Double-lumen endotracheal tube placement is performed to achieve lung separation. The lungs are paired organs interconnected by bronchi and trachea that function as one unit. However, thoracic surgeons may require lung separation and one-lung ventilation to perform certain procedures and provide optimal surgical exposure. Procedures that require one-lung ventilation include lobectomy, pneumonectomy, pleural decortication, bullectomy, bronchopulmonary lavage, esophagogastrectomy, thymectomy, and mediastinal mass resections.
For double-lumen endotracheal tube placement, the anesthesiologist places a tube with two lumens through which to ventilate the lungs. This double-lumen tube is placed in the trachea, with one lumen in either the left or right bronchial main stem; the other lumen remains in the trachea. This allows the clinician to ventilate both lungs or the right/left lung independently. The operative lung is referred to as the surgical lung or nondependent lung. [1, 2, 3, 4] The image below depicts a double-lumen endotracheal tube.
Of the three methods of lung separation—double-lumen endotracheal tube placement, bronchial blocker, and single-lumen endobronchial tube placement—double-lumen endotracheal tube placement is the most common way of separating the two lungs.  It is not only quicker than the other two methods, but it allows for access into an isolated lung, suctioning from the isolated lung, and application of continuous positive airway pressure if required to improve oxygenation. Ventilation of either or both lungs can be easily achieved. In addition, even though a fiberoptic scope is very helpful with double-lumen endotracheal tube placement, it is not absolutely required, which can also be an advantageous in some situations.
However, double-lumen endotracheal tubes may be challenging to place in patients with difficult airways. Double-lumen endotracheal tubes are not meant for postoperative ventilation. In addition, because of their significantly larger size and stiffness, they have a higher propensity for trauma after insertion, which may result in postoperative hoarseness and/or vocal cord lesions.
One-lung ventilation may be indicated for a number of situations. [6, 7] Generally, lung separation may be used to confine infection or bleeding to one lung, separate ventilation to each lung for certain pulmonary pathology, or for severe hypoxemia due to unilateral lung disease. In addition, it may be indicated for lung resection, repair of thoracic aortic aneurysm, esophageal surgery, bronchoalveolar lavage, or thorascopy. 
Absolute indications are as follows:
Isolation of each lung to prevent contamination of a healthy lung (eg, infection, massive hemorrhage)
Control of distribution of ventilation to only one lung (eg, bronchopleural/bronchopleural cutaneous fistulas, unilateral cyst or bullae, major bronchial trauma/disruption)
Unilateral lung lavage
Video-assisted thoracoscopic surgery (VATS)
Relative indications are as follows:
Thoracic aortic aneurysm
Lung volume reduction
Minimally invasive cardiac surgery
Lobectomy (middle and lower lobes)
Mediastinal mass resection
A double-lumen endotracheal tube should not be placed in the following situations:
Airway lesion or tumor
The anatomy of the respiratory system can be divided into 2 major parts, airway anatomy and lung anatomy.
Airway anatomy can be further subdivided into the following 2 segments:
The extrathoracic (superior) airway, which includes the supraglottic, glottic, and infraglottic regions
The intrathoracic (inferior) airway, which includes the trachea, the mainstem bronchi, and multiple bronchial generations (which have as their main function the conduction of air to the alveolar surface)
Lung anatomy includes the lung parenchyma, which carries part of the conduction system but is mainly involved in the gas exchange at the alveolar level. The lung parenchyma is further subdivided into lobes and segments. See the image below.
The trachea is nearly but not quite cylindrical, flattened posteriorly. In cross-section, it is D-shaped, with incomplete cartilaginous rings anteriorly and laterally, and a straight membranous wall posteriorly. The trachea measures about 11 cm in length and is chondromembranous. This structure starts from the inferior part of the larynx (cricoid cartilage) in the neck, opposite the 6th cervical vertebra, to the intervertebral disc between T4-5 vertebrae in the thorax, where it divides at the carina into the right and left bronchi.
