Spectral Analysis Of Cutaneous Vasodilation To Assess Sex-differences In The Response To Local Heating

Spectral analysis of laser-doppler flowmetry (LDF) signals is an emerging non-invasive approach to understanding the physiological underpinnings of cutaneous vasodilation in response to various stimuli. Cutaneous microvascular control during local heat-induced vasodilation is modulated by an array of mechanisms that can be characterized by distinct frequency bands in the LDF signal. The relative contribution (spectral power) of frequency bands (neurogenic, myogenic, metabolic, cardiac and respiratory) to local heat-induced cutaneous vasodilation may be modulated by individual factors such as sex. PURPOSE: To describe sex-related differences in the spectral power of cutaneous vasodilation during local heating. METHODS: 30 healthy young adults (15 females) were instrumented with six LDF probes integrated with local heaters. Probes were placed in a randomized order on the left side of the body on the chest, arm, forearm, abdomen, thigh, and calf. Local heater temperatures were increased from 33 °C to 42 °C and maintained up to 35 min until a stable plateau was reached. LDF signals were extracted into frequency-amplitude estimates using a Morlet mother wavelet to transform the data signal. Absolute amplitude and relative contributions of each frequency band to the average amplitude of the total frequency band was calculated. For each frequency band of interest, wavelet amplitude was log-transformed and evaluated using a linear mixed model, with separate models for the absolute and relative (% of total spectral activity) amplitude. Between-sex differences were transformed into fold-differences for clarity. RESULTS: Males showed significant fold-increases in both absolute and relative wavelet amplitudes associated with neurogenic (1.32 ± 0.13, P = 0.006, 1.19 ± 0.08, P = 0.010), and myogenic (1.29 ± 0.11, P = 0.003, 1.12 ± 0.05, P = 0.016) bands compared to females. Males also showed a significant fold-decrease in relative wavelet amplitude associated with the cardiac band (0.94 ± 0.03, P = 0.045). CONCLUSION: Differences between males and females were detected in the spectral power of the neurogenic, myogenic and cardiac frequency bands, highlighting the utility of this approach in non-invasively identifying individual factors such as sex that modulate cutaneous vasodilation during local heating. Natural Sciences and Engineering Research Council of Canada