Inhalation Injury — Airway and Toxic Gases

Key Points

• Inhalation injury includes upper-airway thermal injury, lower-airway chemical injury, and systemic toxic-gas poisoning; more than one can occur simultaneously.
• An initially normal pulse oximetry reading does not exclude carbon monoxide poisoning.
• Airway edema can progress after presentation and after burn-fluid resuscitation, so repeated airway assessment is essential.
• Progressive hoarseness, stridor, deep facial or neck burns, oropharyngeal edema, inability to handle secretions, and worsening mental status lower the threshold for early intubation.
• Give 100 percent oxygen immediately when significant smoke exposure or carbon monoxide toxicity is possible.
• Hydroxocobalamin is commonly preferred for severe suspected cyanide poisoning from smoke because it does not induce methemoglobinemia.
• Bronchoscopy is useful for diagnosing and grading lower-airway inhalation injury when the result will alter management.
• Routine antibiotics and systemic corticosteroids are not indicated solely for uncomplicated smoke inhalation injury.

Algorithm

1. Remove from exposure, assess airway, breathing, circulation, neurologic status, burn size, and associated trauma.
2. Give 100 percent oxygen immediately and place the patient on continuous cardiac and oxygenation monitoring.
3. Look for airway-risk features and perform serial examinations; obtain expert airway control early if deterioration is likely.
4. Obtain co-oximetry with carboxyhemoglobin, blood gas and lactate in significant exposure, ECG and troponin when cardiac injury is possible, and targeted trauma studies as indicated.
5. Consider nasopharyngoscopy for supraglottic assessment and bronchoscopy for suspected lower-airway injury.
6. Treat bronchospasm, secretions, and respiratory failure with bronchodilators, pulmonary hygiene, suctioning, and lung-protective ventilation.
7. Consider hydroxocobalamin for severe suspected cyanide toxicity and specialist consultation for hyperbaric oxygen in severe carbon monoxide poisoning.
8. Arrange burn-center consultation or transfer and admit patients with airway risk, abnormal gas exchange, significant toxic exposure, or substantial burns.

Clinical Synopsis & Reasoning

Inhalation injury is not a single lesion. It includes thermal injury to the upper airway, chemical injury to the tracheobronchial tree and distal lung, and systemic poisoning from combustion products. The first task is to determine which of these processes is present because their time course and treatment differ. Heat is usually dissipated before reaching the intrathoracic airway, so direct thermal injury is concentrated above the glottis, while smoke particles and irritant gases can produce diffuse bronchial inflammation, mucosal sloughing, bronchospasm, impaired mucociliary clearance, atelectasis, and delayed respiratory failure. Carbon monoxide impairs oxygen delivery by forming carboxyhemoglobin and shifting the oxyhemoglobin dissociation curve, while cyanide impairs cellular oxygen use and may accompany enclosed-space fires involving synthetic materials.

Risk rises after an enclosed-space fire, prolonged smoke exposure, facial or neck burns, soot in the mouth or nose, carbonaceous sputum, hoarseness, stridor, dysphagia, drooling, wheeze, altered mental status, or unexplained metabolic acidosis. Normal initial oxygen saturation does not exclude carbon monoxide poisoning because conventional pulse oximetry cannot distinguish oxyhemoglobin from carboxyhemoglobin. Likewise, a normal chest radiograph early after exposure does not exclude lower-airway injury. Examine the oropharynx, voice, work of breathing, mental status, skin burns, and neurologic findings, and repeatedly reassess because edema can progress after fluid resuscitation.

The airway decision is based on trajectory rather than a single sign. Stridor, progressive hoarseness, respiratory distress, deep facial or neck burns, significant oropharyngeal edema, inability to handle secretions, worsening mental status, or anticipated transfer with a tenuous airway should prompt early expert airway control. Waiting for severe obstruction can make intubation substantially more difficult. Flexible nasopharyngoscopy can help evaluate supraglottic edema in a cooperative patient, while bronchoscopy is the most direct method to grade lower-airway soot, erythema, edema, ulceration, and sloughing when the result will influence management.

Treatment Strategy & Disposition

Immediately remove the patient from exposure and administer 100 percent oxygen by nonrebreather mask or through the ventilator if intubated. Oxygen should not be withheld while awaiting a carboxyhemoglobin result. Secure intravenous access, treat associated burns and trauma, and obtain early consultation with a burn center for significant inhalation injury or major burns. If airway compromise is developing, perform controlled endotracheal intubation with the most experienced available operator, appropriate backup devices, and a surgical-airway plan. A smaller-than-expected endotracheal tube may be required because of edema.

