Lung separation techniques are designed to facilitate surgical exposure and provide one-lung ventilation (OLV) in patients undergoing thoracic, mediastinal, cardiac, vascular, esophageal, or selective spine surgery.^1–3 Lung separation can be achieved with two different techniques. The first involves the double-lumen endotracheal tube (DLT) technique. This device is made of disposable polyvinyl, chloride material, or silicone material.^4,5 The DLT is a bifurcated tube with both an endotracheal and an endobronchial lumen and can be used to selectively achieve separation of either the right or left lung.^6,7 Over time, several modifications have been made to the DLT to improve quality of placement and patient safety. A newly designed VivaSight® DLT has an integrated camera, allowing continuous visualization of tube position within the trachea.⁸ In addition, there is the ECOM (Endotracheal Cardiac output Monitor)-DLT® that has multiple flexible surface sensors attached to the endotracheal cuff of the DLT that, when connected to a monitor measure the aortic blood flow by the bioimpedance method. Based upon an algorithm, it can record cardiac output, stroke volume, and systemic vascular resistances.⁹ The second technique involves using an endotracheal blocker to block the mainstem bronchus to allow lung collapse distal to the occlusion.^10,11 Currently, there are several bronchial blockers clinically available to facilitate lung separation and provide OLV. Initially, a single-lumen endotracheal tube with an incorporated bronchial blocker, such as the torque control blocker Univent was used.¹² Presently, endobronchial blockers are used independently through a single-lumen endotracheal tube. Several are available: the wire-guided endobronchial blocker (Arndt blocker)¹³ (Cook Critical Care, Bloomington, IN), the Cohen tip-deflecting endobronchial blocker¹⁴ (Cook Critical Care, Bloomington, IN), the Fuji Uniblocker¹⁵ (Fuji Corp, Tokyo Japan), or the EZ-Blocker^16,17 (Teleflex Medical, Morrisville, NC).

The most common indications for lung separation and OLV are for providing a still operative field and surgical exposure or for lung isolation, for prevention of contamination to the contralateral lung from bleeding or pus material, and during the application of differential lung ventilation or for continuing of the airway gas exchange, such as bronchopleural fistula, and during a lung lavage.¹⁸

Double-Lumen Endotracheal Tubes

There are two versions of DLTs; a left-sided and a right-sided, which are designed to accommodate the unique anatomy of each mainstem bronchus. DLTs are available from different manufactures: Mallinckrodt Broncho-Cath (St. Louis, MO), Sheridan Sheri-I Bronch (Argyle, NY), Rüsch (Duluth, GA), Portex (Keene, NH), VivaSight DLT from Ambu (St. Louis, MO), the Silbroncho from Fuji (Japan), and the ECOM-DLT (San Juan Capistrano, CA). The sizes of the DLTs vary among manufactures. The smallest available is 26 French (Fr) followed by 28, 32, 33, 35, 37, 39, and 41 Fr. Table 16.1 displays the external and internal diameters of the different-sized DLTs and the size of the flexible fiberoptic bronchoscope recommended.

Size Selection of the Double-Lumen Endotracheal Tubes

A properly sized DLT is one in which the main body of the tube passes without resistance through the glottis and advances easily within the trachea, and in which the bronchial component passes into the selected bronchus without difficulty or resistance. A DLT that is too small in size requires a larger endobronchial cuff volume (i.e., >3.0 mL) for effective blockade, which might increase the incidence of malposition, or can result in a DLT that is too short to be properly positioned in the target bronchus, resulting in failure to achieve lung separation. A DLT that is too small may migrate deeply into a bronchus, resulting in airway trauma or development of a pneumothorax if both the tracheal and the endobronchial lumen are inserted into one bronchus, resulting in an overinflated large tidal volume into a single lobe.^19,20 Fig. 16.1 displays an undersized left-sided DLT that migrated distally into the left-main stem bronchus producing a pneumothorax and lack of ventilation in the right lung and left lower lobe.

