While bronchoscopy can be helpful for many diagnostic purposes, we will focus on the key indications in most ICUs including evaluation for infection, hemoptysis, airway inspection, and inhalation injury.
Evaluation of Parenchymal Infiltrates
Bronchoscopy with collection of samples by BAL or bronchial washings may be helpful to identify infectious pathogens in the lower airways when cultures of tracheobronchial secretions or nasal swab for viral polymerase chain reaction (PCR) are unrevealing. It allows for directed sampling of the lower respiratory tract.5 Thus, it is more specific than blind methods of obtaining tracheobronchial samples and may help distinguish between infection and colonization. However, this may not be useful in cases of uncomplicated community acquired pneumonia although it may be valuable in cases of poor response to empiric antimicrobial therapy, clinical progression of infection, and in immunocompromised patients in whom the differential diagnosis includes opportunistic pathogens.6
In addition to BAL, sterile samples using a protected specimen brush (PSB) can also be obtained by flexible bronchoscopy. Transbronchial lung biopsy remains a controversial procedure when evaluating for infection. It carries a high risk for pneumothorax as well as hemorrhage in mechanically ventilated patients and should be considered only in selected cases.7 With experienced personnel, transbronchial biopsy while on mechanical ventilation may be preferred over surgical lung biopsy and can provide useful information to impact a change in therapy.8
Bronchoscopy can rapidly identify the location and extent of bleeding within the airways. If the source of bleeding is not readily discernible, segmental lavages can be performed to locate the area where fresh blood is recovered. In cases of mild to moderate hemoptysis, flexible bronchoscopy has a diagnostic and therapeutic role but rigid bronchoscopy is preferred in massive hemoptysis.
For mild to moderate hemoptysis, cold saline, diluted epinephrine, and fibrin precursors can be instilled into the site of bleeding.9 In massive hemoptysis, a rigid bronchoscope provides better control of the airway, ventilation during the procedure, visualization and more effective aspiration of blood and clots.9 Flexible bronchoscopy permits visualization of more distal airways but has limited suctioning capabilities. It does, however, allow for some basic procedures for airway maintenance and immediate control of bleeding, while awaiting more definitive procedures. For example, an endobronchial blocker (a Fogarty balloon-tipped catheter) can be introduced through the flexible bronchoscope in order to tamponade a bleeding bronchial subsegment. In cases where a bleeding endobronchial lesion is identified, electrocautery, cryosurgery and laser photocoagulation can be used.10
Airway inspection is frequently used in the positioning of an ETT or endobronchial tube, especially when airway management is difficult due to anatomical reasons. It can be performed prior to intubation if a difficult airway is anticipated and can also be used to guide ETT placement when direct laryngoscopy is not possible, such as in cases of head and neck anatomical anomalies due to congenital conditions or as a result of surgery or cancer. It is used in cases where intubation needs to be performed without sedation. Airway inspection can also reveal airway lesions. Finally, flexible bronchoscopy may be used in patients who have undergone lung transplantations to monitor the integrity of anastomotic sites.11
Inhalation of large amounts of smoke and particulate matter can result in significant inflammation and irritation of the airways.12 This in turn can cause pulmonary edema, cast formation, airway obstruction, ventilation/perfusion (V/Q) mismatch and the loss of pulmonary vasoconstriction. Bronchoscopic evaluation helps identify patients with airway obstruction and those with severe airway injury who might require more aggressive airway management.13 Some patients may benefit from early intubation and mechanical ventilation in anticipation of possible complications as a result of the injury and clinicians should therefore have a low threshold to perform flexible bronchoscopy in these patients.