Application of flexible bronchoscopy in inhalation lung injury

Inhalation injury is a major cause of morbidity and mortality in burn patients. It is, along with age and total burn surface area (TBSA), one of the three most significant predictors of death after thermal injury. The incidence of inhalational injury in burn patients who require hospitalization ranges from 20% to 30%. There is a reported mortality in this same population of 30%. The incidence of respiratory failure is significant after inhalational injuries, with hypoxemia, pneumonia, and respiratory failure with prolonged ventilatory support and extended hospitalizations being common [1‐4]. As acute inhalational injury is an uncommon presentation to most institutions, a standard approach to its assessment and management, especially using flexible bronchoscopy, has not received significant attention [5].

On November 15, 2010, a significant fire occurred in a residential building on Jiaozhou Road, in Shanghai, China, which is still known as the "11.15" fire. Fifty-eight people were reported dead and burn patients were sent to a number of hospitals throughout Shanghai. Twenty-three patients were admitted and treated in our three hospitals; bronchoscopy played an important role in the management of twenty of these patients. We report here our experience in the assessment and management of these patients.

The study includes all patients who were injured in the fire on Jiaozhou Road, in Shanghai, China on November 15, 2010 and admitted to the following three hospitals: Shanghai Changhai Hospital (20 patients), Shanghai Changzheng Hospital (2 patients) and Shanghai Putuo District People's Hospital (1 case). Excluded were two patients at Changhai Hospital who refused bronchoscopy and a three year old with mild symptoms. The remaining 20 patients had bronchoscopy performed as part of their medical management. The patient population consisted of fourteen males and six females. The patients’ ages ranged from 16-83 years old with an average age of 54.2 ± 8.1 years. Patients had experienced smoke inhalational ranging from 10-120 minutes. Of the twenty patients enrolled, three had grade 2 surface burns, one each of 1%, 4% and 5% total body surface area. In addition one patient had a lower limb crush injury syndrome.

The initial bronchoscopy on all patients was performed within the 18-72 hours of admission to the hospital. An Olympus BF260 videobronchoscope (Olympus Medical Systems Corporation; Tokyo, Japan) was used to perform all airway evaluations. Follow-up airway inspection was conducted according to the patients’ condition.

At the time of the initial bronchoscopic evaluation of the patients, the location of the inhalational injury was described: (a) upper airway injury (burn limited to the larynx and glottis), (b) large airway injury (burn involving the trachea and bronchial tree), or (c) peripheral airway injury (burn involves the terminal bronchioles and/or alveoli) [6].

The visual classification of mucosal airway injury by Chou, et al. was used in the description of bronchoscopic findings of all patients [7]. G0 designates a negative airway examination; G1 mild edema and hyperemia, with or without carbon soot; G2 severe edema and congestion of the airway mucosa, with or without carbon soot; and G3 bronchial ulcers and/or necrosis with the absence of a cough reflex and bronchial secretions. The Gb designation was established for cases that bronchoscopic findings were unclear and mucosal biopsy was performed and found to be positive.

The factors, which most significantly affect the prognosis of patients with burns, are: total body surface area burn, the age of the patient, and the presence of inhalational injury. The reported incidence of inhalational injury burn complications occurs in 7-20% of patients requiring hospitalization [8]. Inhalational injury from burns can increase mortality by 20% and the occurrence of pneumonia by up to 40% [9]. Clinically significant inhalational injuries often do not manifest for three to four days after the exposure [10]. Complications of inhalational injury are not uncommon in patients with burns, coma, or other severe unexplained clinical symptoms [1, 11, 12]. There are many cases that are easily missed due to inhalation injury that can occur irrespective of burn injuries and clinical manifestations are often not apparent. It is reported that inhalation lung injury can occur in patients with no body surface burn; however, its clinical manifestations are not consistent and can vary from no obvious symptoms to severe respiratory failure [13].

