Chapter 90: Bronchoscopy

In 1897, Gustav Killian first viewed the trachea and mainstem bronchi via a rigid tube, the prototype for the rigid bronchoscope. Later that year, he removed a bone from the right mainstem of one of his patients, the first known therapeutic use of the bronchoscope. In the early 1900s, Chevalier Jackson added an electrical light source to the distal end of the bronchoscope as well as a suction channel. The flexible bronchoscope was first used in clinical practice in 1967 by Shigeto Ikeda in Japan and by the late 1980s, the videobronchoscope was introduced by Asahi Pentax. For the first time this allowed for visualization of the airways on a screen rather than through the eyepiece of the scope.

Flexible fiberoptic bronchoscopy is an integral and vital skill and has become a common procedure in the intensive care unit (ICU). It allows for real-time imaging of the airways from the vocal cords to the subsegmental bronchi. It can be diagnostic and/or therapeutic such as for airway inspection, foreign body removal, suctioning of secretions, collection of samples and placement of devices or drugs within the airway.

Bronchoscopy is not a physiologically neutral procedure and continuous monitoring of heart rate, blood pressure and oxygenation must be done during and after the procedure. In ICU patients, ventilator parameters are also monitored to ensure that adequate tidal volumes are delivered and airway pressures are not excessively elevated. The following changes must be taken into account and anticipated during bronchoscopy.

Increased airway resistance. Partial occlusion of the airway by a bronchoscope can increase airway resistance, which can effect peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) as well as delivered tidal volume. These changes can have hemodynamic consequences in patients who may already have cardiovascular instability.

Decreased lung compliance. Bronchoscopy can decrease lung compliance by alveolar collapse from suctioning or surfactant loss after bronchoalveolar lavage (BAL). These effects can be especially significant in patients with decreased compliance, such as acute respiratory distress syndrome (ARDS), pneumonia, atelectasis, and chronic obstructive pulmonary disease (COPD).

Gas exchange. The most common gas exchange abnormality is transient hypoxemia from airway obstruction, alveolar collapse, fluid within the alveoli during BAL or bronchospasm. Oxygenation is likely to worsen in a critically ill patient because of the bronchoscope in the airways or endotracheal tube (ETT) blocking airflow. In patients who are not mechanically ventilated, continuous positive airway pressure (CPAP) applied via full-face mask has been effective in recruiting alveoli and increasing the efficiency of gas exchange in hypoxemic patients.¹ Sedation given to a spontaneously breathing patient can also suppress ventilation and gas exchange. Additionally, small increases in PaCO₂ can occur and may need to be monitored in severely hypercapnic patients. Changes in both PaCO₂ and PaO₂ may be more dramatic during suctioning.² Patients should be preoxygenated with 100% oxygen prior to and during bronchoscopy.

Cardiovascular effects. Changes in intrathoracic pressure especially during coughing may affect venous return and afterload of the left ventricle. Changes in vascular tone from hypoxemia can also result in significant hemodynamic changes. In a small proportion of patients major arrhythmias may develop.²

The reasons for bronchoscopy in the ICU are generally similar to those in the non-ICU setting but are usually focused to a few specific indications and may be either diagnostic, therapeutic or both. The majority of ICU patients who undergo bronchoscopy are mechanically ventilated.³ The most common reason for diagnostic bronchoscopy is collection of lower respiratory tract samples for culture while the most common therapeutic indication is removal of mucus plugs or bronchial secretions.⁴

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

Evaluation of Hemoptysis

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

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 Injury

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.

Therapeutic uses of flexible bronchoscopy in the ICU sometimes overlap with diagnostic indications and can include treatment of atelectasis, removal of foreign bodies, removal of bronchial secretions and placements of drugs or devices.

Persistent and/or Recurrent Atelectasis

Atelectasis is a common complication in ICU patients and a major cause for delayed recovery due to shunting and worsened hypoxemia. When atelectasis is caused by mucous plugging, flexible bronchoscopy can suction retained secretions, especially those that are thick and tenacious. In this scenario, a bronchial wash or lavage with normal saline can help loosen and access secretions by suctioning. Adjunctive measures such as chest physiotherapy and nebulizers are then instituted to maintain airway patency.^3,11

Foreign Body Removal

Flexible bronchoscopy can locate foreign bodies within the airways. Removal can be accomplished with small forceps, baskets, and Fogarty balloon catheters that are inserted through the working channel. However, a flexible bronchoscope has limited capacity to grasp and remove objects and a rigid bronchoscope may be necessary if the object is large or if airway protection is necessary during the procedure.

