Thoracic Anesthesia

PART 1

The Principles of Thoracic Anesthesia


CHAPTERS


5
Lung Separation Techniques

Andrew D. Shaw
Katherine Grichnik
Atilio Barbeito
Javier Campos

Lung separation allows the anesthesiologist to provide one-lung ventilation (OLV) in patients undergoing lung resection surgery. It is also utilized to facilitate access to other thoracic structures such as the heart, the esophagus, mediastinal lymph nodes, the thoracic aorta, and the thoracic vertebrae.1,2 In addition to facilitating surgical exposure, lung separation is also indicated for prevention of contamination of the contralateral lung from bleeding, pus material, or saline lavage (in cases of hemoptysis, purulent drainage, and lung lavage, respectively), and to allow positive pressure ventilation and adequate gas exchange in the presence of a large bronchopleural fistula.

Two main techniques are used for lung separation. The first one involves a device made of disposable polyvinylchloride material, the double-lumen endotracheal tube (DLT).3 The DLT is a bifurcated tube with both an endotracheal and an endobronchial lumen and can be used to achieve isolation of either the right or left lung. The second technique involves blockade of a mainstem bronchus to allow lung collapse distal to the occlusion.4

This chapter reviews the insertion techniques and complications for both types of devices and will provide some practical recommendations for their safe and effective use.

DOUBLE-LUMEN ENDOTRACHEAL TUBES

Double-lumen endotracheal tubes (DLT) have been used in thoracic anesthesia for lung separation and one-lung ventilation (OLV) for more than 50 years, since the report of Carlens and Bjork in 1950.5They provide excellent operating conditions when sized and placed correctly, and allow access to both ventilated and collapsed lungs for secretion clearance, independent ventilation, and bronchoscopic inspection. Today they are the commonest method of securing lung isolation and are available in sizes ranging from 26 to 41 F, with the Bronco-Cath DLT from Mallinckrodt being the most popular in North America. Other manufacturers include Argyle (Sheridan), Rusch and Portex. The Silbroncho, a newer DLT by Fuji Systems, is also available in a left-sided version only (Figure 5–1A). This device features a shorter, wire-reinforced endobronchial tip and a reduced bronchial cuff size.6 This design should provide a greater margin of safety, although its clinical effectiveness has not been reported.

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Figure 5–1. A. The Silbroncho left-sided DLT. B. The Cliny right-sided DLT. Notice the long oblique bronchial cuff and the two ventilation slots for the right upper lobe (arrows). (Reproduced with permission from Campos J. Lung isolation. In: Slinger P., ed. Principles and Practice of Anesthesia for Thoracic Surgery. New York: Springer, 2011, p. 235. Copyright © Springer Science + Business Media, LLC 2011.)

Choices—Left or Right?

Traditionally, thoracic anesthesiologists would place a DLT on the side contralateral to the surgical procedure. However, before the advent of routine fiberoptic bronchoscopy, incorrect placement was common and lead to a high incidence of avoidable hypoxemia secondary to right upper lobe obstruction. In light of this, it became the norm to place a left-sided tube for all procedures except a left pneumonectomy or left-sided main bronchial sleeve resection. This practice has become widespread and is probably the most common policy in use today. Some practitioners even advocate that a left-sided tube be used for all procedures, and withdrawn into the trachea when necessary. It is true that a right-sided tube is harder to insert and place correctly, but it is also true that a well-placed right-sided tube makes surgery on the proximal left lung airways far easier. Indications for right-sided tube placement are summarized in Table 5–1.

Table 5–1. Indications for a Right-Sided Double-Lumen Endotracheal Tube

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There are important anatomic differences between the two main bronchi, and appreciation of these allows understanding of the problems one is likely to encounter when placing a DLT. The right main bronchus is shorter, arises from the carina at a more acute angle, and gives off the right upper lobe bronchus much earlier (ie, closer to the carina—usually at about 1.5-2 cm) than its left-sided equivalent. As a result, it is very easy to inadvertently occlude the right upper lobe with the bronchial portion of the tube and thus leave only the middle and lower lobes available for ventilation. There are some design features of right-sided tubes that reduce the chance of this happening, but they do not eliminate this problem entirely.

