Techniques to achieve lung isolation during general anesthesia

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 tube [DLTs], bronchial blocker [BB], specialized single-lumen endotracheal tube [ETT]) and selection of the most appropriate device for various clinical situations.

To ensure correct positioning of either a DLT or a BB, expertise in laryngoscopy and flexible intubating scope (FIS) techniques are necessary. General principles for these techniques are reviewed in separate topics. (See "Airway management for general anesthesia in adults" and "Anesthesia for adult bronchoscopy", section on 'Anesthetic techniques for flexible bronchoscopy'.)

Indications, contraindications, physiology, strategies for ventilation and management of hypoxemia, and complications of OLV are reviewed separately. (See "Intraoperative one-lung ventilation".)

AIRWAY ANATOMY — 

A working knowledge of tracheobronchial anatomy is essential for successful airway endoscopy and placement of a lung isolation device. In one trial, 39 percent of anesthesiologists with limited thoracic experience were unable to successfully achieve lung isolation due to unfamiliarity with the endoscopic view of the airway [1]. This failure rate was independent of which device was selected.

Airway anatomy 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 [2]. The average tracheal diameter is 22 mm in males and 19 mm in females (figure 1) [3]. The cricoid cartilage is the narrowest portion of the airway in adults with an average diameter of 17 mm in males and 13 mm in females.

●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 double-lumen endotracheal tube (DLT) can be challenging (see 'Placement of right-sided DLTs' 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) [4]. For this reason, maintaining ideal position of a lung isolation device is generally easier on the left than on the right side. (See 'Placement of left-sided DLTs' 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.

DEVICE SELECTION

General considerations — Selection of a lung isolation device is based on patient-specific and procedure-specific considerations. Lung isolation may be achieved with the following devices and methods [5]:

●Double-lumen endotracheal tube (DLT) – A DLT is most commonly used, and a left DLT is preferred in most scenarios. A DLT has separate tracheal and bronchial lumens; essentially, it is two tubes connected side by side.

A DLT permits isolation, selective ventilation, and intermittent suctioning of either lung [6-8]. The shorter tracheal lumen has a high-volume, low-pressure tracheal cuff and is positioned with the opening above the tracheal carina. DLTs are labeled either left- or right-sided, depending on which mainstem bronchus the longer tube is designed to fit (figure 2 and figure 3). 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. 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).

A left DLT is the most commonly used device for lung isolation for most surgical procedures, as discussed below.

●Bronchial blocker (BB) – A BB is commonly placed via a single-lumen endotracheal tube (ETT), but may also be placed via a tracheostomy, or through a supraglottic airway (SGA) [9]. Placed within the mainstem bronchus, inflation of the low-volume, high-pressure BB balloon will impede flow to that entire lung.

The need for tube exchange (to a single-lumen ETT) at the end of the surgical procedure is avoided with use of a BB inserted via a large (≥8 mm inner diameter [ID]) single-lumen ETT to achieve lung isolation. Thus, risks associated with tube exchange at the end of a surgical procedure are avoided if postoperative controlled ventilation will be necessary. (See "Intraoperative one-lung ventilation", section on 'Re-expanding the nonventilated lung'.)

A BB may also be used to isolate a smaller specific lung segment in rare situations. (See 'Need for selective lobar blockade' below.)

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

Basic characteristics of commercially available BBs are summarized in the table (table 1). These include:

•Arndt wire-guided endobronchial blocker (picture 7)

•Cohen tip-deflecting endobronchial blocker (picture 8)

•Fuji Univent (picture 9)

•Univent tube with a Fuji Uniblocker (picture 10)

•Rusch EZ-Blocker (picture 11), which may be used for bilateral surgery without the need for repositioning

●Single-lumen ETT positioned into a mainstem bronchus – Insertion of a single-lumen ETT (picture 12) into a mainstem bronchus may be the most available and familiar option to achieve lung isolation in some clinical scenarios, particularly for patients who are not in an operating room setting.

