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Anaesthesia - single lung ventilation at Starship

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This guideline aims to facilitate successful Single Lung Ventilation (SLV) in children using the equipment available in Starship Hospital at the time of writing. It does not cover details of the conduct of thoracic anaesthesia and analgesia in children.

Potential Indications

  1. Prevention of contamination of one lung from the other eg. infection, haemorrhage.
  2. Control the distribution of ventilation eg bronchopulmonary fistula, lung cyst or bullae.
  3. Extensive bronchopulmonary lavage
  4. Assist in improved surgical exposure eg. thoracoscopic surgery, non pulmonary surgery.

Background Knowledge

Anatomy

A basic knowledge of airway anatomy is required to provide safe and effective anaesthesia for one lung ventilation in children.

Figure 1. Bronchoscopic view of Trachea and Major Bronchi

bronchoscopic view 

Recognition of the variable origin of the Right Upper Lobe (RUL) bronchus is of particular importance: in the majority of patients it originates from the right main bronchus, distal to the carina. However, even allowing for the age of the child, this distance can be extremely variable. A RUL bronchus originating at the carina or even from the trachea is not unknown ("Pig Bronchus", ≈1-2% of population), producing a three lumen carina together with a right sided Intermediate bronchus (Fig 2.), and has significant implications for selecting possible single lung ventilation strategies (see below).

Figure 2. 3-lumen carina with "Pig" Bronchus

Right sided bronchus

The internal diameter of the trachea depends upon age and subsequently gender in post pubertal patients. The trachea is roughly cylindrical in shape with an Antero Posterior (AP) diameter slightly less than the corresponding transverse diameter (assuming no intrinsic or extrinsic narrowing or compression) . Pubertal growth in the female trachea tends to commence  at a slightly earlier age than the male but stops by about 15 years of age. In boys tracheal enlargement can continue for several more years (Fig 3a+b). 

Fig 3a. Mean AP & Transverse diameters and Fig 3b. Mean Cross sectional (cm2) area of children by age

Mean AP and transverse                 Mean cross sectional


Useful References:

Cross-Sectional Shape of the Child's Trachea by Computed Tomography. NT Griscom. Am J Roentgenol 1983.140 (6), 1103-1106. 
Dimensions of the Growing Trachea Related to Age and Gender.Gnscom &WohI. Am J R 1986. 146. 233-237.

It is important to realise that the figures quoted relate to mean values sampled from a single  population from North America and that there can be a wide variation even within this population. There may be significant diferences in actual size within our local population! Given this variation it is recommended that you analyse each patient's own radiological studies for greater accuracy (see below).

Imaging

Almost all patients will have had a CXR to review and many will have had a CT scan. Review of the imaging allows:

  1. Confirmation of the clinical diagnosis and correct side for operation. Extent of any pulmonary disease may indicate likely respiratory reserve under general anaesthesia. This may be significant if obtaining SLV may be difficult and/or prolonged.
  2. Assessment of the central airways (Fig 4):  
    1. Tracheal shape and dimensions on axial scans 
    2. Carinal and major bronchial anatomy on coronal scan.
 Normal carina  Pig bronchus small  Tracheal cross section
Figure 4.1 Normal carina Figure 4.2 "Pig bronchus" Figure 4.3  Tracheal cross section

Airway options

  • Single Lumen Tube (SLT) (endobronchial intubation)
  • Double Lumen Tube (DLT)
  • Univent tube*
  • Endobronchial blocker+
  • Do without!

*Not discussed further since no longer available at Starship Hospital.
+ Very rarely other methods may be used eg Fogarty arterial embolectomy catheters in neonates etc. These will not be discussed further in this resource.

As will be discussed the most significant factor influencing your method of achieving Single Lung Ventilation (SLV) is the age and thus size of the patient. Other factors include the size and availability of bronchoscopes, patient factors such as airway and respiratory problems and available skills.

Equipment required for confirmation of lung isolation in Starship Hospital Operating Rooms

Flexible bronchoscopy 

Sizes available
2.2mm (OD) No suction port; very fragile!
3.1mm (OD) • Light source and image display options: camera stack for thoracoscopy or
  video laryngoscope (CMAC) screen (both have recording options).

• Ultrastop
• Lubricant
• Appropriate size bronchoscope connector to allow ventilation during bronchoscopy
• Appropriate size suction catheters for ETT and DLT

Single Lumen ETT (SLT)

  • Deliberate endobronchial intubation of non operative side
  • Standard ETT used (smaller size?)

Sizes available (see Table 1 below for more detail): 

Sheridan Uncuffed ETT: ID 2.0 -7.0mm.

Sheridan Cuffed ETT: ID 5.5-7.0 mm.

MicroCuff ETT: 3.0-5.0 mm. (NB no Murphy's eye, Fig.5) 

Figure 5.   Uncuffed ETT with Murphy's eye v Microcuff ETT (no Murphy's eye)

 Murphy's eye  No murphys eye

Table 1.  Internal and external dimensions of available ETT's at Starship Hospital

Table1 ETTs

Potential Advantages Potential Disadvantages
Quick & easy placement  LMB intubation more difficult than RMB.
Applicable to all ages Uncuffed ETT may prevent adequate seal of bronchus. 
Cuffed ETT may require smaller size and thus reduced ventilation  and increased risk of blockage.
Lack of Murphy's eye increases risk of inadequate ventilation of  Right upper lobe when RMB intubated.
No special equipment needed  Unable to ventilate/suction operative lung without repositioning  ETT.

Double Lumen Tube (DLT)

Disposable right and left (more commonly used) sided DLT's available.

