Reactive hyperaemia augments local heat-induced skin hyperaemia

Abstract

New findings: What is the central question of this study? It is valuable to be able to monitor disease- or treatment-related changes in the microcirculation. Laser Doppler flowmetry with local heating allows non-invasive monitoring of the skin microcirculation and its ability to vasodilate. Does reactive hyperaemia augment the increase in skin blood flow elicited by local heating? What is the main finding and its importance? The addition of reactive hyperaemia to local heating results in greater vasodilatation than heating alone. Thus, reactive hyperaemia can augment local heat-induced hyperaemia in the skin.

Abstract: The skin circulation has been proposed as a model of generalized microvascular function that could be monitored non-invasively using laser Doppler flowmetry (LDF). The response to heat hyperaemia (HH) is commonly used to monitor disease- or treatment-related changes in microvascular function. We hypothesized that reactive hyperaemia would augment the increase in skin blood flow elicited by local heating. Fourteen healthy young adults were subjected to three different conditions: reactive hyperaemia (RH; skin temperature controlled at 33°C), heat hyperaemia (HH; 42°C held for 40 min) and HH+RH. Two Peltier-controlled thermomodules with LDF probes were placed on the right forearm to monitor skin blood flow continuously. A cuff was placed on the right upper arm to elicit RH by inflation to 220 mmHg for 5 min. This procedure was performed with the skin temperature at 33°C and again after 40 min of local heating to 42°C. Beat-by-beat mean arterial pressure (MAP) obtained by a photoplethysmographic sensor on the middle finger of the left hand allowed calculation of cutaneous vascular conductance (CVC) as LDF/MAP. Both HH and RH increased LDF (P < 0.0001 and P < 0.0001, respectively) and CVC (P = 0.0001 and P < 0.0001, respectively) above baseline values. The LDF and CVC values were significantly higher during HH+RH when compared with RH or HH alone (P < 0.0001). In summary, HH+RH resulted in greater vasodilatation when compared with HH or RH alone. These results indicate that RH can augment local heat-induced hyperaemia in the skin.

Keywords: local heating; microvasculature; vascular conductance; vasodilatation.