Visualization of the airways for diagnosis or treatment can involve the use of either flexible or rigid bronchoscopes. Flexible bronchoscopes generally are used for evaluation and biopsy, whereas rigid bronchoscopes are uniquely capable of establishing and maintaining airway control in a life-threatening situation such as acute upper airway obstruction or massive hemoptysis. Although these procedures often can be used interchangeably, the rigid bronchoscope is uniquely suitable for applications that require precise airway measurement (e.g., tracheal stricture) or a large working port (e.g., endobronchial tumor).

ANATOMY OF THE TRACHEA AND CONTIGUOUS UPPER AIRWAYS

The trachea extends from the cricoid cartilage of C6 to the origin of the left and right main stem bronchi at the carina (T6). In normal adults, the trachea is 12 cm long (range 9–15 cm). The normal trachea is approximately 16 mm in lateral diameter and 14 mm in anteroposterior diameter. The anterior wall of the trachea is composed of cartilaginous horseshoe-shaped rings, and the posterior wall is a continuous membranous wall (Fig. 52-1).

The left mainstem bronchus, approximately 4.5 cm in length, is oriented at 45 degrees to the axis of the trachea. The right mainstem bronchus is much shorter (1.5 cm) and is oriented more vertically (25 degrees). The right mainstem bronchus gives rise to the right upper lobe bronchus at the level of the carina. The right upper lobe has three segments corresponding to the apical (B1), posterior (B2), and anterior (B3) segments. The airway distal to the right upper lobe orifice is the bronchus intermedius. The bronchus intermedius extends 2 cm from the right upper lobe to the right middle lobe bronchus. The middle lobe bronchus is 1.2–1.5 cm in length and has a diameter of 8 mm. The middle lobe has a medial (B4) and lateral (B5) segment. The superior segment (B6) of the lower lobe arises at the level of the middle lobe bronchus. The orientation of the basilar segment orifices (B7–10) is variable, and these generally are considered collectively (i.e., composite basilar segmentectomy).

The origin of the left upper lobe bronchus is lower than that of the right upper lobe bronchus. The left upper lobe orifice branches into upper and lower divisions. The upper division is approximately 1 cm long and gives rise to three segments, two of which are often combined (e.g., B1 + B2 and B3). The lower division is composed of the superior (B4) and inferior (B5) divisions of the lingula. The lower lobe superior segment (B6) has a similar course to the right side. There are only three basilar segments (B8–10; the B7 segment is absent) in the left lower lobe compared with five in the right lower lobe. Similar to the right side, the basilar segments are vertical in orientation and generally considered as a composite structure.

The principal advantages of flexible versus rigid bronchoscopy are detailed in Table 52-1. The diagnostic and therapeutic indications are summarized in Table 52-2.

*Smaller-diameter rigid scopes not only have smaller distal lumens, but also these scopes bend slightly when examining the left tracheobronchial tree. Visualization can be improved by placing a flexible scope through the rigid scope.

PREPROCEDURE EVALUATION

Patients undergoing bronchoscopy should have a normal platelet count, prothrombin time, and partial thromboplastin time to minimize the risk of bleeding. Because the lung is a noncompressible site and prone to bleeding, patients undergoing transbronchial biopsy should have relatively normal blood urea nitrogen and creatinine levels. Relevant past medical history includes a recent myocardial infarction or documented arrhythmias. Asthma frequently is exacerbated by bronchoscopy and may require pretreatment with bronchodilators.

The label high-risk bronchoscopy usually is reserved for patients with a labile PO₂ or evidence of CO₂ retention. Bronchoscopy will decrease arterial PO₂ by 10–20 mm Hg under optimal conditions—more if the patient's ventilatory mechanics are impaired.^1,2 It is important to recognize CO₂ retention before the procedure is performed to avoid sedative-related hypercarbic effects. High-risk bronchoscopy should be performed through an endotracheal tube to facilitate positive-pressure ventilation and oxygen delivery if necessary.

The specific preprocedure evaluation for patients undergoing rigid bronchoscopy includes an examination for concomitant neck injury or cervical disease. In addition, the ventilatory inefficiencies during rigid bronchoscopy make patients with poor lung compliance a particularly high-risk group.

PREMEDICATION

Patients undergoing flexible bronchoscopy benefit from sedation. Although a number of medications have been used, the most common combination used today is an IV narcotic and a benzodiazepine. The most popular benzodiazepine is midazolam (Versed). Midazolam is a short-acting benzodiazepine that decreases anxiety and impairs memory retention. Midazolam is also associated with respiratory depression and hypotension. A typical starting dose is 2 mg IV (1 mg IV in an elderly person).

