DLT, Double-lumen endotracheal tube; ETT, endotracheal tube; WEB, wire-guided endobronchial blocker.
From Campos JH. Lung separation techniques. In Kaplan JA, Slinger PD, eds. Thoracic Anesthesia. 3rd ed. Philadelphia: Churchill Livingstone; 2003.
(1) Bronchial blockers consist of catheters with an inflatable balloon that blocks the bronchus. A separate ETT is then placed into the trachea. Bronchial blockers are very useful in patients in whom the securing of the airway is anticipated to be difficult. Current options for stand-alone bronchial blockers include the 8 Fr-Fogarty embolectomy catheter and the wire-guided endobronchial blocker (WEB). The Fogarty catheter is useful in pediatric patients because it comes in smaller sizes. These blockers are inserted through a conventional ETT and guided into the appropriate bronchus using a bronchoscope.
(2) The Univent tube consists of an integrated ETT with a second lumen for a deployable bronchial blocker. After intubation of the trachea has been performed, the blocker is advanced into the bronchus with the aid of the fiberoptic bronchoscope. This tube is as easy to pass into the trachea as a single-lumen tube. The Univent tube is available in sizes from 6 to 9 mm internal diameter (although accounting for the blocker channel, the outer diameter is greater than that of a corresponding-sized ETT). Being of a shape and size more similar to conventional ETTs, the Univent may be a good alternative to a DLT in patients with difficult airways.
(3) DLTs consist of two bonded catheters, each with its own lumen; one lumen is used for ventilating the trachea and the other for ventilating the bronchus. Several types of DLTs have been used in thoracic surgery. The Carlens tube is a left-sided DLT with a carinal hook to aid in stabilization of the tube. Insertion is difficult, and the hook can cause vocal cord damage. A White tube is a right-sided DLT with a carinal hook.
(4) The Robertshaw DLT is available as a right- or left-sided DLT without a carinal hook. Disposable polyvinyl chloride tubes are available in French sizes 26, 28, 35, 37, 39, and 41. These correspond to internal lumen diameters ranging from 3.4 to 5 mm, respectively. Although the presence of dual lumens limits the internal diameter of each, the external diameter of a DLT is very large. The 37 Fr-DLT has an outer diameter equivalent to that of a standard 11.0 mm ID ETT. For this reason, DLTs are not used for small children; the external diameter of the 26 Fr-DLT is 7.5 mm. Sizing of DLTs is determined by patient height, usually leading to use of 35- to 37-Fr tubes in female patients and 39- to 41-Fr tubes in male patients.
(5) Modifications have been made in right-sided tubes to allow ventilation through a slot in the endobronchial cuff. It is thought that a greater margin of safety is associated with the use of a left-sided DLT for all right and left thoracotomies unless a left-sided tube is contraindicated.
(6) Contraindications to the use of DLTs include internal lesions of the trachea or main bronchi; compression of the trachea or main bronchi by an external mass; or the presence of a descending thoracic aortic aneurysm, which can compress or erode the left main bronchus. In these circumstances, it may be possible to use a DLT with the bronchial lumen on the unaffected side. Another contraindication is a difficult airway in which direct laryngoscopy is impossible. Intubation with the large DLT can pose a challenge even in patients with a normal airway; insertion in those with poor airway anatomy may require a creative approach.
b) Placement of DLTs
(1) The DLT has two curves along its length to aid in its placement. A stylet aids placement through the larynx. Some practitioners prefer the Macintosh blade for intubation because it offers greater clearance for the tube and may decrease the chance of balloon rupture from the teeth.
(2) For laryngoscopy, the lubricated DLT is advanced with the distal curve concave anteriorly until the vocal cords are passed. The stylet is usually removed at this point. The tube is then rotated 90 degrees toward the bronchus to be intubated and advanced to around 27 cm depth in female patients or 29 cm in male patients or until resistance is met.
(3) Usually the stylet is removed after the tube has passed the glottis because of concern about the rigid tube causing mucosal damage. One study found that the success of initial placement was significantly improved by keeping the stylet in place until the tube was fully situated in the bronchus. This technique was not associated with increased tissue trauma.
(5) Overinflation of the bronchial cuff can cause its lumen to be narrowed or occluded and increases the risk of tearing the bronchus. Unlike most tracheal high-volume, low-pressure cuffs, the bronchial cuff holds a small volume and can produce high pressures on the endobronchial mucosa. For that reason, the bronchial cuff should be deflated during the procedure once OLV is no longer needed.
c) Auscultation of breath sounds after placement of a DLT
(2) Verify bilaterally equal breath sounds. If breath sounds are present on only one side, both lumens are in the same bronchus. Deflate the cuff and withdraw the tube 1 to 2 cm at a time until breath sounds are equal bilaterally.
(6) Verify that breath sounds are equal at the apex of the lung and at the lateral lung. If the apex is diminished, withdraw the tube until upper lung sounds return.
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