Diagnosis

Inhalation injury

Etiology

Cause [cuk]

• Direct heat from fire

• Toxic chemicals in the smoke: carbon monoxide, ammonia, carbon dioxide, hydrogen cyanide, aldehydes, sulfur dioxides, and nitrogen dioxide

Pathophysiology [t5c]

1. Carbon monoxide impairs tissue oxygenation by decreasing oxygen carrying capacity of blood, shifting oxygen-hemoglobin dissociation curve to the left, binding myoglobin and terminal cytochrome oxidase.

2. Upper airway injury:

   • Thermal injury --> erythema, ulcerations, edema and external compression of the airway

   • Damage of ciliary function impairs physiological clearance --> increased risk of bacterial infection

   • Increased production of thick secretions can cause distal airway obstruction, atelectasis, and impaired gas exchange

3. Tracheobronchial injury: usually caused by chemicals in smoke

   • Inflammatory response

   • Bronchoconstriction

   • Increased vascular permeability, and vasodilation

   • Exudate leading to alveolar collapse

   • Ventilation-perfusion mismatch as a primary mechanism of hypoxemia

4. Parenchymal injury:

   • Injury to the lung parenchyma is characterized by atelectasis and alveolar collapse resulting in increased transvascular fluid flux, a decrease in surfactant, and a loss of hypoxic vasoconstriction and therefore impaired oxygenation

Complications [cuk]

• Pneumonia

• Acute respiratory distress syndrome

• Pulmonary edema

• Subglottic stenosis

• Bronchiectasis

• Bronchiolitis obliterans

• Brain damage (carbon monoxide poisoning)

Epidemiology

Incidence per 100.000 [fug][ak6][t5c][boz][q93][hws]

Approach

• Blood test: blood count, electrolytes, blood urea nitrogen, creatinine, lactate level, and toxicology screen

• Blood gas: carboxyhemoglobin level (CO-oximetry), methemoglobin, cyanide

• Chest x-ray

• Nasopharyngoscopy

• Direct laryngoscopy

• Bronchoscopy

• Ventilation-perfusion (V/Q) scan

Treatment

1. Respiratory support [fiv]

2. Fluid resuscitation and cardiovascular stabilization

3. Pain control

4. Local management of burn wounds

5. Profylaxis: thromboprophylaxis, antimicrobial therapy

6. Nutrition support

7. Treatment of complications: exacerbation of underlying medical comorbidities, sepsis, ileus, abdominal compartment syndrome, extremity compartment syndrome, pulmonary edema, adult respiratory distress syndrome, pressure-related wounds

Differential diagnoses

Acute respiratory distress syndrome, Asthma, COPD, Heart failure, Interstitial lung disease, Pneumonia, Pneumonitis, Pneumothorax, Pulmonary embolism