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Critical Care and Resuscitation

Lung Isolation in the Patient With a Difficult Airway

Collins, Stephen R. MD*; Titus, Brian J. MD, PhD*; Campos, Javier H. MD†; Blank, Randal S. MD, PhD*

Author Information

From the *Department of Anesthesiology, University of Virginia Health System, Charlottesville, Virginia

†Department of Anesthesia, University of Iowa Healthcare, Iowa City, Iowa.

Published ahead of print November 17, 2017.

Accepted for publication October 3, 2017.

Funding: None.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website.

Reprints will not be available from the authors.

Address correspondence to Randal S. Blank, MD, PhD, Department of Anesthesiology, Thoracic Anesthesia, University of Virginia Health System, PO Box 800710-0710, Charlottesville, VA 22908. Address e-mail to [email protected].

doi: 10.1213/ANE.0000000000002637

Abstract

In a landmark paper more than 60 years ago, the risk of failure to intubate apneic patients after neuromuscular blockade was recognized and anatomical features predicting difficult laryngoscopic intubation defined.1 In subsequent years, various predictors have been described and strategies developed to assess the likelihood of potential airway difficulty—Mallampati’s original schema2,3 and later modification,4 various anatomic descriptors such as protruding maxillary incisors, short neck, or receding mandible,5 weighted risk factor scoring systems,6 multivariate airway risk indices,7 and logistic regression–derived clinical models.8 Identified predictors of difficult intubation share common characteristics in that they have high sensitivity but low specificity and low positive predictive value with regard to intubation failure.9 While no standard or comprehensive definition exists for the term “difficult airway,” strategies for difficult airway management have been developed into well-defined algorithms based on expert consensus and available evidence over the past few decades. Probably the best known and most frequently applied of these algorithms is the American Society of Anesthesiologists Task Force’s “Difficult Airway Algorithm,” most recently revised in 2013, which attempts to guide practitioners in recognizing and developing strategies to manage patients with a difficult airway.10 Because the correct positioning of any lung isolation device requires traversing the trachea and positioning within a main bronchus, the “difficult” lower airway should also be considered. Thus, any anatomic abnormality of the lower (tracheobronchial) airway may render placement of a lung isolation device more difficult or hazardous. Such abnormalities include distal tracheal or bronchial lesions and/or a history of previous lung surgery which may distort the lower airway.

Selective lung or lobar collapse is indicated to improve surgical exposure for a number of thoracic procedures. Less frequently, lung isolation may be required to prevent life-threatening contamination of a nondiseased lung or to permit ventilation in the context of bronchopleural fistula or severe unilateral lung disease. Lung isolation in patients with either a suspected or unanticipated difficult airway may be particularly challenging. This review considers specific approaches for lung isolation in the patient with a difficult airway. Lung isolation in the patient with difficult airway anatomy has been previously reviewed, both by one of the authors, Campos,11 and by Brodsky.12 However, recent developments in, and improved experience with, both airway management devices and techniques warrant a modern update. These include newer lung isolation devices such as the Silbroncho and VivaSight-DL (Ambu, Copenhagen, Denmark) double lumen endobroncial tubes (DLTs), an expanding array of videolaryngoscopy equipment, and new endobronchial blocking devices and evolving techniques which combine intubation modalities (eg, use of direct laryngoscopy or videolaryngoscopy with fiberoptic bronchoscope–guided intubation).

