Transcutaneous oximetry, laser Doppler fluxmetry, and capillary microscopy: Variability in patients with advanced atherosclerotic disease of the lower extremity

Purpose. Noninvasive methods of studying the microcirculation have been adv ocated in patients with advanced peripheral vascular disease to assess skin viability. Good reliability is a prerequisite for such parameters. This st udy was carried out to evaluate the variability of three methods: transcuta neous oxygen tension measurement (tc.pO(2)), 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 inde x <0.5). Tc.pO(2) was performed on the dorsum of the foot and measured unde r baseline conditions, during 4 minutes of O-2-inhalation, and during reper fusion after 3 minutes of tourniquet occlusion. dLDF was performed on the p almar skin of the hallux, at rest, and during reperfusion after 3 minutes o f tourniquet occlusion. CM was performed at the nailfold of the hallux; cap illary density, morphologic changes of the capillaries, and perfusion with fluorescein were studied. Results. Increased tc.pO(2) rates during the oxygen inhalation and reperfus ion tests are well-reproducible and show discriminative power. Resting tc.p O(2) seems less valuable. Some dLDF parameters are highly reproducible, but only resting flux and the flux increase rate during reperfusion demonstrat e discriminative power. CM is highly reproducible as performed by one obser ver. The capillary morphology score allows for severity grading. Conclusion. Controversies on interpretation and cutoff values of microcircu latory parameters could well be associated with the variability of some of the parameters. Only parameters with adequate reproducibility and discrimin atory power can be used to evaluate intervention procedures or to determine amputation levels.