Diagnosis of Inhalation Injury

Explanation

Inhalation injury is the leading determinant of mortality in burns, and its recognition rests on the history of a closed space fire plus a set of physical findings. Carbonaceous sputum, meaning sputum or saliva stained black with soot, is the finding with the highest diagnostic value among those listed because it is direct physical evidence that the products of combustion reached the tracheobronchial tree. Its presence implies both thermal injury to the upper airway and chemical injury to the lower airway from aldehydes, acids and other irritants, which produce mucosal oedema, sloughing, cast formation and progressive obstruction over the following hours. Tachypnoea and a reduced oxygen saturation are sensitive markers of respiratory distress but are entirely non-specific, since they occur with pain, anxiety, carbon monoxide poisoning, hypoxia at the scene or a chest injury without any airway burn. Hoarseness is a genuinely alarming sign because it suggests laryngeal oedema and impending upper airway obstruction, and it should prompt urgent airway assessment, but a substantial lower airway injury can be present without it, so it is less confirmatory. Other supportive findings include facial burns, singed nasal vibrissae, soot in the oropharynx, stridor and a depressed conscious level. Fibreoptic bronchoscopy is the diagnostic gold standard, and any patient with confirmed injury should be intubated early before oedema makes intubation impossible.

Why each option

A.

Correct. Carbonaceous sputum is direct evidence that soot and products of combustion have been inhaled into the tracheobronchial tree, confirming significant inhalation injury.

B.

Tachypnoea indicates respiratory distress but is non-specific and can result from pain, anxiety, carbon monoxide exposure or chest wall injury.

C.

Hoarseness strongly suggests laryngeal oedema and impending obstruction and demands urgent airway assessment, but lower airway injury can occur without it, so it is less confirmatory.

D.

A low oxygen saturation reflects impaired gas exchange from many causes and does not by itself demonstrate that combustion products entered the airway.

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