Ease of insertion and positioning — DLTs are positioned slightly faster, more easily, and are less likely to become malpositioned during surgery than BBs. Time required to place a lung isolation device is a measurable surrogate for ease of insertion. A 2015 meta-analysis of 39 trials comparing efficacy and adverse effects of DLTs versus BBs 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) [10,11]. (See 'Placement of left-sided DLTs' below.)

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 BB could be placed within one to four minutes by experienced thoracic anesthesiologists [6-8,12]. However, anesthesiologists with limited experience with lung isolation required six to nine minutes to place either a left DLT or a BB in one trial, and one-third of all devices were not properly positioned after their attempts [1].

Subjective experience is also a factor in evaluating ease of insertion. For example, although the time of insertion of an EZ-Blocker was longer compared with a DLT, ratings of ease were comparable or better for this blocker in some trials [12,13].

Reduced need for intraoperative repositioning — Despite proper placement of a lung isolation device, subsequent malpositioning can result from changes in the patient's position (eg, from supine to lateral), extension or flexion of the head, overinflation of the device cuff, or surgical manipulations.

●Left DLT versus right DLT – Left-sided DLTs are easier to position and have a larger margin for error compared with right-sided DLTs, due to the longer length of the left mainstem bronchus [14,15]. The 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 [4]. (See 'Airway anatomy' above.)

Positioning of a right DLT requires precision in both depth of insertion and rotation to maintain the 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 'Placement of right-sided DLTs' below). As a result, malpositioning of right DLTs is a concern. 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 one-lung ventilation (OLV) in most patients [16]. For these reasons, we restrict their use to situations in which a right DLT is specifically indicated, such as left mainstem surgery and left pneumonectomy. (See 'Left mainstem surgery and left pneumonectomy' below.)

●Left DLT versus BB – Compared with a left DLT, BBs are more likely to require repositioning, particularly when placed within the short right mainstem bronchus to achieve right lung isolation [7,17-19]. In one study comparing types of BBs, 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); the balloon design for this blocker is now spherical [7].

While malpositioning is generally a benign inconvenience, rare life-threatening complications can occur. In one case report, a BB 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 BB balloon [20]. 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].

Accessibility of the nonventilated lung — DLTs provide superior access to the nonventilated lung. This allows:

●Access to the nonventilated lung for bronchoscopy when necessary, and for suctioning of blood or secretions. In contrast, the center lumen in BBs is too small (1.4 to 2 mm) to allow passage of a flexible intubating scope (FIS) 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 BB balloon during any reexpansion efforts.

●Application of CPAP to the nonventilated lung during OLV through a DLT. This has also been described with use of a Univent blocker (picture 9) [22,23].

●Bronchoscopic confirmation that the intended lobar take-off is occluded before the surgeon staples and transects the bronchus (eg, for lung lobectomy procedures).

Prevention of soiling — Massive hemoptysis or unilateral pulmonary infections (eg, bronchiectasis, lung abscess, infected cyst) that produce copious amounts of purulent material require lung isolation to protect the contralateral “good” lung from contamination. To prevent soiling, lung isolation must be achieved as quickly as possible using whichever device is available and familiar to the operator

●Double lumen tube – A DLT is typically selected to provide a better seal and superior access for suctioning compared with a BB [24-31]. Placement of a DLT allows lung isolation to be established before the source is identified, and the ability to ventilate, suction, or insert a FIS into the pathologic lung is maintained. 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 soiling necessitates lung isolation in the intensive care unit (ICU) for a prolonged period. (See "Evaluation and management of life-threatening hemoptysis".)

●Bronchial blocker – With an ETT in situ, soiling may be prevented by placing a BB in the mainstem bronchus of the pathologic lung [32]. However, placement of a BB using an FIS may be difficult if profuse bleeding or secretion obscures the bronchoscopic views. Using a BB in these situations also limits access to the pathologic lung once the blocker is in place. Importantly, lung isolation and protection may be compromised if the bronchial blocker is dislodged by the weight of blood or infection pushing on the BB balloon. This risk increases if the patient requires surgical intervention in the lateral position.

