The techniques of lung isolation are used to selectively ventilate the lung within 1 hemithorax while the nearly motionless lung is operated on in the contralateral hemithorax. Collapse of the nondependent lung produces less trauma than surgical retraction and offers better exposure of structures within the hemithorax.58,59 The airways of the operated lung can be incised while positive pressure ventilation continues in the other lung. During thoracoscopic surgery, collapse of the operated lung is essential to provide adequate visualization of structures within the pleural cavity. Although many surgical procedures are greatly facilitated by the use of isolation techniques, most procedures are feasible without isolation.
Single lung isolation is absolutely indicated under certain clinical conditions. When one lung contains either blood or infectious secretions, isolation of the lungs becomes imperative to prevent spillage of contents into the unaffected lung. Isolated lung ventilation is essential when a bronchopleural or bronchocutaneous fistula would render positive pressure ventilation difficult or impossible. Further, directing ventilation toward the healthier lung may result in better oxygenation and ventilation.60 Some procedures require isolated ventilation, including open procedures on the trachea and mainstem bronchi, such as sleeve and carinal resections, and bronchopulmonary lavage for pulmonary alveolar proteinosis.
Design of Double-Lumen Tubes
Isolated lung ventilation usually is accomplished through a double-lumen endotracheal tube. The central shaft of a double-lumen endotracheal tube is cylindrical and contains a septum that divides it into 2 symmetric "D"-shaped lumens. At the proximal end of each lumen is a short length of tubing that creates a "Y" shape that permits independent attachment for ventilatory apparatus, clamping, or opening to atmospheric pressure. At the distal end, the shaft is surrounded by an inflatable tracheal cuff. The tracheal lumen terminates just below the tracheal cuff. The other lumen has a cylindrical extension, curved to fit into 1 of the mainstem bronchi, and carries an inflatable circumferential bronchial cuff. After the double-lumen endotracheal tube has been properly placed within the patient's airway, the bronchial cuff permits the bronchial lumen to be used for positive pressure ventilation or exclusion of the hemithorax in which it resides. The tracheal cuff provides a seal that directs pressurized gas from the tracheal lumen into the other bronchus. Thus a properly placed double-lumen endotracheal tube permits selective ventilation or collapse of either lung.
Double-lumen endotracheal tubes are manufactured with selective bronchial extensions intended for placement into either the left or right mainstem bronchus. The left main stem bronchus arises at a more acute angle with reference to the tracheal axis, but it is long enough to easily accommodate the endobronchial extension with its inflatable cuff. In contrast, the right mainstem bronchus is nearly a direct extension of the trachea, but it contains a branch to the right upper lobe bronchus that arises very close to the tracheal bifurcation (Fig. 54-12). A right-sided double-lumen endotracheal tube has a fenestration within the bronchial extension and an elaborately shaped cuff to permit a seal without airflow obstruction. Because of these considerations, right-sided tubes are more difficult to insert and require more maintenance to ensure continuous ventilation of all lobes of the right lung. In the absence of a specific indication for a right-sided double-lumen endotracheal tube, a left-sided tube is strongly preferred.
Schematic representation of the most proximal and most distal acceptable positions of left- and right-sided double-lumen tubes and the relative margins of safety in positioning the various tubes. A. All left-sided double-lumen tubes. B. Mallinckrodt right-sided double-lumen tube has an "s"-shaped balloon for the occlusion of the right mainstem bronchus. C. Rusch right-sided double-lumen tubes use a "c"-shaped cuff on the endobronchial tube that seals off the right mainstem and isolates the right upper lobe. LMS, length of mainstem bronchus; LUL, left upper lobe; MS, margin of safety; RMS, length of right mainstem bronchus; RUL, right upper lobe.
Placement of Double-Lumen Tubes
Before placement of a double-lumen endotracheal tube, all necessary equipment including a laryngoscope, several double-lumen endotracheal tubes, and a fiberoptic scope should be assembled and tested. The type of tube is chosen based on the surgical procedure, and its size is based on the patient's body habitus (Table 54-5). Direct laryngoscopy with a curved (Macintosh) laryngoscope blade is preferred because the glottic opening is better exposed by it as compared to a straight blade. The double-lumen endotracheal tube is held with its bronchial curve oriented anteriorly and its tracheal-pharyngeal curve oriented to the right. The tube is advanced through the glottic opening until the bronchial cuff just passes the vocal cords. If a stylet was used, it is removed.
