Cardiovascular regulation during head-up tilt in healthy 20–30-year-old and 70–75-year-old men

Abstract

This study compared the heart rate, finger arterial pressure (AP) and electromyographic (EMG) activity of selected anti-gravity muscles during the initial and prolonged phases of orthostatic stress in healthy young and older men. Beat-by-beat recordings of heart rate, finger systolic pressure, diastolic pressure and mean AP were made during supine rest and 5 min of 90 degrees head-up tilt (HUT) in 18 young (23+/-1 years) and 15 older (73+/-1 years) men. The EMG activity of the soleus, tibialis anterior and vastus medialis muscles was recorded. During the first 30 s following 90 degrees HUT (immediate response), the young men exhibited significant (P<0.05) decreases in finger systolic pressure, diastolic pressure and mean AP, followed by a sustained increase in finger AP during the 5 min following 90 degrees HUT (prolonged response). The immediate and prolonged finger AP and diastolic pressure responses were not significantly different (P>0.05) from the values at supine rest for the older men. The mean root mean square EMG activity of the soleus, tibialis anterior and vastus medialis muscles during 90 degrees HUT was not significantly different (P>0.05) from that at supine rest for either group. These results demonstrate that, when compared with healthy older men, young men show larger reductions in finger AP during the initial phase of orthostatic stress. However, during the prolonged phase of orthostatic stress, older men maintain resting finger AP, whereas young men demonstrate a reflex overshoot in finger AP. Finally, differences in lower-limb anti-gravity muscle activation do not account for the contrasting finger AP responses of healthy young and older men.

Arterial blood pressure response to head-up tilt test and orthostatic tolerance in nurses

“…However, similar BP responses during HUT were reported in healthy subjects by Gabbett et al [29], who conducted a 90°HUT test on young males, and observed that a BP overshoot in an early stage of HUT to about 10 mmHg above the supine value. It has been widely accepted that considerable individual variations exist in orthostatic tolerance [25,26,30,31].…”

Contribuição dos grandes vasos arteriais na adaptação cardiovascular a ortostase

“…The acute cardiac frequency increase in response to the rapid change into the orthostatic posture, in general occurring within the fi rst seconds after standing upright, although present in all individuals, decreases in magnitude with age, and can be delayed 118 . This decrease in the variability of the cardiac frequency observed in elderly patients, when compared to young individuals in the orthostatic versus the supine posture, has been attributed to a decrease in the recruitment of baroreceptor activity when the upright position is adopted 17,117,118 .…”

“…However, the analysis of cardiac frequency in healthy individuals in the sitting posture has shown that cardiac frequency decreases with age in both sexes 116,117 . The studies utilizing the IT to assess the cardiovascular adaptation to orthostatic stress also reported a signifi cantly lower cardiac frequency in elderly individuals 17,117,118 . We know that the resting cardiac frequency is modulated, in part, by the equilibrium between the sympathetic and the parasympathetic tonus, with a predominance of the latter.…”

“…The hydrostatic opposition to the venous return, the third-space loss of fl uid, venous return decrease and cardiac output reduction, all of which are hemodynamic alterations secondary to the gravitational effect, act as multiple stimuli, generating a variety of compensatory mechanisms 16,17 . Additionally, the gravitational stress can be aggravated by the level of physical activity, environmental temperature, and drug use and by several physiopathological processes, all capable of augmenting the disparity between the vascular volumetric capacity and blood fl ow volume [18][19][20] .…”

SAPHIR - a multi-scale, multi-resolution modeling environment targeting blood pressure regulation and fluid homeostasis

“…However, this is not the case at the cardiac frequency scale. Indeed, the effect of pleural pressure on the heart is quite well elucidated [22]. Nonetheless, to our knowledge, the reciprocal effect of heart on pleural pressure is not clear: the beating heart can be considered as a volume and/or pressure change generator inside the rib cage as evidenced by its effect on lung volume [23].…”