In 8 patients (6 female, 2 male; age 62 + 8,7 years) with acute deep vein thrombosis (first clinical signs < 24 hours, excluding isolated calf vein thrombosis) red blood cell velocity (RBCV) in capillaries of the medial ankle of the affected leg as well as of the contralateral leg was measured by means of a Laser-Doppler-Anemometer (CAM 1, K&K Technology, Exeter, UK). Measurements were performed after a resting period of 20 minutes in supine position, the ankle at heart level. Velocity was measured in 5 different capillaries and the mean velocity out of these values was calculated. Afterwards venous occlusion was performed on the level of the proximal calf. After 10 minutes of venous occlusion velocity measurements were repeated. The same procedure was repeated on the contralateral leg afterwards. Initial velocity was statistically significant lower in the affected leg (DVT) (0,68 + 0,34 mm/s) as compared with the contralateral leg (CONT) (1,01 + 0,32 mm/s; p<0,05). In both, the affected leg as well as the contralateral leg RBCV decreased during venous occlusion. The values found during venous occlusion were not statistically significant different (0,38 + 0,21 mm/s in DVT and 0,35 + 0,28 mm/s in CONT; n.s.). However the relative decrease in the affected leg was significantly lower as compared to the contralateral leg (44,1 + 12,8 % vs 65,3 + 17,8%; p<0,05).

Laser-Doppler-Anemometer allows the velocity measurement in capillaries not laying parallel to the skin surface. Therefor this method is no further limited to nailfold capillaries, but can be used at any area of the skin.

Aim of the present study was to compare the velocity measured by the LaserDoppler-Anemometer and by frame to frame at the very same time and in the very same capillary (synchronious velocity measurement). Using an angle of 30 ^o nailfold capillaries can be focused good enough to perform frame to frame velocity measurements. Additionally the 30 ^o angle is enough to allow velocity measurements by the Laser-Doppler-Anemometer. During velocity measurement using the Laser-Doppler-Anemometer the capillary had been recorded on video tape to perform off line frame to frame measurement later.

We performed 78 measurements in 36 volunteers (18 male, 18 female; age 24 + 2,5 years).

Frame to frame: 0,49 + 0,3 7 mm/s; Laser-Doppler-Anemometer: 1, 11 + 0, 8 6 mm/s.

Even if these mean values are significantly different (p<0,0001) there is a good correlation of the two methods (R = 0,873; y = 0,1 + 2,04 x; y: velocity measured by Laser-Doppler-Anemometer, x: velocity measured by frame to frame).

Velocity measurement by Laser-Doppler-Anemometer is a valid method to evaluate Blood Flow Velocity in Capillaries of the human skin (compared with frame to frame method). It offers the ability of velocity measurements in any area of the skin unlimited to the nailfold capillaries.

In 11 non smokers (6 male, 5 female, age 24 + 2,6 years) and in 12 smokers 6 male, 6 female; age 25 + 1,9 years) Red Blood Cell Velocity (RBCV) in the Capillaries of the metacarpal segment of DIG II of the left hand was measured before and during application of a nicotine blaster to the deltoid muscle of the left arm by means of a Laser-Doppler-Anemometer (CAM 1, K&K Instruments, Exter, UK). Volunteers were placed in a comfortable chair with their left hand positioned under the microscope, slightly below heart level. After a resting period of 15 minutes the velocity in 6. different capillaries at the metacarpal segment of DIG II was measured. Mean velocity was calculated out of these 6 measurements. A nicotine blaster () was applicated to the deltoid muscle of the left arm. Velocity measurements were repeated in the same procedure after 20 minutes. Before application of the blaster RBCV tended to be lower in smokers as compared to non-smokers (n.s.). In both groups, smokers and non-smokers RBCV decreased during, application of the nicotine blaster. In non-smokers from 0,8 + 0,3mm/s to 0,45 + 0,24 mm/s (p<0,05), in smokers from 0,74 + 0,28 mm/s to 0,59 + 0,23 mm/s (p<0,05). The relative decrease of velocity during nicotine application was significantly higher in non-smokers (43,8 + 7,5%) as compared to smokers (20,3 + 19.8 %, p<0,05).