Rhythmical variations of haemoglobin oxygenation in cutaneous capillaries

The consequences of rhythmical arteriolar vasomotion for nutrition and the tissue oxygen supply to human skin are largely unknown. In the study presented here, the periodic variations of haemoglobin oxygenation in the small cutaneous vessels have been evaluated with a new reflection spectrophotometer. For the assessment of spatial variations, we examined 24 different sites in 20 healthy volunteers. For quantification of the relatively long duration of periodic variations, a Digital Fourier Transformation with a specially programmed filter was used. In 265 out of 480 spectra (55.2%), periodic variations of the haemoglobin oxygenation were found. The average of the main frequency of waves was 7.0 +/- 2.5 cycles per minute. The occurrence of variations of haemoglobin oxygenation depended on the measuring site. In the gluteal region, variations were observed in 17 out of 20 subjects, on the palms in 16 out of 20, at the foot plantar in 18 out of 20 in comparison to the cheek (8/20), the lip (5/20) and the eyelid (6/20). On the head we observed significantly more variations per minute than in the lower extremities. Because these variations, with duration of up to 30 s, have a relatively slow dynamic compared with heart rate and breathing frequency, consequences for the cutaneous diffusion and metabolism of other substrates are very likely.