Does Bronchoscopic Evaluation of Inhalation Injury Severity Predict Outcome?

Although fiber-optic bronchoscopy is essential in the diagnosis of smoke inhalation injury (INH), controversy still exists over whether or not the visualized severity of the mucosal injury predicts clinically meaningful outcomes. The purpose of this study was to assess whether the grade of mucosal INH severity was associated with various outcomes among adult burn patients. We conducted a retrospective review of all patients requiring greater than or equal to 48 hours of mechanical ventilation who were admitted between January 1, 2007 and June 1, 2014 to an adult regional American Burn Association-verified burn center. Bronchoscopy was performed on all subjects at burn center admission and grading of severity was documented using the grades 0 to 4 abbreviated injury score (AIS). Subjects with grade 1 or 2 injury formed the low-grade INH group, whereas those with grade 3 or 4 injury formed the high-grade INH group. Values are shown as the median (first to third quartiles). A P value less than .05 was considered significant. The study population consisted of 160 subjects (age, 48 [35-60] years; %TBSA burn, 28 [19-39.9]; % full thickness burn, 12.8 [0-30]; and 61% with INH). There were no significant differences in age, %TBSA burn, or % full thickness burn between subjects with different individual INH severity grades. Oxygenation on the day of injury worsened significantly as the severity of INH increased, but otherwise there were no significant differences in 24 and 48-hour fluid requirements, duration of ventilation, ventilator free days, incidence of acute respiratory distress syndrome, or mortality between subjects with different individual grades of INH severity. Subjects with high-grade INH showed statistically insignificant trends toward larger 48-hour fluid volumes (P = .07), poorer oxygenation over the first 3 post burn days (P = .055), longer duration of ventilation (P = .08), and fewer ventilator free days (P = .047) than low-grade INH. High-grade and low-grade INH subjects did not differ significantly in the incidence of acute respiratory distress syndrome or mortality. The individual grades of the 0 to 4 AIS INH severity grading scale were not particularly robust in the prediction of various outcomes among a population of adult burn patients. However, clinically relevant trends toward worsened oxygenation over postburn days 0 to 3, longer duration of mechanical ventilation, and reduced ventilator-free days in association with more severe INH were identified when subjects were broadly stratified into low-grade (grades 1and 2) INH and high-grade (grades 3 and 4) INH. This suggests that there may clinically meaningful differences between patients with less and more severe INH, and that further refinement of the grades 0 to 4 AIS INH severity should be subjected to additional investigation.