Table 54-5 Choice of Double-Lumen Endotracheal Tube ||Download (.pdf)
Table 54-5 Choice of Double-Lumen Endotracheal Tube
|Tube Size (Fr)|
|Patient Height||M||F||Depth of Insertion (cm)|
There are 2 methods for the cannulation of the desired bronchus, empiric or "blind placement" and direct vision using fiberoptic assistance. In the first method, the tracheopharyngeal curve is then rotated anteriorly until the proximal end of the double-lumen endotracheal tube just passes the midsagittal axis. The bronchial curve should now be oriented to the side dictated by the type of tube, after which it is then advanced until moderate resistance to further insertion is encountered. A bifurcated connector is attached to the 2 lumens, and the tracheal cuff is inflated. Intubation of the trachea is then confirmed by capnography, auscultation, and observation of chest excursion. Once it has been determined that both lungs can be adequately ventilated, it is safe to proceed with confirmation that the tube is positioned to allow isolation of the 2 lungs. Correct placement can be determined by a series auscultation maneuvers whereby the tracheal and bronchial lumens are ventilated independently. However, this technique is time-consuming and may often prove inaccurate. The alternative method uses a bronchoscope to confirm placement. Each lumen of the bifurcated double-lumen endotracheal tube connector is fitted with a fenestrated membrane covered by a removable cap. While the lungs are ventilated with positive pressure, the fenestrated membrane on the tracheal lumen is uncovered, and the bronchoscope is passed through it into the double-lumen endotracheal tube to confirm placement. The alternative method of tube placement, which uses direct observation via a fiberoptic bronchoscope, is the most efficient method for confirming appropriate anatomic placement. The bronchoscope is steadily advanced through the tracheal lumen until its tip just exits from the distal opening. If the tube is properly positioned, the carina should be seen just beyond the opening, and the medial wall of the endobronchial extension should be seen entering the contralateral bronchus. The bronchial cuff should be entirely contained within the contralateral bronchus, while an unobstructed view of the opening into the ipsilateral bronchus is enjoyed. Disposable double-lumen tubes usually feature a prominent band around the endobronchial extension several millimeters above the endobronchial cuff to facilitate positioning. When ideally positioned, the band should lie at the level of the carina. It may be necessary to slightly advance or withdraw the tube to achieve the ideal position. Once anatomically correct tube position has been confirmed, it is secured in place and the endobronchial cuff is gently inflated under direct bronchoscopic visualization to ensure that the cuff does not herniate into the trachea. Each time the patient is repositioned, it is advisable to verify the position of the double-lumen endotracheal tube.
An alternative method of tube placement eliminates the possibility of placing the endobronchial extension in the wrong bronchus. The tube is passed through the cords and rotated as for the first method. It is advanced only until the tip of the bronchial extension is 20 to 22 cm beyond the central incisors as determined by markings on the shaft. The bronchial cuff is then inflated to seal against the wall of the trachea. An anesthetic circuit is attached to the connector for the bronchial lumen, and intubation of the trachea is confirmed. The bronchoscope is then passed into the bronchial lumen. After the tip of the bronchoscope has entered the trachea, it is advanced under direct visualization past the carina into the desired mainstem bronchus (Figs. 54-13 and 54-14). After the bronchoscope is advanced as far as possible, the bronchial cuff is deflated. Using the bronchoscope as a directing stylet, the double-lumen endotracheal tube is advanced until gentle resistance is met. The bronchoscope is withdrawn and placed in the tracheal lumen to confirm unimpeded access to the ipsilateral bronchus as in the first method. Once placement is confirmed, the tube is secured.
