Bronchoscopy, Mediastinoscopy, and Chamberlain Procedure

Frederick W. Lombard
Jorn Karhausen

Case Vignette

With the growing use of computed tomographic (CT) scanning, pulmonary lesions are being diagnosed with increasing frequency. In fact, incidental lesions found on chest x-ray (CXR) or CT have become the most common manifestation of lung cancer.¹ A lesion larger than 3 cm in diameter is considered a mass, and as such has a greater likelihood of being malignant.¹ A single pulmonary lesion that is less than 3 cm in diameter, completely surrounded by pulmonary parenchyma, and is not associated with atelectasis or adenopathy is defined as a solitary pulmonary nodule (SPN).¹ While as many as one-third of SPNs represent primary malignancies, and nearly one quarter may be solitary metastases, the differential diagnosis of an SPN is broad and includes vascular diseases, infections, inflammatory conditions, congenital abnormalities and benign tumors.¹

In managing patients with suspected lung cancer, the goals are to determine an accurate histological diagnosis and stage the disease, if the lesion is malignant. This information is critical, not only to predict resectability, but also to avoid unnecessary surgery and provide the patient with prognostic information. Flexible fiberoptic bronchoscopy (FOB) and mediastinoscopy are the standard methods used for staging non-small cell lung cancer (NSCLC), the most prevalent type of lung cancer.

FLEXIBLE FIBEROPTIC BRONCHOSCOPY

Flexible fiberoptic bronchoscopy (FOB) is utilized extensively in the initial evaluation of patients suspected of having lung carcinoma. FOB enables direct visualization of the bronchial mucosa down to the level of the segmental and proximal subsegmental bronchi. At these levels direct visually guided biopsy is possible. FOB also enables endobronchial brushing and bronchoalveolar lavage (BAL) of disease beyond direct visualization.

Since its introduction into clinical practice in the early 1970s, FOB technology has undergone continuous improvement and innovation. Transbronchial needle aspiration (TBNA) was added in the early 1980s, a technique that has now been refined by the addition of image guidance, such as endobronchial ultrasound (EBUS), to enhance diagnostic precision. EBUS can be used for diagnostic aspiration of both mediastinal lymph nodes and central parenchymal lung lesions, not visible during routine bronchoscopy.² The more recent addition of fluorescence-reflectance bronchoscopy may also increase sensitivity in detecting early endobronchial lesions, such as moderate or severe dysplasia, carcinoma in situ and microinvasive cancer.²

The role of FOB in the evaluation of patients with lung cancer is twofold: (1) to confirm the diagnosis of cancer and determine the histology, and (2) to rule out the presence of endobronchial tumor in the proximal airways, ie, tumor staging.

In patients with clinical or radiographic evidence of endobronchial disease, such as hemoptysis or lobar atelectasis, FOB has a high yield, and FOB may provide a histologic diagnosis of lung cancer in up to 90% of cases. However, in patients with SPN the yield is much lower, and the level of evidence supporting bronchoscopy in this population is therefore lower. Nevertheless, almost 10% of patients with SPN may have evidence of an endobronchial lesion, and these lesions are best diagnosed using bronchoscopy.³

Indications for Flexible Fiberoptic Bronchoscopy

The utility of FOB extends well beyond its role in lung cancer. The diagnostic and therapeutic indications for FOB are summarized in Table 10–1.

Table 10–1. Indications for Flexible Fiberoptic Bronchoscopy

Procedural Complications

Flexible bronchoscopy, even when combined with biopsy, TBNA or BAL, is a very safe procedure. Reported mortality rates are 0.02% to 0.04%^4,5 and major complications occur in 0.12% to 0.5% of patients during simple bronchoscopies. However, when combined with TBNA complications have been reported in up to 6.8%.^4,5

HYPOXEMIA

Hypoxemia is common during flexible bronchoscopy, especially when additional procedures such as BAL are performed, during which substantial decreases in arterial oxygen tension (PaO₂) may occur. Hypoventilation, the most frequent cause of hypoxemia during bronchoscopy, may result from respiratory depression due to sedation, increased airway resistance or airway circuit leaks. Oxygen supplementation is therefore required during the procedure and often following the procedure, depending on the patient’s pulmonary function and degree of residual sedation.

CARDIAC ARRHYTHMIAS

Both brady- and tachy-arrhythmias have been reported during fiberoptic bronchoscopy. Arrhythmias most commonly occur as a result of autonomic stimulation due to passing the endoscope through the vocal cords, or during procedures such as TBNA or BAL. Physiological derangements such as hypoxia or hypercarbia should be ruled out as potential contributing factors.

BRONCHOSPASM

Bronchospasm seldom complicates FOB in the general population, but may be more common in patients with reactive airways disease.⁶ Nevertheless, even in patients with more severe reactive airways disease (forced expiratory volume in 1 second bronchoscopy, BAL and biopsy are generally well tolerated. Premedication with a bronchodilator may prevent decreases in postoperative FEV₁ and is recommended in patients with reactive airways disease.⁷

BLEEDING

While FOB is rarely complicated by significant hemorrhage, TBNA may result in substantial bleeding in 1.6% to 4.4% of cases.^8,9 Patient risk factors for bleeding include immunosuppression, uremia, pulmonary hypertension, liver disease, coagulation disorders, and thrombocytopenia. Patients with superior vena cava syndrome have a further increased risk for bleeding due to venous engorgement.

