Low-intensity laser irradiation (830 nm) reduces skin blood flow in humans

Low-intensity (therapeutic) laser therapy (LILT) has become a popular therapeutic modality for use by physiotherapists in the clinical management of a wide variety of conditions, including the promotion of wound repair and as an hypo-algesic agent. Nevertheless, the scientific data in support of the continued application of lasers in the clinic remains sparse, although recent studies have demonstrated a number of quantifiable biological effects of low-intensity laser, including laser-mediated increases in human median nerve conduction latency in vivo. In the present study, the effect of irradiation with low-intensity laser (1.5 J cm(-2); 830 nm) on forearm skin blood flow in humans has been assessed using a laser Doppler flowmeter: (1) under resting conditions; (2) with concomitant measurement of antidromic median nerve conduction latency; and (3) after raising skin blood flow by immersion of the arm in water at 45 degrees C for a period of 10 min. Under resting conditions and with concomitant measurement of nerve conduction latencies, irradiation at the parameters stated produced no dramatic change in the measured red cell flux signal (RCFS). However, when the latter was raised by pre-heating the limb, laser irradiation effected a significant reduction in measured flux when compared to placebo at 20 min postirradiation. Such an effect of LILT indicates a laser-induced reduction in skin blood flow. These findings may have importance to our further understanding of laser's effects in vivo and its putative clinical efficacy.