Abstract
Purpose. Noninvasive methods of studying the microcirculation have been advocated in patients with advanced peripheral vascular disease to assess skin viability. Good reliability is a prerequisite for such parameters. This study was carried out to evaluate the variability of three methods: transcutaneous oxygen tension measurement (tc.pO9, diode laser Doppler fluxmetry (dLDF), and capillary microscopy (CM).
Methods. Repeated measurements were performed in 20 patients with restpain or severe disabling intermittent claudication (ankle/brachial pressure index <0.5). Tc.pO2 was performed on the dorsum of the foot and measured under baseline conditions, during 4 minutes of O2-inhalation, and during reperfusion after 3 minutes of tourniquet occlusion. dLDF was performed on the palmar skin of the hallux, at rest, and during reperfusion after 3 minutes of tourniquet occlusion. CM was performed at the nailfold of the hallux; capillary density, morphologic changes of the capillaries, and perfusion with fluorescein were studied.
Results. Increased tc.pO2 rates during the oxygen inhalation and reperfusion tests are well-reproducible and show discriminative power. Resting tc.pO2 seems less valuable. Some dLDF parameters are highly reproducible, but only resting flux and the flux increase rate during reperfusion demonstrate discriminative power. CM is highly reproducible as performed by one observer. The capillary morphology score allows for severity grading.
Conclusion. Controversies on interpretation and cutoff values of microcirculatory parameters could well be associated with the variability of some of the parameters. Only parameters with adequate reproducibility and discriminatory power can be used to evaluate intervention procedures or to determine amputation levels.
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