PNEUMOTHORAX

Although uncommon, pneumothorax requiring pleural drainage may complicate approximately 3.5% of cases where TBNA is performed.¹⁰ Positive pressure ventilation increases the risk for pneumothorax during TBNA.¹¹ While the signs and symptoms of pneumothorax may be delayed after TBNA, it is very uncommon for a pneumothorax to develop more than 1 hour after the procedure.^12,13 It is therefore recommended to obtain a CXR at least 1 hour after TBNA to exclude this complication.

FEVER

Fever is common following FOB and may occur in up to 18.2% of patients. When combined with BAL the incidence further increases from 37% to 52.5%.^14,15 Bacteremia rates however are lower, occurring in 6.5% of patients following bronchoscopy with BAL.¹⁶ This rate compares favorably to rates of 2.3% to 11.8% following direct laryngoscopy and intubation,^17,18 and no association with infectious sequelae has been established. Pro-inflammatory cytokines from alveolar macrophages are thought to play a role in the observed febrile reaction.¹⁹ Therefore, unless the procedure involves incision of the respiratory tract mucosa, or drainage of an abscess or empyema, published guidelines do not recommend antibiotic prophylaxis against endocarditis.²⁰

Anesthetic Management for Fiberoptic Bronchoscopy Procedures

PREOPERATIVE ASSESSMENT

Most patients with lung cancer have a history of smoking and therefore have some degree of chronic obstructive pulmonary disease. The preoperative assessment should identify reversible reactive airway disease, which warrants preoperative bronchodilator therapy.^6,7 A history of chemo or radiation therapy should alert the anesthesiologist to the possible risk of pulmonary oxygen toxicity, in which case the lowest possible inspired oxygen partial pressures (FiO₂) should be used.

MONITORING

FOB can be performed in awake patients under local anesthesia or under general anesthesia. Regardless of the anesthetic approach, standard monitoring should include ECG, pulse oximetry, and noninvasive blood pressure monitoring.

AWAKE BRONCHOSCOPY

When performed in the awake patient, adequate local anesthesia is the most important component of the anesthetic. Relying on heavy sedation to suppress laryngeal and airway reflexes could result in hypoventilation and hypoxemia, especially in patients with limited respiratory reserve. Multiple topical nasal and oral applications of any commercially available local anesthetic preparation for this use usually suffice. Blocking individual nerves or transtracheal injections of a local anesthetic solution are rarely required. A topical vasoconstrictor (such as oxymetazoline) and a systemic antisialagogue (such as glycopyrrolate) are usually administered as well. Supplemental oxygen therapy should be administered routinely.

BRONCHOSCOPY UNDER GENERAL ANESTHESIA

When FOB is scheduled in addition to surgical procedures that require general anesthesia, general endotracheal anesthesia with positive pressure ventilation is the preferred technique. Either an inhalational or intravenous anesthetic approach, combined with a short-acting muscle relaxant, would be acceptable. The endotracheal tube should be secured with the tip of the tube well above the carina to allow an unobstructed view of the carina. It is important to use an endotracheal tube with an internal diameter of at least 8.0 mm to diminish the detrimental effects of the functional reduction in internal diameter. A 5.7 mm bronchoscope will occupy only 10% to 15% of the cross-sectional area of the trachea, but 40% of a 9.0 mm tube and 66% of a 7.0 mm endotracheal tube.⁷ The endotracheal tube could be trimmed in length to further reduce resistance, but this is seldom required. Additionally, PEEP should be avoided and ventilator settings should allow sufficient time for expiration. Failing to do so may result in distal air trapping.

Spontaneous ventilation should be avoided due to the increase in effective airway resistance and work of breathing. An endotracheal tube connector with a perforated diaphragm, designed to minimize circuit leaks, allows the use of positive pressure ventilation during bronchoscopy. Nevertheless, circuit leaks often render tidal volume monitoring unreliable, and ventilation should be monitored by paying attention to chest wall movement and capnography. Ventilation could be adjusted by adjusting the inspiratory pressure and respiratory rate. However, because the FOB procedure is of short duration, hypercapnia could be tolerated, and attention should rather be focused on maintaining arterial oxygen saturation and avoiding lung injury due to air trapping. Should arterial desaturation occur despite a high FiO₂, the bronchoscope should be removed and the lungs manually ventilated until oxygenation has been restored. Even though pneumothorax is rare, this complication should be ruled out if arterial desaturation does not resolve readily, or is associated with hypotension.

Some centers employ laryngeal mask airways for FOB, with either controlled ventilation (if the peak airway pressure can be maintained <25 cm H₂O) or spontaneous ventilation. Injection of local anesthetic down the suction channel of the bronchoscope facilitates passage of the instrument, and this approach permits examination of the glottis and immediate subglottic trachea. It also reduces the number of direct laryngos-copies if the case immediately precedes a lung resection.

RIGID BRONCHOSCOPY

While routine rigid bronchoscopy has been supplanted by FOB for most cases, it is still widely used and has even experienced a resurgence with the introduction of laser airway surgery and the advent of airway stents over the past 2 decades.²¹ The rigid bronchoscope is a straight hollow metal tube through which direct access to the central airways can be obtained (Figure 10–1). It has a blunted distal opening, which is beveled to facilitate lifting of the epiglottis and atraumatic intubation of the airway. The distal end of the bronchoscope has side vents, which enables ventilation of the opposite lung when the distal opening is advanced into a main stem bronchus. These side vents may result in an air-leak into the pharynx during positive pressure ventilation when not advanced beyond the vocal cords. The proximal opening is adapted to accommodate attachments, provide side port ventilation, and permit insertion of surgical instruments.

Figure 10–1. A and B. Standard rigid bronchoscopy equipment.

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