Interventional Pulmonology: Advanced Bronchoscopy in the Critically Ill

The interventional pulmonologist plays an integral role in the management of critically ill patients with respiratory failure due to central airway obstruction, massive hemoptysis, and complications of thoracic surgery or radiation therapy. Bronchoscopy offers a minimally invasive diagnostic and therapeutic tool to palliate airway obstruction, providing symptomatic relief and potentially serving as a means to extubation.

Interventional pulmonology (IP) is a rapidly growing field that focuses on minimally invasive diagnostic and therapeutic techniques for complex airway, mediastinal, lung, and pleural diseases. The interventional pulmonologist is trained in pulmonary medicine and critical care medicine, with subsequent dedicated fellowship training in IP (Lamb et al. Chest. 2010;137[1]:195). Interventional bronchoscopy requires skills to manage the complex airway with both flexible and rigid bronchoscopy, as well as mechanical ventilation.

Safe rigid bronchoscopy for foreign body removal was introduced by Gustav Killian, a laryngologist, in 1897 (Becker. J Bronchol. 1995;2: 77). Rigid bronchoscopy began to diminish as a useful modality in the decades after the introduction of the flexible bronchofiberscope by Ikeda in 1962. An ACCP survey of North American pulmonary bronchoscopists published in 1991 revealed that 91.6% did not perform rigid bronchoscopy routinely in practice (Prakash et al. Chest. 1991;100[6]:1668). Although flexible bronchoscopy dramatically changed the field of pulmonary medicine, IP has recently reinvigorated the use of rigid bronchoscopy to augment management of central airway obstruction.

Managing Central Airway Obstruction
A small percentage of respiratory failure is due to central airway obstruction. Airway obstruction may be due to a multitude of causes, whether benign or malignant, endoluminal or extrinsic, mechanical or functional. A high degree of morbidity is associated with such airflow obstruction (Ernst et al. Am J Respir Crit Care Med. 2004;169[12]: 1278). The “reserve” in airway diameter is so great that exertional symptoms may not be present until a loss of approximately 50% is experienced, roughly 7 to 10 mm at the level of the trachea. Failure to extubate a patient may reflect tracheal pathology, such as dynamic airway collapse or tracheal stenosis. Artificial airways may bypass central airway obstructions, therefore limiting the benefit of ventilator waveforms. CT scanning with both dynamic imaging (Lee et al. Chest. 2007;131[3]: 758) and 3-D reconstruction has greatly advanced examining the airway anatomy. CT virtual bronchoscopy affords noninvasive diagnostics of airway patency (Boiselle et al. Respiration. 2003; 70[4]:383). However, bronchoscopy remains the gold standard for direct visual inspection of airway obstruction.

In the management of malignant airway obstruction, bronchoscopy is often palliative and serves as a bridge to further oncologic therapy. This can often be implemented in conjunction with external beam radiation therapy or systemic chemotherapy. In benign airway obstruction, such as tracheal stenosis or tracheobronchomalacia, bronchoscopy can palliate the airway with temporizing measures, such as balloon dilatation or airway stenting.

Anesthetic choices and airway control are of key importance when approaching the patient with central airway obstruction. There must be constant communication between the bronchoscopist and the intensivist or anesthesiologist. In high-grade obstruction, rigid bronchoscopy is the instrument of choice, as you can bypass the obstruction under visualization, and it offers a secure airway with the ability to ventilate. Ventilation can be achieved with either an open circuit (jet ventilation) or a closed circuit (volume- or pressure-control). Hand-ventilation may offer a lower risk of barotrauma and the ability to identify changes, such as an acute obstruction, more readily.

If there are no immediate options for surgical resection, obstructions are best handled by rigid bronchoscopy in an operating room. Inevitably, flexible bronchoscopy is also required to navigate beyond obstructions for planning, examining distal airways, and cleaning the airways of secretions or blood.

Mechanical Debulking, Bronchoplasty, and Ablative Bronchoscopy
For patients in respiratory failure, “therapeutic,” or palliative, bronchoscopy can lead to successful extubation in select patients, decreased hospitalization, and lower health-care costs (Colt et al. Chest. 1997[1];112:202). If airway patency can be regained, then there is a greater chance of liberation from mechanical ventilation. Therapeutic bronchoscopy often provides a bridge to the institution of further therapies, such as radiation therapy or chemotherapy. Malignant airway obstruction can be relieved with mechanical efforts or ablative interventions. The mechanical approach focuses upon “core-out” or forceps debulking, when the obstruction is endoluminal, and may or may not include ablative therapies. This acute relief minimizes postobstructive manifestations, stabilizes the airway, and minimizes tumor burden for external beam radiation therapy (Eichenhorn et al. Chest. 1986;89[6]:782). In benign obstructions, such as tracheal stenosis (Fig 1) seen with the prolonged use of artificial airways, bronchoscopic dilatation with serial rigid bronchoscopes, dilators, or balloons can palliate the airway. Although there are limited survival data, relief of airway obstruction (Fig 2) leads to relief of symptoms, in most cases.