Bronchoscopic guide for placement of single-lung ventilation devices. A. The bronchoscope is situated in the distal trachea. In this view, the carina is clearly visualized along with the anterior cartilaginous rings and the posterior striated membranous portion of the trachea. The takeoff of the right mainstem bronchus is more aligned with the trachea, predisposing for endobronchal intubation of the right mainstem bronchus when an endotracheal tube is advanced too far. The easiest way of absolutely identifying the main carina is to locate the right upper lobe (or the scar of the previously resected right upper lobe). Confirmation of the "true" left and right mainstem bronchi is the best way to ensure proper placement of the selective lung ventilation device. B. The bronchoscope is in the right mainstem bronchus, just proximal to the bronchus intermedius, which begins below the origin of the right upper lobe. Origin of the right upper lobe is variable but usually arises 1 to 1.5 cm past the carina between 2 and 4 o'clock. C. The bronchoscope is in right upper lobe bronchus. The right upper lobe branches into 3 segments: apical, posterior, and anterior. These 3 orifices are typically arranged in a "V" pattern, but they can also be oriented in a line. D. The bronchoscope is in the distal bronchus intermedius. The right middle lobe, which is to the right, immediately splits into the lateral and medial segments. It is possible to advance a double-lumen endotracheal tube distal enough down the right side that the endobronchial lumen will be in the right inferior lobe and that the tracheal lumen will expose the right middle lobe. The right middle lobe's lateral segment orifice could be confused for the right upper lobe orifice, but the right middle lobe's lateral segment does not subdivide like the right upper lobe. E. The bronchoscope is in the distal left mainstem bronchus. This view reveals the left upper and lower lobe bronchi. It is important to ensure that left-sided double-lumen tubes have not been too far advanced, leading to selective intubation of the left upper or lower lobes.
Schematic diagram portraying the use of the fiberoptic bronchoscope to insert a left-sided double-lumen tube. A. The double-lumen tube can be put into the trachea in a conventional manner, and both lungs can be ventilated by both lumens. The fiberoptic bronchoscope may be inserted into the left lumen of the double-lumen tube through a self-sealing diaphragm in the elbow connector to the left lumen; this allows continued positive pressure ventilation of both lungs through the right lumen without creating a leak. After the fiberoptic bronchoscope has been passed into the left mainstem bronchus (B), it is used as a stylet for the after-coming left lumen (C). The fiberoptic bronchoscope is then withdrawn. Final precise positioning of the double-lumen tube is performed with the fiberoptic bronchoscope in the right lumen. [From Benumof JL. Separation of the two lungs (double-lumen tube and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]
Occasionally, double-lumen endotracheal tubes may be malpositioned. Three possible reasons are (1) the tube is so deeply inserted that the tracheal opening is beyond the carina; (2) the tube is not inserted far enough so that the bronchial cuff is above the carina; or (3) the endobronchial extension has entered the incorrect bronchus so that the tracheal lumen opening is trapped against the lateral wall of the trachea on the ipsilateral side (Fig. 54-15). Gently withdrawing or advancing the tube under direct bronchoscopic visualization should reveal and correct either of the first 2 causes. If the endobronchial extension is not in the correct bronchus, the tube is repositioned by inserting the fiberoptic bronchoscope in the endobronchial lumen and withdrawing the tube and scope until the carina is encountered, after which the tube and scope are advanced down the appropriate mainstem bronchus.
There are 3 major (involving a whole lung) malpositions of a left-sided double-lumen endotracheal tube. The tube can be in too far on the left (both lumens are in the left mainstem bronchus), out too far (both lumens are in the trachea), or down the right mainstem bronchus (at least the left lumen is in the right mainstem bronchus). In each of these 3 malpositions, the left cuff, when fully inflated, can completely block the right lumen. Inflation and deflation of the left cuff while the left lumen is clamped creates a breath sound—differential diagnosis of tube malposition. (See text for full explanation). L, left; R, right; -, decreased. [From Benumof JL. Separation of the two lungs (double-lumen tube and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia: WB Saunders; 1987.]
Right-sided tubes require more vigilance and confirmation that the fenestration supplying the right upper lobe bronchus is positioned correctly. This is accomplished by passing the bronchoscope into the endobronchial lumen and observing the upper lobe bronchial orifice through the fenestration in the lateral wall of the endobronchial extension (Fig. 54-16).
