Relationship between pulse amplitude and thermal exchange in the finger: the effect of smoking.

In 24 healthy volunteers finger pulse amplitude and heart rate (HR) were monitored by pulse plethysmography and thermal exchange from the finger and were compared before and after the smoking of a single cigarette. Thermal exchange was measured using a direct calorimeter consisting of a recording bath and a reference bath, both of which were filled with water at 18 degree C. The subject immersed the two distal phalanx of a finger into the recording bath. The water thermal gradient between both baths after 4 min of finger immersion and the maximal value of heat loss from the finger to the water were recorded. Decreases in the water thermal gradient (from 6.06 to 5.33 degrees C, P less than 0.05) in maximal value of heat loss (from 22.5 to 18.75 w.m-2, P less than 0.01) and in plethysmographic wave amplitude (from 25.8 to 14.6 mm, P less than 0.01) and increased HR (from 72 to 83 beats min-1) were observed in smokers. These changes were not statistically significant in non-smokers. Water thermal gradient and maximal value of heat loss correlated with plethysmographic wave amplitude before and after smoking but not with HR in the 24 subjects studied. The present study shows a good relationship between vascular phenomena and thermal exchange in the fingers. The variations of finger pulse amplitude provide an adequate and sensitive adjustment of thermal exchange since the effects of smoking a single cigarette can be detected by both PWA and calorimetric measurements in the finger.