Facial burns expose patients to a higher risk of respiratory problems, and early prophylactic intubation might be life-saving. Therefore, the early detection of the need for intubation in those with facial burns is important. [9] Several sets of criteria (e.g., the American Burn Association guidelines or Denver criteria) have been established and suggest early intubation in burn patients. [10, 11]
Traditionally, the diagnosis of inhalation injury has usually been based on a combination of clinical evaluations, such as patient history or physical examinations. Some physical findings have been considered indicators of a higher likelihood of laryngeal edema or inhalation injuries above the glottis and thus a greater need for intubation. A previous study (Vivó, C et al) demonstrated that stridor, shortness of breath, facial burns, singed nasal hairs, cough, soot in the oral cavity and history of being in an enclosed space with the fire should be strongly considered indicators for early intubation. [12] However, physical examinations are usually subjective evaluations. Diagnostic modalities such as laboratory examinations or chest X-ray may objectively contribute to the evaluation of inhalation injury. Arterial blood gas analysis was described as a good tool for the early detection of inhalation injury, while (Onishi, S. et al) carboxyhemoglobin levels (HbCO) were considered a useful predictor of inhalation injury below the glottis. [13, 14] In addition, the utility of chest X-rays (increased perihilar or peribronchial infiltration, ground glass haziness of the lung, or other signs that may indicate pulmonary edema or respiratory distress) or even computed tomographic scans (bronchial wall thickness) for the detection of significant inhalation injuries have also been reported. [14]
Similar to the findings of previous studies and current guidelines for facial burn management, in the current study, patients who were intubated in the ED had significantly more positive signs on physical examinations or abnormal blood gas analysis results (Table 1). However, after undergoing bronchoscopy as a definitive evaluation, 39.7% of the intubated patients were not found to have airway injuries (Fig. 1). This fact indicates that some airway protection procedures might be considered overresuscitation, and more objective evaluations of the indication for early intubation are needed. Positive signs on physical examination may be indicators for intubation in the ED but may not correlate with the presence of inhalation injury.
In addition to the evaluation of patients who underwent intubation in the ED, patients with inhalation injuries who truly needed airway protection were analyzed. Compared with patients without inhalation injuries, patients with inhalation injuries were significantly more likely to have some positive signs on physical examination, abnormal laboratory examinations and positive findings on CXR in univariate analyses (Table 2). However, further MLR analysis in the current study revealed that most positive signs on physical examinations, laboratory examinations and CXR results could not significantly predict inhalation injury. However, shortness of breath is an easy-to-identify sign that was an independent risk factor for inhalation injury in facial burn patients. The presence of shortness of breath in facial burn patients was associated with a 3.376-fold higher odds of inhalation injury (p = 0.027, odds ratio = 3.376, 95% CI.=3.133–3.601). In addition, a high TBSA may also be independently predictive of inhalation injury. Every one percent increase in the TBSA was associated with a 1.038-fold increase in the odds of inhalation injury (p = 0.001, odds ratio = 1.038, 95% CI.=1.022–1.049)
In the current study, positive correlations between TBSA and the odds of inhalation injury and intubation were both observed. It is noteworthy that the proportion of intubated patients was higher than the proportion with inhalation injuries, regardless of the TBSA (Fig. 2). All patients with a high TBSA (> 60%) were intubated in the ED, even if they had no sign of inhalation injury. This implied that for severe burn patients (with a higher TBSA), inhalation injury is not the only indication for intubation. Steinvall, I and Liffner, G et al reported that acute respiratory distress syndrome can develop in burn patients without inhalation injury due to an inflammatory process mediated by the effect of the burn, and this physiopathological process is not associated with inhalation injury. [15, 16] Dries et al also reported that critical burn patients may develop several lung injuries, such as sepsis, ventilator-induced lung injury or systemic inflammation, in addition to inhalation injury. [17]
In the current study, ten patients (8.3%, 10/121) underwent delayed intubation after admission. They were not intubated on admission to the ED. Most of these patients (80%, 8/10) were intubated because they needed to undergo surgery under general anesthesia (four patients) or they had complications of severe burn injuries (TBSA > 50%) (four patients). Only two patients had delayed symptoms of inhalation injury (shortness of breath or hoarseness) (Table 4). Among the patients who underwent intubation, there were 33 (27.3%, 33/121) patients without inhalation injuries (bronchoscopy grade = 0), although they remained intubated for longer than 3 days. Upper airway edema usually resolves within 2–3 days. These prolonged intubations implied that these patients were not intubated only due to airway edema, a common complication of inhalation injury, but also other reasons. Therefore, in addition to the management of inhalation injury, intubation still plays a significant role in stabilizing and treating other associated injuries. Airway management, as a part of resuscitation, should be considered for all burn-associated injuries not only inhalation injuries.
The major limitations of this study are its retrospective nature and the small patient sample, which was obtained from a single institution. In addition, there were some patients with missing records of physical examinations and reasons for intubation. The aforementioned limitations notwithstanding, the results provide important information about the role of airway protection in the management of facial burn patients. A prospective study with a larger patient sample size should be designed to determine the accurate indications for endotracheal tube intubation in the ED.