Smoke Inhalation Injury in Horse: An Overview

Introduction Smoke inhalation produces edema, congestion and necrosis of both the upper and lower respiratory tract. Smoke inhalation injury is the major cause of death among fire victims, and is a stronger determinant of mortality than severity of cutaneous burns. Smoke inhalation damages both the upper and lower respiratory tracts via thermal and chemical (toxic) mechanisms. Upper respiratory tract injury primarily results from thermal injury due to inhalation of air and particles heated to 150°C. Thermal damage to the lower respiratory tract is less common, but can occur due to inhalation of superheated particles (<5 μm). The majority of lower respiratory tract damage results from inhalation of toxic chemicals. The severity of lower airway injury is dependent on duration of exposure, solubility of the chemicals, and size of the chemicals in smoke. Highly water-soluble gases—such as aldehydes, ammonia, chlorine, hydrogen chloride, and sulfur dioxide—produce rapid pulmonary injury. Water insoluble gases—nitrogen and phosgene oxide—causes delayed pulmonary injury. Carbon monoxide toxicity, common with smoke inhalation, does not cause direct airway damage, but exacerbates tissue hypoxia by impairing oxygen delivery and utilization.