Multiple modalities are available for thermal ablation of endobronchial neoplasm. These are safely implemented if the Fio₂ can be safely reduced below 0.4 to avoid airway fires. Nd:YAG laser is probably the most established. Through photocoagulation and photonecrosis, Nd:YAG laser devascularizes the tumor, allowing the bronchoscopist to encounter less bleeding during subsequent mechanical debulking. Following combined modality bronchoscopy, patients experience palliation of symptoms, such as cough and dyspnea with low morbidity; however, there are still only limited studies that show the quantitative improvement in quality of life with validated measures (Mantovani G et al. Clin Lung Cancer. 2000;1[4]:277).

Airway Stents
Although bronchoscopic palliation of malignant airway obstruction can be achieved with mechanical and ablative means alone, debulking may not always be feasible. Airway integrity can also be impaired by extrinsic compression (Fig 3). In these circumstances, stents of various kinds (Fig 4) can be placed to support the airways. In certain cases of respiratory failure, stents in conjunction with endotracheal intubation may facilitate liberation from the ventilator. Great care and thought must be taken before deciding to place a stent but also in choosing the stent type (metallic, silicon, or hybrid) (Lund et al. Chest. 2007; 132[4]:1107). Although of relatively low risk, stents should not be placed in all situations of airway obstruction. Complications of stent insertion include in-stent obstruction due to mucous plugging or granulation tissue, stent migration, and, less often, airway perforation secondary to a fractured metallic stent. Stents themselves may extend benign focal stenoses into longer areas of scar, rendering them unresectable (Grillo. Ann Thorac Surg. 2000;70[4]: 1142). If surgical resection is feasible, then stent placement may not be appropriate; or if a stent was already inserted, it should be removed as early as possible.

Managing Hemoptysis
Large-volume hemoptysis can be seen in malignancy or its treatment, bronchiectasis, vascular anomalies, and other disease states. Radiographic imaging may not reveal the bleeding source, thus localization and possible intervention with bronchoscopy may be required. Ablative therapies for endobronchial malignancy can be implemented; however, tamponade with blocker devices or instillation of epinephrine or thrombin is often required to temporize bleeding. Although smaller bleeds may be handled with the flexible bronchoscope, it is most prudent to utilize rigid bronchoscopy for definitive airway control and tamponade, as well as ease of suction. Often, bronchoscopy complements or guides angio-invasive procedures for definitive control of vascular sources.

Surgical and Radiation Catastrophes
Respiratory failure may present as a complication of lung surgery, such as surgical stump breakdown or bronchial fistula. Airway or alveolar fistulae, as a result of malignant involvement, may also occur following external beam radiation to thoracic structures or after percutaneous thermal ablation. These conditions can often be successfully managed via bronchoscopy as a less invasive alternative to operative interventions with low morbidity, especially if surgical repair is not feasible or advised.

Summary
Central airway obstruction can be life-threatening and, often, patients require mechanical ventilation and ICU care. Immediate bronchoscopic palliation offers the intensivist an opportunity to extubate and minimize health-care costs, as well as ICU length of stay (Colt et al. Chest. 1997;112[1]:202). Adverse events related to bronchoscopy and interventions, such as stent migration, mucous plugging of stents, or hemoptysis, obligate the interventionalist to always be available. The realm of IP is broad across bronchoscopy (see box), with limited outcomes data. As part of their quality improvement initiative, the American College of Chest Physicians has undertaken prospective data collection of diagnostic and interventional bronchoscopy outcomes based upon the work of several international IP programs (Ernst et al. Chest. 2008;134[3]: 514). Interventional bronchoscopy offers minimally invasive therapies at all levels of disease safely and effectively.

The Realm of Interventional Pulmonology

Advanced Diagnostic Bronchoscopy
•Transbronchial biopsy
•Transbronchial needle aspiration (TBNA)
•Endobronchial ultrasound (EBUS), convex and radial probe
•Thoracic fluoroscopy
•Electromagnetic and virtual navigational bronchoscopy
•Autofluorescence bronchoscopy (AF)
•Narrow band imaging (NBI)
•Endoscopic optical coherence tomography
•Endocytoscopy
•Alveoloscopy and fibered confocal microendoscopy

Therapeutic Bronchoscopy and Artificial Airways
•Airway stents: self-expanding metallic, silicon, and hybrid; placement and removal
•Balloon bronchoplasty and mechanical airway dilatation
•Laser bronchoscopy, Nd:YAG, and KTP
•Electrocautery
•Argon plasma coagulation (APC)
•Cryotherapy
•Endobronchial brachytherapy
•Photodynamic therapy
•Endoscopic abscess drainage
•Fistula and stump closure
•Foreign body removal
•Percutaneous tracheostomy
•T-tube placement
•Transtracheal oxygen
•Intrabronchial one-way valves
•Endoscopic lung volume reduction
•Bronchial thermoplasty
•Whole lung lavage

Dr. Mohit Chawla
Assistant Attending, Pulmonary Service,
Department of Medicine;
Director, Interventional Pulmonology;
Co-Director, Complex Airway Service;
Critical Care Service, Department of
Anesthesiology; and
Thoracic Service, Department of Surgery
Memorial Sloan-Kettering Cancer Center
New York, NY