Lung isolation techniques

INTRODUCTION — Lung isolation and one lung ventilation (OLV) are routinely used to facilitate surgical exposure for intrathoracic procedures involving the lungs, esophagus, anterior mediastinal structures, or aorta, as well as for selected orthopedic spine procedures. Less commonly, lung isolation may be necessary to prevent soiling of the contralateral lung when unilateral massive pulmonary hemorrhage or abscess is present, or to avoid ventilation of a unilateral bronchopleural fistula, lung cyst, or bullae.

This topic will discuss specific devices used for lung isolation (eg, double-lumen endotracheal tubes or bronchial blockers) and selection of the most appropriate device for various clinical situations.

The indications, physiology, ventilation strategies, management of hypoxemia, and complications of OLV are reviewed separately. (See "One lung ventilation: General principles".)

AIRWAY ANATOMY — Expertise in both laryngoscopy and fiberoptic bronchoscopy (FOB) is necessary to ensure correct positioning of either a double-lumen endotracheal tube (DLT) or a bronchial blocker. Details regarding positioning are noted below [1]:

●(See 'Positioning left double-lumen tubes' below.)

●(See 'Positioning right double-lumen tubes' below.)

●(See 'Positioning bronchial blockers' below.)

A working knowledge of tracheobronchial anatomy is essential for successful lung isolation. In one trial, 39 percent of anesthesiologists with limited thoracic experience were unable to successfully achieve lung separation due to unfamiliarity with the endoscopic view of the airway [2]. This failure rate was independent of which device was selected.

A review of airway anatomy is available online at www.thoracic-anesthesia.com and is summarized below:

●Trachea – The trachea arises from the cricoid cartilage and extends caudally in the midline to the tracheal carina. Anterolaterally, the trachea is composed of 18 to 22 C-shaped cartilaginous rings. The ends of each "C" ring are linked posteriorly by the superficial membranous wall and the trachealis muscle, resulting in the normal ovoid appearance of the adult trachea.

The length of the adult trachea averages 12 cm [3]. The average tracheal diameter is 22 mm in men and 19 mm in women (figure 1) [4]. The cricoid cartilage is the narrowest portion of the airway in adults with an average diameter of 17 mm in men and 13 mm in women.

●Carina – At the carina, the trachea bifurcates into the right and left mainstem bronchi. Viewed endoscopically from the trachea, the carina can be identified by a sharp bifurcation in the 12 to 6 o'clock position and the symmetrical large calibers of the right and left mainstem bronchi (picture 1). The subsequent second-generation bifurcations within each mainstem bronchus (leading to the lobes) are generally not visible. Relative to the trachea, the takeoff of the right mainstem bronchus is in a more vertical plane (at a 20 to 30 degree angle), while the takeoff of the left mainstem bronchus is in a more horizontal plane (at a 40 to 50 degree angle).

●Right mainstem bronchus – The right mainstem bronchus is very short compared with the left mainstem bronchus (approximately 1.9 cm long in men and 1.5 cm long in women). As a result, positioning a right-sided DLT can be challenging (see 'Positioning right double-lumen tubes' below). The right mainstem bronchus gives rise to the right upper lobe (RUL) bronchus at the 3 to 4 o'clock position and the bronchus intermedius (picture 2). The trifurcation of the RUL bronchus into apical, anterior, and posterior segments results in a distinct endoscopic triangle formation, which can be useful in differentiating the right from the left bronchial tree (picture 3). The bronchus intermedius leads to the right middle lobe (RML) bronchus and the right lower lobe (RLL) bronchus (picture 4). In contrast to all other bifurcations, which lead to equally sized bronchi, the ratio of the RML bronchus to the RLL bronchus is approximately 2:3. The longitudinal muscle bundles form the posterior wall of the trachea and continue into both the right and left mainstem bronchi, then into the lower lobes of each lung. Following the path of these longitudinal bundles aids in distinguishing the RLL bronchus from the RML bronchus.

●Left mainstem bronchus – The left mainstem bronchus is long compared with the right mainstem bronchus (approximately 4.9 cm in men and 4.4 cm in women) (picture 5) [5]. For this reason, maintaining ideal position of a lung isolation device is generally easier on the left than on the right side. (See 'Positioning left double-lumen tubes' below.)

The left mainstem bronchus bifurcates equally into a left upper lobe (LUL) bronchus and left lower lobe (LLL) bronchus, and may be mistaken for the tracheal carina (picture 6). However, in contrast to the tracheal carina, the LUL/LLL carina is less sharp and leads to smaller-caliber openings, each with visible bifurcations. Like the RLL bronchus, the longitudinal muscle bundles continue into the LLL bronchus, allowing it to be easily distinguished from the LUL.

TYPES OF LUNG ISOLATION DEVICES — The three types of lung isolation devices are [6]:

●Left or right double-lumen endobronchial tube (DLT)

●Bronchial blocker placement via a single-lumen endotracheal tube (ETT)

●Placement of a single-lumen ETT into a mainstem bronchus

Double-lumen endobronchial tubes

Overview of double-lumen tubes — A DLT permits isolation, selective ventilation, and intermittent suctioning of either lung [7-9]. A DLT has separate tracheal and bronchial lumens; essentially, it is two tubes connected side by side. The shorter tube has a high-volume, low-pressure tracheal cuff and gives rise to the tracheal lumen which is positioned just above the carina. With both left and right DLTs, the smaller low-volume, high-pressure bronchial cuff is ideally positioned just below the tracheal carina but before the takeoff of any lobar bronchi. DLTs are labelled either left- or right-sided depending on which mainstem bronchus the longer tube is designed to fit (figure 2 and figure 3). The cuffs, their pilot balloons, and the connection site at the top of each of the two tubes are all color-coded (white for the tracheal tube and blue for the endobronchial tube).