THE DIFFICULT AIRWAY AND LUNG ISOLATION CONSIDERATIONS

Establishing lung isolation with a DLT in patients who are difficult to intubate may be especially challenging. In the clinical context of a difficult airway and the need for lung isolation, securing the airway first is the primary goal. Awake fiberoptic intubation with a DLT has been described,13 but is problematic given the large size of this tube and greater difficulty in blunting the laryngeal and carinal stimulation resulting from DLT placement. If a single-lumen tube (SLT) is used to secure the airway, an endobronchial blocker may be the safest means of establishing lung isolation as it avoids the need for a tube exchange. Characteristics of patients at risk for difficult DLT placement include poor mouth opening (Mallampati 3 or 4), prominent upper incisors and a receding mandible, limited cervical mobility, and a history of head/neck trauma, radiation, or tumor resection (hemiglossectomy, radical neck dissection). Patients who require nasotracheal intubation or have an existing SLT or tracheostomy in place may be best managed with a bronchial blocker. Use of an SLT may be more desirable if postoperative ventilator support is required as the bronchial blocker may simply be removed at case end. In many cases, lung isolation in the patient with lower tracheobronchial tree abnormalities (intraluminal mass, extrinsic compression distortion, deviation, or tortuosity) or the need for selective lobar blockade may be best achieved by a bronchial blocker. Examples of such patients include those who have undergone previous lung resection(s). In these cases, a flexible fiberoptic airway examination under anesthesia may help to define the lower airway anatomy before lung isolation. Regardless of surgical history, a review of relevant airway imaging (neck and chest radiographs, chest computerized tomography scans) should be considered essential before airway management and lung isolation.

DLT PLACEMENT AND THE DIFFICULT AIRWAY

The DLT has been the most commonly used lung isolation device since the introduction of the Carlens14 tube in 1949. Importantly, the DLT and the Univent tube (Fuji Systems, Tokyo, Japan) have been described as “difficult tubes” because of an increased rigidity and their large outside diameter.14 Left-sided (versus right-sided) DLTs are generally preferred and more commonly utilized because their greater “margin of safety,” a term that refers to the extent that a DLT may be moved within the tracheobronchial tree without obstructing a conducting airway.15 In an 8-year study of 1170 patients involving left-sided DLT placement for thoracic procedures, difficulty with intubation was encountered in 2.6% of patients.16 Lung isolation with the DLT was successful in over 98% of cases. Right-sided DLTs are less often selected for lung isolation because of (1) the typically shorter right mainstem bronchus and resultant lower margin of safety and (2) the more frequent anatomic variation in the length of the right mainstem bronchus and the origin of the right upper lobe (RUL) bronchus. These tubes incorporate a modified slot on the endobronchial lumen to allow ventilation of the RUL,17 offer advantages for procedures or pathologies involving the left mainstem bronchus, and can produce effective lung isolation when compared with either a SLT/bronchial blocker combination or a modified left-sided DLT.18,19 While right-sided DLTs may be more prone to dislodgement, both prospective and retrospective studies support the efficacy and safety of the right-sided DLT for left-sided surgery.19,20 The right-sided DLT may be specifically indicated in patients presenting with thoracic aortic aneurysms compressing the trachea or left main bronchus, as placement of a left-sided DLT may be difficult and/or hazardous.21,22 A right-sided DLT may also be indicated when the site of surgery involves the left mainstem bronchus (left-sided pneumonectomy, lung transplantation, sleeve resection). Effective positioning of the right-sided DLT requires an anatomically normal RUL—originating from a right mainstem bronchus of adequate dimension (at least 23 mm in length).

The first DLT design was left sided with a carinal hook and 2 bundled round lumens, a design that produced high airflow resistance and rendered suctioning difficult.23 More recent, modified DLTs, based on the Robertshaw design,24 have no carinal hook, possess 2-dimensional–shaped lumens, which reduces airflow resistance, and are available in a variety of sizes (26–41 Fr). Modern DLTs have blue-colored, low-pressure, low-volume endobronchial cuffs that facilitate identification on fiberoptic bronchoscopy. Placement is generally confirmed with the fiberoptic bronchoscope, as auscultation alone is unreliable.25 The popularity of the DLT for lung isolation may be explained by several specific advantages over bronchial blockers. Conversion from 2-lung ventilation to 1-lung ventilation (OLV) (and vice versa) is easy, rapid, and reliable when using a DLT. DLT lumens accommodate suction catheters to clear blood or secretions, reducing airflow resistance during OLV.26 They require marginally less time for lung collapse and may require repositioning less frequently.27 Each lung can also be easily inspected with fiberoptic bronchoscopy, ventilated, collapsed, and reexpanded.12

