Laser Doppler flowmetry, a reliable technique for measuring pharmacologically induced changes in cutaneous blood flow?

Laser Doppler flowmetry (LDF) affords a reliable non-invasive method of investigating acute changes in total cutaneous perfusion. However, the reproducibility of measurements of resting blood flow is considered to be poor. Therefore, the potential use of LDF to monitor pharmacological influences on cutaneous perfusion over time may be limited to the investigation of drug-induced changes of the response pattern to standardized provocation procedures. The present study was undertaken to evaluate the reproducibility of cutaneous vasomotor reflexes induced by various test stimuli. Measurements were made in the morning and in the afternoon of the same day at two different skin sites (finger-tip and forearm) in six healthy subjects. Each of the following six interventions induced highly reproducible decreases of total cutaneous flow: Deep inspiration, Vasalva manoeuvre, venous occlusion, arrest of arterial blood flow (followed by reactive hyperaemia), passive head-up tilting and a cold pressor test. The decrease in blood flow was more pronounced at the finger-tip except after venous occlusion. During the cold pressor test, skin perfusion was more persistently reduced at the finger-tip than at the other site. The anatomical and functional differences in the skin between the finger-tip and the forearm may also explain the absence of reactive hyperaemia at the finger-tip. Considering the excellent reproducibility of the resting baseline values and of the changes in total blood flow after standardized provocation tests within the same day, it seems possible that LDF could be a suitable method for the short-term investigation of drug effects on circulation. The long-term day-to-day reproducibility of both baseline blood flow and vasomotor reflexes remains to be further clarified.