Once the DLT is properly seated, both the tracheal and bronchial cuffs are inflated. To achieve selective one lung ventilation (OLV), the tube/lumen for the contralateral lung is clamped. For example, with left-sided DLTs, the bronchial (blue) lumen provides ventilation to the left lung while the tracheal (white) lumen ventilates the right. To selectively ventilate the right lung, flow to the left lung is stopped by clamping the bronchial (blue) lumen proximal to the bronchoscopy port. Conversely, to ventilate the left lung, the tracheal (white) lumen would need to be clamped. Once clamped, the bronchoscopy port on the same side is opened to allow passive lung deflation. Collapse of the nonventilated lung can be facilitated by various maneuvers. (See "One lung ventilation: General principles", section on 'Improving deflation of the nonventilated lung'.)

Choice of a left versus a right DLT is discussed below. (See 'Left versus right double-lumen tubes' below.)

Selecting double-lumen tube size — The largest DLT likely to fit easily within the mainstem bronchus should be used. Although there is no consensus regarding how to select a DLT size for an individual patient, we suggest using the patient's sex and height to choose an appropriate DLT tube size since this method is both simple and effective (table 1) [10]. Studies have demonstrated a correlation between height and left bronchial diameter [11,12]. Other methods are based on radiographic measurements of bronchial and/or cricoid ring diameter [12-15]. Limitations of radiologic measurements include availability of appropriate films, difficulty in scaling film measurements to the patient's actual size, and significant discrepancies in actual DLT sizes from different manufacturers (table 2) [14-17].

An appropriate DLT size should result in an air leak when the bronchial cuff is deflated, but should be airtight when the cuff is inflated with a volume that is <3 mL [13]. Generally, the bronchial diameter of the ideal DLT should be 1 to 2 mm smaller than the diameter of the patient's mainstem bronchus [10]. The insertion of an oversized DLT may traumatize or even rupture the trachea or bronchus [18,19]. Insertion of a DLT that is too small may lead to inadequate lung isolation, increased airway resistance, overinflation of the bronchial cuff, or accidental passage far enough into the bronchus to obstruct the upper lobe of the lung [11,20-22]. (See 'Minimizing airway trauma' below.)

Positioning left double-lumen tubes — Left DLTs are generally easier to place than right DLTs. The endobronchial tip is inserted through the vocal cords under direct laryngoscopy, the stylet is removed, and the DLT is rotated 90 degrees to the left while being advanced. However, studies have shown that 24 to 39 percent of "blind" insertions of a left DLT without fiberoptic bronchoscopy (FOB) confirmation will result in endobronchial intubation of the right mainstem bronchus [20,23]. This is due to the more vertical position of the right mainstem bronchus, which aligns it with the trachea. Turning the patient's head to the right and tilting it toward the right shoulder while advancing the tube may help to avoid the right mainstem bronchus during insertion of a left-sided DLT. In one study, this maneuver resulted in successful placement in the left mainstem bronchus in 92 percent of blind left DLT insertions [23].

Traditionally, the position of a left DLT is confirmed by auscultation. Initially, auscultation is performed with both the tracheal and bronchial cuffs inflated; ventilation through both lumens should result in equal bilateral breath sounds if the DLT is properly inserted. Then the tracheal lumen is clamped, and ventilation should result in breath sounds on the left but not the right side. Next the bronchial lumen is clamped, and subsequent ventilation should result in breath sounds on the right but not the left side. An algorithm to correct malposition using the auscultation method is provided (algorithm 1).

Now FOB is the gold standard for confirming ideal DLT position. For commonly-used adult DLT sizes (35 to 41 French [Fr] (table 1)), a bronchoscope <4 mm in diameter will pass through both lumens. For a 32 Fr DLT, a bronchoscope <3.4 mm in diameter is necessary. In a series of 200 procedures in which the DLT position was checked by auscultation followed by bronchoscopy, malpositioning of the DLT was identified by auscultation in 28 patients; however, subsequent FOB identified malpositioning in an additional 79 patients [24]. Malpositioning of a DLT is the most common cause of intraoperative hypoxemia during OLV [25]. In a review of 1170 procedures (1166 with left DLTs), hypoxemia during OLV occurred in 3 percent, with DLT malposition accounting for >60 percent of these cases [20].

If the left DLT is ideally positioned, the initial bronchoscopic view from the tracheal lumen shows the inflated blue bronchial balloon just visible beyond the carina on the left side without herniation into the trachea (figure 4). Identifying the characteristic appearance of the right upper lobe (RUL) bronchus on the right, and viewing the right middle lobe (RML) and right lower lobe (RLL) originating from the bronchus intermedius further confirms correct insertion of the left bronchial tube into the left mainstem bronchus. If the expected RUL and bronchus intermedius views are not identified, or resistance is encountered while the DLT is being placed, FOB should be used to visualize the tracheobronchial anatomy during insertion. This is accomplished by deflating both cuffs of the left DLT and pulling it back with the bronchoscope positioned at the tip of the bronchial lumen until the carina comes into view. The bronchoscope is then advanced into the left main bronchus to be used as guide over which the left DLT slides into position.

