Abstract
During upright tilting, blood is translocated to the dependent veins of the legs and compensatory circulatory adjustments are necessary to maintain arterial pressure. For examination of the effect of age on these responses, seven young (23 ± 1 yr) and seven older (70 ± 3 yr) men were head-up tilted to 60°in a thermoneutral condition and during passive heating with water- perfused suits. Measurements included heart rate (HR), cardiac output (Q̇(c); acetylene rebreathing technique), central venous pressure (CVP), blood pressures, forearm blood flow (venous occlusion plethysmography), splanchnic and renal blood flows (indocyanine green and p-aminohippurate clearance), and esophageal and mean skin temperatures. In response to tilting in the thermoneutral condition, CVP and stroke volume decreased to a greater extent in the young men, but HR increased more, such that the fall in Q̇(c) was similar between the two groups in the upright posture. The rise in splanchnic vascular resistance (SVR) was greater in the older men, but the young men increased forearm vascular resistance (FVR) to a greater extent than the older men. The fall in Q̇(c) during combined heat stress and tilting was greater in the young compared with older men. Only four of the young men versus six of the older men were able to finish the second tilt without becoming presyncopal. In summary, the older men relied on a greater increase in SVR to compensate for a reduced ability to constrict the skin and muscle circulations (as determined by changes in FVR) during head-up tilting.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
| Volume | 276 |
| Issue number | 1 45-1 |
| State | Published - Jan 1 1999 |
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All Science Journal Classification (ASJC) codes
- Physiology
- Physiology (medical)
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Age, splanchnic vasoconstriction, and heat stress during tilting. / Minson, Christopher T.; Wladkowski, Stacey L.; Pawelczyk, James Anthony; Kenney, Jr., William Lawrence.
In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 276, No. 1 45-1, 01.01.1999.Research output: Contribution to journal › Article
TY - JOUR
T1 - Age, splanchnic vasoconstriction, and heat stress during tilting
AU - Minson, Christopher T.
AU - Wladkowski, Stacey L.
AU - Pawelczyk, James Anthony
AU - Kenney, Jr., William Lawrence
PY - 1999/1/1
Y1 - 1999/1/1
N2 - During upright tilting, blood is translocated to the dependent veins of the legs and compensatory circulatory adjustments are necessary to maintain arterial pressure. For examination of the effect of age on these responses, seven young (23 ± 1 yr) and seven older (70 ± 3 yr) men were head-up tilted to 60°in a thermoneutral condition and during passive heating with water- perfused suits. Measurements included heart rate (HR), cardiac output (Q̇(c); acetylene rebreathing technique), central venous pressure (CVP), blood pressures, forearm blood flow (venous occlusion plethysmography), splanchnic and renal blood flows (indocyanine green and p-aminohippurate clearance), and esophageal and mean skin temperatures. In response to tilting in the thermoneutral condition, CVP and stroke volume decreased to a greater extent in the young men, but HR increased more, such that the fall in Q̇(c) was similar between the two groups in the upright posture. The rise in splanchnic vascular resistance (SVR) was greater in the older men, but the young men increased forearm vascular resistance (FVR) to a greater extent than the older men. The fall in Q̇(c) during combined heat stress and tilting was greater in the young compared with older men. Only four of the young men versus six of the older men were able to finish the second tilt without becoming presyncopal. In summary, the older men relied on a greater increase in SVR to compensate for a reduced ability to constrict the skin and muscle circulations (as determined by changes in FVR) during head-up tilting.
AB - During upright tilting, blood is translocated to the dependent veins of the legs and compensatory circulatory adjustments are necessary to maintain arterial pressure. For examination of the effect of age on these responses, seven young (23 ± 1 yr) and seven older (70 ± 3 yr) men were head-up tilted to 60°in a thermoneutral condition and during passive heating with water- perfused suits. Measurements included heart rate (HR), cardiac output (Q̇(c); acetylene rebreathing technique), central venous pressure (CVP), blood pressures, forearm blood flow (venous occlusion plethysmography), splanchnic and renal blood flows (indocyanine green and p-aminohippurate clearance), and esophageal and mean skin temperatures. In response to tilting in the thermoneutral condition, CVP and stroke volume decreased to a greater extent in the young men, but HR increased more, such that the fall in Q̇(c) was similar between the two groups in the upright posture. The rise in splanchnic vascular resistance (SVR) was greater in the older men, but the young men increased forearm vascular resistance (FVR) to a greater extent than the older men. The fall in Q̇(c) during combined heat stress and tilting was greater in the young compared with older men. Only four of the young men versus six of the older men were able to finish the second tilt without becoming presyncopal. In summary, the older men relied on a greater increase in SVR to compensate for a reduced ability to constrict the skin and muscle circulations (as determined by changes in FVR) during head-up tilting.
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UR - http://www.scopus.com/inward/citedby.url?scp=0032919284&partnerID=8YFLogxK
M3 - Article
C2 - 9887196
AN - SCOPUS:0032919284
VL - 276
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6119
IS - 1 45-1
ER -