Insertion and proper placement of a DLT, however, may be especially challenging in a patient with a difficult airway. Intubation with a DLT is generally more difficult relative to placement of a SLT because of both tube characteristics and required laryngoscopy grade. DLTs are more rigid and larger than conventional SLTs. The tracheal cuff can be torn when passed over the upper teeth, particularly prominent incisors. In one of the largest studies of left-sided DLTs (1169 consecutive intubations),16 the bronchial cuff was torn once and the tracheal cuff 11 times (0.9%). If a difficult intubation is anticipated, simple methods can be used to protect the tracheal cuff of a DLT and avoid damage.28–30 This may include utilizing a lubricated tooth guard, lubricating both cuffs of the DLT, and/or use of videolaryngoscopy for visualization of airway structures during tube placement and passage. Direct flexible fiberoptic bronchoscopic DLT insertion and positioning may be considered a gold standard.31 Case reports have described other laryngoscopes and techniques for DLT placement in patients for whom difficult laryngoscopy was anticipated or demonstrated. These include the Bullard laryngoscope (Gyrus ACMI, Southborough, MA),32 WuScope (Achi Corp, Fremont, CA),33 Glidescope (Verathon, Seattle, WA),34,35 Airtraq (Prodol Limited, Viscaya, Spain),36 Bonfils intubation fiberscope (Karl Storz, Tuttlingen, Germany),37 Pentax-Airway Scope (Pentax Corporation, Tokyo, Japan),38,39 McGrath MAC video laryngoscope (Aircraft Medical, Ltd, Edinburgh, UK),40 and lighted stylets either alone41–43 or with intubating laryngeal mask assistance.44 More recent studies comparing direct laryngoscopy with video laryngoscopy for DLT placement including the Glidescope,45–48 McGrath,49–51 Airtraq,36,52–55 OptiScope (Clarus Medical, Minneapolis, MN),56 and Trachway (Markstein Sichtec Medical Corporation, Taichung, Taiwan)57 highlight the utility of video laryngoscope–guided DLT intubation.58 Other approaches for DLT placement in patients with a difficult airway include direct laryngoscopy using the retromolar approach59 and awake nasotracheal intubation followed by oral DLT insertion under general anesthesia.60 Fiberoptic-assisted tracheal intubation in anesthetized61 and awake patients with known difficult airways62 or cervical spine disease is another effective approach and in awake patients allows for neurologic assessment after intubation and patient positioning.13 While there is yet no definitive consensus on whether videolaryngoscopic techniques improve airway management for the placement of DLTs, clinical experience and small studies have begun to suggest this. Based on a small (60 patient) study in patients with predicted normal laryngoscopy, for example, the Glidescope Videolaryngoscope has been demonstrated as easier to use than the Macintosh laryngoscope.48 In a 2012 study of 48 consecutive patients requiring lung isolation and 2 failed attempts at tracheal intubation using a Macintosh laryngoscope, the CEL-100 Videolaryngoscope led to significant improvement in glottic visualization with nearly 90% success rate for subsequent DLT insertion.63 The combined use of a video laryngoscope and a flexible bronchoscope used as a video stylet may also improve intubation success in patients with predicted difficult airways and has been reported to rescue failed laryngoscopy attempts in such patients.64

A clinical example may be illustrative: the anesthesiologist is presented with a patient for left upper lobectomy. He/she is morbidly obese, with mildly limited mouth opening, prominent upper incisors, a short mandibulo-hyoid distance, and moderately limited neck extension. Mallampati class is 3. Clinical evaluation predicts that glottic visualization and intubation via a direct laryngoscopic technique is likely to be difficult and possibly traumatic. If a DLT is desired, the anesthesiologist might reasonably choose a videolaryngoscope (specific device based on preference, experience, and availability) and attempt a primary VL-based intubation. If glottic visualization is adequate, but the DLT cannot be guided into the trachea (a frequently encountered problem in this scenario), the VL technique may be combined with a bronchoscopic approach whereby the fiberoptic bronchoscope (placed through the bronchial lumen) is used as a directable stylet under VL guidance to reach the glottis and subsequently intubate the trachea. This combined technique has the additional benefit of permitting the continuous monitoring of DLT passage through the vocal cords (via VL), allowing the anesthesiologist to change management as needed to ensure successful and atraumatic intubation. Ultimately, the choice of airway management and lung isolation device(s) will depend on practitioner proficiency and personal preference, as well as the availability of these devices.

