The effect of short-term dependency and immobility on skin temperature and colour in the hand.

The effects of short-term dependency and immobility on skin temperature were assessed in two experiments. In the first study, ten volunteers hung their left arm dependent and motionless while using their right hand for light office work. After 30 minutes, the dependent left hands were cooler (mean=0.9 degrees C: 95% CI=0.7-1.1) than the active right hands and exhibited a deeper colour with significantly increased green intensity (P=0.03) as assessed on digital images. In the second study, seven volunteers submerged both their hands in water at 15 degrees C for 15 minutes. The left arm was then left dependent and motionless while the right hand was placed on the table and its fingers were flexed and extended every 10 seconds. The left hands remained cooler than the right and were a median of 3.6 (range 2.9-4.5) degrees C cooler after 60 minutes. These studies demonstrate that skin temperature and colour differences between the hands, which are sometimes used to support the diagnosis of CRPS-1, can be produced and maintained by short-term immobility and dependency of the hand.