Evaluating the association between bronchoscopic severity of burns-related smoke inhalation injury and clinical outcomes: A systematic review and meta-analysis.

Abstract

One-third of major burns are complicated by burns-related smoke inhalation injury (BII), which increases mortality risk. Fibreoptic bronchoscopy is the gold standard for BII diagnosis, with the Abbreviated Injury Score (AIS) being the most widely used grading system. While BII severity has been linked to poorer outcomes, this is the first systematic review and meta-analysis evaluating the association between bronchoscopic grading of BII and mortality, pneumonia, and acute respiratory distress syndrome (ARDS). Primary human clinical studies assessing BII severity via bronchoscopy were reviewed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework. Outcomes included mortality, pneumonia, ARDS, and intubation. Meta-analyses were conducted using random-effects models to determine risk differences (RD) with 95 % confidence intervals (CI). Further analyses explored alternative grading systems and thresholds for defining milder or more severe injury. Of 457 studies screened, 30 were included, with 12 providing sufficient data for meta-analysis. More severe BII (AIS grades 3-4) was associated with higher risks of pneumonia (RD: 0.319, 95 % CI: 0.020-0.618, p = 0.037) and ARDS (RD: 0.242, 95 % CI: 0.118-0.367, p < 0.001) compared to milder BII (AIS grades 1-2). While mortality was also higher for more severe BII (RD: 0.068, 95 % CI: -0.017-0.153, p = 0.116), there was insufficient statistical evidence to support this association. Findings were inconsistent in further analyses accounting for alternative grading systems and severity thresholds. Higher bronchoscopic grades of BII are associated with increased pneumonia and ARDS. However, substantial study heterogeneity and inconsistent grading methodologies limit confidence in these associations. While AIS remains the most widely used classification, other systems with differing definitions of severity further complicate comparisons. Future research should focus on standardising bronchoscopic classification and integrating objective clinical parameters for improved risk stratification.