In addition, an undersized DLT might present a higher resistance to gas flow and increase intrinsic autopositive end-expiratory pressure as compared with the wider lumen of larger DLTs.²¹ In a study performed in adult cadavers, it was shown that the cricoid ring diameter never exceeds the diameter of the glottis. If a DLT encounters resistance when passing the glottis, it is likely that the DLT would encounter resistance while passing the cricoid ring.²² An oversized DLT can potentially produce trauma to the airway,²³ therefore it is important to select the appropriate size for the patient to prevent complications.

A common challenge with the appropriate size selection of a DLT is the lack of objective guidelines to demonstrate the optimal method to determine the best size for the patient. There is no universal consensus on the best method of selecting the size of the DLT. Some studies have selected the left-sided DLT based on height and sex of the patient. Using this method, unfortunately, the appropriated size of the left-sided DLT could not be predicted in the Asian patient population.²⁴ Others have reported that the measurement of the tracheal diameter at the level of the clavicle on the preoperative posterior anterior chest radiograph can be used to determine proper left-sided DLT size. These methods lead to a 90% increase in the use of larger left-sided lumen tubes (i.e., 41 Fr DLT in men and 39 Fr in women).²⁵ However, a study involving Asian patients by Chow et al.²⁶ using the same methodology of Brodsky et al.²⁵ found this approach less reliable. In the Chow et al. study,²⁶ the overall positive predictive value for the proper left size of a left-sided DLT was 77% for men and 45% for women. This method and the patient’s sex and height seem to have limited use in patients with smaller statures.

An interesting study by Amar et al.²⁷ involving thoracic anesthesiologists, has shown that the use of a smaller DLT (35 Fr left-sided DLT) rather than a conventionally large-sized DLT (i.e., 39 or 41 Fr) was not associated with any difference in clinical intraoperative outcomes, regardless of the patient size or gender in 300 patients undergoing thoracic surgery requiring lung separation. However, in their study, only 51 (35%) of the patients who received a 35 Fr DLT were males and 92 (65%) were females. In practice, ­women usually receive a 35 FrDLT; therefore the question of whether or not a 35 Fr is favorable for all patients remains unclear.

A different method to predict the proper size of a right-sided or left-sided DLT is a three-dimensional image reconstruction of tracheobronchial anatomy generated from spiral computed tomography (CT) scans combined with superimposed transparencies of DLTs.²⁸

Another interesting alternative is the use of tracheal ultrasonography measurements combined with clinical parameters to select the appropriate size of a left-sided DLT. Roldi et al.²⁹ has combined the ultrasound measurement of the tracheal diameter with the patient lying in supine position, and the probe placed just above the sternoclavicular junction to the neck in transverse view. They were able to estimate the tracheal diameter and measure it in mm. Fig. 16.2 displays the tracheal ultrasound examination with the linear probe placed perpendicular to the neck (panel A), the outer tracheal diameter is measured on this transverse view (mm) (panel B). Their study showed that patients’ height and sex, plus the use of tracheal ultrasonography to measure the tracheal diameter, optimized the proper selection of a left-sided DLT, reducing significantly the use of oversized and underside DLTs. One of the limitations with this method is that it requires expertise in tracheal ultrasonography.

The information derived from these studies suggests that chest radiographs, CT scans, and ultrasonography of the trachea are valuable tools when selecting a proper DLT size, in addition to their proven value in assessment of any abnormal tracheobronchial anatomy. These images and measurements should be reviewed before placement of a DLT. Particular emphasis should be made in viewing a posterior-anterior chest radiograph to assess the shadow of tracheobronchial anatomy along with bronchial bifurcation. It is estimated that in 75% of the films, the left mainstem bronchus shadow is seen. Fig. 16.3 shows the anatomic changes that occur in a 60-year-old man with severe chronic obstructive pulmonary disease (COPD) in which the deviated trachea and narrow bronchus can be appreciated. It is crucial to recognize any distorted anatomy identified in the film before placement of DLTs.³⁰