●Endobronchial intubation with an ETT – In remote locations out of the operating room, endobronchial intubation of the “good” lung with a single-lumen ETT may be the familiar and the only option available. The ETT should be positioned in the main stem bronchus of the “good” lung that requires protection. This may be difficult in the presence of massive hemoptysis or copious secretions. For right mainstem bronchus placement, the ETT should be turned to the right as it is advanced. For the left mainstem bronchus, turn the patient’s head to the right, then advance with the ETT turned to the left. Successful placement is confirmed if breath sounds are only auscultated from the “good” lung. FIS should be used to confirm placement when available.

Left mainstem surgery and left pneumonectomy — We use a right-sided DLT for left pneumonectomy and other procedures involving resection of the left mainstem bronchus. Use of a left DLT or BB 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 an airway suction catheter has become entrapped in the bronchial staple line [33]. The anesthesia provider must ensure that any device placed in the bronchus on the surgical side has been completely retracted prior to staple deployment. These risks are minimized by using a right DLT instead of a BB or left-sided DLT for left pneumonectomy or bronchial surgery [34].

Presence of an endotracheal tube — In patients with a single-lumen ETT placed before arrival in the operating room, a BB may be the simple option, particularly if prolonged postoperative mechanical ventilation is anticipated (see 'Need for postoperative ventilation' below). The use of a DLT would require tube exchanges at the beginning and the end of the surgical procedure, potentially increasing the risk of complications.

Presence of a tracheostomy — In a patient with a tracheostomy, we use a BB 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 [35-40]. Alternatively, the BB may be placed orally through the vocal cords, then alongside the tracheostomy tube [39,41]. Flexible fiberoptic bronchoscopy is typically used to confirm optimal placement [40]. Although there are reports of small DLTs being placed via a tracheostomy, positioning can be difficult [42,43].

Anticipated difficult airway — Securing the airway is the primary goal [37]. Most commonly, whether the patient is awake or sedated, the difficult airway is first secured with a single-lumen ETT (picture 12) [35]. The next decision is whether to use a BB or to exchange the single-lumen ETT for a DLT:

●For left-sided lung isolation, the use of a BB is a reasonable and straightforward option.

●For right-sided lung isolation, the risk of BB displacement from the short right mainstem bronchus must be weighed against the potential risks of exchanging for a DLT.

Exchanging a single-lumen ETT for a DLT incurs the risk of exchange failure and airway injury [37]. To minimize risk, an airway exchanger with a hollow center as well as universal adaptors to facilitate oxygenation should be used [44]. 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 [23].

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 [35,45]. Furthermore, topical local anesthesia is often inadequate to blunt the intense laryngeal and carinal stimulation that occurs during DLT placement.

Establishing lung isolation in patients who may be difficult to intubate is addressed in the algorithm (algorithm 1). Securing the airway is the primary goal [35]. General considerations for difficult airway management are discussed separately. (See "Management of the anatomically difficult airway for general anesthesia in adults".)

Abnormal tracheobronchial anatomy — In patients with distorted or abnormal tracheobronchial anatomy (eg, a pericarinal lesion), lung isolation may be best achieved with a BB [35]. 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 BB under direct bronchoscopic guidance may provide temporary occlusion of the fistula to permit healing or maintenance of respiratory stability until surgical repair is achieved [46].

Most patients with abnormal tracheobronchial anatomy can be managed with a BB, but some may have anatomy that hinders proper placement of either a DLT or a BB.

