Simultaneous assessment of muscle and skin blood fluxes with the laser-Doppler technique.

The laser-Doppler technique was used to assess local muscle and skin blood fluxes at the lower limb in 20 healthy volunteers. After puncturing the anterior tibial muscle with a steel cannula, a single-fibre probe with a diameter of 0.5 mm was inserted into the muscle. Simultaneously, the skin blood flux was measured at calf and foot. The muscle blood flux at rest was 3.5 to 4 times higher than the skin blood flux at calf or foot. The spatial variability of the muscle blood flux at three different sites of measurement was considerable and tended to be higher than in the skin of the calf. After an arterial occlusion lasting 3 min, peak flux was reached in the muscle after 18.7 +/- 9.8 s, in the skin of the calf after 16.8 +/- 9.3 s, and in the skin of the foot after 22.9 +/- 14.6 s (NS). The relative flux increase during reactive hyperaemia was significantly lower in the muscle (2.7 +/- 1.3) than in the skin of the calf (3.9 +/- 1.9; p<0.05) or the foot (5.1 +/- 3.5; p<0.005). The reproducibility of reactive hyperaemia response in muscle was excellent with unchanged probe position, but exhibited a marked variability on different days. The laser-Doppler technique provides the possibility for simultaneous measurement of flow dynamics in muscle and skin with a high temporal resolution. Methodological problems include differences in probe geometry of the single-fibre compared to standard probes and differences in optical properties of the tissues. Direct comparison of flux values may, therefore, be subject to criticism, but not the comparative analysis of relative flux changes. The influence of tissue trauma on muscle blood flux has to be considered for the analysis of flux data.