F1
Figure 1.:
Airway exchange catheters useful in the management of the difficult airway and need for endotracheal tube placement or exchange. Top, Cook Airway Exchange Catheter. Bottom, Cook Flex Tip Airway Exchange Catheter.

If the airway is difficult and risk of failed DLT insertion high, an SLT may first be placed and then exchanged for a DLT. In such situations the dictum “first secure the airway” is fundamental and lung isolation is a secondary concern. Additional considerations include whether a DLT is required or simply preferred, how best to intubate (eg, nasal versus oral, awake versus postinduction), and whether positive pressure ventilation will be needed after surgery.65 Bronchial blockers are discussed later in this review; their insertion inside or outside an SLT when difficult intubation is anticipated may minimize the risks of airway trauma and/or airway loss associated with DLT intubation. Further, if a standard SLT with a bronchial blocker is placed, the intubation method may follow well-defined algorithms for difficult airway management,10 eliminating the need for an additional tube exchange at case conclusion if the patient requires postoperative ventilatory support. Patients who require lung isolation and are at high risk for difficult DLT insertion may be intubated first using an SLT with the aid of a flexible fiberoptic bronchoscope either awake or after induction of general anesthesia if mask ventilation is easily performed. Airway exchange catheters (AECs) may be used to facilitate the SLT to DLT exchange and back again at the completion of surgery if required (Figure 1). The use of an AEC for DLT placement should follow specific guidelines. The AEC should be of sufficient length (>70 cm) to ensure tracheal introduction of the DLT, possess a flexible distal tip to avoid airway trauma with outer markings to control depth of insertion, and contain a hollow central channel for jet ventilation. The Aintree tube exchanger (Cook Medical, Bloomington, IN) has a large internal diameter to allow for fiberoptic bronchoscopic guidance and can be used to place an SLT in patients with a difficult airway. Because the Aintree is not long enough (56 cm) to directly allow DLT insertion, however, it must be switched to a standard AEC for DLT insertion. The AEC should be lubricated and tested for fit within the DLT before the exchange is initiated. The AEC is advanced into the SLT to the desired depth (typically 20–25 cm at the teeth or gumline), and after cuff deflation, the SLT is gradually withdrawn while the AEC is advanced at the same rate. The anesthesiologist should carefully monitor AEC depth by noting the depth markings on the device. The AEC should not be inserted beyond 25 cm at the teeth in adults to minimize the risk of tracheobronchial tree injury or barotrauma with jet ventilation66,67 and should never be advanced against resistance. Once the SLT has been removed, the pretested DLT is advanced over the lubricated AEC. A direct laryngoscope or VL may be used to displace pharyngeal tissue and elevate supraglottic tissue and may facilitate exchange. If resistance to DLT advancement occurs (typically at the glottic level), a 90° counterclockwise rotation may relieve impingement. As discussed below, the design and construction of the Fuji Silbroncho DLT (Fuji Systems, Tokyo, Japan) may facilitate introduction over an introducing device such as the AEC. If attempted airway exchange fails, jet ventilation via the AEC may serve as a rescue technique as may oxygen insufflation or manual ventilation through the AEC. With jet ventilation, an inline regulator can keep driving pressures of 15–50 psi, though barotrauma has been reported over a wide range of driving pressures including those as low as 15 psi.68 The AEC should be positioned within the trachea (not a bronchus) before initiating this rescue technique. In a large retrospective analysis69 of airway exchange failure, failed intubation during attempted airway exchange was determined in 73 of 527 (13.8%) cases, with an overall injury rate of 7.8%. Exchange failures and airway injury were most frequent with attempted DLT placement; failure rates of tube exchange were 9.3% for SLT to SLT exchange, 39.9% for SLT to DLT exchange, and 0% for DLT to SLT exchange. One potential strategy to reduce the incidence of tube impingement during DLT to SLT exchange is to place an AEC in each lumen of the DLT.70