Next, the bronchoscope is passed down into the bronchial lumen (figure 5) to ensure that the bronchial tube has not been advanced too far (figure 6). This is necessary since occlusion of the left upper lobe (LUL) bronchus is a risk if the tube migrates distally (eg, during patient positioning). For this reason, it is also critically important to reconfirm tube position after any change in patient position. In one study, 32 percent of well-positioned DLTs became malpositioned after turning the patient to a lateral position [25]. In another study, lateral positioning caused 0.92 +/- 1.15 cm displacement of the bronchial tip in 37 of 50 patients, usually in a proximal direction [26].

While bronchoscopy remains the gold standard for confirmation of DLT position, one study demonstrated that inserting the DLT to a predetermined depth based on the preoperative computed tomography distance from the vocal cords to the carina resulted in less frequent need to reposition the DLT compared with blind insertion of a DLT [27]. Also, use of a video-enhanced left DLT with a high-resolution camera and light source embedded on the distal end of the tracheal lumen may facilitate accurate placement and allow continuous video monitoring of DLT position during surgery [28-30].

Positioning right double-lumen tubes — In contrast to a left DLT, the bronchial lumen of a right DLT has two orifices, one on the side wall that should be aligned with the takeoff of the RUL bronchus, and one at the tip of the tube to ventilate both the RML and RLL (figure 7).

Once the endobronchial tip of the right DLT is passed through the vocal cords under direct laryngoscopy, the stylet is removed, and the DLT is rotated 90 degrees to the right and slightly advanced until the tip of the bronchial lumen is in the mid-trachea. From this mid-tracheal position, the bronchoscope is subsequently passed through the bronchial lumen to inspect the patient's right bronchial tree anatomy and to ensure that proper right DLT placement will be feasible. In 3 percent of patients, the RUL bronchus originates at the level of the carina or even within the trachea [31,32]; in such cases, ideal positioning of a right DLT (with the bronchial cuff between the carina and the RUL bronchus) may not be possible. Next, the right DLT is then advanced into the right mainstem bronchus under direct bronchoscopic visualization (figure 7).

Optimal alignment of the bronchial side orifice of the right DLT with the RUL bronchial orifice occurs in two dimensions, requiring insertion to both the appropriate depth and optimal rotation of the DLT. This may be challenging because the RUL bronchus is often difficult to visualize through the opaque tube. When the position of the RUL bronchus is unclear, FOB identification of the bronchus intermedius and the direction of the RML/RLL carina can be helpful. This landmark is followed up proximally since the anterolateral aspect of this carina is often proximal to the orifice of the RUL bronchus within the mainstem bronchus (figure 7). Once the side orifice of the bronchial tube is thought to be aligned with the RUL bronchial orifice, the bronchoscope is withdrawn and reinserted through the tracheal lumen to confirm that the right bronchial cuff appears to be correctly positioned within the right mainstem bronchus between the carina and the RUL bronchus (figure 7).

Because the right mainstem bronchus is relatively short, proper positioning of the right bronchial cuff while maintaining alignment of the tube side orifice with the RUL bronchial orifice can be difficult [5]. If the device is placed slightly deep, occlusion of the RUL bronchus may occur, but if placed too close to the carina it may herniate proximally preventing adequate lung isolation.

Once ideal positioning of the right-sided lung isolation device is achieved, its location can easily shift during patient repositioning (eg, from supine to lateral position, during neck extension or flexion, or during surgical manipulation), and shifting is more likely with right compared with left DLTs. Since the margin of error for placement and maintenance of right DLT positioning is low, rechecking position with FOB is prudent after any change in patient position and critically important if hypoxemia develops.

Minimizing airway trauma — Airway rupture is rare with DLTs (<0.2 percent), but is associated with mortality as high as 42 percent [19,33,34]. In reviews of airway rupture, the most frequently cited factor was overdistension of either the bronchial or the tracheal cuff of the DLT [19,22]. Potential risk factors for airway rupture included:

●Direct trauma:

•Insertion with too much force

•Tube too large for bronchus

•Tube advanced with stylet in place

•Movement of the tube with cuffs inflated

●Cuff overinflation:

•Inflation of a volume that is too large. Although underinflation of the bronchial cuff may lead to incomplete collapse of the nonventilated lung or inadequate ventilation of the ventilated lung, overinflation can damage the tracheobronchial mucosa. Ideally, an appropriately sized DLT is used (see 'Selecting double-lumen tube size' above), and inflation of the bronchial cuff is with the lowest volume that provides an air-tight bronchial seal. In one study, an air-tight seal was achieved with lower bronchial cuff volumes by monitoring the capnometry tracing during cuff inflation to determine when carbon dioxide gas sampling from the nonventilated lung became a flat line, rather than by using a cuff inflator device to inflate the cuff to a pressure of 20 cm H₂O [35].

•Inflation that is too rapid.

•Undersized tube that requires a large cuff volume to achieve an adequate seal.

•Cuff distention due to use of nitrous oxide (N₂O).