Sizes available - see Table 2 below 

Rusch 26Fr (left sided only)

Mallinckrodt 28Fr (Left sided only), 35Fr, 37Fr, 39Fr (right & left sided)

Left sided DLT preferred because of ease of insertion and accurate positioning. Variation in RUL bronchial anatomy means that accurate and reliable positioning of a Right sided DLT to produce effective RUL ventilation can be difficult.

Contraindications to Left DLT use include left pneumonectomy and complex surgery around the hilum/LMB (both extremely rare in paediatric practice).

  lumens

Table 2. Internal and external dimensions of Mallinckrodt (*Rusch) DLT's available at SSH

DLT size (FR) OD mm "limiting" lumen ID mm Appropriate FOB size
26* 8.7 ? 2.2
28 9.3 3.1 2.2
35 11.7 4.8 ≥3.1
37 12.3 5.1 ≥3.1
39 13.0 5.3 ≥3.1

Checking adequacy of DLT placement:

Clinical check involves:
- inspection for chest movement
- auscultation 
- "feel" for compliance changes when manually ventilating.

Assuming Left sided DLT & both cuffs inflated:

DLT chart 1

Bronchoscopic check: Tracheal lumen view*: Lumen should be above carina to allow unimpeded view and ventilation of RMB. Proximal end of bronchial (blue) cuff should be visible in LMB sufficiently distal to carina to prevent possible proximal herniation and obstruction. Bronchoscope must be small enough to safely pass down at least the tracheal lumen (preferably both lumens) of DLT and long enough to exit bronchial lumen of DLT. Check before placement! See Table 2.

 DLT chart 2

Arndt Endobronchial Blocker

AEB 1

Notes:

Blocker parts colour coded for ease of recognition in vivo where small size, secretions and poor bronchoscopic view inhibit easy visualization: Catheter- yellow ; Balloon -blue. 

Coloured (dependent on manufacturer) line on ETT allows orientation through FOB view.

Originally designed to be placed with the aid of a flexible bronchoscope passed down an ETT ("Coaxial" placement) with the aid of the supplied introducer and removable distal wire loop:

AEB 2              

AEB 3

However due to the physical constraints (see below) imposed by the size of available bronchoscopes and smaller ETT needed in infants and babies a "Parallel" technique is used. This involves positioning the BB outside of the ETT. This is most commonly done "blindly" before intubation. Correct position is confirmed with a FOB passed down an ETT before the balloon is inflated. Repositioning can be done at this time, particularly from RMB to LMB.

ETT diagram

Sizes of BB available:

Catheter size (Fr) Length (cm) OD (mm) Balloon size (ml) Min. ETT (ID mm)
for coaxial tech. with*
2.2 FOB 3.1 FOB
5 50 1.7  0.5 - 2  4.5  6.0
65  2.3  2 - 6 5.5  6.5 
78   4 - 8 6.5  7.5 

*NB sufficient internal cross sectional area must remain to allow 1. Safe and easy passage of FOB/BB and 2. in difficult placement or children with limited reserve, effective ventilation and oxygenation. 

Always confirm safe combination of sizes & check shape and integrity of balloon prior to placement.

Coaxial placement  

General rule: FOB OD +BB OD < ETT ID

The ETT must have sufficient internal diameter(ID) to allow easy and safe passage of both FOB and BB during placement. Beware the risk of disrupting BB position when removing the FOB. 

Sufficient cross sectional area must remain to allow effective ventilation if the patient has low respiratory reserve and/or placement is prolonged. Check for fit before intubating and lubricate both FOB and BB. 

Parallel placement

General rule: ETT OD +BB OD < Trachea ID 

Consider using a cuffed ETT since it may help stabilize adjacent BB catheter.

Advantages Disadvantages
"Normal" intubation/ETT  Slower to place
Allows Lung/lobar occlusion  Needs FOB for placement?
High Vol/Low pressure cuff less traumatic?  Lung collapse slower than with DLT
Central port allows suction of air/secretions and delivery of-O2 /PEEP   PEEP Balloon fragile
Can be placed in patients with difficult intubations/airway Risk of catheter/balloon migration (esp.  Right side):
1. Loss of lung isolation
2. Potential airway occlusion
Can be placed via nasal route/ETT Balloon maybe too small for bronchial occlusion
Can be placed via tracheostomy Once wire loop removed can't be replaced (except 9Fr catheter) 
Removed without extubation   

Lung spirometry

Provides additional useful confirmation of lung separation, and continuous monitoring of compliance changes during surgery and following therapeutic interventions, including reinflation at the end of surgery.

 lung spirometry 

Potential Discussion Points

  1. Use of a cuffed ETT may help stabilize a Bronchial Blocker placed using the external ,parallel technique. 
  2. Parallel placement via the nasal route has also been advocated by some to aid stabilization and thus reduce the risk of BB dislodgement.
  3. In adult practice, routine checking of  DLT/BB placement with the FOB is often  recommended at key moments ie following insertion, movement from the supine to lateral position or when clinical suspicion is aroused.

    In paediatric  practice this may not be feasible due to a lack of an appropriately  sized FOB. In addition, passage of an FOB may increase the risk of dislodgement of a BB (coaxially or parallel placed). Repositioning the BB into the appropriate main/lobar bronchus, especially if the child is in the lateral position and/or  surgery has commenced can be extremely difficult! Remember that with the exception of the 9Fr BB the distal wire guide loop once removed can not be replaced. Regular clinical assessment (inspection, auscultation)  together with continuous spirometry may provide a quicker and less problematic alternative.

Single Lung Ventilation (SLV) set up Wizard

Click on the following link to view the SLV set up Wizard.

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Document Control

  • Document type: Clinical Guideline
  • Services responsible: Paediatric Anaesthesia
  • Author(s): Peggy Yip, Henrik Hack
  • Editor: Greg Williams

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