The core curriculum asks us to list 'the available types of tracheal tube and identifies their applications', which presumably includes double-lumen tubes.
The intermediate curriculum goes one step further in seeking a suitable description of 'placement of double lumen endobronchial tubes and bronchial blockers'.
Both double-lumen tubes and endobronchial blockers may feature in Final FRCA questions on one-lung ventilation.
Lung isolation and selective one-lung ventilation is used during a number of surgeries in the thoracic region
This is normally achieved through the use of double-lumen endotracheal tubes or bronchial blockers
Trachea
The adult trachea begins at the lower border of the cricoid cartilage at C6
It ends at the carina at T4 (Angle of Louis), although this may be as low as T6 during inspiration
It is 10-12cm in length, although this increases by up to 2cm during inspiration
Diameter approximates to the size of patient's index finger:
Men: 15-25mm
Women: 10-20mm
Main bronchi
The trachea bifurcates at the carina into right and left main bronchi at the level of T4-T6
The right main bronchus is:
Shorter - as the RUL bronchus arises after 2.5cm
Wider - as it supplies the larger lung
More vertically (25°) orientated with respect to the carina
The left main bronchus is:
Longer - 5cm
More horizontally (45°) orientated as it must pass laterally under the aortic arch to reach the hilum of the left lung
Considerations for DLTs
As the right main bronchus is shorter, there is a risk the bronchial cuff of a right-sided DLT could obscure the RUL bronchus
Right-sided DLTs therefore have an orifice on the lateral side of the endobronchial portion to facilitate ventilation of the right upper lobe
However, to obviate the risk of RUL bronchial obstruction entirely, a left-sided DLT is generally preferred regardless of the operative side
There are exceptions, with indications for a right-sided DLT including:
Surgery involving the left main bronchus e.g. left pneumonectomy, left lung transplant, repair of left-sided tracheobronchial disruption
Proximal obstruction of the left main bronchus
Severe distortion of the left main bronchus e.g. thoracic aortic aneurysm, enlarged left atrium
Airway device
Advantages
Disadvantages
DLT
Quicker to place Can ventilate either lung Less prone to displacement Facilitates suctioning of either lung
Difficult to place if abnormal anatomy Limited sizes Not ideal for post-operative ventilation High risk of airway trauma Not suitable if <35kg Reduced ID of each lumen increases resistance
Bronchial blocker
Easy size selection Can be used with standard ETT Easily withdrawn for post-operative ventilation Selective lobar isolation possible Less airway trauma Suitable for use with tracheostomies
Takes more time to insert Suction of isolated lung less effective Difficult to alternate sides More prone to displacement
DLTs are the default choice
Bronchial blockers may be preferential in:
Paediatric patients
Tracheostomy patients
Those with difficult glottic or tracheal anatomy
Those in whom selective lobar isolation is desired
Double-lumen endotracheal tubes
The DLT has many features in common with a standard ETT
There are some key differences, arranged below from proximal (ventilator end) to distal
Special features of the DLT
Soft silicon portion of the ventilator connector, to ensure that it can be clamped safely without fracturing
Y-shaped catheter mount often comes with the tube to connect the two lumens to the breathing circuit
Two lumens (duh!) each with their own bevel
Lumens are colour coded:
White or clear = tracheal
Blue = bronchial
Two curves; the standard anterior curve and a second right or left bronchial lumen curve
Each lumen has its own cuff with colour-coded pilot balloons (same colours as above)
The cuffs differ in their nature:
Tracheal cuff: a standard low-pressure, high-volume cuff
Bronchial cuff: a high-pressure, low-volume cuff which risks mucosal injury if a smaller tube used (need greater cuff inflation) for prolonged surgery
There are specially designed, eccentric-shaped cuffs for right-sided DLTs, which prevent the obstruction of the right upper lobe bronchus
Types of DLT
Modern DLTs
Single-use, latex-free PVC tubes
Require an introducer (stylet) to facilitate placement
Made by the usual suspects; Mallinckrodt, Portex, Smith Medical etc.