Fentanyl is the most popular narcotic. A short-acting potent narcotic, fentanyl contributes a sedative effect as well as cough suppression. It is associated with respiratory depression and hypotension as well. A typical starting dose is 50 g IV (25 g IV in an elderly person).

MONITORING

All endoscopic procedures carry the risk of cardiac arrhythmia. Although elective outpatient bronchoscopy is rarely associated with arrhythmias, perioperative therapeutic bronchoscopies can be associated with atrial arrhythmias and bradycardias. All patients must have continuous electrocardiographic monitoring for the duration of the procedure. Patients receiving midazolam or fentanyl sedation should have blood pressure monitoring during and after bronchoscopy, and all patients should receive supplemental oxygen and have continuous oxygen saturation monitoring.

FLEXIBLE BRONCHOSCOPY TECHNIQUE

Anesthesia

Flexible bronchoscopy can be performed with topical anesthesia. The medications used are either benzocaine and tetracaine (Cetacaine) or lidocaine (Xylocaine). Cetacaine is a combination of agents that is particularly well suited for bronchoscopy. The rapid onset of Cetacaine is attributable to the action of benzocaine, and its extended duration (typically 30–60 minutes) is owing to the action of butamben and tetracaine. Typically, only four to five sprays are used to avoid inducing methemoglobinemia. Methemoglobinemia occurs when more than 1% of the heme iron is oxidized to the ferric form. The oxidized hemoglobin (i.e., methemoglobin) is incapable of reversibly binding oxygen. Methemoglobinemia is readily treated with an infusion of methylene blue.

To perform a well-tolerated bronchoscopy, three anatomic areas need to be anesthetized: the hypopharynx, larynx, and trachea. The hypopharynx can be anesthetized directly with Cetacaine or lidocaine sprays oriented behind the tongue. Some bronchoscopists prefer to have the patient gargle with lidocaine or swallow Xylocaine jelly.

The larynx can be anesthetized using a combination of techniques. An effective initial approach is to use a nebulizer. Nebulization can deliver lidocaine to the larynx and trachea. A nebulizer connected to a pressurized oxygen source can be used to synchronize the sprays with deep inspiration. A hole cut in the oxygen tubing is occluded intermittently with a finger to produce a forceful spray. This technique facilitates the delivery of lidocaine to the larynx and the trachea. Lidocaine also can be instilled into the larynx under direct vision using the flexible bronchoscope.

The trachea typically is anesthetized with 5 mL of 1% lidocaine after the bronchoscope has passed through the vocal cords. Additional lidocaine is administered at the level of the main stem bronchi bilaterally.

Flexible Bronchoscope Equipment

The bronchoscope consists of a handle and an insertion tube that contains the optical bundle and a working channel. The handle controls the distal segment of the insertion tube. The distal portion of the scope bends in a single 270-degree arc to facilitate examination of the entire airway. The optical bundle contains a fiberoptic light bundle and a second bundle for either digital or fiberoptic imaging. The working channel can be used to suction, pass instruments, and lavage the airways.

Basic Technique

In the nonintubated patient, the bronchoscope is introduced either through the mouth or the nose. Transnasal introduction is used commonly as an outpatient procedure (Fig. 52-2). This approach has the advantage of maintaining proper alignment of the bronchoscope as well as permitting the patient to comfortably swallow secretions. After proper application of topical anesthetics, the bronchoscope is gently passed through the nasal passages into the posterior pharynx.

In thoracic surgical patients, previously traumatized nasal passages and the presence of nasogastric tubes make oral introduction the preferred method (Fig. 52-3). The patient is asked to hold a circular bite block in his or her teeth. The bronchoscope is lubricated and the tip curved. While the operator is looking into the open mouth—not through the bronchoscope—the lighted tip of the bronchoscope is positioned over the glottis. Holding this position in the midline, the operator then looks through the bronchoscope, and the vocal cords are visualized with minimal movements. Then 5 mL of 1% lidocaine is instilled onto the vocal cords. Note the vocal cord mobility with phonation. The bronchoscope is passed through the vocal cords, and another 5 mL of lidocaine is instilled into the trachea. Additional lidocaine may be necessary in the main stem bronchi.

