Thermoregulatory responses of patients with extensive healed burns

Two groups (A, n = 4; B, n = 6) of young male subjects with deep second- and third-degree healed burns (burned area: 48.6 +/- 3.6 and 23.7 +/- 3.1% of the total skin surface area in groups A and B, respectively) and a group of healthy subjects (C, n = 10) underwent a 3-h exposure to 40 degrees C, 50% rh, stepping on a bench 32 cm high, at a rate of 12 steps/min (Vo2 = 1.05 +/- 0.06 l X min-1). Rectal temperature (Tre), mean skin temperature (Tsk), and heart rate (HR) of group A were significantly higher than those of groups B and C; i.e., at the end of the 1st h Tre was 38.7, 37.9, and 37.7 degrees C; Tsk was 37.3, 36.4, and 37.0 degrees C; HR was 151, 105, and 110 beats X min-1 in groups A, B and C respectively. Maximal evaporative cooling capacity (Emax) was 4.9 +/- 0.1, 7.2 +/- 0.5, and 10.2 +/- 0.4 W X kg-1 in groups A, B and C, respectively, while the required evaporation capacity for thermoequilibrium (Ereq) was similar in all groups (6.7 +/- 0.1, 6.8 +/- 0.1, and 6.6 +/- 0.1 W X kg-1). Total sweat rate (msw) was 594 +/- 13, 602 +/- 29, and 485 +/- 34 g X h-1 in groups A, B and C, respectively, msw normalized to healthy skin area (msw/AH) was 671 +/- 75, 449 +/- 29, and 280 +/- 16 g X h-1 X m-2 in groups A, B and C, respectively. Sweating sensitivity normalized to healthy skin area (msw/AH X delta Tre) was similar in all three groups. It is suggested that the similarity between groups B and C can be explained by the compensatory sweating from the healthy skin of group B, which was sufficient because Emax greater than Ereq. In group A, Emax less than Ereq; therefore thermoequilibrium could not be maintained despite high compensatory sweat rate from the healthy skin. The similarity in msw/AH X delta Tre supports the assumption that elevation in Tre is the main drive of sweat regulation and that sweat rate is a function of delta Tre and healthy skin surface area.