Methods of Insertion of Double-Lumen Endotracheal Tubes

Fig. 16.4 shows the most common indications for the use of a DLT for lung separation. Two techniques are most commonly used by anesthesiologists when inserting and placing a DLT. The first is a blind technique, when the DLT is passed with direct laryngoscopy, then it is turned to the left (for a left-sided DLT) or right (for a right-sided DLT) after the endobronchial cuff has passed beyond the vocal cords. The DLT is then advanced until it reaches the depth of insertion at the teeth, which is approximately 29 cm for both men and women if the patient’s height is at least 170 cm.³¹ The second technique involves the use of the flexible fiberoptic bronchoscope as a guide to the selected main bronchus, where the tip of the endobronchial lumen is guided after the DLT is passed the vocal cords. A study by Boucek et al.³² comparing the blind technique versus the fiberoptic bronchoscopy–guided technique, showed that of the 32 patients who underwent the blind technique approach, primary success occurred in 30 patients. In contrast, in the 27 patients receiving the brochoscopy-guided technique, primary success was initially achieved only in 21 patients, and eventually successfully placed in 25 patients. In addition, two patients in each group required an alternative method for tube placement. Fig. 16.5A shows the blind method technique and Fig. 16.5B shows a flexible fiberoptic bronchoscopy guidance technique for placement of a left-sided DLT.

In recent years, video laryngoscopy has been introduced as an important tool in the management of patients with expected or unexpected difficult airways. Clinical studies have shown that video laryngoscopies improve visualization of laryngeal structures and facilitate insertion of DLTs at first pass.³³ In a study by Purugganan et al.,³⁴ the use of the C-MAC video laryngoscope has been compared with the standard Macintosh blade and with the Miller blade during DLT intubation in patients with normal airways. The authors showed that video laryngoscopy was similar to the views obtained with a Miller blade while passing a DLT. In contrast, the Macintosh blade group has reported higher difficult intubations with the DLTs. Another study by Russell et al.,³⁵ comparing a GlideScope® with the Macintosh laryngoscope for a DLT intubation, showed that the overall rate of successful endobronchial intubation was easier with the Macintosh blade compared with the GlideScope®. In addition, the incidence of postoperative voice changes was less common in the Macintosh group, therefore the authors do not recommend the routine use of the GlideScope® for DLT insertion in patients with normal airways. In contrast, a recent study by Chastel et al.,³⁶ using the Airtraq DL® video laryngoscope during placement of a DLT, showed an improved exposure of the supraglottis during insertion of the DLT in patients with normal airways. In the views using the Airtraq DL® video laryngoscopy, patients were graded Cormack and Lehane I (on the Cormack-Lehane grading system), as compared with the Macintosh laryngoscopy. A recent study by El-Tahan et al.,³⁷ comparing the Macintosh laryngoscope blade with video laryngoscopes (GlideScope®, Airtraq®, and King Vision® video laryngoscope), showed that first pass success while passing a DLT was similar with all the four laryngoscopes studied. However, rupture of the tracheal cuff of the DLT occurred in the Macintosh, the ­GlideScope®, and the King® video laryngoscopes, whereas none were reported within in the Airtraq®. The incidence of sore throat was not different among the groups studied.

An interesting report was published by Liu et al.,³⁸ who performed a systematic review and metaanalysis of 12 studies comparing the use of video laryngoscopes versus the Macintosh laryngoscope during intubation with DLTs. They concluded that video laryngoscopy use for DLT ­intubation was superior to the Macintosh groups. Of interest, the authors showed an increased incidence of malposition rates at first pass of the DLT in the groups intubated with video laryngoscopy. It is possible that diverting the attention to the monitor screen contributed to the loss of orientation of the rotation of the DLT by the anesthesiologist. There is no designated stylet for a DLT. When anon ­channeled video laryngoscopy devices such as the GlideScope, the DLT should be curved to mimic the shape of the blade prior to intubation. Overall, the use of a video laryngoscope while inserting a DLT has a learning curve and will depend on the experience of the operator and the clinical necessity at laryngoscopy.

Left-Sided Double-Lumen Endotracheal Tubes

Left-sided DLT is the most commonly used device to achieve lung separation because it has a greater margin of safety than right-sided DLT.^39–42 The indications for a left-sided DLT include lung separation: that is, any operation that requires surgical exposure of the chest cavity with a lung collapse. Left-sided DLT is mandatory in cases of lung isolation to protect the dependent lung from a contralateral contamination, such as a lung abscess, lung cyst, pulmonary hemorrhage, or bronchopulmonary lavage. In addition, a left-sided DLT is used in cases for control and continuity of the airway gas exchange when bronchopleural fistula or giant bullae are present. Contraindication for placement, such as difficult airway or obstruction, to the entrance of the left main stem bronchus precludes the use of the left-sided DLT. Box 16.1 displays the indications and contraindications for left-sided DLT.

