Double-Lumen Endotracheal Tube Placement

Background

Double-lumen endotracheal tube (DLT) placement is the most common technique to achieve lung separation. The lungs are paired organs interconnected by bronchi and trachea that function as one unit. However, isolation of one side from another may be required to optimize visualization for certain surgical procedures within the thoracic cavity, such as operations on the lung tissue, esophagus, mediastinal structures, thoracic vasculature, and thoracic spine. Additionally, lung isolation allows for management of certain pathological conditions of the lung including unilateral lung hemorrhage, infection, trauma, bullous disease, or bronchopleural fistula. 

The DLT, comprising two parrallel lumens, is placed through the vocal cords into the trachea with the shorter tracheal lumen terminating in the trachea, and a second, longer lumen extending into either the left or right main bronchus. Each lumen has a cuff that is inflated to create a seal. This allows the clinician to ventilate both lungs or the right or left lungs independently. ^{[1, 2, 3, 4]}  The ventilated lung is referred to as the dependent or non-operative lung. A DLT is designated as either left or right, depending on which bronchus the bronchial lumen is designed to terminate in. Left-sided DLTs are used more frequently as they are significantly easier to place without obstructing the upper lobe bronchus. A right DLT includes an orifice along the bronchial tube to align with and ventilate the RUL. The image below depicts a double-lumen endotracheal tube.

Compared to other methods of lung separation (bronchial blocker, and single-lumen endobronchial tube placement) a DLT is advantageous because both lungs can be accessed for ventilation, fiberoptic visualisation, suctioning, or application of CPAP. It is also quicker and easier to place than a bronchial blocker. ^[5]  

However, because of their significantly larger size and stiffness, DLTs have a higher propensity for trauma after insertion, may be challenging to place in patients with difficult airways, and are not intented for post-operative ventilation. In addition, right-sided DLTs are difficult to place without obstructing the right upper lobe bronchus.

Indications

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. ^[8]

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

• Pneumonectomy

• Lung volume reduction

• Minimally invasive cardiac surgery

• Upper lobectomy

• Esophageal procedures

• Lobectomy (middle and lower lobes)

• Mediastinal mass resection

• Thymectomy

• Bilateral sympathectomies

Contraindications

A double-lumen endotracheal tube should not be placed in the following situations:

• Difficult airway

• Small patients

• Airway lesion or tumor

Relevant Anatomy

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 overlying the trachealis muscle that runs longitutidinaly along the posterior wall of the trachea. 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). The right main bronchus is shorter and steeper than the left, with its upper lobe branch take-off occuring closer to the carina. Knowledge of the tracheal-bronchial anatomy and it's endoscopic appearance is vital for successful placement confirmation with the bronchoscope.

For more information about the relevant anatomy, see Lung Anatomy, Trachea Anatomy, and Bronchial Anatomy.

Tube Selection

A left DLT is most commonly used as it avoids inadvertent obstruction of the right upper lobe (RUL) bronchus that can occur with a right DLT. Right-sided tubes may be required for left pneumonectomy, left lung transplant, or when there are anatomical distortions of the left main bronchus. DLTs are sized by their external diameter measured in French Guage, and are available in 35 Fr, 37 Fr, 39 Fr, and 41 Fr for adults, and 26 Fr, 28 Fr, and 32 Fr for children.

Traditionally, and still most commonly, gender and height are used to select DLT size, however, this alone may lead to frequent under or over-sizing of the DLT. Roldi and collegues report a 60% incidence of missized DLTs with height/gender correlation alone. ^[9]  Use of tracheal or bronchial diameter measurements from plain film, comuted tomography, or ultrasound modalities has been suggested to improve accuracy of sizing by some, ^[10]  while others show poor correlation. ^[11]  Hence debate still exists in best method of DLT size selection. An optimally sized DLT is the largest tube to fit easily into the main bronchus while still allowing a leak around the tube with the bronchial cuff deflated, and not requiring more than 3mL (or manufacturer's recommendation) of air to the bronchial cuff to create a seal. DLTs that are too large or small can lead to airway trauma, malpositioning, or suboptimal lung isolation.

Using height/gender method, 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

For pediatric patients, size is chosen by age: 26 Fr for 8–10yrs, 28 Fr for 10–12yrs, and 32 Fr for 12–14yrs.

A study by Seymour et al. showed that the mean diameter of cricoid ring is similar to main stem bronchus. ^[12] Therefore, if the tube cannot be advanced easily through that part of the 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.

Tube Insertion

The most common method of placement involves direct laryngoscopy to intubate the trachea, followed by blind advancement to achieve endobronchial intubation. ^[13] The distal, bronchial tube is held with the tip directed upward. As it passes through the glottis, the stylet is removed and the tube is advanced and rotated 90 degrees (towards the side to be intubated) until resistance is felt; this depth is usually between 28 and 30 cm. At this point the bronchial lumen should be sitting within the bronchus, with the tracheal lumen above the carina. 

The tracheal cuff is inflated, and ventilation is provided through both lumens. Chest rise, breath sounds, and end-tidal CO₂ on the capnogram all tell the clinician that the tube is in the airway. At this point, correct tube placement is verified via bronchoscopy (see position verification).

Alternatively, after the DLT is passed through the cords into the trachea, its advancedment may be guided directly with the fiberoptic bronchoscope. This is, however, more time consuming, but may lead to increased accuracy of initial placement especially with a right-sided DLT. ^{[13, 14]}

Position Verification

After the tube is placed, its placement should be confirmed. Although sequential auscultation is the traditional and widely available method, it is not as accurate as fiberoptic examination, which is preferred.

Auscultation

After placement of the double-lumen endotracheal tube, the tracheal cuff is inflated and ventilation through both lumens is attempted. The patient should have bilateral breath sounds.

Next, the bronchial cuff is inflated, the tracheal lumen is clamped, and bronchial lumen ventilated. One-sided breath sounds should be heard, only over the desired lung field.

Next, 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 only. 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. ^[15] 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. ^[16] Auscultation should always be supplemented with fiberoptic evaluation and repeated each time the patient is repositioned.

Fiberoptic bronchoscope

The flexible, fiberoptic bronchoscope is first passed through the bronchoscopy port down the tracheal lumen. The tracheal lumen should terminate above the carina, and the bronchial lumen should be seen entering the intended bronchus, with the blue bronchial cuff just visible below the carina. Knowledge of tracheal bronchial anatomy is essential to identify landmarks and orientation. The bronchoscope is then removed from the tracheal lumen and passed down the bronchial lumen to confirm patency and correct location. In the case of a right DLT, the RUL orifice in the bronchial tube should be assessed to align with the RUL bronchus. 

Correct DLT placement should be verified after placement, after patient repositioning, and periodically throughout the surgery. In particular, when the patient position is changed to lateral, as is commonly done for thoracic surgeries, 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. ^[17]

DLT with integrated camera

The VivaSight-DL (ETView Ltd) is a novel DLT with a camera embeded at the tip of the tracheal lumen, which when connected by cable to the monitor, allows endotracheal visualisaiton. It has been reported to lead to faster placement of the DLT, faster recognition and correction of malposition, and decreased need for fiberoptic bronchoscopy, however, it has been linked to increased airway trauma, trouble with lens fogging, and overheating of tracheal tube tip due to extended camera connection. ^[18]

Troubleshooting

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)

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.

Right-Sided Procedure

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. ^[5]

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. ^[3]