●Preexisting airway pathology:

•Congenital airway wall abnormalities

•Airway wall weakness from tumor infiltration or infection

•Airway distortion (mediastinal lymph node, intrabronchial, or extrabronchial tumors)

•Leukemia, lymphoma, patients receiving steroids

•Hypotension with hypoperfusion to the airway

●Difficult intubation and/or multiple attempts to adjust the position of the DLT

To reduce the risk of airway rupture, we suggest:

●Routinely review chest imaging for airway abnormalities

●Remove DLT stylet after passing the vocal cords

●Use FOB guidance if resistance is encountered during blind advancement

●If bronchial cuff volume >3 mL is needed, consider a larger-size DLT

●Avoid N₂O

Bronchial blockers

Overview of bronchial blockers — A bronchial blocker may be used to achieve lung isolation instead of a DLT. If properly placed within the mainstem bronchus, inflation of the low-volume, high-pressure bronchial blocker balloon will result in impeded flow to that entire lung. In rare situations, a bronchial blocker may be used for isolation of a smaller specific lung segment. (See 'Ability to achieve selective lobar blockade' below.)

Bronchial blockers have a hollow center channel that can be used to apply continuous positive airway pressure (CPAP) to prevent atelectasis, or conversely, apply suction to assist in collapsing the lung. (See "One lung ventilation: General principles", section on 'Improving deflation of the nonventilated lung'.)

Rationales for choosing a bronchial blocker rather than a DLT are discussed below. (See 'Double-lumen tubes versus bronchial blockers' below.)

Positioning bronchial blockers — Bronchial blockers may be used with an oral, nasotracheal, or tracheostomy tube. Typically, a bronchial blocker is placed through the lumen of a standard single-lumen ETT, with use of a FOB for final positioning [36]. However, if the ETT is too small to accommodate both the bronchial blocker and the FOB, the bronchoscope may be placed separately through the glottis on one side of the ETT. The bronchial blocker is then passed via the ETT and positioned with FOB assistance to visualize airway anatomy during final positioning.

Each type of commercially available bronchial blocker has a unique mechanism to assist placement, but all require FOB guidance. Basic characteristics of these bronchial blockers are summarized in the table (table 3).

●Arndt wire-guided endobronchial blocker (picture 7) – The tip of the Arndt blocker has a nylon wire loop through which the bronchoscope is threaded. The blocker and bronchoscope are then inserted together, and the bronchoscope is used to directly guide the Arndt blocker into position.

●Cohen tip-deflecting endobronchial blocker (picture 8) – The tip of the Cohen blocker can be deflected to the right or left by turning a wheel at the proximal end of the blocker.

●Fuji Univent (picture 9) – The Univent is a single-lumen tube with an external channel that houses a built-in bronchial blocker. This blocker is composed of a malleable material that allows the preshaped tip to be positioned by applying rotational torque to its proximal end. The blocker of the Univent tube is also available separately as the Fuji Uniblocker (picture 10).

●Rusch EZ-Blocker (picture 11) – The EZ-Blocker is "Y" shaped and has two bronchial blockers. Under FOB guidance, the Y-connection between the two blockers is seated on the carina, with one blocker within each mainstem bronchus. This blocker may be used for bilateral surgery without the need for repositioning.

Single-lumen endotracheal tubes

Overview of single-lumen tubes — Lung isolation is possible by placing a single-lumen ETT within the right or left mainstem bronchus, resulting in ventilation of only the intubated lung. A single-lumen ETT placed in an endobronchial position (without a bronchial blocker) is rarely used for lung isolation in adults due to lack of access to the nonventilated lung and difficulty in achieving an optimal position in the bronchus [10]. However, endobronchial intubation with a single-lumen ETT may be useful in selected patients with abnormal tracheobronchial anatomy, as well as in emergency situations [37]. These include unilateral pulmonary hemorrhage or copious purulent material, when immediate isolation of the healthy lung is necessary, but preferred lung isolation devices, particularly DLTs or bronchial blockers, are not readily available. (See 'Abnormal tracheobronchial anatomy' below and 'Need for unilateral lung protection' below.)

Positioning single-lumen tubes

●Standard single-lumen tube – For a standard ETT, the length of the cuff and the tube beyond it (>4 cm) are longer than a DLT. As a result, when the cuff of a standard ETT is positioned within the mainstem bronchus, as is necessary for lung separation, obstruction of the upper lobe bronchus may occur, particularly with placement in the right bronchus [38].

●Specialized single-lumen endobronchial tubes – Specialized long single-lumen ETTs are preferred if endobronchial placement of a single-lumen tube is necessary. These specifically designed tubes can be used in the endotracheal position, then passed into a mainstem bronchus using FOB guidance (picture 12) [37]. This technique is particularly useful for carinal resection.

DEVICE CHOICE: GENERAL CONSIDERATIONS — A left-sided double-lumen endobronchial tube (DLT) is typically selected to achieve one lung ventilation (OLV), but a right-sided DLT or a bronchial blocker may be selected in certain situations, as noted below.

Double-lumen tubes versus bronchial blockers — Lung isolation is most commonly achieved with a DLT due to faster and easier positioning compared with various types of bronchial blockers (see 'Positioning left double-lumen tubes' above). Compared with a left DLT, bronchial blockers are also more likely to require repositioning facilitated by fiberoptic bronchoscopy (FOB) during surgery, particularly when placed within the short right mainstem bronchus to achieve right lung isolation [8,39,40]. Although some studies have found that time for lung deflation is longer after placement of a bronchial blocker compared with a DLT [41], others have found the opposite result [42].

