Influence of body water distribution on skin thickness: measurements usinghigh-frequency ultrasound

Background Although it is known that the skin acts as a water reservoir and participates in the fluid content of the whole body, no method has been es tablished to quantify the fluid shifts in superficial tissue. Objectives The aim of this study was to investigate changes in dermal and s ubcutis thickness and echodensity at the forehead and lower leg by high-fre quency (20 MHz) ultrasound under various physiological conditions influenci ng water balance. Methods These parameters were measured in the skin of 20 healthy male volun teers at baseline and successively at 30 min after lying down, in a head-do wn position, after physical activity and after infusion of 10 mL kg(-1) bod y weight of Ringer's solution. Results Dermal thickness at the forehead showed a significant increase from baseline to a horizontal position and a further increase in the head-down position. Physical activity did not lead to further changes, whereas after fluid infusion the dermal thickness also increased markedly. The echodensit y showed inverse changes, with decreasing values. The thickness of the subc utis increased slightly from baseline to a lying position and decreased in the head-down position and after fluid infusion. At the lower leg, skin thi ckness decreased slightly in the head-down position with elevated legs, and increased after fluid infusion. Conclusions Our results show that slight changes in the water distribution of the body influence the thickness and the echodensity of the dermis. Chan ges are more pronounced at the forehead than on the lower legs. Further, th e fluid storage takes place mainly in the dermis and not in the subcutis. H igh-frequency ultrasound is able to quantify these effects and is a sensiti ve method for measuring fluid intake and balance during anaesthesia and the rapy.