A CAUSAL RELATIONSHIP BETWEEN FLUCTUATIONS IN THERMOREGULATORY SKIN PERFUSION AND RESPIRATORY MOVEMENTS IN MAN

The relationship between regular respiration with normal tidal volume and spontaneous fluctuations in blood; flow through skin arteriovenous anastomoses (AVAs) was investigated. Laser Doppler measurements from skin areas known to contain arteriovenous anastomoses, ultrasound Dopp ler measurements from the radial artery and respiratory movements were recorded simultaneously in 7 supine human subjects in a thermoneutral environment. The phase relationship between respiration and the onset of sudden arteriovenous anastomoses vasoconstrictions was calculated in each subject. A few seconds before a vasoconstriction, there was a clear tendency towards synchrony in the respiration recordings, indica ting that some respiration-phase-dependent event precedes the vasocons trictions. Since arteriovenous anastomoses constrictions are accompani ed by specific changes in heart rate and blood pressure, our findings link respiration to low-frequency heart rate and blood-pressure variab ility in humans.