Mechanism of orthostatic intolerance in microgravity
Abstract：AIM:To observe the changes of pressure- volume(P- V) relationship of the femoral veins of rabbits after exposure to simulated weightlessness and to explore the mechanism of orthostatic intolerance in microgravity. METHODS:Sixteen healthy male New Zealand rabbits were subjected to head- down tilt(HDT) at - 20O to simulate the condition of weightlessness, and were randomly divided into 21 d HDT group,10 d HDT group and control group(8 in each),with another 8 serving as normal control group.The P- V relationships of the femoral veins were investigated after the exposure. RESULTS:The femoral vein P- V relationship curves of HDT groups tended to shift to greater volume change ratio than that of control group(P< 0.01), and the shift was more obvious in 21d HDT group(P< 0.01).B1 and B2 in the quadratic equations of 21d HDT group[Inflow: B1=(3.6± 1.6)× 10- 2,B2=( 3.3± 2.8)× 10- 4;outflow:B1=(4.2± 1.8)× 10- 2,B2=( 4.6± 3.4)× 10- 4]were significantly higher than the value of 10 d HDT group[Inflow:B1=(1.7± 0.6)× 10- 2,B2=(0.8± 0.6)× 10- 4;outflow:B1=(2.1± 0.6)× 10- 2,B2=( 1.3± 0.7)× 10- 4]and control group[Inflow:B1=(1.3± 0.6)× 10- 2,B2=( 0.4± 0.3)× 10- 4;outflow:B1=(1.8± 1.0)× 10- 2,B2=( 0.8± 0.8)× 10- 4] during inflow and outflow(P< 0.01). CONCLUSION:The femoral venous compliance increases after weightlessness simulation,companied by obvious structural changes in the wall of the femoral veins.
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Publication Date：2003-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：4( 3694-3696 )