The nineteen patients in our study were conscious at admission, only 15% (three cases) of the patients had body surface burns, and there were no obvious breathing difficulties within the first hour after presentation. Without a high degree of clinical suspicion, the presence of inhalational injury in most of our patients would not have been recognized. By identifying injury early, those patients’ with more advanced exposures can be closely observed, allowing quick clinical response to any change in their medical condition. Particularly in patients without surface burns, the lack of the findings of an early inhalational injury could result in the delay of treatment.

Bronchoscopy is considered the ‘gold standard’ for early evaluation of upper airway injury and can be used to help predict acute lung injury [1, 14]. Even when the initial chest examination, chest x-ray, and blood gasses are normal, bronchoscopy can identify large airway injury, a precursor to respiratory complications due to inhalational injury [13, 15, 16]. One hundred percent of the patients (n = 20) in our study, had bronchoscopic findings of large airway injury, involving both the trachea and proximal bronchial tree. This finding occurred when only 60% of the patients were found to have fine moist rales on chest examination and 75% of patients had computed tomography examinations demonstrating pulmonary exudative changes. Bronchoscopy is therefore a very important tool in the initial evaluation of patients with suspected inhalational lung injury.

Bronchoscopic findings in patients with inhalational injury include: congestion, edema, mucosal ulceration and necrosis. When the inhaled matter contains carbon based soot, the carbon soot will adhere to the mucosal surfaces of all visible airways [13]. Some patients with mild symptoms do not have any visible bronchoscopic findings consistent with inhalational injury. Despite the lack of macroscopic findings, bronchial mucosal biopsies often demonstrate microscopic evidence of inflammatory changes to the airway. When inhalational injury involves the full-thickness of the mucosa as well as the submucosa, the cough reflex as well as mucus secretion production and eventually clearance can become problematic [17]. These patients will have no cough and limited to no secretions when bronchoscopy is performed [10]. In our study, no biopsies were acquired as the treating doctors considered that they would not add to the treatment of the patients. On the contrarary this intervention was considered that it would jeopardize patients health. Classification of inhalational injury by bronchoscopy can be important in the management of patients, despite the fact that no direct link between bronchoscopic grade and mortality has been definitively established.

Gore et al. [13] describes that it is safe to perform flexible bronchoscopy in inhalation lung injury patients, even those with mild airway obstruction. In many cases, it is the personal experience of the clinician that is often the constraining factor for the use bronchoscopy. Those physicians with more experience tend to use bronchoscopy more readily than those who do not. The patients in our study did not demonstrate any clinical problems during our bronchoscopic evaluation of their airways, even those at the G2 level. Bronchoscopy is also of therapeutic value in the management of patients with inhalation lung injury [18, 19]. Patients with airway Grade G0 and Gb findings have acute inflammation of the mucous membrane as the main change to the airway, thus there is no bronchoscopic intervention indicated. On the other hand, patients with Grade G3 findings can have necrotic tissue and inflammatory exudates blocking the airway lumen. Immediate intervention with the bronchoscope can be very effective in managing these patients. There are different points of view regarding intervening on the carbon soot findings in patients with Grade G1 and G2; in most instances no intervention is most appropriate. Grade 2 patients can also develop pseudomembranes. In our eight G2 patients, this was an early manifestation of more significant airways disease. We resected the majority of pseudomembranes which were felt to be clinically detrimental to the patients, as complete resection led to more significant mucosal bleeding. Concern always exists that the airways will scar or develop stenosis after an inhalational injury. We identified no significant residual findings at the late bronchoscopic re-examination of the airways, which was consistent with the results reported by Irrazabal et al. [19] From our and reported findings, the recovery time of a bronchial mucosa is longer in Grade G2 injury patients as compared to those with Grade G1 injury. That is, patients with severe inhalation lung injury need a long time for airway mucosal repair, while patients with mild inhalation lung injury need a short time for airway mucosal repair.

In conclusion, the flexible bronchoscope has great value in the diagnosis of inhalation injury without any complications and it should be incorporated into routine clinical practice. The use of flexible bronchoscopy must be done so with the knowledge that the airways will heal themselves if given the appropriate time. The identification of an injury or a pseudomembrane that is not creating a problem for the patient at that time should be left to heal, only using therapeutic procedures for the more significant airways injuries or in patients with respiratory need.