New clinically relevant sheep model of severe respiratory failure secondary to combined smoke inhalation/cutaneous flame burn injury

Objectives: To develop a predictable, dose-dependent, clinically relevant m odel of severe respiratory failure associated with a 40% total body surface area, full-thickness (third-degree) cutaneous flame burn and smoke inhalat ion injury in adult sheep. Design: Model development. Setting: Research laboratory, Subjects: Adult female sheep (n = 22). Interventions: Animals were divided into three groups, determined by the nu mber of smoke breaths administered (24, 36, 48) for a graded inhalation inj ury. The smoke was insufflated into a tracheostomy with a modified bee smok er at airway temperatures <40 degrees C. All animals concurrently received a 40% total body surface area (third-degree) cutaneous flame burn to the bo dy (flanks). After injury, the animals were placed on volume-controlled ven tilation to achieve PaO2 >60 mm Hg and PaCO2 <40 mm Hg. Arterial blood gase s and ventilator settings were monitored every 6 hrs postinjury for up to 7 days. Measurements and Main Results: All animals survived the induction of injury . In the 24 smoke breath/40% total body surface area burn (24/40) group, Pa O2/FIO2, never decreased below 300, and peak inspiratory pressure was consi stently <14 cm H2O with normal arterial blood gases throughout the observat ion period. With 36 smoke breaths/40% total body surface area burn (36/40) (n = 7), all animals had PaO2/FIO2 of <200 and peak inspiratory pressure of 26 cm H2O within 40-48 hrs, as 30% died during the study period. With 48 s moke breaths/40% total body surface area burn (48/40) (n = 12), all animals developed respiratory distress syndrome (RDS) in 24-30 hrs, but none survi ved the experimental period. Conclusions: Development of RDS by smoke and cutaneous flame burn injury de pends on smoke inhalation dose, A combination of 36 breaths of smoke and a 40% total body surface area (third-degree) cutaneous flame burn injury can induce severe RDS (PaO2/FIO2 <200) within 40-48 hrs to allow evaluation of various treatment modalities of RDS.