Viva Questions on Double Lumen Tube (DLT) - MD Anaesthesiology Exam

SECTION 1: HISTORY & DESIGN

• Mallinckrodt (Sheridan) DLT - most commonly used disposable PVC
• Rusch DLT
• Phycon/Silbroncho DLT (Fuji Systems - silicone, wire-reinforced, beveled bronchial orifice)
• VivaSight DLT (with integrated camera for continuous visual confirmation)
• ECOM-DLT (measures cardiac output via bioimpedance)

SECTION 2: ANATOMY & RATIONALE

1. The right bronchus diverges at a less acute (more vertical) angle from the trachea; the left diverges more horizontally
2. The right bronchus has upper, middle, and lower lobe branches; the left has only upper and lower lobe branches
3. The right upper lobe bronchus orifice is 1-2.5 cm from the carina; the left main bronchus bifurcates about 5 cm from the carina
4. Anatomic variation exists - the right upper lobe bronchus occasionally arises from the trachea itself

• A tracheal lumen (opening above the carina, with a high-volume low-pressure tracheal cuff)
• A bronchial lumen (passing into the main bronchus, with a low-volume bronchial cuff - usually blue)
• Two separate 15 mm connectors (tracheal and bronchial)
• A right-sided DLT also has a ventilation slot/portal in the bronchial cuff for right upper lobe ventilation

SECTION 3: SIZES AND SELECTION

• Women <1.6 m (63 in) → 35 Fr
• Women >1.6 m → 37 Fr
• Men <1.7 m (67 in) → 39 Fr
• Men >1.7 m → 41 Fr

• Chest X-ray: tracheal width can be measured; left main bronchus width ≈ 0.68 × tracheal width
• CT scan: allows direct measurement of tracheobronchial dimensions; MDCT reveals abnormal anatomy before placement
• Ultrasound: 2D tracheal ultrasound measurements have been validated against CT and can guide size selection

SECTION 4: INDICATIONS

1. Massive hemoptysis - isolation of the bleeding lung to protect the healthy lung
2. Pulmonary abscess / infected cyst - prevent spillage to contralateral lung
3. Bronchopleural fistula - prevent loss of ventilation through the fistula
4. Giant unilateral bullae or cyst - prevent rupture with positive-pressure ventilation
5. Tracheobronchial disruption

• Thoracic aortic aneurysm surgery
• Pneumonectomy, lobectomy, segmentectomy
• Video-assisted thoracoscopic surgery (VATS)

• Esophageal surgery
• Thoracoscopy
• Spine surgery requiring transthoracic approach
• Minimally invasive cardiac surgery

1. Distorted anatomy of the left main bronchus (by intrabronchial or extrabronchial mass)
2. Compression of the left main bronchus by a descending thoracic aortic aneurysm
3. Left-sided pneumonectomy
4. Left-sided single lung transplantation
5. Left-sided sleeve resection (DLT must be on the contralateral side to avoid interference with bronchial anastomosis)

SECTION 5: INSERTION TECHNIQUE

1. Pre-check the tube: inflate tracheal cuff (up to 20 mL) and bronchial cuff (3 mL syringe); apply water-soluble lubricant liberally; insert and lubricate the stylet in the bronchial lumen without disturbing preformed curvature
2. Use a Macintosh (curved) laryngoscope blade - provides the largest area for passage of the large tube
3. Pass the tube with the distal concave curvature facing anteriorly
4. Once the bronchial tip clears the vocal cords, remove the stylet
5. Rotate 90 degrees counterclockwise (for left-sided DLT) so the bronchial lumen enters the left main bronchus
6. Advance until mild resistance is felt (typically 28-29 cm at teeth for a 170 cm patient)
7. Inflate the tracheal cuff and confirm bilateral ventilation
8. Confirm position by auscultation (3-step method) then fiberoptic bronchoscopy

• Step 1: Bilateral ventilation - inflate tracheal cuff to minimal leak seal; auscultate for bilateral breath sounds
• Step 2: Clamp the tracheal lumen ("clamp the short side short"), open the distal port; ventilate via bronchial lumen; inflate bronchial cuff to minimal volume sealing the open tracheal port; auscultate for unilateral (left) breath sounds only
• Step 3: Release tracheal clamp and close port; auscultate for return of bilateral breath sounds