All the currently available right-sided DLT have an orifice cut through the bronchial portion of the tube, usually distal to the cuff, which may itself be offset (Figure 5–2). This is to permit ventilation of the right upper lobe (RUL), and ideally the orifice is placed directly opposite the right upper lobe bronchus. In practice this is difficult and most practitioners are happy if they can see the RUL bronchus through the orifice, as this usually permits good ventilation of the RUL during OLV. Newer designs attempt to facilitate positioning and ventilation of the RUL. An example is the right-sided DLT by Cliny (Create Medic Co. Ltd, Yokohama, Japan), which has a long bronchial cuff with two ventilation slots for the right upper lobe (Figure 5–1B). This device may prove useful in patients with a very short right mainstem bronchus.7

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Figure 5–2. A. The Sheridan right-sided DLT. B. The Mallinckrodt right-sided DLT.

In about 1 in 250 patients a porcine bronchus will be encountered.8 Here, the right upper lobe bronchus originates directly from the trachea, usually within 2 cm of the carina, but sometimes as much as 6 cm. In this situation, a right-sided tube necessarily occludes the RUL, and a left-sided tube is preferable.

Sizing-Practical Considerations

Much has been written about the best size DLT to use, and how best to make the selection. In general, most female patients will be well served with a 37-F size, and most male patients with a 39 F. This is of course an oversimplification, but is not a bad starting point. When considering whether to vary from this policy, patient height is more important than weight as it better predicts tracheal length, which is the prime determinant of whether a tube of a given size provides effective lung isolation. Tubes that are too small cause far more trouble than tubes that are too large, because the problems they cause do not declare themselves until the case is well underway and lung isolation unsatisfactory. A tube that is too large will not fit, a situation that declares itself much earlier in the case, when there is still time to correct the problem. Tubes that are too small do not sit well in the main bronchus, require higher cuff volumes (the bronchial cuffs are not designed to contain more than 3 mL of air) and become dislodged easily. This leads to repeated attempts to improve their position, disruption to the surgery, repeated need for bronchoscopy, and repeated interruptions to ventilation. A correctly sized tube passes smoothly through the glottis and comes to rest at a distance of approximately 29 cm from the incisors in both men and women. In one study performed in adult cadavers, it was shown that the cricoid ring diameter never exceeds the diameter of the glottis. Thus, if a DLT encounters resistance when passing the glottis, it is likely that the DLT would also encounter resistance while passing the cricoid ring.9

Sizing—Reported Studies

Most of the published literature focuses on the left-sided DLT in part because the right-sided DLT is used less commonly. There are reports of complications related to the use of an undersized DLT. A tension pneumothorax and pneumomediastinum occurred after the endobronchial tip of an undersized DLT had migrated too far into the left lower bronchus, and the whole tidal volume was delivered into a single lobe.10 Smaller DLTs also provide more resistance to gas flow and will develop more auto-positive end-expiratory pressure when compared with larger DLTs.11 Airway-related complications have similarly been reported with the use of undersized left-sided DLTs.12

Brodsky et al13 reported that measurement of the tracheal diameter at the level of the clavicle on the preoperative posteroanterior chest radiograph can be used to determine the proper left-sided DLT size. This approach lead to the use of larger left-sided DLTs (ie, 41 F in men and 39 F in women). However, a study involving Asian patients by Chow et al14 using the same method found this approach less reliable. In their study, Chow et al found that the overall positive predictive value for the correct size of a left-sided DLT was 77% for men and 45% for women. Therefore, this method may be less useful in patients of smaller stature such as women and people of Asian descent.

Amar et al15 have shown that the use of a smaller DLT (35-F left-sided) was not associated with any difference in clinical intraoperative outcomes, regardless of patient size or gender. However, in their study, of the 35% of patients who received a DLT, 92 (65%) were female. In practice, many women will usually receive a 35-F DLT anyway; therefore the question of whether or not a 35 F for all patients is favorable remains unclear.

A different alternative that has been suggested in order 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.16 This is unlikely to become an everyday habit however, because of the time required to generate the 3D images, and the fact that most of the time a 37- or 39-F tube will suffice.

