compared with normal subjects, cardiac output and stroke volume were somewhat lower both in supine and in sitting, though the two groups had the same slope for the increase in cardiac output in relation to oxygen uptake during work. As in healthy subjects, heart rate in relation to oxygen uptake did not differ between supine and sitting positions during work. Thus, in spite of haemodynamic differences compared to normal subjects the general pattern of circulatory adaptation at rest and during work in an upright body position compared to supine was not different from normal. In the supine position the pulmonary artery wedge pressure was higher on the average than in normal subjects and in some patients it also increased more in relation to the rise of cardiac output with exercise. The pressures in the pulmonary artery, as well as the systolic pressures in the right ventricle, on the average increased more steeply in relation to cardiac output with exercise compared with healthy subjects and these pressure increases appeared to be related to the severity of the systemic hypertension.

Key Words:

• body position
• cardiac output
• circulatory adaptation
• essential hypertension
• exercise
• pulmonal artery pressure