Schematic diagram portraying the use of a fiberoptic bronchoscope to determine precise right-sided double-lumen tube position. A. When the fiberoptic bronchoscope is passed down the left (tracheal) lumen, the endoscopist should see a clear straight-ahead view of the tracheal carina and the right lumen going off into the right mainstem bronchus. B. When the fiberoptic bronchoscope is passed down the right (bronchial) lumen, the endoscopist should see the bronchial carina off in the distance; when the fiberoptic bronchoscope is flexed cephalad and passed through the right upper lobe ventilation slot, the right upper lobe bronchial orifice should be visualized. [From Benumof JL. Separation of the two lungs (double-lumen tube and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]
Although confirmation of position through direct visualization with a fiberoptic bronchoscope usually is rapid and definitive, it is not always feasible. Further, although it assures anatomically correct position, it does not ensure functional isolation of the left and right lungs. Functional isolation is tested by selectively ventilating 1 lung while the other is vented to the atmosphere, and unilateral ventilation of the intended lung is confirmed by auscultation and visual or tactile observation. The opposite lung then is ventilated, and the test is repeated. A test for functional isolation should always be used when the double-lumen endotracheal tube is placed to prevent spillage of liquid from one lung to the other.
Complications associated with double-lumen endotracheal tubes can be divided into 2 types, those resulting from malposition of the tube and those caused by trauma to the tracheobronchial tree.
Malposition may lead to failure either to ventilate segments of the dependent lung or to collapse the operative lung. Failure to ventilate segments of the ventilated lung can occur if the bronchial lumen obstructs the origin of the upper lobe bronchus, which frequently manifests by hypoxemia and increased peak airway pressures. A common cause of upper lobe obstruction is distal migration of the endobronchial lumen associated with flexion of the neck. Upper lobe obstruction is more common when a right-sided double-lumen endotracheal tube is inserted. Failure to collapse the nonventilated lung may interfere with the operation.
Cephalad migration of the double-lumen endotracheal tube can be caused by surgical manipulation, neck extension (occurs with placement of patient into lateral decubitus position), or by traction on an inadequately secured tube. As the tube withdraws, the bronchial cuff herniates over the carina into the trachea. When partially herniated, increased cuff pressure may force the cuff further into the trachea. The herniated cuff may partially or fully obstruct the contralateral mainstem bronchus, making that lung difficult or impossible to collapse (or ventilate).
Malposition of the tube should be suspected when there is a sudden increase in peak airway pressure, when hypoxemia occurs, or when inflation of the nonventilated lung is detected. Vigilance should be heightened immediately after repositioning the patient and during surgical manipulation near the hilum of the lung. At the first suspicion of a malpositioned double-lumen endotracheal tube, tube position should be confirmed immediately by fiberoptic bronchoscopy. If it is difficult to discern anatomy during an open thoracotomy, the surgeon may be able to manually guide the endobronchial lumen of the double-lumen endotracheal tube into the desired mainstem bronchus.
Trauma to the tracheobronchial tree by double-lumen endotracheal tubes may include minor insults, such as ecchymosis of the mucous membranes, and more severe ones, like arytenoid dislocation or vocal cord rupture. Catastrophic tracheobronchial rupture has been reported.61-66 The multiple lumen design and relatively large size of double-lumen endotracheal tubes make them stiffer than conventional endotracheal tubes, thus increasing the risk of damage from forceful advancement against resistance. The stiffness is further increased by use of a rigid stylet during tube placement. Therefore, when use of a stylet is required for intubation of the trachea, it should be withdrawn before the bronchial lumen of the double-lumen endotracheal tube is advanced into the mainstem bronchus.
Injuries also may result from excessive pressure in either the tracheal or bronchial cuffs, leading to tissue necrosis or rupture. The small size and high-pressure bronchial cuff increases the risk of tissue injury from overinflation. Cuff pressure should be regularly monitored by palpation of the pilot balloon or by use of a calibrated device.
Failure to obtain a complete seal is especially hazardous when the double-lumen endotracheal tube is used to protect 1 lung from liquid contents within the other. The leak may allow spillage of liquid into the unaffected lung. Liquids include saline during bronchopulmonary lavage, pus from unilateral empyema, and blood from airway hemorrhage. In patients in whom a spillage occurs, a failed seal can lead to severe morbidity or death.
The principal contraindication to the use of a double-lumen endotracheal tube is the presence of a lumenal airway mass that may be dislodged or may prevent passage of the tube. Relative contraindications include critical dependence on bilateral mechanical ventilation in patients unable to tolerate its interruption, patients requiring rapid placement of an endotracheal tube to avoid aspiration of gastric contents, and patients in whom conventional tracheal intubation is judged to be difficult.
