Changes in blood flow in the skin and muscle with phototherapy.

Abstract

Extract: The electrocapacitance plethysmograph with local counterpressure was adapted for measurement of total blood flow and blood flow through the muscle and skin in 20 icteric preterm infants. Measurements were recorded from each infant, before and during phototherapy. In 10 infants in study I, the incubator was set to maintain skin temperature of 36.5° initially and during phototherapy and no attempt was made to alter the incubator settings. Total blood flow was found to increase by a mean of 116% due primarily to increased skin blood flow (224%) and to a lesser extent, muscle blood flow (35%). Concomitant increases in heart rate, respiration rate, skin and incubator temperature were found, but no change was observed in rectal temperature. In 10 infants in study II, the skin temperature was kept constant at 36.5° before and during phototherapy by adjustment of incubator temperature. Significant increases, but of lesser magnitude, were observed in skin (52%) and total blood flow (37%), whereas muscle blood flow remained unchanged. Rectal temperature fell by a mean of 0.6° and respiration rate and heart rate remained unchanged. Speculation: During phototherapy both an increase in surface temperature and the direct effect of light results in augmentation of total blood flow. Increasing skin temperature appears to affect blood flow in both skin and muscle, whereas the direct effect of light from phototherapy lamps appears to affect skin blood flow only and to a lesser degree. The augmentation in skin blood flow should increase the efficiency of phototherapy. However, in small or sick infants the metabolic demands due to increasing temperature may outweigh any benefit from increasing blood flow.