Taken as a group, these studies suggest that chest radiographs and CT scans may be valuable tools for selection of the correct DLT size. As such these images should certainly be reviewed before placement of a DLT as they will alert the operator to the presence of abnormal anatomy. In addition, the preoperative CT scan will provide the distance to the epidural space should an epidural catheter be part of the anesthetic plan.

DLT Insertion Technique

Double-lumen tubes may be placed “blind” or using a fiberoptic bronchoscope. In the blind technique the DLT is introduced into the glottis during direct laryngoscopy. The tip is passed through the glottis with the tip pointing anteriorly and the entire tube then turned 90 degrees 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 further into the trachea until the depth of insertion at the teeth is approximately 29 cm (for patients who are at least 170 cm tall).17 Rotating the patient’s head slightly to the opposite side as the tube is advanced into its final position helps the tip of the DLT find the correct main bronchus. Correct location may then be confirmed using a fiberoptic bronchoscope—see the following pages for details.

The second technique employs fiberoptic bronchoscopy, where the tip of the endobronchial lumen is guided into position bronchoscopically after the DLT passes the vocal cords. A study by Boucek et al18 compared the blind technique with the fiberoptic technique and showed that of the 32 patients who underwent the blind technique, primary success occurred in 30 patients. In contrast, in the 27 patients receiving the bronchoscopy-guided technique, primary success was achieved only in 21 patients and eventual success in 25 patients. This study also showed that the time spent placing a DLT was an average of 88 seconds for the blind technique and 181 seconds for the fiberoptic method. Although both methods resulted in successful placement in the majority of patients, more time was required when the fiberoptic technique was used. Figure 5–3 shows both the blind technique and the fiberoptic technique for placement of a left-sided DLT. The most important aspect of the fiberoptic technique is to confirm visualization of the trifurcation of the RUL bronchus from the right main bronchus—there is no other place in the tracheobronchial tree where this image is seen, and it therefore confirms that the position is correct. Figure 5–4A and B illustrates the optimal position of a right- and left-sided DLT, respectively, together with the bronchoscopic views that should be obtained in each case.

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Figure 5–3. A. The blind method technique for placement of a left-sided DLT. The endobronchial lumen is in an anterior position during initial insertion (left figure); the DLT is then passed through the glottic opening using direct laryngoscopy and rotated 90 degrees to the left (center figure); the DLT is finally advanced until moderate resistance is felt, indicating the endobronchial lumen of the DLT has entered the bronchus (right figure). (Reproduced with permission from Campos JH.68B. The fiberoptic bronchoscopy guidance technique for placement of a left-sided DLT. The DLT is inserted into the trachea using direct laryngoscopy (left figure). The fiberoptic bronchoscope is then inserted through the endobronchial lumen and the tracheal carina and the left main stem bronchus visualized (center figure). The DLT is rotated 90 degrees to the left and, with the aid of the fiberoptic bronchoscope; the tube is advanced to the optimal position into the left main stem bronchus (right figure). (Reproduced with permission from Campos JH.68)

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Figure 5–4. A. Optimal position of a right-sided DLT. Insert A shows the take-off of the right-upper lobe bronchus with its three segments (apical, anterior and posterior) as seen when the fiberoptic bronchoscope emerges from the opening slot located in the endobronchial lumen of the DLT. Insert B shows an unobstructed bronchoscopic view of the entrance of the left mainstem bronchus when the fiberscope is passed through the tracheal lumen of the DLT and the edge of the fully inflated endobronchial cuff is positioned below the tracheal carina in the right mainstem bronchus. (Reproduced with permission from Campos JH.67B. Optimal position of a left-sided DLT. Insert (a) shows an unobstructed bronchoscopic view of the entrance of the right mainstem bronchus when the fiberscope is passed through the tracheal lumen of the DLT and the edge of the fully inflated endobronchial cuff is below the tracheal carina in the left mainstem bronchus. Insert (b) shows the take-off of the right-upper lobe bronchus with its three segments (apical, anterior and posterior); this landmark should be used to reconfirm the location of the right bronchus. Insert (c) shows an unobstructed bronchoscopic view of the left-upper and left-lower bronchi when the fiberoptic bronchoscope is advanced through the endobronchial lumen of the DLT. (Reproduced with permission from Campos JH.67)

