QS16. The Effects of Variations in the Skin Surface Temperature on Capillary Blood Flow Using Video-capillaroscopy

Abstract

Purpose: Video-capillaroscopy (VC) can be used to evaluate real-time flow of red blood cells in capillaries at a depth of 1-mm from the skin surface. Therefore, this device could be used in microsurgery to assess the perfusion of flaps, replanted fingers, skin grafts, and keloids. The details of capillary changes during skin cooling under VC observations are not known. By investigating the adaptations of capillaries after cooling using VC, we determined the effects of temperature on skin capillaries with those at room temperature, establishing temperature criteria for future VC applications. Therefore, we observed and compared VC findings on skin areas often used for flap harvest at a normal and lower body temperature. Methods: Twenty healthy Japanese adults were included. Skin capillaries were observed at the lateral thigh, forearm, mid-axillary line, abdomen, and fingertip using VC (GOKO Bscan-Z). Ice packs were used to lower the skin temperature to less than 35°C. The VC findings were recorded for three minutes before and after cooling. By means of the ImageJ software, we measured the total blood vessel area (pixels) as a percentage of the total area of the visual field (pixels). Also, we measured the blood flow velocity (μm/s) using GOKO-VIP software and the results for both temperatures (normal and after cooling) were then compared. Results: The average age and BMI were 37.5±9.72 years and 22.4±2.45 kg/m2 respectively. The mean arterial pressure was 89.4±3.1 mmHg. In accordance with the Fitzpatrick phenotype, eleven patients were type II, five were type III, and four were type IV. The average skin temperature before and after cooling were 36.4±0.2°C and 34.7±0.8°, respectively. The blood vessel areas were significantly different before and after cooling in all anatomical areas (p <.001). The average reduction rate of the vessel area after cooling was 63% for the thigh, 30% for the forearm, 43.3% for the mid-axillary line, 35% for the abdomen, and 65% for fingertips. The mean reduction rate of the vessel area was significantly different among anatomic regions (p <.001). The average blood flow velocities were significantly different before and after cooling in all anatomical areas (p <.001). The average blood flow velocity reduction rate after cooling was 75.7% for the thigh, 55.3% for the forearm, 68.9% for the mid-axillary line, 61.6% for the abdomen, and 79.2% for fingertips. The average blood flow velocity reduction rate after cooling was significantly different among anatomic regions (p <.001). Conclusion: Decrease in skin surface temperature resulted in capillary vasoconstriction and a decrease of capillary blood flow velocity in all areas. When VC is used for flap monitoring, it is important to keep the observation area warm since decreasing the temperature in the monitored area might result in the false diagnosis of arterial occlusion.