Treat bronchospasm with inhaled beta agonists and use aggressive pulmonary hygiene, suctioning, humidification, positioning, and early mobilization when feasible. Mechanical ventilation should use lung-protective principles if acute lung injury develops. Routine prophylactic antibiotics are not indicated solely because soot or inhalation injury is present; antibiotics are reserved for documented or strongly suspected infection. Corticosteroids are not routinely recommended for smoke inhalation injury because benefit has not been established and adverse effects can be meaningful.

For carbon monoxide toxicity, continue high-flow oxygen until symptoms resolve and carboxyhemoglobin falls, recognizing that treatment decisions are driven by clinical severity rather than the number alone. Discuss hyperbaric oxygen with a hyperbaric or poison-control specialist for severe neurologic manifestations, loss of consciousness, significant cardiac ischemia, severe acidosis, pregnancy with clinically important exposure, or other high-risk features. For suspected cyanide toxicity in a critically ill smoke-exposed patient, especially with cardiovascular collapse or marked lactic acidosis after an enclosed-space fire, hydroxocobalamin is the preferred empiric antidote in many systems because it does not worsen oxygen carrying capacity. Disposition depends on airway risk, toxic exposure, burn severity, oxygen requirement, bronchoscopy findings, and associated injuries. Patients with evolving airway edema, abnormal gas exchange, significant toxic exposure, or bronchoscopic injury generally require monitored admission.

Epidemiology / Risk Factors

• Inhalation injury is a major contributor to morbidity and mortality after structure fires and is more likely after enclosed-space exposure.
• Carbon monoxide is a common toxic component of fire smoke and can cause severe neurologic or cardiac toxicity without obvious external burns.
• Cyanide exposure is most concerning in enclosed fires involving combustion of nitrogen-containing synthetic materials.
• Older adults, pregnant patients, people with cardiovascular disease, and patients with prolonged loss of consciousness may have lower physiologic reserve after carbon monoxide exposure.
• Lower-airway injury can evolve over the first 24 to 48 hours even when early imaging is unrevealing.

Investigations

Toxic Gas Clues

Pharmacology

Prognosis / Complications

• Outcome depends on duration of hypoxia, severity of airway and parenchymal injury, toxic-gas burden, burn size, age, and associated trauma.
• Early airway control before severe edema develops reduces the risk of a difficult rescue airway.
• Mild carbon monoxide poisoning often resolves with oxygen, but delayed neurocognitive symptoms can occur after apparent recovery.
• Severe cyanide toxicity can cause rapid cardiovascular collapse and death unless oxygenation, resuscitation, and antidotal therapy are delivered promptly.
• Bronchoscopic inhalation injury severity correlates imperfectly with outcome and should be interpreted with the full clinical course.

Patient Education / Counseling

• Explain that breathing problems can worsen after smoke exposure even if the patient initially feels better.
• Advise patients discharged after a minor exposure to return for dyspnea, chest pain, confusion, syncope, persistent vomiting, new neurologic symptoms, or worsening cough.
• After carbon monoxide exposure, discuss the possibility of delayed cognitive, mood, memory, or gait symptoms and the need for reevaluation if these develop.
• Encourage functioning smoke detectors, safe heating practices, and carbon monoxide detectors in homes with fuel-burning appliances.
• Patients with significant burn or inhalation injury should receive burn-center follow-up and rehabilitation planning as appropriate.

Notes

The absence of visible facial burns does not exclude serious inhalation injury, and soot by itself does not mandate intubation. The safest approach is to combine exposure history, voice and swallowing changes, direct airway findings, work of breathing, mental status, and expected clinical trajectory. In a patient who clearly needs an airway, earlier controlled intubation is preferable to waiting for severe edema.

Toxic-gas management should occur in parallel with burn and trauma care. Carbon monoxide and cyanide can coexist, and both may be present before a conventional chest radiograph becomes abnormal. Poison-center, hyperbaric, toxicology, and burn-center consultation can help with complex exposures, but these consultations should not delay oxygen, ventilation, antidote administration when indicated, or airway control.

References

1. American Burn Association Clinical Practice Guidelines — Link
2. American Burn Association Guidelines for Burn Patient Referral — Link
3. CDC Emergency Response Card: Hydrogen Fluoride and Other Chemical Emergencies — Link
4. American Heart Association 2025 Special Circumstances of Resuscitation — Link