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°C, 50% rh, stepping on a bench 32 cm high, at a rate of 12 steps/min (V̇O₂ = 1.05 ± 0.06 1.min^-1). Rectal temperature (T(re)), mean skin temperature (T̄(sk)), 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 T(re) was 38.7, 37.9, and 37.7°C; T̄(sk) was 37.3, 36.4, and 37.o°C; HR was 151, 105, and 110 beats.min^-1 in groups A, B and C respectively. Maximal evaporative cooling capacity (E(max)) was 4.9 ± 0.1, 7.2 ± 0.5, and 10.2 ± 0.4 W.kg^-1 in groups A, B and C, respectively, while the required evaporation capacity for thermoequilibrium (E(req)) was similar in all groups (6.7 ± 6.8 ± 0.1, and 6.6 ± 0.1 W.kg^-1). Total sweat rate (Ṁ(sw)) was 594 ± 13, 602 ± 29, and 485 ± 34 g.h^-1 in groups A, B and C, respectively. M(sw) normalized to healthy skin area (Ṁ(sw)/AH) was 671 ± 75, 449 ± 29, and 280 ± 16 g.h^-1.m^-2 in groups A, B, and C, respectively. Sweating sensitivity normalized to healthy skin area (Ṁ(sw/AH X ΔT(re)) 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 E(max) > E(req). In group A, E(max) < E(req); therefore thermoequilibrium could not be maintained despite high compensatory sweat rate from the healthy skin. The similarity in M(sw)/AH X ΔT(re) supports the assumption that elevation in T(re) is the main drive of sweat regulation and that sweat rate is a function of ΔT(re) and healthy skin surface area.