Need for postoperative ventilation — In the postoperative setting, single-lumen ETTs are often preferred over DLTs due to physician and nursing staff familiarity in the ICU. Standard single-lumen ETTs also cause less irritation of the carina and less minor airway trauma. Of note, the preference for single-lumen ETTs is not related to airway resistance. In a study comparing airway devices for small adults, a 37 French DLT had less airway resistance than a 7.5 mm ID ETT [30].

When postoperative ventilation is anticipated, a BB may be a reasonable choice. At the end of the surgical procedure, the blocker balloon is deflated, and the blocker is then simply removed. In contrast, if a DLT is used intraoperatively, it would need to be exchanged for a single lumen tube at the end of the case.

If only a short period of postoperative ventilation is necessary, a left DLT may be temporarily 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.

Need for selective lobar blockade — For patients at high risk for hypoxemia during one-lung ventilation (OLV; eg, patients with severe pulmonary disease or prior lung resection who would not tolerate collapse of the entire lung), a BB may be used to achieve collapse of only a single lung lobe on the surgical side rather than an entire lung [47,48]. The goal is to limit the extent of hypoxemia while providing adequate surgical exposure. (See "Intraoperative one-lung ventilation", section on 'Management of hypoxemia'.)

Thoracic aortic surgery — For aortic arch and descending thoracic aortic surgery, lung isolation is commonly achieved with a left DLT or a left-sided BB (see "Anesthesia for open descending thoracic aortic surgery", section on 'Induction and airway management'). A right-sided DLT is also an option. In patients where the left mainstem bronchus is distorted from extrinsic aortic compression, placement of a left DLT may be difficult, and relatively contraindicated as manipulation into the left mainstem risks aneurysm rupture [49,50].

Minimally invasive cardiac surgery — OLV is necessary for selected minimally invasive cardiac surgical procedures. For minimally invasive coronary artery bypass, access is through the left chest. For these patients, if postoperative ventilation is planned, use of a BB avoids the need to exchange a DLT for a single-lumen ETT at the end of the procedure (see 'Need for postoperative ventilation' above). Intraoperative malposition has not been reported to occur with a higher incidence with the use of BBs compared with DLTs during these cardiac surgical procedures [51-53]. For minimally invasive mitral valve surgery where the access is through the right chest, a DLT with exchange to a single lumen tube at the end of the case for postoperative ventilation may be preferred over placing a BB in the short right main stem bronchus, which is at risk of malpositioning.

PLACEMENT OF LUNG ISOLATION DEVICES — 

We suggest that lung isolation devices be positioned with bronchoscopic guidance using a flexible intubating scope (FIS), and with confirmation by auscultation.

Double-lumen tubes

Selection of double-lumen tube (DLT) 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 typically use the patient's sex and height to choose an appropriate DLT tube size since this method is simple and effective (table 2) [17]. Studies have demonstrated a correlation between height and left bronchial diameter [54,55]. Other methods are based on radiographic measurements of bronchial and/or cricoid ring diameter (table 3) [55-58]. 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 [57-60].

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 [56]. Generally, the bronchial diameter of the ideal DLT should be 1 to 2 mm smaller than the diameter of the patient's mainstem bronchus [17]. The insertion of an oversized DLT may traumatize or even rupture the trachea or bronchus [61,62]. 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 [14,21,54,63]. (See 'Avoiding airway trauma' below.)

General considerations for DLT placement — The endobronchial tip of a double-lumen tube (DLT) is inserted through the vocal cords under direct laryngoscopy, and the stylet is removed. The tracheal cuff is then inflated to facilitate ventilation. For surgical procedures in the lateral position, the DLT may shift during positioning. To minimize the risk of airway trauma and obstruction, leave the bronchial cuff deflated during this stage. Once the patient is positioned and proper placement of the bronchial lumen is confirmed, the bronchial cuff is inflated. (See 'Placement of left-sided DLTs' below and 'Placement of right-sided DLTs' below.)

