Comparative study of the upper and lower limb skin blood flow control mechanisms in patients with essential hypertension

OBJECTIVE: To investigate limb specific differences in cutaneous vascular function in patients (n=33) with essential hypertension (EHT). METHODS: In this observational cross-sectional study, baseline skin blood flow and the response to local heating were measured with a laser Doppler flowmeter (LDF) from the volar region of the forearm and the gaiter area of the foot at supine rest. The fractal analysis, detrended fluctuation analysis (DFA), was used to calculate the correlation properties of skin blood flow, LDF signal. The paired t-test and repeated measures ANOVA were used to determine the response to local heating and compare the scaling exponents of different anatomical locations respectively. RESULTS: We found three linear scaling regions that describe the fractal behavior of LDF signal with their slopes, scaling exponents. For cardiac (α(C)) and cardio-respiratory (α(CR)) scaling exponents, thermal hyperemia (T) induced greater change in the leg (α(C)=1.49 ± 0.26; α(CT)=1.62 ± 0.20 p<0.01 and α(CR)=0.84 ± 0.29 α(CRT)=0.42 ± 0.28 p<0.001) than in forearm (α(C)=1.28 ± 0.13; α(CT)=1.33 ± 0.13 p>0.05 and α(CR)=0.73 ± 0.15; α(CRT)=0.65 ± 0.018 p<0.05). Local scaling exponents (α(L) ≈ α(LT) ~ 1) were not significantly different (p>0.05) and, local lines did not shift in parallel with local heating in both extremities. CONCLUSION: The results of the present study suggest that skin microvascular function is impaired in both extremities in EHT patients. However, myogenic response is not uniform in both extremities and pronounced response to local thermal hyperemia has been observed in the gaiter area compared with the volar region. Further studies are needed to determine if these limb specific microvascular differences is the result of posture-induced structural and functional adaptation.