With either technique, the final position will be confirmed fiberoptically prior to surgery commencing. This is best performed immediately after tube placement and again once the patient is placed in the lateral position for surgery. Tubes often migrate out during patient positioning, and often a small degree of neck flexion will replace the tip of the bronchial lumen into its correct location. Ideally, the blue edge of the bronchial cuff will be visible in the main bronchus when it is inflated and in good position. The bronchial cuff is unlike the tracheal cuff and is not designed to minimize inflation pressure. It is essential therefore that the bronchial cuff is not overinflated as all this will do is increase the pressure applied to the bronchial mucosa and increase the risk of an ischemic lesion.

Problems and Complications

The most common problems and complications arising from the use of DLTs are incorrect placement and damage to the airways. A malpositioned DLT does not permit collapse of the operative lung, and may partially collapse the ventilated or dependent lung, producing hypoxemia. A common cause of malposition is dislodgement of the endobronchial cuff because of overinflation, surgical manipulation of the bronchus, or extension of the head and neck during or after patient positioning.19

Airway trauma and damage to the membranous part of the trachea or main bronchus continue to be associated with the use of DLTs.12,20 This complication can develop at any time the DLT is in position or during extubation.21-23 A 25-year review of the literature by Fitzmaurice and Brodsky24 found that most airway injuries were associated with undersized DLTs, particularly in women who received a 35- or 37-F disposable DLT. It is likely that airway damage occurs when an undersized DLT migrates distally into the bronchus and the main tracheal body of the DLT comes into contact with the bronchus, producing lacerations or rupture of the airway. Airway damage during the use of DLTs can present as unexpected air leaks, subcutaneous emphysema, and massive airway bleeding into the lumen of the DLT, or protrusion of the endotracheal or endobronchial cuff into the surgical field.

Another serious problem that may occur is the development of tension pneumothorax in the dependent, ventilated lung.25,26 This complication is particularly important to detect promptly as the treatment is immediate decompression of the non-operative-side pneumothorax. This can be achieved either directly, across the mediastinum, or by turning the patient and placing a cannula through the chest wall. If the diagnosis is wrong however, the patient now has an extra pneumothorax and chest tube to deal with postoperatively. We routinely place an esophageal stethoscope (a regular stethoscope attached to an esophageal temperature probe) and confirm auscultation of breath sounds during OLV in order to either confirm or rule this diagnosis out whenever it is suspected.

Less serious complications with the use of the DLT have been reported by Knoll et al.27 In their comparative study between the DLT and the endobronchial blocker, the development of postoperative hoarseness occurred significantly more commonly in the DLT group when compared to the endobronchial blocker group; however, the incidence of bronchial injuries was comparable between groups.

BRONCHIAL BLOCKERS

Balloon blockade of the right or left mainstem bronchus offers another strategy for achieving lung separation to facilitate thoracic surgical procedures.4 As blockage of the endobronchial lumen results in distal lung collapse; this method can also be used to selectively achieve lobar collapse when the bronchial blocker is placed in a more distal bronchus.28-34 There are multiple types of endobronchial blockers including independent catheters that are inserted into a normal endotracheal tube (ETT) after intubation (Arndt blocker,35 Cohen tip-deflecting endobronchial blocker,36 Fuji Uniblocker)37,38 and those that are mounted within a specialized endotracheal tube (the Univent tube).4

Independent Bronchial Blockers

There are multiple independent bronchial blockers, which are designed to be inserted into an in situ endotracheal tube after successful intubation. The three major types commonly used in the United States are the Arndt endobronchial blocker, the Cohen endobronchial blocker, and the Fuji Uniblocker.37,38

The primary advantage of an independent blockers include the ability to use the blocker in a patient with a preexisting ETT,39 after a difficult airway is secured through any variety of mechanisms,40 for use in trauma patients who may urgently and unexpectedly require one-lung ventilation.41,42 Additional uses are in post-pneumonectomy patients, who may require selective one-lobe ventilation43 or to control unilateral pulmonary hemorrhage.44

ARNDT BLOCKER

The Arndt blocker35 is relatively unique in that it utilizes a wire loop attached to a FOB, which allows the anesthesiologist to guide the blocker into the correct position. This blocker is available as a 5-, 7-, or 9-F catheter and in 65 cm and 78 cm lengths; within the blocker itself is an inner 1.4 mm diameter lumen that houses a flexible nylon wire ending in a small flexible loop distally. This loop is retractable and thus can be cinched to a fiberoptic bronchoscope (FOB), which can then be used to guide the blocker into the correct position within the selected bronchus. After placement, the guidewire can be removed and the inner lumen used for lung deflation or insufflation of oxygen if needed.

