Study On The Effect And Mechanism Of External Pressure On Skin Blood Flow At Lower Limb

Nowadays, more and more people wear various tight-fit garments, such as foundation wear, stockings, tight pants, jeans and etc. Garment pressure caused by these garments may have positive or negative influence on body type and physiological system, so the safety and comfort begin to draw more and more attentions from consumers, clothing designers, engineers and researchers.This study focused on the effect of external pressure on skin blood flow (SBF). Five male post-graduate students were recruited for this study. Pressures of various magnitudes were exerted on ankles or calves respectively by using sphygmomanometer, under which the SBF was observed. Alternating protocol between non-pressure and pressure was employed. The influence of pressure on SBF was investigated in terms of pressure magnitudes, postures and compression regions. The wavelet analysis was also carried out on SBF signals to find out the mechanism. The results could be concluded as follows: (1) SBF increased when external pressure was exerted on the lower limb, and the increment became higher with the increasing of pressure; (2) as the pressure magnitude exceeding a certain level (around 35mmHg), the increment began to decline, this level for supine posture was lower than that for sitting posture, while it was higher for ankle than that for calf; (3) however, if the pressure was further higher, the SBF turned to decrease. The wavelet analysis on SBF signals revealed that the peak amplitude of myogenic activity increased and its corresponding frequency decreased under pressure.When external pressure is loaded on skin, the metarterioles embedded in the skin are compressed, vascular resistance increases. According to Poiseuille's law, blood flow in metarterioles decreases. Consequently, the opening time to reach the required concentration of oxygen in the connecting capillaries increases. Therefore, open-close frequency of capillaries decreased and open rate increased, resulting in the increase of SBF. When the pressure acting on metarteriole is higher than the inside blood pressure, they could be squashed and thus the blood flow in the connecting capillaries in the skin is blocked. The increase and decrease of SBF under pressure were the result of the balance between above two effects. The findings in this study can provide not only physiological basis to the pressure design and development of tight-fit garments, but also scientific instructions to customers.