SECTION 6: CONFIRMATION OF POSITION

1. Pass FOB through the tracheal lumen: the carina should be visible, the blue bronchial cuff should be just below and to the left of the carina - the top edge of the blue cuff should be visible at the left main bronchus entrance
2. Pass FOB through the bronchial lumen: both left upper lobe (LUL) and left lower lobe (LLL) orifices should be visible; the longitudinal elastic bundles (posterior membranous wall) can orient anterior-posterior direction

1. Bronchial cuff herniation over the carina
2. Bronchial cuff deflation
3. Inadequate bronchial cuff inflation
4. Surgical manipulation displacing the tube
5. Head/neck extension shifting tube cranially

• Chest ultrasonography: has been used to confirm position with comparable sensitivity to auscultation and can detect correct placement
• Auscultation (3-step method) - not as sensitive as FOB
• Chest X-ray (post-positioning)

SECTION 7: MALPOSITION - 6 TYPES

1. Wrong bronchus - DLT directed to the opposite bronchus. Wrong lung collapses. High airway pressures, inadequate separation, instability. A left-DLT in the right bronchus obstructs the right upper lobe. Immediate correction required.
2. Too deep - Bronchial lumen advanced too far. Breath sounds diminished over contralateral side. Correct by withdrawing the tube until the tracheal lumen opening is above the carina.
3. Not deep enough (tracheal position) - Bronchial lumen opening is above the carina. Bilateral ventilation heard through both lumens; when ventilating through tracheal lumen only, no breath sounds are heard (inflated bronchial cuff obstructs gas flow). Deflate cuff, rotate, and advance the tube.
4. Right upper lobe obstruction with right-sided DLT - The ventilation slot fails to overlie the right upper lobe orifice. The margin of safety is only 1-8 mm. Reposition under FOB guidance; disposable right-sided DLTs with slanted "doughnut" cuffs offer a slightly larger margin.
5. Left upper lobe obstruction with left-sided DLT - The mean distance from the carina to the left upper lobe orifice is 5.4 ± 0.7 cm (men) and 5 ± 0.7 cm (women). The average distance between tracheal and bronchial lumen openings on disposable left DLTs is 6.9 cm - meaning LUL obstruction is possible even with the tracheal lumen above the carina. (20% variation in blue cuff positioning exists between tubes due to manufacturing.)
6. Bronchial cuff herniation - The bronchial cuff herniates over the carina, obstructing ventilation to the dependent lung.

1. Overinflation of the bronchial cuff
2. Surgical manipulation of the bronchus
3. Extension of the head and neck during or after patient positioning

SECTION 8: COMPLICATIONS

1. Hypoxemia - due to tube malplacement, tube occlusion, or excessive venous admixture during one-lung ventilation
2. Traumatic laryngitis - from the large, stiff tube
3. Tracheobronchial rupture - from traumatic placement or overinflation of the endobronchial cuff (more common with PVC tubes due to less compliant cuffs)
4. Inadvertent suturing/stapling of tube to bronchus - detected as inability to withdraw the tube during attempted extubation

1. Overinflation of the bronchial cuff
2. Forceful rotation of the tube during insertion
3. Use in patients with abnormal tracheobronchial anatomy
4. PVC tubes are less compliant than red rubber tubes and more prone to causing bronchial injury if overinflated

• DLTs cause more postoperative sore throat, hoarseness, and airway injuries than bronchial blockers
• BBs are more prone to intraoperative dislodgement than DLTs
• Both provide equivalent quality and time of lung collapse (meta-analysis of 39 RCTs)
• DLTs are quicker to place and less likely to be incorrectly positioned than BBs

SECTION 9: ONE-LUNG VENTILATION (OLV)

1. Increased shunt fraction (non-ventilated lung continues to receive blood flow - the entire right heart output to the collapsed lung contributes to shunt)
2. Hypoxic pulmonary vasoconstriction (HPV) in the non-ventilated lung limits the shunt (reduces blood flow to collapsed lung by up to 50%)
3. Decreased PaO2 (expected drop)
4. Increased airway pressures in the ventilated lung
5. Risk of atelectasis in the dependent (ventilated) lung from high FiO2