To identify which is the right mainstem bronchus while placing a left-sided DLT, the fiberoptic bronchoscope is advanced through the tracheal lumen below the main tracheal carina to the right side approximately 1 to 2 cm, at which point the orifice of the right upper lobe (RUL) bronchus is seen at 3 to 4 o’clock on the lateral wall. By advancing the fiberoptic bronchoscope inside the right upper bronchus, it should display a clear view of three orifices (apical, anterior, and posterior segments). This is the only structure of the tracheobronchial tree that has three orifices.⁴² Identifying the RUL orifice should be part of the routine bronchoscopy in thoracic anesthesia because, with secretion and in the lateral position, it not always easy to recognize the proper cranial orientation. Fig. 16.6 shows the most commonly used DLT. Fig. 16.7 shows the optimal position of the left-sided DLT as seen with a fiberoptic bronchoscope. Fig. 16.8 shows the correct position where the semilunar blue cuff is in view at the carina and the incorrect position in which that cuff edge is not seen by the fiberoptic bronchoscope.

Right-Sided Double-Lumen Endotracheal Tubes

There are specific clinical situations in which the use of a right-sided DLT is indicated. Box 16.2 lists the indication for use of a right-sided DLT. The anatomic differences between the right and left mainstem bronchus are reflected in fundamentally different designs of the right-sided and left-sided DLTs. Because the right mainstem bronchus is shorter than the left bronchus, and because the RUL bronchus originates at a distance of 1.5 to 2.0 cm from the carina, techniques using right endobronchial intubation must take into account the location and potential obstruction of the orifice of the RUL bronchus. The right-sided DLT incorporates a modified cuff with a ventilating opening orifice that rides off the orifice of the RUL that allows ventilation of the RUL. Fig. 16.10 displays the Mallinckrodt right-side DLT.

Ehrenfeld et al.⁴⁸ retrospectively reviewed thoracic surgical anesthetics automated anesthesia information management systems, comparing the frequency of right- and left-sided Mallinckrodt tube use by thoracic anesthesiologists. They examined the incidence, duration, and severity of hypoxemia (oxygen saturation [SpO₂] < 90%), hypercapnia (end-tidal carbon dioxide [EtCO2] > 45 mm Hg), and high airway pressures (peak inspiratory pressure > 35 cm H2O) for lung and chest wall surgery patients. Right- (n = 241) and left- (n = 450) sided tubes were almost exclusively used on the side contralateral to surgery. There were no differences in the incidence or duration of hypoxemia, hypercarbia, or high airway pressures.

Because of the additional orifice on the right-sided DLT to allow ventilation through the RUL bronchus, the right-sided DLT requires a precise optimal placement. To increase the margin of safety of the right-sided Broncho-Cath DLT, the opening slot of the ventilating orifice for the right upper bronchus lobe has been widened and consists of an enlarged area of the lateral orifice, this modification has increased the alignment between the opening slot and the RUL bronchus.⁴⁹

Placement Technique for a Right-Sided Double-Lumen Endotracheal Tube

The preferred technique for placement of a right-sided DLT is with the fiberoptic bronchoscopy-guidance technique. After the right-sided DLT is passed beyond the vocal cords under direct laryngoscopy, the fiberoptic bronchoscope is advanced through the endobronchial lumen. Before advancing the DLT, the tracheal carina, the entrance of the right mainstem bronchus, and the entrance of the RUL bronchus are identified, then the DLT is rotated 90 degrees to the right and advanced with the aid of the fiberoptic bronchoscope. The optimal position of a right-sided DLT is one that provides good alignment between the endobronchial lumen opening slot and visualizes the three segments of the RUL bronchus. A clear view of the bronchus intermedius and the right lower lobe bronchus should be seen from the endobronchial lumen. From the tracheal view, the optimal position for a right-sided DLT provides a view of the edge of the blue cuff of the endobronchial balloon when inflated just below tracheal carina and a full view of the entrance of the left mainstem bronchus. Fig. 16.11 shows the optimal position of a right-sided DLT seen from the endobronchial or endotracheal view with a fiberoptic bronchoscope.