Proper placement and functioning of the blocker rests on choosing the proper single lumen ETT size for use with the blocker. In general (for use in adults), a 7-F blocker requires a 7.5-mm internal diameter (ID) ETT, and a 9-F blocker requires at least an 8.0-mm ID single-lumen ETT. The balloon on the Arndt blocker is a high-volume, low-pressure cuff and comes in an elliptical or spherical shape.

Placement and Positioning of the Arndt Blocker

After intubation or with a preexisting ETT and selection of the correct size bronchial blocker, the bronchial blocker should be lubricated and the balloon checked, and the FOB should be prepared. The size of blocker may be dictated by the ETT size and the choice of a spherical versus elliptical balloon rests on the goal of the surgery; the spherical blocker is more secure with less opportunity to become malpositioned in the short right mainstem bronchus or for selective lobar intubation, whereas the elliptical or the spherical blocker may both be used in the left mainstem bronchus. Appropriate lubrication of the blocker and the FOB are encouraged for ease of insertion.

There are multiple suggestions in the literature for placement of an Arndt endobronchial blocker; the following is one stepwise process that has been advocated by many: First, the multiconnector port is examined and the various attachment ports identified for the bronchial blocker, the FOB and for attachment to the ventilator. Next, the bronchial blocker is inserted through its port (the lumen with the screw top), the FOB is inserted through its port, and, after both the FOB and the bronchial blocker are beyond the entire multiconnector port lumen, the blocker guide wire loop is tightened to secure it to the FOB. Next, the combined multiconnector port/FOB/bronchial blocker are inserted into the existing endotracheal tube, the multiport connector is attached to the top of the ETT and the ventilator tubing attached to the appropriate ventilation sideport. After resumption of ventilation with assurance of end tidal CO2, the FOB/blocker combination should be advanced distally to the desired bronchus under fiberoptic visualization. When the deflated cuff of the blocker is beyond the entrance of the bronchus, the guide loop is loosened and the FOB withdrawn to the carina. This position allows visualization of the blocker as it advances into the correct bronchial lumen. The blocker cuff is then fully inflated under direct visualization with 4 to 8 mL of air to completely fill the bronchial lumen.

A simplified approach is possible when blocking the right lung: due to the ease of insertion of the blocker into the right mainstem bronchus given its alignment with the trachea, it is possible to insert the Arndt blocker and the FOB in the lumen of the endotracheal tube without the wireguide loop attachment. The blocker can then be advanced into the right mainstem bronchus under FOB visualization. However, due to the relatively shorter right mainstem bronchus, the blocker’s cuff should be deflated and the blocker advanced 1 cm before repositioning the patient into the left lateral decubitus position, to avoid blocker retraction into the trachea with the move. It is always necessary to reconfirm blocker position after the surgical positioning is completed.

After corroboration of the correct position of the blocker and its balloon, the wire loop can be withdrawn to convert the 1.4 mm channel into an open port to allow lung deflation. One version of the Arndt blocker has a cone-shaped device that can be attached to this 1.4 mm channel for connection to a low level of suction. This may both facilitate lung collapse but could also be used to suction very thin secretions.45 Of note, the wire loop must be at least retracted into the central lumen, if not removed from the channel, to avoid inclusion in the stapling line of the bronchus with any proximal surgical resection.46 Prior to inflation of the bronchial balloon, many practitioners choose to hold patients apneic for 1 to 2 minutes to facilitate operative lung collapse. Optimal positioning of the Arndt blocker is achieved when the blocker balloon’s outer surface is visualized fiberoptically about 5 mm below the tracheal carina in the operative side bronchus and no leakage of air is noted around the blocker. Figure 5–5 illustrates the placement of an Arndt blocker.