A 2015 meta-analysis of 39 trials comparing efficacy and adverse effects of DLTs versus bronchial blockers noted that DLTs were typically positioned more quickly (mean difference 51 seconds faster; 95% CI 8-94 seconds faster) and were more likely to be correctly positioned (odds ratio [OR] 2.70, 95% CI 1.18-6.18) [43,44]. However, blockers were associated with a lower incidence of sore throat (OR 0.39, 95% CI 0.23-0.68), hoarseness (OR 0.43, 95% CI 0.24-0.75), and airway injury (OR 0.35, 95% CI 0.17-0.72). Also, there are no reports of airway rupture resulting from bronchial blocker placement, as has been reported for DLTs [19,22].

When lung isolation is necessary to prevent soiling or contamination from one lung to the other (eg, due to bleeding or infection), we select a DLT rather than a bronchial blocker because lung isolation can be established before the source is identified, a DLT is less likely to become malpositioned, and the ability to ventilate, suction, or employ FOB is maintained for the pathologic lung. Also, a DLT may be preferred for patients with copious or thick airway secretions, since the suction channel of a bronchial blocker may not allow for adequate suctioning of such secretions. (See 'Need for unilateral lung protection' below.)

Placement of a bronchial blocker is typically selected to achieve lung isolation in patients with a difficult airway (particularly if awake intubation is necessary), for those with a tracheostomy or abnormal tracheobronchial anatomy, or if an endotracheal tube has been previously inserted or prolonged postoperative mechanical ventilation is planned. These situations are discussed below:

●(See 'Anticipated difficult airway' below.)

●(See 'Presence of a tracheostomy' below.)

●(See 'Abnormal tracheobronchial anatomy' below.)

●(See 'Presence of an endotracheal tube' below.)

●(See 'Need for postoperative ventilation' below.)

Infrequently, a bronchial blocker may be advantageous to achieve collapse of only a single lung lobe rather than an entire lung (eg, patients with severe pulmonary disease or prior resections who would not tolerate collapse of the entire lung) [45,46] (see 'Ability to achieve selective lobar blockade' below). Selective lobar blockade is not possible with DLTs.

Left versus right double-lumen tubes — Left DLTs are most commonly selected because of easier positioning and a larger margin for error compared with right DLTs, due to the longer length of the left mainstem bronchus [10,20,47]. Left bronchus length is 4 to 6 cm for males, and 3 to 5 cm for females, compared with only 1 to 2 cm length for the right mainstem bronchus [5]. (See 'Airway anatomy' above.)

Positioning of a right DLT requires precision in both depth of insertion and rotation to maintain proper position of the bronchial cuff within the short right mainstem bronchus, and to precisely align the side ventilation orifice with the take-off of the right upper lobe (RUL) bronchus (see 'Positioning right double-lumen tubes' above). Right DLTs are also more challenging to maintain in position compared with left DLTs; thus, complications due to malpositioning may be more common. In one small trial, adequate positioning of a right DLT was maintained in only 37 percent of cases after turning the patient to lie in a lateral decubitus position, and repositioning was required to achieve adequate OLV in most patients [48]. For these reasons, we restrict their use to situations in which a right DLT is specifically indicated such as [10]:

●Left pneumonectomy (see 'Left pneumonectomy or bronchial surgery' below)

●Distorted anatomy of the entrance of the left mainstem bronchus due to external or intraluminal left bronchial compression (eg, tumor, descending thoracic aortic aneurysm)

●Site of surgery that involves the left mainstem bronchus (eg, left-sided lung transplantation, tracheobronchial disruption, pneumonectomy, sleeve resection)

Comparison of specific parameters

Accessibility of the nonventilated lung — DLTs provide superior access to the nonventilated lung because they allow:

●Access to the nonventilated lung for bronchoscopy when necessary, and for suctioning of blood or secretions. In contrast, the center lumen in bronchial blockers is too small (1.4 to 2 mm) to allow passage of a bronchoscope or suction catheter, although suction may be applied to this lumen to assist with lung deflation.

●Reexpansion of the nonventilated lung without loss of lung isolation. In contrast, lung isolation is lost with deflation of the bronchial blocker balloon during any reexpansion efforts.

●Continuous positive airway pressure (CPAP) application to the nonventilated lung during OLV is possible through a DLT, and has also been described with use of a Univent bronchial blocker (picture 9) [49,50].

Ease of insertion — Time required to place a lung isolation device is a measurable surrogate for ease of insertion. In several trials, the time from laryngoscopy to successful lung isolation is slightly shorter for left DLTs compared with bronchial blockers [7-9,51].

The experience of the anesthesiologist is often a more significant factor for speed of device placement than the selected device itself. For example, either a left DLT or a bronchial blocker could be placed within one to four minutes by experienced thoracic anesthesiologists [7-9,51]. However, anesthesiologists with limited experience with lung isolation required six to nine minutes to place either a left DLT or a bronchial blocker in one trial, and one-third of all devices were not properly positioned after their attempts [2].

Subjective experience is also a factor in evaluating ease of insertion. For example, although time of insertion of an EZ-Blocker bronchial blocker was longer compared with a DLT, ratings of ease were comparable or better for this blocker in some trials [51,52].