Upgraded versions include:
The VivaSight 2 left-sided DLT (Ambu); it features a tracheal lumen camera to facilitate positioning
The Silbroncho DLT (Fuji); it features a flexible wire-reinforced bronchial lumen, which can conform with an acutely angulated bronchus
The original DLT was the Carlens tube, a left-sided DLT
Use a carinal hook to aid positioning, which could cause trauma to larynx or carina
Its right-sided equivalent was the White DLT
They suffered from having small lumens, with consequent higher airway resistance and difficulty suctioning secretions
The Robertshaw DLT was an improved version of the Carlens tube
Made of red rubber
No carinal hook
Larger lumens
Came in small, medium and large sizes
DLT sizing
Height (cm)
DLT size (Fr)
Approx. depth of insertion (cm)
AEC size (Fr)
<155
35
27
11
155 - 165
37
28
11
165 - 175
39
29
14
>175
41
30
14
DLTs use the French (Fr) gauge system, where 1Fr = an outer diameter of 1/3rdmm
I.e. a 37Fr tube corresponds to an outer diameter of ~12mm
One can also size the tube based on the patient's relevant main bronchus diameter (e.g. on pre-operative CT), although this is not infallible
Insertion
Select the appropriate size tube (see above)
With the patient anaesthetised, insert the tube in a standard orientation i.e. primary curve facing anteriorly
Insert the DLT such that the tip is just through the vocal cords, then remove the stylet
Turn the DLT 90° towards the intended side of bronchial intubation, commonly a 90° anti-clockwise turn, which helps traverse the thyroid cartilage
Advance the tube until an appropriate depth is reached
Inflate the tracheal cuff and perform standard checks to ensure endotracheal intubation has occurred
Checking positioning (presumes left DLT)
Clamp the tracheal lumen and open it to air
This causes all ventilation to occur via the bronchial lumen, and so there should be predominant ventilation of the left lung
One should also be able to feel a degree of air leak from the open tracheal lumen as air flows from the left main bronchus back to the trachea in a retrograde fashion
Inflate the bronchial cuff (1-2ml of air)
This should stop the flow of air from the tracheal lumen as the left lung is isolated
Unclamp the tracheal lumen and instead clamp the bronchial lumen
This should cease any airflow to the left lung and instead cause unilateral right lung ventilation
If both lungs ventilate, it implies the tube is inserted to too shallow a depth
If there is poor right lung ventilation or resistance, it implies the tube is inserted too deeply with occlusion of the tracheal lumen e.g. at the carina or in the LMB
If the above is satisfactory, proceed to bronchoscopic checks
Clamp the tracheal lumen i.e. left lung ventilation only
Insert the flexible bronchoscope into the tracheal lumen
Identify:
Carina
Bronchial lumen in left main bronchus
Right main bronchus, confirmed by presence of right upper lobe bronchus and its characteristic '3-leaf clover' or 'mercedes benz' orientation of segmental bronchi
Can deflate cuffs and adjust tube position to optimise bronchial cuff within the left main bronchus, ensuring no herniation
If a right-sided DLT is inserted, an additional bronchoscopic check is required to ensure no occlusion of the right upper lobe bronchus
One should perform these checks at insertion, after positioning the patient on the operating table, and prior to one-lung ventilation
Complication
Failure of intubation/isolation
Malposition
Hypoxaemia
Traumatic laryngitis
Tracheo-bronchial injury
Acute lung injury
Segmental or lobar collapse
Re-expansion pulmonary oedema
Accidental suturing of tube to bronchus during surgery
Blockage of upper lobe bronchus
Malposition
Displacement and migration of the DLT can occur during patient (re-)positioning
It manifests as poor lung compliance, increased peak inspiratory pressure, reduced tidal volume and hypoxia
The overall management is with immediate deflation of the bronchial cuff:
Will allow two-lung ventilation if incorrect bronchus intubated
Will allow two-lung ventilation if the DLT has migrated proximally
Restore ventilation to the upper lobes if the DLT has migrated distally
This can then be followed by definitive repositioning of the DLT with a fibrescope
Incorrect bronchus intubated
Evidenced by the wrong side being ventilated when the tracheal lumen is clamped and the bronchial cuff is inflated
Corrected by using the flexible bronchoscope via the bronchial lumen to aid withdrawing of the tube (with cuffs down) and re-advancement down the correct bronchus
Position is then re-checked
Tip too shallow
The commonest malpositioning complication
Evidenced by:
Failure of lung isolation with both lungs ventilated via the bronchial lumen
Difficulty ventilating either lung via the tracheal lumen (as bronchial cuff obscuring distal trachea)
Corrected by advancing the tube under bronchoscopic guidance
Tip too deep
Evidenced by poor ventilation of the upper lobe ± hypoxia during ventilation via the bronchial lumen
May also have difficulty ventilating either lung via the tracheal lumen (as tracheal lumen is abbutting carina or is in a main bronchus)
Corrected by withdrawing the tube under bronchoscopic guidance
Airway trauma
Often manifests as minor airway trauma as with any intubation e.g. hoarse voice, sore throat
More significant trauma is rare e.g. arytenoid dislocation, vocal cord injury, airway rupture
Overinflation of the cuffs, particularly the bronchial cuff, can lead to mucosal injury with the risk of scar formation and stenosis
Endobronchial blockers and alternatives
The endobronchial blocker is an alternative to the DLT
Comparable efficacy of lung isolation vs. DLT in elective thoracic surgery
Beneficial in certain patient groups:
Distorted anatomy not amenable to DLT
Paediatric patients
Tracheostomy patients
Selective lobar isolation required
Types
Typically a 9Fr, 78cm long catheter
Has a distal cuff inflated via a pilot balloon
Different types include:
The Arndt blocker (dependent)
Features a wire loop at the distal end to allow coupling to the bronchoscope
The Cohen blocker (independent)
Features a proximal end clickwheel which allows the operator to control the degree of catheter tip deflection and thus guide positioning
The Rusch EZ-blocker
Features a Y-shaped tip which sits on the carina, with both arms having a distal balloon
Allows the operator to selectively ventilate either lung without having to reposition the blocker
Insertion
Patient intubated using standard ETT (size 8.0 recommended)
A multi-port adapter is connected to the ETT 15mm connector
Blocker advanced using a paediatric bronchoscope into the desired main bronchus
'Scope is withdrawn to the trachea to check appropriate positioning
When position satisfactory, balloon is inflated to seal off the desired bronchus
The blocker position is secured via the multi-port adapter
Endobronchial intubation using a standard endotracheal tube
Benefits from being rapidly achievable and familiar, without the need for specialist equipment
Suffers from a high risk of bronchial damage and limited options for managing hypoxaemia during one-lung ventilation
Using non-specialised catheters to block a main bronchus in lieu of a bronchial blocker