Gravity effects on lower limb perfusion observed during a series of parabolic flights

Abstract

The present observational study simultaneously measured four key factors (arterial oxygenation, superficial tissue oxygenation, peripheral skin temperature, toe systolic pressure) to determine the impact on lower limb perfusion in altered gravity conditions. 24 healthy test subjects (16 male, 8 female) took part onboard a series of parabolic flights. When comparing lower limb perfusion values to 1G (control/Earth's gravity) the study found: 1) no significant difference between arterial oxygenation values in hyper or microgravity was detected when using a pulse oximeter; 2) a significant difference in superficial tissue oxygenation in hyper and microgravity was detected by white light spectroscopy; 3) a significant difference in skin temperature of the foot was detected by thermography in hyper and microgravity; 4) an insufficient sample could be obtained for toe systolic pressure. Reduction in superficial tissue oxygenation and peripheral skin temperature in microgravity compared to 1G, potentially suggests a reduction in blood flow. White light spectroscopy and thermography devices demonstrated they functioned as usual in altered gravity conditions potentially offering a quick, reliable method of assessing the acute effects of hyper and microgravity on lower limb perfusion. These methods may be useful to predict healing potential when injuries occur and highlight early warning signs of tissue damage due to poor perfusion. However, additional work to further establish the impact on oxygen transport in the superficial tissues in both acute and sustained microgravity would be beneficial.