Physiological responses to postural change in young and old healthy individuals.

The cardiovascular responses to 70 degrees head-up tilt were compared in 9 healthy young, mean age 31 +/- (S.D.) 3.2 years, and 8 healthy elderly subjects, mean age 71 +/- 5.1 years. After 10 minutes tilt, qualitatively similar responses were found in the two groups. Quantitatively, however, heart rate, stroke volume, cardiac output, and peripheral resistance showed smaller differences between the supine and tilt positions in the older group. Blood pressure and plasma volume changes were similar in both groups. There is an age-associated effect in the cardiovascular response to change in posture in healthy people that resembles that found in congestive cardiac failure.