Answer:

Absolute and relative indications for lung separation are listed in Table 2.2. Several techniques can be used to provide single-lung ventilation, including DLTs, bronchial blocking catheters passed inside or outside an ETT, bronchial blocking catheters incorporated within an ETT (Univent® ETT, Teleflex, Triangle Park, NC), or conventional ETTs placed endobronchially. Newer DLTs include the VivaSight®, ET (ETView Medical Ltd, Misgav, Israel), a left DLT with a high-resolution built-in video camera at the tip of the tracheal lumen that provides a continuous view of the airway; the Silbroncho® (Teleflex, Triangle Park, NC) left DLT constructed of silicone with a wire reinforced tip; and the Cliny® (Create Medic Co, Ltd, Yokohama, Japan) right DLT, a device with an oblong cuff and two ventilation slots for the right upper lobe. Currently, DLTs remain the most common method for achieving lung isolation. Although DLTs of variable design and material have been used in the past (e.g., Robertshaw, Carlens, and White), the models most commonly used today are disposable and made of polyvinylchloride. Such a tube was chosen for this procedure. Several manufacturers produce right and left DLTs that are available in six sizes: 28, 32 (only one manufacturer), 35, 37, 39, and 41 French (size in French = 3.14 × external diameter in millimeters or 4 × the internal diameter + 2). Although the general rule is that average-sized Caucasian men usually accommodate a 39 French and average-sized women a 37 French.

A variety of techniques have been described based on measurements of airway size derived from radiographic or computed tomographic imaging, but these have been questioned across gender and ethnicity. A properly sized DLT should pass atraumatically through the glottis, advance easily into the trachea and bronchus, and exhibit an air leak when the bronchial cuff is deflated.

Bronchial blockers (see section C.9) are a good option for lung isolation in patients who have difficult airways, when postoperative mechanical ventilation is needed, in case of a fresh tracheostomy, or in the pediatric population. Lobar blockade can also be accomplished by using a blocker, especially after pneumonectomy or in case one-lung ventilation (OLV) is not tolerated. Disadvantages of blockers include slow lung collapse, especially in patients with severe COPD, dislodgment of the catheter tip during surgical manipulation of the hilum or being stapled in the bronchial stump.

Independent of the technique chosen, single-lung ventilation is associated with certain disadvantages and complications. The most notable is the large and variable alveolar-to-arterial oxygen tension difference (P_[A-a]O₂) that occurs because of continued perfusion to the nondependent nonventilated lung. The incidence of severe hypoxemia and hypercarbia is relatively small and often the result of DLT malposition resulting from overinflation of the endobronchial cuff, surgical manipulation of the bronchus, or head extension/flexion during positioning in the lateral decubitus. Traumatic laryngitis and tracheobronchial rupture secondary to bronchial cuff overinflation, forceful placement, or airway pathology have also been reported as potential complication of DLT placement.

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