Increased tissue oxygenation explains the attenuation of hyperemia upon repetitive pneumatic compression of the lower leg.

The rapid hyperemia evoked by muscle compression is short lived and was recently shown to undergo a rapid decrease even in spite of continuing mechanical stimulation. The present study aims at investigating the mechanisms underlying this attenuation, which include local metabolic mechanisms, desensitization of mechanosensitive pathways, and reduced efficacy of the muscle pump. In 10 healthy subjects, short sequences of mechanical compressions ( = 3-6; 150 mmHg) of the lower leg were delivered at different interstimulus intervals (ranging from 20 to 160 s) through a customized pneumatic device. Hemodynamic monitoring included near-infrared spectroscopy, detecting tissue oxygenation and blood volume in calf muscles, and simultaneous echo-Doppler measurement of arterial (superficial femoral artery) and venous (femoral vein) blood flow. The results indicate that ) a long-lasting (>100 s) increase in local tissue oxygenation follows compression-induced hyperemia, ) compression-induced hyperemia exhibits different patterns of attenuation depending on the interstimulus interval, ) the amplitude of the hyperemia is not correlated with the amount of blood volume displaced by the compression, and ) the extent of attenuation negatively correlates with tissue oxygenation ( = -0,78, < 0.05). Increased tissue oxygenation appears to be the key factor for the attenuation of hyperemia upon repetitive compressive stimulation. Tissue oxygenation monitoring is suggested as a useful integration in medical treatments aimed at improving local circulation by repetitive tissue compression. This study shows that ) the hyperemia induced by muscle compression produces a long-lasting increase in tissue oxygenation, ) the hyperemia produced by subsequent muscle compressions exhibits different patterns of attenuation at different interstimulus intervals, and ) the extent of attenuation of the compression-induced hyperemia is proportional to the level of oxygenation achieved in the tissue. The results support the concept that tissue oxygenation is a key variable in blood flow regulation.