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Figure 5–5. A. Placement of an Arndt bronchial blocker through a single-lumen endotracheal tube. Note how the fiberoptic bronchoscope is advanced through the loop of the bronchial blocker guidewire. (Reproduced with permission from Campos JH.68B. Optimal position of a bronchial blocker in the left mainstem bronchus. The proximal edge of the fully inflated cuff is approximately 5 to 10 mm below the tracheal carina. Inserts (a) and (b) are bronchoscopic views of a bronchial blocker in the right and left mainstem bronchi respectively. (Reproduced with permission from Campos JH.2 © Elsevier.)

COHEN FLEXITIP ENDOBRONCHIAL BLOCKER

The Cohen bronchial blocker was designed with a wheel-controlled device to achieve deflection of the distal blocker tip and a torque grip at 55 cm for blocker rotation, both designed to facilitate guidance of the blocker into the desired bronchus.2,36 This blocker also features a pre-angled distal tip to improve the maneuverability of the device. Of note, when viewed through a FOB, one can see an arrow at the distal tip above the balloon to indicate which direction the tip deflects. This blocker is only available in size 9 F and 65 cm in length and has a spherically shaped high-volume, low-pressure balloon and side holes near the distal end to facilitate lung deflation. The Cohen blocker also comes with a multiport adaptor for in situ use of the blocker while maintaining ventilation.

Placement and Positioning of the Cohen Endobronchial Blocker

The Cohen blocker should be used with an 8.0-mm ID or greater single-lumen ETT; preparation includes testing the blocker balloon, deflation of the balloon and lubrication of the blocker prior to attachment and insertion into the ETT lumen. After securing the multiconnector port and placing the endobronchial blocker into the ETT, FOB is used to observe the movement of the blocker into the desired mainstem bronchus. The wheel device is used to deflect the blocker tip and the torque grip to guide and position the blocker correctly.

The blocker is relatively easy to place in the right mainstem bronchus and the inflated balloon (with 4-8 mL of air) should be visualized with the FOB 5 mm caudal to the tracheal carina on the right. Intubation of the left mainstem bronchus may be more challenging; guiding the blocker into the left mainstem bronchus can be facilitated by advancing the tip of the single-lumen ETT to the carina, just cranial to the entrance of the left bronchus. Then, a leftward twist of the Cohen blocker facilitates entrance to the left mainstem bronchus. After the blocker is observed within the left bronchus, the single-lumen ETT is withdrawn a few centimeters. Similar to the right side, the blocker’s balloon should be positioned approximately 5 mm distal to the trachea carina.

FUJI UNIBLOCKER

The Fuji Uniblocker bronchial blocker is available in 4.5 and 9 F sizes; it is 65 cm in length and features a high-volume balloon made of silicone. This blocker has two unique features. One is that the balloon is made of a material that impairs the diffusion of gas into or out of the cuff. Thus, with a maximal inflation of 6 mL of air, the blocker’s transmitted pressure is always less than 30 mm Hg, a pressure thought to be safe for the bronchial mucosa.47 Second, the Fuji Uniblocker features a swivel connector with torque control built into the shaft of the blocker to optimize control of the blocker’s movements.

Placement and Positioning of the Fuji Uniblocker

An 8.0 ETT is required for placement of the Fuji Uniblocker most commonly used in adults—the size 9 F. Similar to the other blockers, the Fuji Uniblocker is advanced into and through an ETT using a FOB and the torque control shaft used to position the blocker within the desired bronchus. Also similar to the other endobronchial blockers, the edge of the blocker’s inflated balloon should be viewed 5 mm below the tracheal carina on the right but on the left should it should be seen at least 5 to 10 mm below the trachea carina.