Alternative Methods of Lung Isolation
When collapse of the left lung and ventilation of the right is required or use of a double-lumen endotracheal tube is not feasible, a bronchial blocker can be placed in the left mainstem bronchus. In addition, this strategy eliminates the risk of losing the airway while changing the endotracheal tube at the end of the case for patients requiring postoperative ventilation. Specific bronchial blockers having a patent central lumen to permit deflation of the distal airway have been developed. The Ardnt® catheter has a nylon loop that is used to ensnare the distal portion of the fiberoptic scope as it is advanced in the selected mainstem bronchus.67,68 The loop is loosened and advanced distal to the fiberoptic scope. Another variation, the Cohen endobronchial blocker®, incorporates a small wheel that is used to deflect the tip of the catheter into the selected bronchus.69,70 Under direct vision, the catheter is slowly withdrawn until the inflated balloon is just distal to the level of the carina. In an emergency, an angled Fogarty catheter is inserted through the endotracheal tube under radiographic or fiberoptic guidance into the desired bronchus.71 Absence of a patent lumen extending below the balloon of Fogarty catheters prevents suctioning or oxygen delivery to the occluded lung segment. Bronchial blockers produce less risk of hoarseness and vocal cord injury,72 but they are more difficult to use when the surgeon requests intermittent insufflation or for application of continuous positive airway pressure (CPAP) to the operative lung.
Endobronchial intubation with a single-lumen tube offers an alternative to the double-lumen endotracheal tube that can be especially useful in emergencies. Disadvantages of using a single-lumen tube include loss of ability to selectively ventilate or suction the contralateral lung and increased difficulty in placing or ascertaining correct placement of the tube. Endobronchial intubation is especially useful for patients who require emergent tracheal intubation for massive hemoptysis. For adults, endobronchial intubation requires a tube of adequate length, often more than 31 cm, to ensure that the entire cuff is placed below the carina. Occasionally, it may be necessary to extend the tube using a length of tubing and a connector. Although endobronchial intubation of the right side is easier, there is inherent difficulty in preserving ventilation to the right upper lobe. Mainstem intubation is facilitated using a fiberoptic bronchoscope as a directing stylet. Blind left mainstem placement can be achieved with a 92% success rate by turning the head to the right after the tube has passed through the vocal cords and by then rotating the tube 180 degree so that the convex curve faces posteriorly before advancing it.73
The Univent tube is a single-lumen endotracheal tube that contains a bronchial blocker that passes through a small channel within the wall of an endotracheal tube. The bronchial blocker carries a low-pressure, high-volume cuff and has an internal lumen that can be used for suctioning the collapsed lung or for providing CPAP or high-frequency jet ventilation (Fig. 54-17).74 Initial tube placement in the trachea is accomplished as for any single-lumen tube, then it is rotated 90 degree toward the lung into which the blocker will be passed and advanced (Fig. 54-18). The blocker is then advanced into the targeted mainstem bronchus, after which the tracheal cuff is inflated and the tube is secured. The depth of the blocker is adjusted and confirmed using a flexible bronchoscope passed through the main lumen of the tube. Additional techniques to assist in placing the blocker include rotation of the head and placing the fiberoptic scope in the opposite lung to divert the blocker into the contralateral side. The tube offers the advantage of allowing easy conversion from single- to 2-lung ventilation (and vice versa), and it is suitable for long-term use in an intensive care unit (ICU) setting. The mobility of the blocker and large volume of its cuff increase the likelihood of proximal migration, with herniation of the cuff into the trachea.
Close-up of the Univent tube shows 2 lumens. The small tube is retracted into the small lumen before intubation. [Modified from Kamaya H, Krishna PR. New endotracheal tube (Univent tube) for selective blockade of one lung. Anesthesiology. 1985;63:342.]
The sequential steps of the fiberoptic-aided method of inserting and positioning the Univent bronchial blocker in the left mainstem bronchus are illustrated. One- and two-lung ventilation is achieved by simply inflating and deflating, respectively, the bronchial blocker balloon. FOB, fiberoptic bronchoscope. [From Benumof JL. Separation of two lungs (double-lumen and bronchial blocker intubation). In: Benumof JL, ed. Anesthesia for Thoracic Surgery. Philadelphia, PA: WB Saunders; 1995.]