Removal of Bronchial Secretions

Bronchoscopy can also be used to remove secretions that are thick, tenacious, impacted or present distally within the airways, which may not be accessible by in-line suctioning. Clearing of the airways in this manner can improve ventilator parameters and hasten recovery and ventilator weaning.

Placement of Drugs or Devices

Devices including stents, endobronchial blockers, double-lumen ETTs as well as therapeutic coagulants for hemoptysis can be delivered or placed with a flexible bronchoscope. Additionally, while seldom used (< 1%), flexible bronchoscopy may be helpful to better visualize the laryngeal opening and vocal cords during a difficult intubation.^2,4 However, this should be done by an experienced bronchoscopist and preferably in the earlier stages of intubation rather than a rescue maneuver after multiple attempts at direct laryngoscopy.²

In mechanically ventilated patients, bronchoscopy is usually performed through the ETT or tracheostomy tube. While the bronchoscope may occupy ~10% of the tracheal lumen it will typically occlude ~50% of the ETT.¹⁴ The bronchoscope is introduced into the airway without disconnection from the mechanical ventilator via an adapted valve, which allows for continued ventilation and maintenance of PEEP during the procedure.

Prior to the procedure, many patients will require increased sedation and analgesia to help minimize coughing, dyspnea and discomfort during the procedure. Clinicians should be skilled and credentialed in delivering conscious sedation. Continuous vital sign monitoring is required to detect physiologic changes as previously described. Additionally, nebulized or instilled 1% lidocaine may help to locally anesthetize the airway as well as reduce the overall dose sedation required during the procedure.¹⁵

In order to obtain respiratory secretions through BAL, the tip of the flexible bronchoscope is first wedged into the lumen of a target airway, thereby isolating a particular segment from the rest of the tracheobronchial tree. Isotonic saline is then instilled by syringe through the working channel of the bronchoscope and then aspirated back into the same syringe. Several aliquots (3-6) are instilled sequentially and range from 50 to 100 mL each. Each aliquot should have an expected return of 40% to 70% of the initial volume depending on the segment being evaluated.³ The aliquots from a single lavage can be mixed together and sent for microbiological analysis, including differential cell counts and quantitative cultures and cytopathology.

A PSB is a double lumen catheter brush with an occluding plug to prevent contamination from airway secretions when the catheter is passed through the flexible bronchoscope channel. Samples from a PSB are felt to be more representative of infection since contamination is minimized.

In general, flexible bronchoscopy is a safe and well tolerated procedure. Table 90–1 shows a quick checklist to review prior to the procedure to help minimize complications. Table 90–2 lists general contraindications.

Bronchoscopy should be delayed if a pneumothorax is present and can be reconsidered once it has resolved or addressed by chest tube drainage. Increased intracranial pressure is considered a relative contraindication to bronchoscopy. However, deep sedation with paralysis while monitoring cerebral hemodynamics may minimize complications if the procedure is considered necessary.

The complication rate from bronchoscopy is low and reported to range from 0.08% to 1.08%. Most complications are from biopsies especially bleeding and pneumothorax. The risk of pneumothorax related to transbronchial biopsy is somewhat higher in the ICU given the lack of fluoroscopy and positive airway pressure.¹⁶ A chest X-ray is generally recommended for patients undergoing transbronchial biopsy to assess for pneumothorax but is not routinely ordered following flexible bronchoscopy.

Other complications include increased airway resistance related to blockage of airways by the bronchoscope. Bronchospasm/laryngospasm may occur due to airway irritation, especially in patients with known COPD. This, in turn, can result in increased airway resistance with elevated peak airway pressures. Patients may experience hypotension secondary to sedation given for the procedure. Hypoxemia can result from bronchospasm and increased airway resistance. Cardiac arrhythmias are also a known complication and highlight the importance of continuous monitoring of vital signs.

Following the procedure, patients can experience persistent hypoxemia from (V/Q) mismatch due to lavage fluid installation or persistent bronchospasm. Patients may also experience fever, which is usually self-limited and has been reported in 9% to 16% of patients undergoing the procedure.¹⁶