Which of the following is/are true about inhalation injury in burn patients?

B. Its presence characteristically necessitates administration of resuscitation fluids in excess of estimated volume

C. When moderate or severe, it exerts a comorbid effect that is related to both extent of burn and the age of the patient.

D. It increases the prevalence of bronchopneumonia.

E. Prophylactic high-frequency ventilation reduces the occurrence of pneumonia and the mortality in burn patients with inhalation injury.

DISCUSSION: Extensive inflammatory changes are evoked in the airway following the inhalation of smoke and other irritating products of incomplete combustion. Clinical signs are nonspecific and may be delayed. Chest x-rays are also unreliable in detecting even severe inhalation injury. Chest x-rays taken within 24 hours of injury were found to be falsely negative in 92% of 106 patients with inhalation injury. Fiberoptic bronchoscopic examination is the most reliable single means of diagnosing inhalation injury of the large airways, but in patients who inhaled finely particulate smoke the large airways may show little if any inflammatory change. The distance smoke particles travel before deposition in the airways is inversely related to particle size. When the smoke particle mass median diameter is less than 0.5 mm., deposition occurs in the terminal bronchioles and alveoli. In such patients, inhalation injury is best identified by prolonged retention of xenon 133 as assessed by a ventilation perfusion lung scan.

Historically, fluid restriction was recommended for patients with inhalation injury, but in recent years it has become obvious that such patients typically require more resuscitation fluid than the volume estimated by commonly used formulas. Edema of the small airways and occlusion due to endobronchial sloughing and inspissation predispose burn patients to develop pneumonia. In one study, 46% of burn patients with inhalation injury developed pneumonia and 69% of the pneumonias occurred in the first postburn week. The comorbid effect of moderate to severe inhalation injury is related to both age and burn size and increases mortality by a maximum of 20% above that predicted on the basis of age and burn size in patients whose burn injury alone would be associated with a 75% likelihood of death. In patients with only mild inhalation injury there is little if any increase in mortality above that predicted on the basis of age and burn size alone. Prophylactic use of high-frequency percussive ventilation minimizes airway collapse and atelectatic changes, as a consequence of which the incidence of pneumonia is reduced and survival is significantly increased.