COMMON PROBLEMS WITH THE USE OF DLTS IN DIFFICULT AIRWAYS

Common problems and complications associated with DLT use include tube malposition and to a lesser extent airway trauma (Supplemental Digital Content 1, Table 1, https://links.lww.com/AA/C131). Although the overall incidence of major complications with DLT placement is low,16 the risk of airway injury is likely elevated. Airway trauma and tracheobronchial injury are potential complications after DLT placement attempts. Risk factors include multiple intubation attempts, tracheal or bronchial cuff overinflation, use of an AEC, oversized DLT, tracheomalacia, or weakened membranous portion of the trachea secondary to chemoradiation or steroid use. One 1999 review71 identified 33 reports of tracheobronchial rupture caused by DLTs published between 1972 and 1998, though this time span included clinical use of early red rubber DLTs and more modern polyvinyl chloride DLTs. Improper tube selection, bronchial cuff overinflation, and improper or forceful insertion are the most likely causes of tracheal injury.72 Most high-grade tracheal injuries are located in the membranous portion of the tracheobronchial tree (Figure 2), most commonly in the distal trachea or left mainstem bronchus,73–76 and can lead to subcutaneous emphysema, unexpected air leaks, bleeding, or contralateral tension pneumothorax. Airway injuries have been more commonly associated with the distal trachea and/or the left mainstem bronchus. DLT malpositioning may result in either the inadequate collapse of the nonventilated lung or partial collapse of the dependent (ventilated) lung during thoracic surgeries and is a frequent cause of hypoxemia during OLV.77

F2
Figure 2.:
Scar (blue arrow) from high-grade posterior (membranous) tracheal wall injury sustained from placement of 37-Fr left-sided polyvinyl chloride double-lumen endotracheal tube.
F3
Figure 3.:
A, Fuji 40 cm wire–reinforced endotracheal tube. B, Fuji Silbroncho double-lumen endotracheal tube.

Newer DLT designs may lead to improved airway management. The Silbroncho DLT (Fuji Systems) is a unique DLT made of silicone with a wire-reinforced soft, flexible endobronchial tip and resistant silicone tracheal cuff to resist laceration during placement (Figure 3). Two theoretical advantages follow from these modifications. First, the Silbroncho DLT is less likely to cause glottic or tracheobronchial trauma given its softer endobronchial portion and has reduced the incidence of postoperative sore throat when compared to the conventional polyvinyl chloride DLT.78 Second, the tapered tip is more likely to advance easily through the glottic aperture when following an introducing device such as FOB or AEC.47 The VivaSight-DL may also contribute to more effective lung isolation. It is a novel DLT with an integrated camera that allows continuous visualization of its tracheal position. Intraoperative displacement of the DLT may thus be detected visually and easily corrected. One 40-patient randomized study reported that the VivaSight DLT facilitated correct initial positioning and repositioning with faster insertion compared to that of conventional DLTs.79 Another 2015 study of 84 patients was stopped early for device failure, but noted that the device effectively facilitated correct DLT positioning.80

ALTERNATIVE DEVICES FOR LUNG ISOLATION

Clinical scenarios exist for which lung isolation with a DLT is undesirable or contraindicated. The choice of an alternative device requires an evaluation of both upper airway features and tracheobronchial anatomy. Criteria for difficult DLT placement are not well defined, but patients with classic predictors of a “difficult” airway may present special challenges if a DLT is used. Patients with restricted mouth opening, large protruding incisors, short mandibulo-hyoid distances, and limited neck extension, for example, and those with distorted airway anatomy from previous surgeries or radiation therapy may be candidates for an alternative lung isolation device due to the elevated risks associated with DLT placement. Examples of lower tracheobronchial abnormalities impeding safe placement of the DLT include tracheal deviation, compression, or distortion (eg, prior lobectomy of an upper lobe). Figure 4 depicts various tracheobronchial abnormalities complicating lung isolation in patients requiring thoracic surgery. In one 2016 report of patients undergoing right lung surgery after a previous left upper lobectomy, OLV could be achieved with a left-sided DLT in only 12 of 18 patients. Angulation of the left bronchus (due to upward displacement of the remaining lower lobe) significantly affected the correct placement of a left-sided DLT in 6 patients, necessitating use of a right-sided DLT (n = 3) or a bronchial blocker (n = 3).82 Other conditions potentially complicating or preventing DLT placement include tracheal or bronchial lesions, in situ tracheostomy, exclusive nasal airway access, or an in situ SLT in a patient with unstable cervical spine. The size of most DLTs may also preclude passage through a small airway, nasal passage, or tracheostomy stoma. At least 1 report has described a traumatic tracheal tear with a DLT during extubation.74 Finally, a need for postoperative mechanical ventilation may require a DLT to SLT exchange, which may increase the risk of airway loss in patients with difficult airways. Such exchanges have also been implicated in airway trauma including tracheal disruption.67