Auscultation, Flexible Fiberoptic Bronchoscopy, and Ultrasonography When Placing Double-Lumen Endotracheal Tubes

Evidence strongly suggests that auscultation alone may be unreliable for confirmation of proper DLT placement. However, the basic principle of auscultation and clamping maneuvers while testing the proper placement of a DLT must be routinely applied before the use of fiberoptic bronchoscopy. For a left-sided DLT, the endobronchial lumen should be placed below the tracheal carina into the left mainstem bronchus, the depth of tube in a 170 cm tall subject should be approximately 29 cm at the level of the teeth. With both DLT cuffs inflated clamping the limb connector of the tracheal lumen should reveal the absence of breath sounds in the right side of the chest (right hemothorax). If both lungs are being ventilated, the bronchial lumen is too shallow above the carina. After this maneuver is completed, the next step is to ventilate both lungs. Then clamping the limb connector of the endobronchial lumen should reveal the absence of breath sounds on the left side of the chest (left hemothorax). If these maneuvers are unsuccessful, or confusion ensues with breath sounds and the location of the DLT, a fiberoptic bronchoscopy examinations takes precedent. In a study by Klein et al.,⁵⁰ 200 patients were intubated by the blind technique and confirmation of placement of the DLTs was initially done by auscultation, following clamping of one of the ports of the connector of the DLT. A second anesthesiologist with expertise in flexible fiberoptic bronchoscopy reconfirming the placement of the DLT, showed that 35% of the tubes placed were mispositioned with auscultation alone. All detected malpositions were eventually corrected with the use of fiberoptic bronchoscopy.

A study by Campos et al.⁵¹ involving nonthoracic anesthesiologists with very limited experience in lung separation techniques, showed that when placing lung isolation devices (DLTs or bronchial blockers), there was a 38% incidence in unrecognized malpositions even when these devices were placed with the fiberoptic bronchoscope. The possible cause was lack of skills with fiberoptic bronchoscopy and lack of recognition of tracheobronchial anatomy.

Fiberoptic bronchoscopy is essential and mandatory to achieve 100% success in placement and positioning of DLTs, as long as the anesthesiologist is able to recognize proper tracheobronchial anatomy and possesses skills with flexible fiberoptic bronchoscopy. In another study by de Bellis et al.⁵² involving thoracic anesthesiologists, 104 patients were intubated with a left-sided DLT, and they confirmed the optimal position of the DLT initially by using auscultation only. An endoscopist with experience in flexible fiberoptic bronchoscopy was asked to confirm the optimal and proper position after auscultation, and this showed that in 37% of the patients, there were unrecognized malpositions while placing the DLT. All the malpositions were easily corrected with the use of flexible fiberoptic bronchoscopy. This study clearly demonstrates that even experienced thoracic anesthesiologists cannot rely on the optimal position of the DLT with just auscultation; therefore flexible fiberoptic bronchoscopy must be used to obtain optimal position.⁵³ Table 16.2 displays the role of flexible fiberoptic bronchoscopy and DLTs.

Table 16.2

Displays the Role of Flexible Fiberoptic Bronchoscopy and Double-Lumen Tubes

Author	n	End Points	Outcome
Klein et al.50	• 200 L-R DLTs (prospective)	Auscultation/clamping	• 35% malposition
Anesthesiology. 1998;88:346–350		(2nd anesthesiologist) FOB	• FOB all malpositions corrected
Bellis et al.52 Eur J Cardiothorac Surg. 2011;40:912–916	• n = 104 pts, L-DLTs (prospective)	Auscultation/clamping (endoscopist) FOB	• 37% unrecognized malpositions • FOB all corrected
Campos et al.115	• n = 60 pts, DLTs	Anesthesia Simulator	• 23% unrecognized malpositions
Euro J Anaesthesiol. 2011;28:169–174	• n = 27 nonthoracic anesth (prospective)	or Computer DVD training	• Failed placements with FOB

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