Predictive value of bronchoscopy in assessing the severity of inhalation injury

Abstract

Inhalation injury is associated with severe pulmonary complications as inhaled products of combustion cause lung inflammation and loss of natural defenses. A bronchoscopic grading for inhalation injury has been proposed but has not yet been validated in burn patients. In this study, the authors evaluated whether bronchoscopic grading of injury clinically correlated with indices of gas exchange over the first 72 hours or predicted differences in hospitalization outcomes. They conducted a single-center retrospective review of all mechanically ventilated adults with suspected inhalation injury and thermal injury over an 18-month period. All recorded bronchoscopy examinations were reviewed and categorized injury according to the published abbreviated injury score (AIS 0: no injury, 1: mild, 2: moderate, 3: severe, and 4: massive injury). They also compared changes in oxygenation, airway pressures, chest radiograph findings, fluid administration, and early development of pneumonia and organ failure, by severity of inhalation injury according to the AIS. Thirty-two adult patients met inclusion criteria over the study period. This cohort was 69% male with a mean age of 44.5 ± 14 years and a mean % TBSA burn of 33.9 ± 17%. Of these 32 patients, 11 patients (34%) were classified as grade 0, 9 patients (28%) were classified as grade 1, 7 patients (22%) were classified as grade 2, and 5 patients (16%) were classified as grade 3. Measured carboxyhemoglobin levels increased significantly with higher AIS grade. Oxygenation indices were worse as grade worsened by 24, 48, and 72 hours. The incidence of acute respiratory distress syndrome increased by grade of injury: 0, 22, 57, and 80%, respectively, at 24 hours (P < .01), and remained statistically different at 48 and 72 hours. After adjustment for age, % TBSA burn, and full-thickness component, severe inhalation injury (grades 2 and 3) was associated with an increased risk of acute respiratory distress syndrome at 24 and 72 hours, as well as ventilator days >21 days, and a trend toward multiple organ dysfunction syndrome and mortality. Better understanding of the relationship between inhalation injury and lung physiologic sequelae is a burn research priority. The bronchoscopic grading of inhalation injury moderately correlates with early indices of impaired gas exchange in this cohort and may be a promising tool for staging lower airway injury. Prospective studies should definitively answer whether AIS bronchoscopy staging predicts hospitalization outcomes in inhalation injury.