F4
Figure 4.:
Tracheobronchial abnormalities potentially complicating lung isolation. A, Multidetector computer tomography scan of the chest (a) and accompanying 3-dimensional tracheal reconstruction (b) of a 60-year-old male smoker with chronic obstructive pulmonary disease. Note the tracheal displacement to the right side and a narrowing on the bronchial bifurcation reflecting changes associated with age and smoking history (with permission from Campos31). B, Severe compression and deviation of the trachea due to compression of an anterior mediastinal mass (with permission from Campos81). C, Tracheal stenosis. Chest and neck computed tomography scan (left) of a patient with a long segment tracheal stenosis and bronchoscopic view (right) of subglottic stenosis. D, Altered right bronchial anatomy after right upper lobectomy. In the fiberoptic images, the stump of the right mainstem bronchus can be seen. E, Intraluminal carcinoid tumor superior to the carina and obstructing the right main bronchus. F, Fiberoptic bronchoscopy in a patient with a right-sided pneumonectomy. In the fiberoptic image, C represents the tracheal carina, L represents the entrance of the left mainstem bronchus, and R represents the suture line of a right-sided pneumonectomy.

Other modalities for lung isolation include endobronchial blockers and the endobronchial SLT. Bronchial blockers offer select advantages for patients with difficult airway anatomy. The independent bronchial blocker is typically the preferred modality for lung isolation in the following scenarios: (1) when an SLT is the most feasible or safest option, (2) a tube exchange is undesirable or high risk, (3) when airway access is via nasal or tracheostomy tube, (4) when a DLT cannot be properly sized for a small adult or child, or (5) when a stenotic or otherwise abnormal tracheobronchial tree precludes the safe passage of a DLT. Bronchial blockers may be placed and positioned through the lumen or alongside an endotracheal tube that is inserted nasally, orally, or via a tracheostomy stoma. Although older reports suggested that bronchial blockers took longer to position or required more frequent repositions,27 more recent experience suggests that bronchial blockers may be associated with more rapid and complete lung collapse.83 In 1 retrospective review of 302 cases,84 bronchial blockers were effective for both right- and left-sided placement. If selective lobar blockade is needed, a bronchial blocker provides better oxygenation during lung isolation.85 In addition, when compared to DLTs, the use of blockers may result in fewer minor airway injuries.86

SINGLE-LUMEN ENDOTRACHEAL TUBES, ENDOBRONCHIAL BLOCKERS, AND DIFFICULT AIRWAYS

Use of a bronchial blocker to achieve lung isolation avoids the potentially difficult and possibly injurious placement of a DLT. Bronchial blockers have been utilized in patients with restricted mouth opening,87,88 prior surgery or radiation,89 altered lower tracheobronchial anatomy, or the need for selective lobar blockade (Figure 5).90 A number of bronchial blockers are available in the United States. Specific characteristics and placement techniques have been described in previous reports.91 Clinical considerations as well as familiarity, availability, cost, expertise, and personal preference dictate selection and use by the thoracic anesthesiologist. Endobronchial blockers are thin, rigid catheters (outer diameter 5–9 Fr) with an inner lumen and a distal cuff (balloon) at the tip. Inflating the cuff prevents distal airflow, isolating the lung. An SLT with an internal diameter of at least 8.0 mm (10.9 mm OD) is recommended for the commonly used 9-Fr bronchial blocker, though smaller tube sizes may be used.92 The 8.0-mm ETT tube size is comparable in size to that of a 32 Fr DLT (10.7 mm OD). If a smaller SLT is required, a 7.0-Fr blocker (or smaller) may be used. Supplemental Digital Content 1, Table 2, https://links.lww.com/AA/C131, lists the inner and outer diameter of various sized endotracheal tubes and blockers. The Univent tube is a conventional tracheal tube with an additional lumen and enclosed bronchial blocker, permitting the blocker’s passage through a flexible shaft into either bronchus.93 The Univent catheter is also available independently (Uni-blocker; Fuji Systems). Commonly used blockers that can be passed through an in situ SLT include the wire-guided Arndt blocker (Cook Medical, Bloomington, IN),94 the Cohen tip-deflecting blocker (Cook Medical, Bloomington, IN),95 the Fuji Uni-blocker (Fuji Systems), the EZ-blocker (Teleflex Medical, Athlone, Ireland) (Figure 6), and the VivaSight-EB blocker (Ambu, Copenhagen, Denmark) (not pictured).