The trachea should be examined for displacement of the tracheal rings or effacement of the carina. The membranous portion of the trachea should displace anteriorly during expiration and cough. In most cases it is wise to first examine the normal tracheobronchial tree to ensure complete evaluation of the airways. Each segmental orifice must be examined.

Diagnostic procedures can be complicated by bleeding and must be performed in the proper order: washings, brushings, and biopsies. Bronchoalveolar lavage is performed by centering the distal tip of the bronchoscope in a segmental orifice. A volume of normal saline, typically 50–150 mL, is instilled into the distal airway while maintaining occlusion of the segmental airway. The patient is asked to take several deep breaths to draw the lavage fluid into the distal airspaces. The lavage fluid then is aspirated into an appropriate container.

Brushings may be directed at either cytologic or bacteriologic diagnoses. Brushings obtained for cytology must be prepared properly to preserve cellular morphology. Similarly, distal airway brushings for bacterial culture also must be performed properly. So-called covered brush cultures involve a covered sheath with the gelatin plug. The gelatin plug protects the brush from contamination until it is in the distal airway. The plug is expelled, and distal cultures, particularly anaerobic cultures, can be obtained reliably. If the brush is processed properly, quantitative cultures of the distal airway can be obtained.

Complications

The most predictable complication of bronchoscopy is transient hypoxemia. The PaO₂ routinely drops by 10–20 mm Hg during bronchoscopy.^1,2 The relative hypoxemia is worsened by large-volume saline lavage and use of an excessive amount of suction. In most cases the predictable drop in PaO₂ can be prevented with the routine use of supplemental oxygen therapy. Cardiac arrhythmias are unusual during routine bronchoscopy. Hemodynamically significant arrhythmias typically are restricted to procedures associated with hypoxia or hypercarbia. The sedation used for bronchoscopy can contribute to hypercarbia. In a patient with preexisting hypercarbia, the bronchoscopy can be performed without premedication or sedation. If the patient is likely to require high-flow oxygen or mechanical ventilation, it is advisable to intubate the patient during the procedure. A fiberoptic intubation can be performed readily by placing an endotracheal tube over the bronchoscope.

Endoscopic procedures can be associated with fever and bacteremia. Although there is no consensus regarding the use of prophylaxis in patients with artificial heart valves, most practitioners administer prophylactic antibiotics before bronchoscopy. Although transient infiltrates and fever can be observed in 5% of patients after bronchoscopy, postbronchoscopy pneumonia is rare. Proper sterile technique and bronchoscope processing will limit the life-threatening Pseudomonas pneumonia associated with a contaminated bronchoscope.

RIGID BRONCHOSCOPY TECHNIQUE

Anesthesia

Patients undergoing rigid bronchoscopy require general anesthesia. Unique to rigid bronchoscopy, the preprocedural examination must include a careful evaluation of the neck. Severe cervical arthritis may prevent neck extension. Patients with micrognathia, protruding teeth, or a small buccal cavity may pose a problem for rigid bronchoscopy. Patients with near-total tracheal obstruction may not tolerate the supine position or sedation. In these patients, awake rigid bronchoscopy can be performed in the sitting position with adequate topical anesthesia.

Because of the difficulty in controlling the delivery of inhalational anesthetics during rigid bronchoscopy, most anesthesiologists rely on IV anesthetic techniques. In most cases the anesthetics are minimized, and assisted spontaneous ventilation is used to optimize gas exchange. Oxygen is delivered by intermittent positive pressure ventilation or by using the Venturi technique through a sideport.

Rigid Bronchoscope Equipment

The rigid bronchoscope is a hollow stainless steel tube of various diameters. The length of the rigid bronchoscope varies from pediatric sizes (a few inches) to more than 15 inches in adults. The length of the bronchoscope varies with its outer diameter. In adults, 8- to 12-mm bronchoscopes are suitable for most procedures. The major manufacturers of rigid bronchoscopes are the Richard Wolf Company (Germany), the Carl Storz Company (Germany), and the EFER Company (France) (Fig. 52-4).

Most bronchoscopes have a beveled end that facilitates introduction. The Wolf rigid bronchoscopes have an extended flat bevel that facilitates the "coring out" of intraluminal tumor. Most bronchoscopes also have sideports that permit the introduction of suction catheters or laser fibers. In addition, sideports can be used to allow ventilation. In some classifications, the presence or absence of a sideport determines whether the bronchoscope is called a ventilating or nonventilating bronchoscope.

