Smoke Inhalation Injury

By Allison Varnum

Inhalation injury is the leading cause of mortality and morbidity in fire victims with varying degrees of airway injury resulting from the composition of smoke and the duration of exposure. Injuries are classified based on their anatomical location and treatment options depend on the classification of injury. The three categories of injuries are upper airway heat injury, chemical irritation throughout the respiratory tract, and systemic toxicity from inhalation of carbon monoxide or cyanide.

Upper airway damage occurs from direct thermal injury or by chemical irritation. When air exceeding 150 degrees C is inhaled, there is direct damage to the face, oropharynx, and upper airway resulting in immediate injury to the mucosa. Visible facial and neck burns or the presence of progressive hoarseness with a productive cough indicate the oropharynx should be examined for edema, erythema, and ulceration.

Lower airway injury results over a few days with toxins damaging the epithelium and capillary endothelial cells therefore impeding mucociliary and bacterial clearance, facilitating airway obstruction, and causing the loss of surfactant which leads to alveolar collapse and atelectasis while increased capillary permeability contributes to pulmonary and airway edema.

Systemic damage results from carbon monoxide, which has an affinity for hemoglobin 200 times higher than oxygen, crossing the alveolocapillary membrane resulting in tissue hypoxia. Hydrogen cyanide absorbs rapidly into lung tissue and prohibits cellular metabolism which leads to greater tissue hypoxia.

Often, patients with inhalation injury are intubated to protect the airway as obstruction is likely to occur as edema progresses. Mechanical ventilation assists in maintaining adequate oxygenation and implementing measures to assist in bronchial hygiene can help prevent ventilator-associated pneumonia. Because of the potential damage to the airways, patients must be monitored closely for complications such as pneumonia and acute respiratory distress syndrome (ARDS). Lung protective ventilation and prone positioning are recommended for patients suffering from severe respiratory distress.

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