Influences of thigh cuffs on the cardiovascular system during 7-day head-down bed rest.
Thigh cuffs, presently named "bracelets," consist of two straps fixed to the upper part of each thigh, applying a pressure of 30 mmHg. The objective was to evaluate the cardiac, arterial, and venous changes in a group of subjects in head-down tilt (HDT) for 7 days by using thigh cuffs during the daytime, and in a control group not using cuffs. The cardiovascular parameters were measured by echography and Doppler. Seven days in HDT reduced stroke volume in both groups (-10%; P < 0.05). Lower limb vascular resistance decreased more in the cuff group than in the control group (-29 vs. -4%; P < 0.05). Cerebral resistance increased in the control group only (+6%; P < 0.05). The jugular vein increased (+45%; P < 0.05) and femoral and popliteal veins decreased in cross-sectional area in both groups (-45 and -8%, respectively; P < 0.05). Carotid diameter tended to decrease (-5%; not significant) in both groups. Heart rate, blood pressure, cardiac output, and total resistance did not change significantly. After 8 h with thigh cuffs, the cardiac and arterial parameters had recovered their pre-HDT level except for blood pressure (+6%; P < 0.05). Jugular vein size decreased from the pre-HDT level (-21%; P < 0.05), and femoral and popliteal vein size increased (+110 and +136%, respectively; P < 0.05). The thigh cuffs had no effect on the development of orthostatic intolerance during the 7 days in HDT.
Arbeille
P
P
Unité Médecine et Physiologie Spatiale, Departement de Médecine Nucléaire et Ultrasons, Centres Hospitaliers Universitaires Trousseau, 37044 Tours, France. arbeille@med.univ-tours.fr
Herault
S
S
Fomina
G
G
Roumy
J
J
Alferova
I
I
Gharib
C
C
D000222:Adaptation, Physiological; D000328:Adult; D001510:Bed Rest; D002320:Cardiovascular Physiological Phenomena; D003250:Constriction; D018475:Head-Down Tilt / Q000502:physiology*; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology; D012016:Reference Values; D013848:Thigh / Q000098:blood supply*; D013997:Time Factors