• Major cause of death after burns is respiratory tract injury or complications in the respiratory tract
• Problems include:
• Direct inhalation injuries are divided into 3 categories
1. Heat injury to the airway
2. Carbon monoxide poisoning
3. Inhalation of noxious gases
• Heat injury is a rare cause of injury below the vocal cords because the upper airway effectively cools the inspired gases and reflexive closure of the cords halts full inhalation
-Acute edema of the upper tract may cause airway obstruction and asphyxiation without lung damage
-Treatment is primarily supportive with pulmonary toilet, mechanical ventilation (as needed), and antibiotics
• Carbon monoxide poisoning must be considered in every patient in whom inhalation injury is suspected
-ABG and carboxyhemoglobin levels must be measured
-COHgb levels > 5% in nonsmokers and > 10% in smokers indicates carbon monoxide poisoning
-Mild carbon monoxide poisoning (< 20% COHgb) is manifested by headache, slight dyspnea, mild confusion, and diminished visual acuity
-Moderate carbon monoxide poisoning (20-40% COHgb) leads to irritability, impairment of judgement, dim vision, nausea, and fatigability
-Severe carbon monoxide poisoning (40-60% COHgb) produces hallucinations, confusion, ataxia, collapse, and coma
-Levels in excess of 60% COHgb are usually fatal
• Toxic inhalation of different chemicals produces specific respiratory injuries
-Inhalation injury causes severe mucosal edema followed soon by sloughing of the mucosa
-The destroyed mucosa in the larger airways is replaced by a mucopurulent membrane
-Edema fluid enters the airway and, when mixed with the pus, may form casts and plugs in the smaller bronchioles
• Less common causes of respiratory failure are pulmonary embolus and overload pulmonary edema
• Pulmonary emboli usually occur later in the course of treatment after prolonged bed rest and should be suspected if respiratory function suddenly deteriorates
• Pulmonary edema usually occurs only in patients with preexisting heart disease
• Probably the most common cause of respiratory failure is bacterial pneumonia due to either inhalation injury, contamination of the lungs through a tracheostomy or endotracheal tube, airborne infection, or hematogenous spread of bacteria from the burn wound
• Alteration of oropharyngeal normal flora with colonization by pathogens and subsequent aspiration of infected secretion is the most common cause of the lung infections
• Pulmonary insufficiency is associated with systemic sepsis; differentiating acute respiratory distress syndrome (ARDS) from bacterial pneumonia may be difficult