In emergency situations requiring immediate lung isolation (eg, to prevent soiling of a healthy lung with blood or purulent material from the other lung), a single-lumen ETT may be the selected for endobronchial placement to achieve lung isolation. Single-lumen ETTs are readily available in all hospital locations, and clinician familiarity facilitates ease and speed of insertion. (See 'Need for unilateral lung protection' below.)

Quality of lung deflation and reinflation — Overall, the speed and quality of lung deflation (collapse) does not differ between DLTs and bronchial blockers [7,8,51,52].

In one trial, Arndt bronchial blockers required more suction but took only slightly longer to collapse (26 minutes, 2 seconds) compared with Univent blockers (19 minutes, 28 seconds) or DLTs (17 minutes, 54 seconds). This may be because the center lumen of the Arndt bronchial blocker is smaller than that of other bronchial blockers [7].

Need for intraoperative repositioning — After initial placement of a lung isolation device, subsequent malposition due to shifting device position may occur after any changes in the patient's position (eg, from supine to lateral), or during extension or flexion of the head, overinflation of the device cuff, or surgical manipulations. In two trials, bronchial blockers were more likely to require repositioning during surgery than left DLTs [8,39]. In one study, Arndt blockers were more frequently displaced compared with Cohen or Fuji blockers, possibly due to the elliptical shape of the original Arndt balloon design (picture 7); balloon design for this blocker is now spherical [8].

While malpositioning is generally a benign inconvenience, a life-threatening complication may rarely occur. In one case report, a bronchial blocker in the left mainstem bronchus was displaced into the trachea, causing a "ball valve" effect that blocked airflow into either mainstem bronchus, leading to pulseless electrical activity arrest. This was reversed by deflating the bronchial blocker balloon [53]. In another case report, distal migration of the DLT bronchial lumen into a lobar bronchus while ventilating with volume control resulted in tension pneumothorax, pneumomediastinum, and pneumoperitoneum [21].

Ability to achieve selective lobar blockade — For patients at high risk of desaturation during OLV, the anesthesia provider may select a bronchial blocker to achieve blockade of a single lobe on the surgical side, thereby limiting the extent of hypoxemia while providing adequate surgical exposure.

DEVICE CHOICE: SPECIFIC SITUATIONS

Elective thoracic surgery — For most thoracic surgical procedures (eg, lobectomy, wedge resection, thoracoscopy, esophageal surgery), we select a left double-lumen endobronchial tube (DLT) because these devices are positioned slightly faster and are less likely to become malpositioned during surgery compared with bronchial blockers. For lobectomy procedures, another advantage is the ability to confirm occlusion of the intended lobe via fiberoptic bronchoscopy (FOB) before stapling and transecting the bronchus. (See 'Double-lumen tubes versus bronchial blockers' above.)

However, we may select a bronchial blocker for certain situations, as noted above, since blockers provide comparable surgical exposure compare with left DLTs (see 'Double-lumen tubes versus bronchial blockers' above and 'Quality of lung deflation and reinflation' above). Also, there are specific clinical situations in which we would select a right instead of a left DLT. (See 'Left versus right double-lumen tubes' above.)

Left pneumonectomy or bronchial surgery — We use a right DLT for a left pneumonectomy, and for surgical procedures involving left endobronchial lesions or compression of the left mainstem bronchus. Use of a left DLT or bronchial blocker during such procedures would necessitate withdrawal of the device from the operative bronchus into the trachea when the left mainstem bronchus is transected. This risks contamination of the nonoperative side with blood and secretions, as well as exposure of the bronchial stump to positive pressure ventilation.

In rare cases, a lung isolation device or its guidewire has become entrapped in the surgical staple line along the left bronchial stump [54]. Thus, the anesthesia provider must ensure that all parts of any device used in a bronchus on the surgical side have been completely retracted prior to staple deployment. These risks are avoided by using a right DLT instead of a bronchial blocker or left-sided DLT for left pneumonectomy or bronchial surgery [55]. (See 'Left versus right double-lumen tubes' above.)

Minimally invasive cardiac surgery — One lung ventilation (OLV) is necessary for selected minimally invasive cardiac surgical procedures. For such cases, if controlled mechanical ventilation is planned in the postoperative period, use of a bronchial blocker avoids the need to exchange a DLT for a single-lumen endotracheal tube (ETT) at the end of the procedure (see 'Need for postoperative ventilation' below). Intraoperative malposition has not been reported to occur with a higher incidence with use of bronchial blockers compared with DLTs during these cardiac surgical procedures [56-58].

Abnormal tracheobronchial anatomy — In patients with distorted or abnormal tracheobronchial anatomy (eg, a pericarinal lesion), lung isolation may be best achieved with either a bronchial blocker or by placing a single-lumen ETT in the endobronchial position [37]. In these situations, it may be difficult to advance a relatively stiff DLT into position beyond the airway abnormality without causing airway trauma. In addition, if a portion of the tracheobronchial tree is to be resected, a bulky DLT may hinder surgical exposure and reconstruction.

For patients with a bronchopleural fistula (ie, a direct communication between a segment of the bronchial tree and the pleural cavity), precise placement of a bronchial blocker under direct bronchoscopic guidance may provide temporary occlusion of the fistula to permit healing or maintenance of respiratory stability until surgical repair is achieved [59].

