Thoracic surgery: lung isolation techniques

1

What are the indications for lung isolation?

The absolute indications for lung isolation include:

• 1.

  Protection of a healthy lung from contamination by a diseased lung (i.e., hemorrhage, pulmonary infection, or bronchopulmonary lavage)

• 2.

  Provision of differential lung ventilation in the setting of unilateral lung disease (i.e., bronchopulmonary fistula or large pulmonary cysts or bullae)

Lung isolation is relatively indicated to improve surgical exposure for procedures performed in the thoracic cavity. In the setting of difficult airway or severe patient comorbidities, the safety and need for lung isolation should be discussed with the surgeon before proceeding. For small children, surgical exposure is often achieved with CO ₂ pneumothorax or manual retraction of the operative lung, rather than lung isolation.

2

What types of surgical procedures usually require lung isolation?

Thoracic surgical procedures that may require lung isolation include:

• 1.

  Surgery on the lung, bronchus, or pleura

• 2.

  Surgery on the heart, great vessels, or pericardium

• 3.

  Esophageal surgery

• 4.

  Thoracic spine procedures from an anterior approach

3

What are the techniques for achieving lung isolation?

There are three basic techniques for lung isolation:

• 1.

  Left or right double-lumen endotracheal tube (DLT)

• 2.

  Single-lumen endotracheal tube (ETT) with a bronchial blocker (BB)

• 3.

  Single-lumen ETT placed in a mainstem bronchus (MSB)

4

Describe DLTs.

A DLT consists of two ETTs of unequal lengths molded together with high-volume, low-pressure cuffs located proximal to each luminal opening (endotracheal and endobronchial). Each lumen can be used to isolate, selectively ventilate, or deflate the right or left lung independently, and is color-coded (white for tracheal and blue for bronchial) at the luminal cuff and at their respective pilot balloon. The tracheal cuff is proximal to the tip of the endotracheal lumen and is positioned above the carina; the smaller, blue bronchial cuff is proximal to the endobronchial lumen and is positioned within the MSB. Left and right DLTs are designed to have their respective bronchial lumen placed into the corresponding side MSB. The distal end of a DLT is bifurcated, with a color coded airway tube for each lumen, each attaching to a 15 mm circuit connector adapter.

5

How does the right main stem bronchus differ from the left? How does this affect right-sided DLT design?

The right MSB has a wider lumen and leaves the trachea at a straighter trajectory than the left MSB. The right bronchus has three branches (upper, middle, and lower lobes), whereas the left has only two (upper and lower lobes). The left MSB is longer than the right, with the left upper and lower lobe bronchi diverging from the MSB about 5 cm from the carina. On the right, the upper lobe bronchus leaves the MSB about 1.5 to 2 cm from the carina. The right bronchus intermedius continues and divides into the middle and lower lobe bronchi more distally. Of note, the origin of the right upper lobe bronchus is variable and can sometimes arise from the carina or even the trachea (tracheal or porcine bronchus).

Left- and right-sided DLTs differ in the angulation of the endobronchial lumen and in the location of the endobronchial cuff. Right DLTs have a less angulated bronchial lumen to accommodate the trajectory of the right MSB. Also they have a side port and bronchial cuff that is configured to allow ventilation of the right upper lobe bronchus (when properly positioned). The short length of the right MSB and potential anatomic variation can make proper placement of a right DLT difficult.

6

Describe the placement and positioning of DLTs.

Under direct laryngoscopy, the lubricated DLT is passed through the vocal cords with the distal curvature (bronchial tip) concave anteriorly. The stylet is then removed and, as the tip passes the larynx, the tube is rotated 90 degrees toward the side of the bronchus to be intubated. Final positioning can be achieved either by auscultation or with fiberoptic bronchoscopy (FOB).

Using auscultation, the DLT is advanced gently, until resistance is felt when the endobronchial lumen enters the bronchus. In turn, the endobronchial and tracheal cuffs are then inflated and their lumens clamped while the chest is auscultated bilaterally. A properly positioned left DLT will produce breath sounds on the left side exclusively when the endotracheal lumen is clamped and on the right side exclusively when the endobronchial lumen is clamped. The reverse is true for a right DLT. Note that auscultation alone is often unreliable for proper DLT placement, necessitating bronchoscopy.

Using FOB, the bronchoscope is advanced through the endobronchial lumen of the DLT into the trachea and the appropriate side bronchus. Then, using the bronchoscope as a stylet, the DLT is advanced over the scope into the bronchus. Finally, the bronchoscope is withdrawn from the endobronchial lumen and passed through the tracheal lumen to confirm subcarinal position of the bronchial cuff and ensure patency of the opposite side MSB. It is important to note that the DLT can become dislodged during changes in patient position (e.g., turning to lateral decubitus or head movement), and positioning should be reconfirmed after any of these events. Lastly, when using a right-sided DLT, it must be ensured that the endobronchial cuff does not block the right upper lobe bronchial orifice. Because this often presents a challenge, many clinicians use left sided DLTs almost exclusively, even when isolation of the right lung is indicated. See Figure 63.1 .

7

What are the indications for a right DLT?

Right DLTs are indicated when there is left bronchial pathology (i.e., endoluminal tumors, endobronchial compression, trauma, or tracheobronchial disruption), or when the surgical procedure involves the left MSB (i.e., sleeve resection, lung transplantation, or bronchopleural fistula repair). The only contraindication to a right DLT is a porcine bronchus, in which the right upper lobe bronchus arises at or above the carina.

8

How do you select the appropriate size DLT?

The optimal DLT size is the largest one that will pass atraumatically through the glottis and trachea into the bronchus, with only a small air leak detectable when the cuff is deflated. Using the largest possible DLT allows for better ventilation and clearance of secretions, lower ventilating pressures, faster operative lung collapse and less work of breathing during spontaneous ventilation at the end of the procedure. However, larger DLTs may be more difficult to place and/or cause airway trauma. Smaller DLTs may be easier to place, but the endobronchial cuff will require more volume to create an adequate seal, thereby increasing the potential for bronchial injury or cuff herniation across the carina. They are also more likely to become displaced during the procedure.

Unfortunately, there is no reliable guideline for choosing the correct size DLT. MSB diameters do not reliably correlate with gender, height, or weight. The best estimate (when feasible) comes from measuring the airway diameter with radiological imaging. Many anesthesiologists will select 39 to 41 French ([Fr]; 1 Fr = 0.33 mm) DLTs for adult men (using height of 5′10″ as a cut-off) and 35 to 39 Fr DLTs for adult women (using heights of 5′5″ and 5′10″). The smallest DLT is a 26 Fr, which can be used in children as young as 8 years old.