Introduction:
Inhalation injury is one of the most contributory injury patterns to morbidity and mortality surrounding thermal injury. A significant amount of institutional variability exists in the diagnosis, treatment, and outcomes surrounding this independent predictor of mortality. The optimal management of upper airway and inhalation injury has yet to be described in the literature. The institutional algorithm at our regional referral ABA-verified burn center necessitates fiberoptic diagnostic laryngoscopy (DL) on presentation in patients at risk for upper airway and/or inhalation injury in addition to history, physical examination, and adjunct assessments. We sought to determine patterns and characteristics of inhalation injury management over a ten-year experience at our institution.

Methods:
A retrospective review of the burn registry database for all burn admissions between January, 2011 and December, 2020 at our urban nationally verified burn center was performed. Demographics, injury characteristics, complications, and select outcomes were examined. 253 patients with concern for upper airway/inhalation injury underwent DL upon presentation. 18 patients age < 18 were excluded from analysis. 66 patients were excluded due to inability to tolerate or refuse DL, or no clear documentation of the result. 169 patients undergoing DL underwent subsequent chart review and statistical analysis. Categorical data were described as number and percentage (N, %) and compared using Chi-squared and Fisher’s exact test, as appropriate. Continuous data were expressed as median (25th – 75th percentile) and compared using the Wilcoxon-Mann- Whitney test. Univariate followed by multivariate analyses were used to determine independent predictors of a positive finding on DL. Statistical analyses were performed using JMP Pro 16.0.0. 2021 SAS Institute Inc., Cary, NC.

Results:
Of the analyzed group (n=169) mean age was 52 years (SD 17) and patients were mostly male (62%). Mean BMI was 30 kg/m2 (SD 9). Tobacco use was elicited in 81 patients (48%) and 34 patients had known history of COPD (20%). Examination of injury characteristics yielded median ISS of 6 (4 to 10 IQR). 59% of this group had primary airway/inhalation injury without significant cutaneous thermal burns and 143 patients (69%) had < 1% TBSA cutaneous thermal burn. 75 patients (69%) had facial soot or singed nasal hairs concerning for inhalation injury. Of the 169 included patients who underwent DL, the DL was positive for airway injury in n=106 (63%). Examination of tracked complications in patients with positive DL yielded low numbers of complications: unplanned intubation (n=2, 1%), unplanned ICU admission (n=2, 1%), unplanned extubation (n=4, 2%), VAP (n=1, 1%). Median ICU length of stay (LOS) was 2 days (IQR 1 – 6) and average hospital stay was 3 days (IQR 1 – 11). Mortality overall in this group was 5% (n = 8). Subgroup analysis was used to specifically compare patients with positive versus negative DL. Patients with positive DL were of greater age (54 vs 49 years, p. = 0.09), primarily male (63% vs 60%, p = 0.7), had lower BMI (29 vs 30, p = 0.94), were more commonly tobacco users (52% vs 41%, p. = 0.18), and often carried diagnosis of COPD (24% vs 14%, p = 0.15). Median ISS was higher in the positive DL group (10 vs 4, p < 0.0001). TBSA was more often < 1% (85 vs 58, p =. 0.05). Presence of facial burns and soot was significantly associated with positive DL (56 vs 19, p < 0.0001). With positive DL, median ICU LOS, hospital LOS, and mortality were significantly higher (p < 0.0001, p < 0.0001, and p = 0.03, respectively).

Conclusions:
This large series of patients with airway and inhalation injury lends credit to an approach of aggressive diagnosis and subsequent management. Multivariate analysis of factors associated with positive DL highlighted obvious facial burns or soot (OR 15.9, 95% CI, p < 0.0001) and ISS (OR 1.1, 95% CI, p = 0.01) as most predictive. Though rates of tracked complications were too low to further analyze in the DL subgroup, in this series no patient with negative DL on admission required unplanned intubation. Patients with positive DL findings at our institution are placed on an aggressive algorithm that necessitates ICU admission with critical care consultation, a 24-hour period of NPO status, inhaled mucolytic therapy, enhanced pulmonary hygiene, and lung protective ventilatory strategies. As one would predict, positive DL patients exhibited longer ICU LOS, hospital LOS, and mortality. In addition to an aggressive approach to diagnosis and management of inhalation injury patients with risks for upper airway thermal injury and inhalation injury require specialized care in order to minimize complications and optimize outcomes.