In some patients undergoing descending thoracic aortic surgery, aortic compression of the left mainstem bronchus may preclude passage of a left DLT, necessitating use of a right DLT [60]. (See 'Left versus right double-lumen tubes' above.)

Need for unilateral lung protection

Massive hemoptysis — In cases of massive hemoptysis, either a DLT or a single-lumen ETT may be appropriate depending on the specific clinical situation and management plan [61] (see "Evaluation and management of life-threatening hemoptysis"):

●A DLT is often selected by anesthesia providers for isolation of a bleeding lung and prevention of soiling of the contralateral "good" lung, particularly if the bleeding site has not been clearly identified [62,63]. In addition to providing easy access for suctioning and bilateral bronchoscopy, a DLT is the only device that can isolate the affected lung while maintaining the ability to ventilate both lungs. These advantages are particularly important if the risk of continued bleeding necessitates lung isolation in the intensive care unit (ICU) for a prolonged period.

●In an emergency with massive hemoptysis, placement of a DLT may be technically difficult during active bleeding. In such cases, a large single-lumen ETT can be placed in the mainstem bronchus of the nonbleeding lung to protect the patient from asphyxiation due to bleeding from the other lung. With a large caliber ETT, an adult-sized FOB can then be used to clear obstructing clots, localize the bleeding site, and provide local treatment of the cause of bleeding [64,65]. Due to availability and familiarity, a single-lumen ETT may be preferred by pulmonologists and intensivists for such emergencies. However, it can be difficult to determine whether the hemorrhage is from the right or left lung during active bleeding.

●Passage of a bronchial blocker through a previously-placed single-lumen ETT may be used to effectively tamponade bleeding when the site origin is known. However, placement of a bronchial blocker with the aid of FOB may be difficult with profuse bleeding that obscures the bronchoscopic views. Another disadvantage of use of a bronchial blocker is inaccessibility of the bleeding site once the blocker is in place.

Unilateral pulmonary infection — Unilateral pulmonary infections such as bronchiectasis, lung abscess, or an infected cyst can produce copious amounts of purulent material necessitating lung isolation to protect the contralateral lung from contamination [66,67]. To provide a better seal, we typically select a DLT rather than a bronchial blocker [68]. DLTs are also more quickly placed, and have a lower incidence of malpositioning during patient movement. (See 'Double-lumen tubes versus bronchial blockers' above.)

Unilateral lung lavage — A DLT is required for whole lung lavage of each lung (eg, for treatment of pulmonary alveolar proteinosis) [69,70]. (See "Treatment and prognosis of pulmonary alveolar proteinosis in adults", section on 'Whole lung lavage'.)

Presence of an endotracheal tube — A bronchial blocker may be the best option for patients who have already been intubated with a single-lumen ETT before arrival in the operating room, particularly if prolonged postoperative mechanical ventilation is anticipated. Use of a DLT would require tube exchanges at the beginning and the end of the surgical procedure, increasing risk for complications. (See 'Anticipated difficult airway' below and 'Need for postoperative ventilation' below.)

Presence of a tracheostomy — In a patient with a tracheostomy, we use a bronchial blocker placed either within or alongside a disposable cuffed tracheostomy cannula when the tracheostomy is <7 days old, or via reinforced single-lumen ETT if the tracheostomy is mature [37,71-75]. Alternatively, the bronchial blocker may be placed orally through the vocal cords then alongside the tracheostomy tube [74,76]. Flexible fiberoptic bronchoscopy is typically used to confirm optimal placement [75]. Although there are reports of use of a small DLT placed via a tracheostomy, positioning can be difficult [77,78].

Anticipated difficult airway — Establishing lung isolation in patients who may be difficult to intubate is addressed in the algorithm (algorithm 2). Securing the airway first is the primary goal [37].

If difficulty with bag-mask ventilation is also anticipated, awake intubation is necessary. This is best accomplished with a single-lumen ETT [79]. While awake fiberoptic intubation and placement of a DLT has been described, guiding a stiff, large-diameter DLT through the oropharynx over a short, pliable pediatric bronchoscope can be difficult [37,80]. Furthermore, topical local anesthesia is typically inadequate to blunt the intense laryngeal and carinal stimulation that occurs during DLT placement. For patients who cannot be orally intubated, awake nasotracheal intubation with a single-lumen ETT is an option [71,79,81].

If mask ventilation is possible, options include either awake intubation, or intubation after induction of general anesthesia with a single-lumen ETT or a DLT [37]. A video laryngoscope may be used post-induction to guide placement of a DLT [37,82-84].

When a single-lumen ETT is used to secure a difficult airway, insertion of a bronchial blocker is the easiest and safest means to establish lung isolation [37]. Alternatively, the single-lumen ETT can be replaced with a DLT using an exchange catheter after general anesthesia is established. However, this is associated with a risk of exchange failure and airway injury [37]. To minimize risk, the airway exchanger should have a hollow center as well as universal adaptors to facilitate oxygenation as needed, and should be at least 83 cm long [79]. The catheter should not be inserted more than 24 cm at the lips to avoid airway injury during the exchange. Once the single-lumen tube is removed, the endobronchial lumen of the DLT may be threaded over the catheter. Visualization of the DLT advancing over the catheter and through the glottis with a either direct laryngoscopy or video laryngoscopy is ideal [10]. Exchange of a nasotracheal single-lumen ETT for an oral DLT has also been described using FOB guidance [85].

