Spatial and temporal evaluation of locally induced skin trauma recorded with laser Doppler techniques.

The single-fiber laser Doppler flowmetry (SF-LDF) technique has been used to study perfusion within tissues. The insertion of the SF-LDF probe into human skin locally alters microcirculation for more than 70 min after positioning. In this study the SF-LDF and a newly developed laser Doppler imager (LDI) were used to describe the spatial distribution, the intensity, and the temporal course of the trauma following intracutaneous insertion of the probe. The LDI scanned a human skin area of 6 x 6 cm (36 x 36 pixels). A flexible SF-LDF probe was inserted intradermally in the same measuring region. Recordings were performed for 120 min with the two techniques simultaneously. With the SF-LDF probe maximal hyperemia was recorded after 5-30 min. After a gradual and slow decrease most of the subjects reached a steady-state level within 80-100 min. A 3-min tourniquet occlusion test was performed 120 min after SF probe positioning. A significant hyperemic response was recorded, indicating that almost no posttraumatic activity was present at this time. The area of increased perfusion recorded with the LDI had an oval to circular configuration with a maximal extension after 5-10 min (radius 1.5-2 cm, area 8.9 cm2). The zone of maximal hyperemia was distributed adjacent to the intradermal probe, gradually decreasing toward the periphery. No significant hyperemia was shown with LDI after 100 min. There was a concordance between the time courses of the hyperemic response obtained with the two techniques.