• Tidal volume: 5-6 mL/kg (lung-protective strategy)
• PEEP to the dependent (ventilated) lung: 5 cmH2O
• CPAP (5-10 cmH2O) to the non-dependent (collapsed) lung if hypoxemia develops
• FiO2: start at 1.0 initially, reduce to minimize absorption atelectasis
• Monitor for high peak airway pressures

1. Confirm DLT position with FOB
2. Apply CPAP (5-10 cmH2O) to the collapsed (non-dependent) lung
3. Apply PEEP to the ventilated (dependent) lung
4. Increase FiO2 to 1.0
5. Pass a suction catheter through the non-ventilated lumen to assist lung collapse (then remove before surgical stapling)
6. Ask surgeon to temporarily clamp the pulmonary artery to the non-ventilated lung (reduces shunt)
7. Intermittently two-lung ventilate if severe hypoxemia

SECTION 10: DLT vs. BRONCHIAL BLOCKERS

1. Faster to place, less often malpositioned
2. Better lung isolation quality for absolute indications (e.g., hemorrhage, pus, abscess)
3. Allows suctioning of secretions from the isolated lung
4. Allows CPAP to the collapsed lung easily
5. Can alternate OLV to either lung easily
6. Allows independent ventilation of both lungs
7. Superior for bilateral procedures (double lung transplant, bilateral sympathectomy)
8. Gold standard for lung isolation for >50 years

1. Difficult airway (DLT is bulky and hard to place in difficult airways)
2. Already intubated patients (critically ill, ICU)
3. Patient with prior tracheostomy
4. Patients likely to require postoperative ventilation (no need for tube exchange to single-lumen tube)
5. Pediatric patients (no DLT available in small sizes)
6. When tube exchange risk is unacceptable

• Arndt blocker (wire-guided)
• Cohen blocker (tip-deflecting)
• Uniblocker (Fuji)
• EZ-Blocker (Y-shaped, sits at carina)
• Fogarty embolectomy catheter (used in pediatrics and for tamponading bronchial bleeding)

SECTION 11: SPECIAL SITUATIONS

1. Awake fiberoptic intubation with a DLT
2. Use a videolaryngoscope combined with a tube exchange catheter
3. Place a single-lumen tube first, then exchange to DLT using a tube exchange catheter (Silbroncho DLT is particularly designed for this purpose)
4. Consider using a bronchial blocker through the single-lumen tube as an alternative

• DLTs have high resistance to ventilation
• The bronchial cuff risks ischemic damage to the bronchial mucosa
• They are uncomfortable for prolonged intubation
• A bronchial blocker through a standard ETT is preferable if lung isolation is still needed

SECTION 12: ADVANCED/EXAMINER FAVOURITES

• Absolute lung isolation: complete prevention of cross-contamination between lungs (required for hemorrhage, abscess, bronchopleural fistula) - only a DLT with its high-volume seal provides truly reliable absolute isolation; bronchial blockers with their low-pressure cuffs are less reliable
• Relative lung isolation: selective lung collapse for surgical access (VATS, lobectomy) - either DLT or bronchial blocker is acceptable

1. Pre-op review of CT chest to assess tracheobronchial anatomy and plan right-sided DLT size
2. Right-sided DLT selection based on patient height (male/female height criteria)
3. Standard pre-oxygenation and induction
4. Macintosh blade laryngoscopy, pass right-sided DLT with concavity anteriorly, remove stylet after cords, rotate 90° clockwise (right)
5. Auscultation using the 3-step method initially
6. Mandatory fiberoptic bronchoscopy confirmation - confirm blue cuff below carina on right, RUL ventilation slot aligned with RUL orifice
7. Reconfirm after lateral decubitus positioning
8. Manage OLV with lung-protective ventilation (5-6 mL/kg TV, PEEP 5 cmH2O)
9. Have a plan for hypoxemia rescue (CPAP to left lung, FiO2 1.0)

1. Pre-procedure: tracheal width measured by 2D ultrasound can predict correct DLT size (validated against CT measurements)
2. Confirmation of placement: lung sliding sign can confirm which lung is being ventilated; absence of lung sliding on the isolated side confirms isolation
3. May serve as an alternative to FOB for confirming placement when bronchoscopy is unavailable

SECTION 13: QUICK RECALL FACTS FOR VIVA