General considerations for difficult airway management are discussed separately. (See "Management of the difficult airway for general anesthesia in adults".)

Need for postoperative ventilation — Standard single-lumen ETTs cause less irritation of the carina and less minor airway trauma, and are more familiar to nursing staff in a post-anesthesia care unit (PACU) or ICU. A disadvantage of using a DLT compared with a bronchial blocker is the need to exchange a DLT for a single-lumen tube at the end of a surgical procedure in patients who will require prolonged postoperative controlled ventilation.

Some clinicians have the perception that DLTs have higher airway resistance compared with single-lumen ETTs, which would make ventilator weaning more difficult. However, airway resistance is not a compelling reason to change a 37 French (Fr) or larger DLT if the exchange may be difficult. In a study comparing airway devices for small adults, a size 37Fr DLT resulted in less airflow resistance than an ETT with a 7.5 inner diameter (ID) [86]. The device with the highest resistance in this study was a 7.5 mm ID Univent tube since a large portion of its cross-sectional area is occupied by the bronchial blocker channel (picture 9). Thus, a Univent tube <7.5 mm ID should be changed to a standard ETT for postoperative ventilation as soon as possible.

If only a short period of postoperative ventilation is necessary, a left DLT may be left in place. However, a right DLT should not be left in place during the postoperative period because of the likelihood that it will become malpositioned with patient movement.

For bronchial blockers inserted via a large (≥8 mm ID) single-lumen ETT to achieve lung isolation, risks associated with tube exchange are avoided. At the end of the surgical procedure the blocker balloon is deflated and the blocker is then simply removed. In rare instances, unanticipated difficulty with reexpansion of a collapsed lung after use of a bronchial blocker may occur due to inability to deflate the blocker balloon [87]. (See "One lung ventilation: General principles", section on 'Re-expanding the nonventilated lung'.)

SUMMARY AND RECOMMENDATIONS

●Types of lung isolation devices – One lung ventilation (OLV) can be achieved with three general types of devices (see 'Types of lung isolation devices' above):

•Double-lumen endobronchial tube (DLT), either left-sided or right-sided (figure 2 and figure 3)

•Bronchial blocker placed through a standard endotracheal tube (table 3 and picture 7 and picture 8 and picture 9 and picture 10 and picture 11)

•Single-lumen endotracheal tube (ETT) or endobronchial tube, in rare circumstances (picture 12)

●Positioning lung isolation devices – We suggest that lung isolation devices be positioned with fiberoptic bronchoscopy (FOB) guidance (Grade 2C), with confirmation by auscultation (algorithm 1):

•(figure 4) – (See 'Positioning left double-lumen tubes' above.)

•(figure 7) – (See 'Positioning right double-lumen tubes' above.)

•(See 'Positioning bronchial blockers' above.)

●Selection of a lung isolation device

•DLT selection – When lung isolation is necessary to prevent soiling or contamination from one lung to the other (eg, due to bleeding or infection), we typically select a DLT rather than a bronchial blocker because lung isolation can be established before the source is identified, a DLT is less likely to become malpositioned, and maintains the ability to employ FOB, ventilate, or suction the pathologic lung. (See 'Double-lumen tubes versus bronchial blockers' above and 'Need for unilateral lung protection' above.)

-Selecting DLT size – The largest DLT likely to fit easily within the selected mainstem bronchus should be used. We suggest choosing the DLT size based on patient sex and height (table 1), rather than radiographic measurements of bronchial diameter (Grade 2C). (See 'Selecting double-lumen tube size' above.)

-Selecting a left or right DLT

Choice of a left DLT – For most elective thoracic surgical procedures requiring OLV, we suggest using a left DLT rather than a right DLT or a bronchial blocker (Grade 2B). Right DLTs and bronchial blockers are more difficult to place and more likely to move during surgery, requiring repositioning facilitated by FOB. However, bronchial blockers may be associated with fewer complications (eg, sore throat, hoarseness, or airway injury including airway rupture). (See 'Double-lumen tubes versus bronchial blockers' above and 'Left versus right double-lumen tubes' above and 'Elective thoracic surgery' above.)

Choice of a right DLT – For surgery involving the left mainstem bronchus, including left pneumonectomy, we use a right DLT to avoid interference with the surgical field. (See 'Left pneumonectomy or bronchial surgery' above.)

•Bronchial blocker selection – A bronchial blocker rather than a DLT may be preferred for selected patients (see 'Double-lumen tubes versus bronchial blockers' above):

-Abnormal tracheobronchial anatomy (see 'Abnormal tracheobronchial anatomy' above)

-Preexisting presence of an ETT (see 'Presence of an endotracheal tube' above)

-Preexisting presence of a tracheostomy (see 'Presence of a tracheostomy' above)

-Anticipated difficult airway (algorithm 2) (see 'Anticipated difficult airway' above)

-Anticipated prolonged postoperative mechanical ventilation (see 'Need for postoperative ventilation' above)

-Need for collapse of a single lung lobe (see 'Ability to achieve selective lobar blockade' above)

•Single-lumen ETT selection – A single-lumen ETT ≥8 mm internal diameter (ID) placed in an endobronchial position may be selected for lung isolation in emergency circumstances such as massive pulmonary hemorrhage. (See 'Single-lumen endotracheal tubes' above and 'Massive hemoptysis' above.)