Bronchoscopy is the gold standard for confirming ideal DLT position. For commonly-used adult DLT sizes (35 to 41 French [Fr] (table 2)), a flexible intubating scope (FIS) <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 bronchoscopy with a FIS identified malpositioning in an additional 79 patients [64]. Malpositioning of a DLT is the most common cause of intraoperative hypoxemia during one-lung ventilation (OLV) [65]. 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 [14].

To achieve selective OLV, the tube/lumen for the contralateral lung is clamped. For example, with a left-sided DLT, 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 that are described in a separate topic. (See "Intraoperative one-lung ventilation", section on 'Improving deflation of the nonventilated lung'.)

Placement of left-sided DLTs — 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.

●Using a flexible intubating scope (FIS) – 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, a FIS 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 [65]. 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 [66].

●Using auscultation – 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; 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 2).

However, studies have shown that endobronchial intubation of the right mainstem bronchus occurs in 24 to 39 percent of "blind" insertions of a left DLT without use of a FIS [14,67]. 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 [67]. Confirmation with FIS is still recommended after auscultation.

●Other methods – While bronchoscopy remains the gold standard for confirmation of DLT position, one study demonstrated that inserting the DLT to a predetermined depth based on measurements of distance from the vocal cords to the carina on the preoperative computed tomography (CT) study resulted in less frequent need to reposition the DLT compared with blind insertion of a DLT [68]. 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 [69-71].

Placement of right-sided DLTs — 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.

●Using a FIS for initial positioning – 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 [72,73]; 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).

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 [4]. If the device is placed slightly deep, occlusion of the RUL bronchus may occur, but if placed too close to the carina it may retract proximally preventing adequate lung isolation.

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, identification of the bronchus intermedius and the direction of the RML/RLL carina with an FIS 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).

●Use of a FIS for reconfirmation of positioning – 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). Such 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 an FIS is prudent after any change in patient position and critically important if hypoxemia develops. (See 'Reduced need for intraoperative repositioning' above.)

●Using Auscultation – As with left-sided DLTs, auscultation may be used as a preliminary check of right-sided DLT positioning. However, FIS is needed to ensure the side orifice is aligned with the RUL, and that the bronchial cuff is well positioned.

Bronchial blockers (BBs) — Typically, a BB is placed through the lumen of a standard single-lumen ETT, with the use of an FIS [74]. However, if the ETT is too small to accommodate both the BB and the FIS, the bronchoscope may be placed separately through the glottis on one side of the ETT. The BB is then passed via the ETT and positioned with bronchoscopic assistance to visualize airway anatomy during final positioning.

Each type of commercially available BB has a unique mechanism to assist placement (table 1), but all require guidance using an FIS:

●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 BB. 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 BBs. Under FIS 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.

AVOIDING AIRWAY TRAUMA

●Airway rupture – Airway rupture is rare with double-lumen tubes (DLTs; (<0.2 percent) but is associated with mortality as high as 42 percent [62,75,76]. In reviews of airway rupture, the most frequently cited factor was overdistension of either the bronchial or the tracheal cuff of the DLT [62,63].

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. Overinflation can damage the tracheobronchial mucosa. Ideally, an appropriately sized DLT is used (see  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 [77].

-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

-Traumatic airway injury

-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 FIS guidance if resistance is encountered during blind advancement

•Inflating the bronchial cuff of the DLT after the patient is turned to the lateral position

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

-Avoid N₂O

●Postoperative sore throat – Postoperative sore throat is common, occurring in as many as half of patients who have a double-lumen endotracheal tube (DLT) [78]. A 2015 meta-analysis noted that BBs were associated with a lower incidence of sore throat (odds ratio [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) [10,11]. One study noted that ultrasound-guided block of the internal branch of the superior laryngeal nerve with local anesthetic can decrease the incidence and severity of postoperative sore throat after DLT placement [78].

●Other complications – Pneumonia and duration of hospitalization were similar after placement (557/798 patients) compared with DLT placement (41/798) [79].

