Augmentation of Brachial Reactive Hyperemia by Local Forearm Heating: A plethysmography-Based Comparison with the Standard Room-Temperature Protocol
Abstract
Introduction
Reactive hyperemia (RH) is widely used to assess microvascular endothelial function, but its magnitude may be limited when performed on a normally perfused, non-heated forearm. Local skin heating to 43.5°C produces sustained nitric oxide–dependent vasodilation and may augment the RH response.
Material and methods
Twenty healthy adult males (non-smokers, medication-free) underwent standard RH induced by 5-min brachial artery occlusion followed by 3 min reperfusion. ECG and bilateral fingertip plethysmography digital pulse waves were recorded to derive pulse transit time (PTT) and finger-to-finger pulse-arrival-time difference (f–f ΔT). In 11 of these participants, the forearm was then heated with an electric heat pad to 43.5 ± 0.4°C for 25–30 min, and RH was repeated. Indices were calculated from 60–80 cardiac cycles during the first two minutes of reperfusion.
Results
At room temperature, RH increased PTT by about 5%–6% and markedly increased f–f ΔT, consistent with improved distal perfusion. When RH was repeated after local heating, the reactive hyperemia index was significantly higher (about 1.5-fold, p < 0.007), indicating that prior heating enhanced the hyperemic response. In contrast, heated RH did not produce further increases in PTT or f–f ΔT compared with RH at room temperature, suggesting dissociation between enhanced microvascular recruitment and conduit-level stiffness changes.
Conclusions
Performing RH after local forearm heating at 43.5°C amplifies plethysmography-derived hyperemia indices compared with the conventional room-temperature test, mainly by enhancing the endothelial and microvascular component rather than further reducing arterial stiffness. Thermal priming may improve the sensitivity of plethysmography-based endothelial assessment in physiological studies.
© 2026 Momel Ahmed Mnati, Fezaa Shalal Neda, Bassam Talib Al-Gailani, published by Polish Society of Medical Physics
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