To Investigate Reproducibility And Factors Influencing Measurement Parameters Of Postocclusive Reactive Hyperemia In Forearm S

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Date
2006-07
Authors
Tee, Get Bee
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Abstract
A standardized technique to noninvasively assess skin microvascular function in vivo has not been fully developed, so is the analysis of the response it produced. The aim of this thesis was to establish an optimized and reproducible method and analysis of responses from postocclusive reactive hyperemia (PORH) in forearm skin measured using laser Doppler f1uximetry monitoring (LDF). The objectives were: (1} to investigate the influence of occlusion duration on PORH+LDF measurement model (optimization study); [2] to determine the reproducibility of several different laser-Doppler-derived PORH parameters (reproducibility study); [3J to characterize the "effective" occlusion duration in subjects with differing age, gender and menstrual phases (characterization study). Methodology: In the optimization study, 20 healthy male volunteers aged 21-30 years old were studied on 3 separate days in a randomized study manner. The volunteers were then randomized to receive 1, 2 or 3 min occlusion on 3 different days. Skin perfusion was measured before, during and after occlusion using LDF. The magnitude and temporal courses of PORH were expressed as PORHmax (absolute maximal increase in hyperemia perfusion) and Tp (time-to-peak), respectively. Eighteen males were recruited in the reproducibility study. Forearm blood flow was occluded for 3 min. Parameters studied were PORHmax, Tp, PORHpeak (amplitude of peak perfusion), PORH% (percentage of hyperemic response) and PORHmaxlTp (mean velocity of hyperemia increase). Measurement was performed twice within each study day for 2 study days. Coefficient of variation (CV) and intraclass correlation coefficient (ICC) were calculated for each parameter. In the characterization study, 120 subjects were studied (20 subjects each in the age ranges of 21-30 years, 31-40 years, 41-50 years for both genders). Similar study protocol as in the optimization study was applied. Males were studied for 3 study days. Female came for 6 study days: the first 3 days was performed during low estrogenic phase (days 2-5 of menstrual cycle) and subsequent 3 visits were done during high estrogenic (days 10-13). Results: In the optimization study, significant difference (p<0.001) in PORH changes were shown between 1 min (PORHmax 15.39±1.27 AU; Tp 9.16±0.43 s), 2 min (PORHmax 24.84±1.62 AU; Tp 12.56±0.56 s) and 3 min occlusion duration (PORHmax 32.14±1.73 AU, Tp 14.17±0.61 s). Three min occlusion produced significantly greater PORHmax and T p changes. Analysis using ICC showed that all studied parameters, except for PORH%, demonstrated excellent reproducibility for within- and between-day measurements. Satisfactory intraday and interday CVs were obtained for these parameters (intraday, interday CVs for each parameter: PORHmax 4.77,6.50; Tp 8.89, 6.87; PORHpeak 6.50, 8.70; PORHmax/Tp 10.64, 10.65, respectively). The PORHmax and Tp values were the most reproducible magnitude- and temporal-based parameters, respectively. The characterization study showed that for the PORHmax analysis, the occlusion duration should be applied based on age, gender and menstrual phase. PORH response was more homogenous during high estrogenic phase with 2 min found as the "effective" occlusion duration in all female groups. Three min occlusion produced the most significant change in all age ranges in both genders in T p analysis and it was irrespective of menstrual phase. Conclusion: These studies revealed a dependence of PORH+LDF response on occlusion duration. PORHmax and Tp were the most reproducible PORH indices. The occlusion duration applied during the measurement of PORHmax was influenced by age, gender and menstrual phase factors. The measurement based on T p was however independent of these factors.
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A standardized technique to noninvasively assess skin microvascular function , in vivo has not been fully developed
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