SUMMARY AND RECOMMENDATIONS

●Airway anatomy – A working knowledge of tracheobronchial anatomy is essential for successful airway endoscopy and placement of a lung isolation device, as detailed above. (See 'Airway anatomy' above.)

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

•Double-lumen tube (DLT) – We typically select a DLT rather than a bronchial blocker (BB) when lung isolation is necessary to prevent soiling or contamination from one lung to the other (eg, due to bleeding or infection). Advantages of DLTs include ease of insertion and positioning, quality of lung isolation that can be established before the source is identified, less likelihood of malpositioning, and maintenance of the ability to use a FIS, ventilate, or suction the pathologic lung.

•Left-sided versus right-sided DLTs – DLT, either left-sided or right-sided (figure 2 and figure 3).

-Left-sided DLTs – For most elective thoracic surgical procedures requiring OLV, we suggest a left DLТ rather than a right DLΤ or a BB (Grade 2C). Reasons include ease of insertion and positioning, quality of lung isolation, less likely need for intraoperative positioning, and accessibility of the nonventilated lung. (See 'Ease of insertion and positioning' above and 'Reduced need for intraoperative repositioning' above and 'Accessibility of the nonventilated lung' above.)

-Right-sided DLTs – We use a right-sided DLT for left pneumonectomy and other pulmonary resection procedures involving resection of the left mainstem bronchus. (See 'Left mainstem surgery and left pneumonectomy' above.)

-Site-dependent selection of right- or left-sided DLT – In some settings (eg, massive hemoptysis, unilateral pulmonary infection, planned unilateral lung lavage), choice of a left- versus right-sided DLT depends on the side of the pulmonary pathology and planned surgical procedure. (See 'Prevention of soiling' above.)

•Bronchial blockers – A BB is placed through a standard endotracheal tube (ETT), and is often used is often used for patients who already have an ETT or a tracheostomy in place, as well as for those who will need postoperative ventilation, have an anticipated difficult airway or abnormal tracheobronchial anatomy, or may need selective lobar blockade. Basic characteristics of commercially available BBs are summarized in the table (table 1).

•Single-lumen ETT – A specialized or standard single-lumen ETT can be placed within the right or left mainstem bronchus (picture 12), in situations requiring immediate lung isolation (eg, to prevent soiling of a healthy lung with blood or purulent material from the other lung), or in patients with abnormal tracheobronchial anatomy that hinders proper placement of either a DLT or a BB.

●Placement of lung isolation devices – We suggest that lung isolation devices be positioned with bronchoscopic guidance using a flexible intubating scope (FIS) (Grade 2C), and with confirmation by auscultation (algorithm 2).

•Selection of DLT size – The largest DLT likely to fit easily within the selected mainstem bronchus should be used. DLT size is based on patient sex and height (table 2). Alternative methods include radiographic measurements of bronchial diameter (table 3). (See 'Selection of double-lumen tube (DLT) size' above.)

•General considerations for DLT placement – Bronchoscopy is the gold standard for confirming ideal DLT position. (See 'General considerations for DLT placement' above.)

-Placement of left-sided DLT (figure 4) – (See 'Placement of left-sided DLTs' above.)

-Placement of right-sided DLT (figure 7) – (See 'Placement of right-sided DLTs' above.)

•Placement of BBs – Each type of commercially available BB has a unique mechanism to assist placement (table 1), but all require guidance using an FIS (see 'Bronchial blockers (BBs)' above):

-Arndt wire-guided endobronchial blocker (picture 7).

-Cohen tip-deflecting endobronchial blocker (picture 8).

-Fuji Univent (picture 9). The blocker is also available separately as the Fuji Uniblocker (picture 10).

-Rusch EZ-Blocker (picture 11).

●Avoiding airway trauma – Postoperative sore throat is common and higher after use of a DLT compared with a single-lumen ETT. More serious complications (eg, airway trauma with rupture, pneumonia) are rare. (See 'Avoiding airway trauma' above.)