COMPARISON OF INDEPENDENT BRONCHIAL BLOCKERS

A study was conducted comparing the Fuji Uniblocker, the Arndt and the Cohen bronchial blockers to left-sided DLTs for thoracoscopic procedures and open thoracotomy37; all of the bronchial blockers took a longer time to position and required more intraoperative repositioning compared to left-sided DLTs, but resulted in similar surgical exposure. Another report48 examined the Fuji Uniblocker for patients undergoing video-assisted thoracic surgery; the quality of lung collapse was deemed to be greater for left-sided compared to right-sided procedures. Table 5–2 displays the characteristics of the Arndt blocker, the Cohen endobronchial blocker, and the Fuji Uniblocker.

Table 5–2. Characteristics of the Arndt Blocker, the Cohen Flexitip Endobronchial Blocker, and the Fuji Uniblocker

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UNIVENT ENDOTRACHEAL TUBE

The Univent tube consists of an endotracheal tube combined with a bronchial blocker; it is a modified single-lumen tube with an attached, enclosed and movable bronchial blocker within the tube itself. The non-latex blocker is designed as a flexible shaft to facilitate positioning of the blocker past the tip of the endotracheal tube into the right or left mainstem bronchus.49 Of note, the balloon inflates in a high-pressure, low-volume manner that requires 4 to 6 mL of air for selective lobar blockade or 6 to 8 mL of air for mainstem bronchial blockade. Given that it is a high-pressure cuff, it is important to manually palpate and evaluate the bronchial pilot balloon pressure to prevent excessive pressure to the bronchial mucosa; the minimum amount of air needed to seal a bronchus should be used to inflate the blocker balloon. The Univent blocker is useful for selective lung isolation in a patient with a difficult airway, which may preclude dual lumen endotracheal tube placement.50-55 Another attribute of the Univent blocker is an indwelling 2-mm diameter lumen that can be used for suctioning or for oxygen administration into the deflated lung. A potential disadvantage is the smaller internal diameter of the specialized endotracheal tube when compared to an equal size outer diameter regular endotracheal tube, which may result in a relatively higher airflow resistance during mechanical ventilation.

Placement of the Univent blocker/endotracheal tube should include the following steps:

Prior to standard endotracheal intubation, the enclosed bronchial blocker should be lubricated and then fully retracted into its lumen within the endotracheal tube. Intubation of the trachea is achieved through any means chosen (dependent on the difficulty of the airway) followed by FOB placement through a Portex swivel adaptor. Under direct visualization, the bronchial blocker is advanced into the bronchus on the operative side and the bronchial balloon inflated to achieve unilateral lung collapse.

COMPLICATIONS WITH THE USE OF BRONCHIAL BLOCKERS

Serious complications are rare with bronchial blockers and are usually less severe than those related to double-lumen ETT tubes. The most common complication is actually failure to achieve adequate lung isolation and/or separation. This may be due to abnormal bronchial anatomy but may also be due to operator error. Abnormal anatomy is noted when the right upper lobe bronchus branches from the trachea instead of the right mainstem bronchus, precluding the ability of a bronchial blocker to deflate the right upper, middle and lower lobe bronchi simultaneously. More commonly, the bronchial balloon is not inflated or positioned properly, leading to an inadequate seal of the bronchus.56,57 The bronchial balloon can be mistakenly inflated in the trachea or an overinflated bronchial balloon cuff can also migrate cranially and move back into the trachea; both situations cause complete tracheal occlusion with subsequent respiratory failure.58 Air trapping has occurred distal to the blocker leading a pulseless electrical activity arrest; prompt deflation of the bronchial blocker cuff resolved the problem.59 The distal portion of the bronchial blocker and/or the guidewire have been included in the surgical staple line during lobectomy.46,60 Adequate communication with the surgical team regarding the presence of a bronchial blocker is crucial. Structural complications from the blockers themselves that have been reported include shearing the balloon with retraction of the blocker through the multichannel port with an Arndt blocker and a fracture of the blocker cap connector with the Univent blocker.61,62 It has been recommended that independent bronchial blockers be removed with the multiport connector in place rather than through the connector. There have not been any reports of tracheal or bronchial rupture.

LUNG SEPARATION IN THE TRACHEOSTOMIZED PATIENT

The anesthesiologist occasionally encounters a patient that has a tracheostomy in place and requires OLV. Although the stoma provides direct, easy access to the lower airway, it is important to note that the tracheal segment above the carina where the endotracheal tube’s tracheal cuff is to be positioned is short in these cases, and hence more prone to positioning complications. Also, the stoma may be small and restrictive, which may limit the size of the tube or cannula used. Appropriate lubrication should always be used and forceful maneuvers should be avoided in order to avoid airway bleeding, which invariably complicates visualization during FOB.

