Key result
Five weeks of horizontal bedrest increased pressure distension threefold in the tibial artery (from 8% to 24%, P<0.01) and by a third in the brachial artery (from 15% to 20%, P<0.05).
Why the study?
Does 5 weeks of horizontal bedrest increase pressure distension in arteries and arterioles?
Does 5 weeks of horizontal bedrest increase pressure distension in arteries and arterioles?
Prolonged horizontal bedrest significantly increases pressure distension in dependent arteries and arterioles, likely due to the withdrawal of hydrostatic pressure gradients.
Answers are grounded in this paper and cite their sources.
Prolonged bedrest may increase arterial pressure distension risk; leaves open whether countermeasures mitigate vascular effects in immobilized patients.
We hypothesized that exposure to prolonged recumbency (bedrest), and thus reductions of intravascular pressure gradients, increases pressure distension in arteries/arterioles in the legs. Ten subjects underwent 5 wk of horizontal bedrest. Pressure distension was investigated in arteries and arterioles before and after the bedrest, with the subject seated or supine in a hyperbaric chamber with either one arm or a lower leg protruding through a hole in the chamber door. Increased pressure in the vessels of the arm/leg was accomplished by increasing chamber pressure. Vessel diameter and flow were measured in the brachial and posterior tibial arteries using Doppler ultrasonography. Electrical tissue impedance was measured in the test limb. Bedrest increased (P < 0.01) pressure distension threefold in the tibial artery (from 8 +/- 7% to 24 +/- 11%) and by a third (P < 0.05) in the brachial artery (from 15 +/- 9% to 20 +/- 10%). The pressure-induced increase in tibial artery flow was more pronounced (P < 0.01) after (50 +/- 39 ml/min) than before (13 +/- 23 ml/min) bedrest, whereas the brachial artery flow response was unaffected by bedrest. The pressure-induced decrease in tissue impedance in the leg was more pronounced (P < 0.01) after (16 +/- 7%) than before (10 +/- 6%) bedrest, whereas bedrest did not affect the impedance response in the arm. Thus, withdrawal of the hydrostatic pressure gradients that act along the blood vessels in erect posture markedly increases pressure distension in dependent arteries and arterioles.
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Eiken et al. (2008) studied this question. Horizontal bedrest vs. Before bedrest was evaluated on Pressure distension in the tibial artery (p=< 0.01). Five weeks of horizontal bedrest increased pressure distension threefold in the tibial artery (from 8% to 24%, P<0.01) and by a third in the brachial artery (from 15% to 20%, P<0.05).
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