F5
Figure 5.:
Selective blockade of bronchus intermedius in a patient with severe restrictive lung disease and large right lower lobe bronchopleural fistula. A, Advancing bronchial blocker into the right main bronchus. B, Directing and inflating blocker cuff in bronchus intermedius.
F6
Figure 6.:
Four commercially available independent bronchial blockers. A, Arndt Wire-guided blocker. B, Cohen Blocker. C, Fuji Uni-Blocker. D, EZ-Blocker.

The Arndt blocker is a balloon-tipped catheter and contains an inner lumen through which a wire is used to exit the distal end as a flexible wire loop. A FOB may then be used as a stylet to guide the wire loop into the desired bronchus. An 8.0 mm or larger SLT will permit passage of the 9.0-Fr Arndt blocker; the 7.0-Fr Arndt blocker can be passed through a 7.0-mm SLT. The Cohen tip-deflecting endobronchial blocker addresses placement difficulties by incorporating a flexible tip controlled by a rotating wheel device at its proximal end to enable directional control of the blocker tip. The Fuji Uni-blocker is manufactured with a fixed distal curve allowing it to be rotated into position with FOB guidance by rotating the proximal end. The EZ-blocker has a bifurcated (Y shaped) distal end design (with a bronchial cuff on each end) that enables placement of a cuff in both main bronchi so that either lung can be selectively deflated.96 However, with its 7.0-Fr diameter split into 2 lumens, it is difficult to apply suction through or oxygen to the deflated lung. Finally, the VivaSight-EB endobronchial blocker (Ambu, Copenhagen, Denmark) incorporates a specialized SLT with an integrated camera such that the continuous tracheoscopic view permits real-time assessment of blocker position.

The bronchial blocker may be particularly useful when lung isolation is desired in the patient with a difficult airway. The bronchial blocker may be positioned through a nasotracheal tube, tracheostomy, orotracheal tube, or supraglottic device. Reports describing the utility and safety of bronchial blockers for achieving lung isolation and OLV have increased since the first description of modern bronchial blocker use in 1982 by Inoue et al.97 Bronchial blockers are safe and effective for achieving lung isolation for both left- and right-sided operations83 and surgical exposure with blocker use is equivalent to that of left-sided DLTs.27 A recent meta-analysis of bronchial blockers and DLTs in thoracic surgery found that blockers are associated with a lower incidence and severity of airway injury.98 Examples of reported complications with bronchial blockers include malfunction of blocker systems,99 the inclusion of an enclosed bronchial blocker into the surgical staple line during lobectomy,100,101 and rare instances of cuff malposition leading to life-threatening airway obstruction.102 Bronchial blockers are also associated with a lower incidence of airway injury.86 Notably, use of a blocker may take longer than DLT insertion as it requires 2 separate actions (SLT placement and blocker positioning). That longer placement times with bronchial blockers or high malposition rates have been reported in some98 but not all studies103 may suggest both unfamiliarity with blocker use and an intrinsically longer positioning process. Highlighting this issue, one 2006 study found that 39% of anesthesiologists with limited thoracic anesthesia experience were unable to successfully achieve lung separation regardless of the type of lung isolation device due to poor knowledge of endoscopic bronchial anatomy.104 In a 2013 study of 100 patients comparing the EZ-blocker and left-sided DLT,105 the EZ-blocker was rated easier to use, had a lower incidence of postoperative sore throat, and had a lower incidence of postoperative new or worsened airway injury (tracheal or bronchial hematoma). A similar study86 comparing the Arndt wire-guided blocker and left- and right-sided DLTs in 60 patients reported that postoperative hoarseness, sore throat, and vocal cord lesions occurred more frequently in those patients intubated with a DLT (44% vs 17%). Although these studies are small, they underscore potential advantages of SLT and blocker use for lung isolation over that of the larger, more rigid DLT. Supplemental Digital Content 1, Table 3, https://links.lww.com/AA/C131, summarizes key characteristics and advantages of bronchial blockers compared to DLTs.