Early rigid bronchoscopes used a rigid telescope to facilitate distal viewing. The viewing telescopes were produced at various angles to permit visualization of all the lobar bronchi. The flexible bronchoscope, however, has made the viewing telescope largely obsolete. The flexible bronchoscope can be introduced through the working channel of the rigid bronchoscope to provide not only excellent optical resolution but also a maneuverable end and a working channel.

Basic Technique

The bronchoscopist stands at the head of the anesthetized patient. The patient is well oxygenated, and pharyngeal secretions are aspirated. The lips, gingiva, and teeth are inspected carefully. Dental structures are protected with the use of rubber guards or folded damp gauze.

Many operators prefer to position the patient in a "sniffing" position for inserting a rigid bronchoscope. The sniffing position displaces the tongue anteriorly. The patient's maxilla is grasped in the left hand, and the thumb is used to protect the incisors and provide a fulcrum for the bronchoscope (Fig. 52-5). The thumb always should be interposed between the bronchoscope and the patient's teeth or gums. The bronchoscope is inserted into the hypopharynx with the distal tip oriented toward the epiglottis. When the epiglottis is visualized, the distal end of the bronchoscope is advanced just beyond the tip of the epiglottis, and the epiglottis/tongue is gently displaced anteriorly. The displacement of the epiglottis/tongue involves gentle rocking of the bronchoscope on the thumb fulcrum. The bronchoscope should not be touching the patient's teeth or gums. This rocking maneuver should bring the vocal cords into view. The rigid bronchoscope is rotated 90 degrees to facilitate passage of the beveled end of the bronchoscope through the vocal cords. Once the bronchoscope is within the lumen of the trachea, it is rotated another 90 degrees so that the distal tip is oriented posteriorly.

Once the bronchoscope has been introduced successfully into the trachea, the sniffing position is converted to cervical hyperextension (Fig. 52-6). To avoid any inadvertent injury to the major airways, the operator should maintain firm control of the patient's head and the bronchoscope with the left hand. The right hand then can be used for biopsy or suctioning.

Complications

The complications of rigid bronchoscopy are related to inadequate preoperative evaluation or poor technique. Cervical injuries or bleeding complications often can be avoided with appropriate preoperative evaluation. Inadequate visualization during insertion can result in trauma to the vocal cords or proximal airway injury. Perforation typically occurs in the posterior wall of the trachea or main stem bronchi.

A common complication of rigid bronchoscopy is respiratory failure. Assisted ventilation during rigid bronchoscopy does not provide the sustained positive airway pressure that is achieved during endotracheal intubation. Attempts to achieve increased positive airway pressure by packing the mouth or holding the nose and mouth closed generally are ineffective. In the presence of persistent hypoxemia or hypercarbia, it is prudent to remove the rigid bronchoscope and intubate the patient with a standard orotracheal tube. This permits effective positive-pressure ventilation and the recruitment of adequate lung volumes.

SUMMARY

Rigid and flexible bronchoscopy in the hands of the experienced operator can be an effective and safe diagnostic and therapeutic procedure. Complications are minimized by thorough preoperative assessment. Flexible bronchoscopy has several advantages, including avoidance of general anesthesia. In contrast, the rigid bronchoscopy establishes an adequate airway while providing flexible access to the trachea and main stem bronchi. The rigid bronchoscope can be combined with flexible bronchoscopy to maximize the advantages of both approaches.

CASE HISTORY

A 54-year-old smoker presented to the emergency room with rapidly progressive shortness of breath (Fig. 52-7). Chest x-ray demonstrated complete opacification of the left hemithorax. CT scan demonstrated a left main stem bronchial tumor. Rigid bronchoscopy subsequently was used to core out the endobronchial lesion and reestablish left lung inflation.

EDITOR'S COMMENT

These days, rigid bronchoscopy is rarely indicated given the ease and availability of flexible bronchoscopy. However, when required, it is critical that all members of the team know their roles. Therefore, frequent in-service training and simulations are important. Rigid bronchoscopy may also be performed through a tracheostomy. On occasion, patients with a small mouth, anterior larynx, or fused neck will require a tracheostomy for access. When trying to access the main stem airways and beyond, the bronchoscopist on occasion will need to angle the scope outside the patient's body, to the opposite side. Single main stem bronchial intubation is particularly critical when usual techniques of rigid bronchoscopic tamponade are used for bleeding. On occasion, it is difficult to advance the bronchoscope into the trachea, and assistance from the anesthesiologist, who can place a guide wire, can be instrumental to the case.

–RB

REFERENCES