Cold-induced vasodilatation and peripheral blood flow under local cold stress in man at altitude.

The cold-induced vasodilatation (CIVD) response was studied on 17 lowlanders (20-30 years) at Delhi, using a water bath maintained at 4 degrees+/-0.2 degreesC. The temperatures were measured at the tip of the index finger, centre of the palm, over a prominent wrist vein, and orally. Then the subjects were air-lifted to an altitude of 3500 m, where the measurements were repeated at weekly intervals for a period of 3 weeks. After this, they were flown back and retested. For comparison, the study at altitude was done on 10 acclimatised lowlanders and on 10 high-altitude natives. The peripheral blood flow under a local cold stress was calculated. Three types of CIVD responses--viz. typical hunting, proportional control, and continuous rewarmin--were observed. At altitude, the pattern was more or less the same but there was a significant reduction in the response. The responses of the natives were more or less identical to those of the lowlanders at sea level, and responses of the acclimatized lowlanders were better than the fresh inductees, but much less than the natives. The changes in peripheral blood flow was in accordance with the CIVD response.