SINGLE-LUMEN ENDOBRONCHIAL TUBE

Occasionally it may be useful or necessary to achieve lung isolation with an SLT. Under emergent conditions, a standard SLT may be advanced into either mainstem bronchus. This approach, however, is fraught with limitations. First, SLT placement within either main bronchus limits access to the nonintubated bronchus. Second, standard SLTs have a long cuff and long cuff-to-tip distance and are thus not designed for endobronchial placement, as their use is likely to be associated with inadvertent blockage of an upper lobe orifice, particularly on the right. The development of SLTs suitable for endobronchial placement has improved the efficacy of this approach in select clinical scenarios. Fuji currently produces and markets an SLT with the following characteristics: (1) long length (40 cm), (2) wire-reinforced silicone construction, (3) small cuff, and (4) short cuff-to-tip distance (Figure 3). This tube can be placed within either mainstem bronchus and can thus be used to achieve lung isolation and OLV. It may be particularly useful for lung isolation in cases involving (1) distal tracheal and carinal surgery,106 (2) severe tracheal stenosis and/or extrinsic compression, and (3) failed or impossible DLT or blocker placement.

LUNG ISOLATION AND ALTERNATE AIRWAY ACCESS

Patients with an existing tracheostomy present a unique challenge with respect to lung isolation. The distance from tracheostomy site to the carina is shortened and a tracheal stoma may be small or restrictive, potentially leading to malposition if a conventional DLT is placed through the stoma. A shortened version of a DLT for tracheostomy patients exists (Rüsch Tracheopart; Teleflex Medical),107 but is not commercially available in the United States. Other options to achieve lung isolation in a tracheostomized patient include use of a bronchial blocker through an SLT (coaxially or extralumenally) or cuffed tracheostomy tube, placement of a small-sized DLT through the tracheostomy stoma, or oral placement of a DLT or bronchial blocker. Patients with a tracheostomy may be best managed with a bronchial blocker through the stoma in which FOB guidance permits proper positioning while maintaining simultaneous ventilation through a multiport adaptor (Supplemental Digital Content 2, Figure 1, https://links.lww.com/AA/C132). This technique has even been described in chronic tracheostomy stomas108 and newer (fresh) stomas (<2 days old) with success.109

SUMMARY

Lung isolation in the patient with challenging upper and/or lower airway anatomy is challenging. Though DLTs are most commonly used to achieve lung isolation, their use is associated with significant risk of both minor and severe airway injuries. These risks may be greater in patients for whom airway management is inherently challenging. Supplemental Digital Content 3, Figure 2, https://links.lww.com/AA/C133, presents an algorithm for difficult airway management when OLV is indicated.

Of the available alternatives to DLT for lung isolation, bronchial blockers may be the most advantageous for lung isolation in most patients with a difficult airway. Bronchial blockers provide safe and effective lung isolation and can be deployed through any type of airway provided it is of adequate caliber. In specialized cases, the thoracic anesthesiologist may choose a single-lumen endobronchial tube for lung isolation. Anesthesiologists should be familiar with alternatives to the DLT for lung isolation and become proficient in their use.

DISCLOSURES

Name: Stephen R. Collins, MD.

Contribution: This author helped prepare and revise the manuscript.

Name: Brian J. Titus, MD, PhD.

Contribution: This author helped prepare and revise the manuscript.

Name: Javier H. Campos, MD.

Contribution: This author helped prepare and revise the manuscript.

Name: Randal S. Blank, MD, PhD.

Contribution: This author helped prepare and revise the manuscript.

This manuscript was handled by: Avery Tung, MD, FCCM.

REFERENCES

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