The bronchus (from Greek bronkhos "windpipe") is the part of the respiratory system that connects the trachea to the lung parenchyma. It is composed of an extensive branching system of airway passages that transmit the air from the atmosphere to the alveoli (the gas-exchange units).
Double-lumen endotracheal tubes are available in different sizes (35 Fr, 37 Fr, 39 Fr, and 41 Fr) in both right-sided and left-sided versions. For smaller adults and children, smaller size tubes are available (32-Fr left-sided and 28 Fr).
No single predictor can tell what size tube should be used. A large tube has less chance of being dislodged or producing significant resistance to gas flow. However, the placement of a larger tube should never be a goal of its own and the tube should never be advanced against resistance.
The bronchial tip of a properly sized double-lumen endotracheal tube should have a diameter 1-2 mm smaller than the left main bronchus. Therefore, it is very important to review computed tomography scans before to plan for and prepare the right tube. If there is no time, however, the following general guidelines can be used:
A woman shorter than 160 cm should be intubated with a 35-Fr tube
A woman taller than 160 cm should be intubated with a 37-Fr tube
A man shorter than 170 cm should be intubated with a 39-Fr tube
A man taller than 170 cm should be intubated with a 41-Fr tube
A study by Seymour et al showed that the mean diameter of cricoid ring is similar to main stem bronchus.  Therefore, if the tube cannot be advanced easily through that part of airway, it is probably too large and should be changed for a smaller one. Good preparation is important for a smooth and uneventful intubation process. Therefore, it is important that tubes of one size smaller and larger are readily available during the procedure.
During placement, a curved (MacIntosh) laryngoscope blade is used to intubate the airway. The distal, bronchial (blue) tube is held with the tip directed upward. As it passes through the glottis, the stylet is removed. At this point, the tube is advanced and rotated 90 degrees (towards the side to be intubated) and advanced until resistance is felt; this depth is usually between 28-30 cm.
At this point, the tracheal (white) cuff is inflated, breath sounds are auscultated, and end-tidal CO2 is noted on the capnogram to tell the clinician that the tube is in the airway. At this point, correct tube placement is confirmed by direct visualization via bronchoscopy.
The flexible, fiberoptic bronchoscope is passed down the tracheal lumen. The clinician will deflate the tracheal cuff and pull back until the carina is seen. At this point, tracheal cartilaginous rings are anterior and the tracheal membrane is posterior. Advance the tube until the bronchial blue tip enters the left main stem.
At this point, inflate the blue balloon with 1-3 mL of air until the blue cuff is visible in the left main stem. A portion of the blue cuff should be seen seated in the left main stem.
After placement, the patient is positioned laterally on the operating room table. After positioning, the tube should be checked again to validate that it has not moved. The tube can either become malpositioned by coming out or advancing to a deeper level.
When patient position is changed to lateral, the tube can be displaced, mainly due to extension of the neck. Jeong-Hwa et al suggest that this could be prevented by adjusting the position of the tube when patient is still in the supine position, but after the headrest is removed. 
The clinician should check position periodically throughout the surgery.
After the tube is placed, its placement should be confirmed. This step is very important because correct placement might be of paramount importance on patient outcome. The correct placement might be partially confirmed already if fiberoptic bronchoscope was used during tube placement.
There are multiple methods available to confirm placement, including radiographic verification, auscultation, fiberoptic visualization, and various clinical tests such as selective capnography and use of underwater seal. Currently, the use of multiple methods for confirmation of correct tube placement is widely considered to be the standard of care. Auscultation and fiberoptic examination are used most commonly.
Auscultation is a widely available first-line test. After placement of the double-lumen endotracheal tube, the tracheal cuff is inflated and ventilation is attempted. The patient should have bilateral breath sounds and end-tidal CO2 should be noted on capnogram. This tells the clinician that the tube is in the airway.