There are three main alternatives for achieving successful lung separation in the tracheostomized patient: (a) orotracheal intubation using a DLT, (b) insertion of a single-lumen endotracheal tube through the stoma and into the right or left mainstem bronchus, as indicated; or (c) use of a bronchial blocker, either attached to a single-lumen endotracheal tube such as the Univent blocker,63,64 passed independently through a tracheostomy cannula,43 or placed through a single-lumen endotracheal tube.65

The first technique has all the limitations of DLT insertion, plus the difficulty in passing the larger diameter DLT through the site of the stoma, which may be narrow and friable. The second technique, insertion and “mainsteming” of a single lumen tube through the stoma, prevents full deflation and aspiration of secretions in the collapsed lung. Use of a bronchial blocker is generally the most versatile and stable technique, and therefore the preferred one in the authors’ opinion.

When passing a 9-F bronchial blocker through a tracheostomy tube, the recommended flexible FOB size should be 3.5-mm ID, so the independent blocker and the fiberscope can navigate together to achieve optimal position of these devices into the designated bronchus. Alternatively, a smaller diameter bronchial blocker should be chosen for lung isolation, since the internal diameter of an 8.0 tracheostomy cannula is often smaller than a conventional 8.0 ETT.

In some instances when using a tracheostomy cannula, the multiport connector is attached to the ventilating port of the tracheostomy cannula to maintain the bronchial blocker in place. A short-breathing circuit extension may be used to facilitate access to the device and to prevent the weight of the multiport connector and anesthesia circuit from dislodging the tracheal cannula. As in other lung separation techniques, optimal position is achieved with FOB aid.

LUNG COLLAPSE FOLLOWING LUNG SEPARATION

Correct placement of a lung separation device is not necessarily followed by immediate, complete lung collapse. In fact, spontaneous lung deflation may take more than 25 minutes depending on the device used.49 Strategies that may be used to aid lung deflation during lung isolation include de-nitrogenation using 100% inspired oxygen concentration prior to lung collapse,66 a period of apnea prior to inflation of the bronchial blocker cuff, and gentle aspiration of the airways using the fiberoptic endoscope suction channel prior to lung separation.

It is important to note that once lung isolation is achieved, the overall clinical performance is similar for both DLTs and bronchial blockers.37 In one study, the bronchial blockers required longer time to position and were more prone to intraoperative reposition, however. Table 5–3 displays the advantages and disadvantages of DLTs and bronchial blockers.

Table 5–3. Advantages and Disadvantages of Double-Lumen Endotracheal Tubes and Bronchial Blockers

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SUMMARY

Prerequisites for successful lung isolation include knowledge of the normal tracheobronchial anatomy, a thorough preoperative assessment of the patient, including review of the chest x-ray and chest CT scan when available, and familiarity with fiberoptic bronchoscopy equipment and techniques. Additionally, it is important for the anesthesia provider to be familiar with several different lung separation techniques, such as DLT placement and one or more types of bronchial blockers.

Left-sided DLTs are generally used for most thoracic surgery cases given their ease of insertion and the quality of lung separation achieved. A right-sided DLT is recommended for a left-sided pneumonectomy or left-sided bronchial sleeve resection. Bronchial blockers are indicated in patients with a difficult or abnormal airway or those who have a tracheotomy in place, but these devices require more time for placement and are more prone to intraoperative dislodgement. Lung collapse is facilitated by a de-nitrogenation technique using 100% inspired oxygen concentration prior to lung collapse, and a period of apnea and/or gentle aspiration of the airways using the fiberoptic endoscope suction channel prior to lung separation.

Placement of any of these lung isolation devices requires auscultation followed by fiberoptic bronchoscopy in order to obtain a high success rate during lung separation. The optimal position of these devices (DLTs and bronchial blockers) is best achieved using fiberoptic bronchoscopy in both the supine and the lateral decubitus position or whenever repositioning of the device is needed.

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