Next, the tracheal lumen is clamped and opened. The bronchial cuff is inflated with minimal volume to stop the leak (usually about 2 mL of air). At this point, confirmation of separation of lungs can be done with air bubble leak test. One-sided breath sounds should be heard, only over the desired lung field.
Next, with the bronchial cuff up, the tracheal lumen is unclamped and reconnected, the bronchial lumen is clamped, and ventilation is attempted through tracheal lumen. If the tube is positioned correctly, breath sounds should be heard over contralateral hemithorax. Then the bronchial lumen is unclamped and reconnected and bilateral breath sounds should be audible again. This concludes auscultation for correct placement.
Auscultation is not very reliable, however. Smith et al showed that 48% of blindly placed double-lumen endotracheal tubes were malpositioned.  Another study by Alliaume et al showed that malposition was present in 78% of left-sided double-lumen endotracheal tubes and 83% of right-sided double-lumen endotracheal tubes.  Auscultation should always be supplemented with fiberoptic evaluation and repeated each time the patient is repositioned.
The fiberoptic bronchoscope first is advanced through the tracheal lumen to confirm that the bronchial tube is placed in the desired bronchus. For the left bronchus, the cuff should be ideally placed 5 mm below the carina. It is crucial to identify the right bronchus. The right main bronchus gives off the right upper lobe bronchus, which is the only one that has 3 orifices in it. Then examination through the bronchial tube is done to assure tube patency and determine margin of safety. Therefore, orifices to both upper and lower lobes must be identified. Identification of those bronchi confirms correct placement of a left-sided tube.
If the double-lumen endotracheal tube is malpositioned, it may be in the correct bronchus but too deep, in the correct bronchus but too shallow, or in the wrong bronchus. The table below presents physical examination findings for both correct and incorrect positions.
Table. Troubleshooting Left-Sided Double-Lumen Endotracheal Tube Placement (Open Table in a new window)
|Procedure||Too Deep||Too Shallow||Wrong Bronchus||Correct Position|
Both lumen ventilated
Both cuffs up
|Breath sounds heard on the left and right||Breath sounds heard on the left and right||Breath sounds heard on the left and right||Breath sounds heard on the left and right|
Clamp right lumen
Both cuffs inflated
|Breath sounds heard on the left||Breath sounds heard on the left and right||Breath sounds heard on the right||Breath sounds heard on the left|
Clamp left lumen
Both cuffs inflated
|No breath sounds or severely diminished||No breath sounds or severely diminished||No breath sounds or severely diminished||Breath sounds heard on the right|
Clamp left lumen
|Breath sounds heard on the left||Breath sounds heard on the left and right||Breath sounds heard on the right||Breath sounds heard on the left and right|
In addition to physical examination findings, bronchoscopy is of great value in troubleshooting tube malposition and will help to position the tube.
Even a correctly placed tube can relocate at any time. Surgical maneuvers and patient repositioning can result in tube dislodgement, which can manifest as sudden change in compliance and airway pressures and decrease in tidal volume. Again, physical examination and fiberoptic verification should be undertaken and correct placement of the tube confirmed or changed if necessary.
A left-sided double-lumen tube is preferred for both right- and left-sided procedures. However, there are specific situations for which the use of a right-sided tube is warranted, including compression of left mainstem bronchus by external/internal mass, aneurysm of thoracic descending aorta, left lung transplant, left-sided sleeve resection, left-sided pneumonectomy, and left-sided tracheobronchial disruption. 
Right-sided double-lumen endotracheal tubes are designed differently because the right bronchus is shorter than the left bronchus. These tubes have a cuff with a slot in it to facilitate right upper lobe ventilation. The right-sided tube is much more challenging to place. Most of the failures in correct placement stem from not confirming the placement after the patient is moved.
Based on their studies Campos et al have recommended a modified intubation technique when fiberoptic bronchoscope is used to identify the right bronchus and afterward serve as a guide-wire for the tube placement.