One Lung Ventilation: Difference between revisions

Latest revision as of 17:41, 24 September 2024

Introduction

- Pediatric thoracic anesthesia is more challenging than Adults

- DLT is gold standard for children > 8 Yrs

- Available devices for Peds OLV: DLT, BB, Uninvent Tubes, SLT

- Caution with BB due to high pressure balloon cuffs - Many surgical procedures in the chest need OLV, but some can be done without it

ABC”D” OF Pediatric Lung isolation


ABC"D" of Pediatric Lung Isolation
A	Anatomy
B	Bronchoscopy
C	Chest imaging
D	Diameter change with age

Important measurements

- How to know if FOB fits in the Tube?

ODB/IDTT < 0.9

- To allow some ventilation during bronchoscopy

ODB/IDTT < 0.7

Example: smallest FOB in use has OD of 2.2 mm, placing this Scope through 2.5 SLT gives an ODB/IDTT ratio of 2.2/2.5 or 0.88

This ratio is <0.9 but >0.7, the bronchoscope will physically fit inside the TT, but no ventilation will be able to occur!

Tip: Bronchoscopes can become deformed from repeated use and cleaning, and the tip may have a larger diameter than documented

>>> It’s always a good idea to test the fit of the bronchoscope inside a TT before use in the patient

Pediatric Airway Diameters

- Average neonatal trachea has an AP diameter of about 4.3 mm for both males & females

- Trachea grows uniformly in males and females to about 14 mm at the age of 15 yrs old

- At this time, female trachea stops growing, but male trachea continues to grow to 16–18 mm by age of 19

- trachea is elliptical in shape, with the transverse diameter being larger than AP diameter Sizing of airway devices should be based on the smaller (anteroposterior) diameter.

Devices & Approaches

1- Single-Lumen Tracheal Tube

- Simplest option, can be used at any age but mostly used for the very young patients < 6 m.o.s

- Placing SLT in the right mainstem bronchus is easier than the left due to the less acute angle that it takes off from the trachea

- Pros: Simple/ Quick

- Cons: potential for inadequate collapse of operative lung / inability to suction the operative lung / inability to deliver (CPAP) to operative lung / Missing the RUL when doing right mainstem intubation

2- Bronchial Blockers

- Many types, include vascular balloon catheters, the Uniblocker (Fuji Systems), and Arndt endobronchial blocker, Cohen, EZ blocker

- Catheters may be placed either within (Coaxial) or external to the TT (Extra-axial)

- Use of Bronchoscope is imperative during placement of BB

- Deflation of the operative lung occurs by absorption atelectasis and requires a considerably longer period of time

Vascular Devices:

- Fogarty arterial embolectomy catheter, and Miller atrio-septostomy catheter

- No central channel for deflation or CPAP to the operative lung

- Both has angled tip which allows the user to direct the catheter to the desired bronchus.

- Balloon cuffs are high pressure, low volume and should be only inflated and positioned under FOB to avoid damaging bronchial mucosa

Arndt blockers:

- Has four-way adapter, and comes with swivel connector that allows ventilation during placement

- The blocker has a 2 ml cuff and lower inflation pressures.

- Has an inner lumen that contains a flexible nylon wire that extends along the length of the catheter and terminates as a flexible loop

- This loop slides over the bronchoscope and aids in positioning.

- Once the nylon guide is removed, it cannot be reattached, which may make repositioning attempts difficult should the blocker fall out of place.

- Once the nylon wire is removed, the central lumen may be used for suctioning and CPAP

Sizing of BB and FOB for SLTs

- Same sizing principles apply when using BB and FOB together as to when sizing FOB alone

- Typically in pediatrics, two sizes of bronchial blockers are used—5 and 7 Fr BB sized by Fr, divide by 3 to know the size in mm
- When using the coaxial technique, the Arndt bronchial blocker works well.

- However, when using the parallel technique, a bronchial blocker with a stiffer shaft and angled tip should be used.

- This can be accomplished with the 5 Fr Fuji Uniblocker, or a vascular device such as a 5 Fr Fogarty embolectomy catheter, or a 5 Fr Miller atrio-septostomy catheter

3- Univent Tubes

- TT that has a bronchial blocker within a separate lumen.

- If double-lung ventilation is required again, the bronchial blocker may be deflated and withdrawn into the tracheal lumen again

- Available Univent pediatric sizes: 3.5 and 4.5 mm ID

- Size of a Univent TT refers to the ID, where the OD will be much larger than the equivalent sized SLT

- Main disadvantage is that cross-sectional diameter of the ventilation lumen is smaller in order to accommodate the blocker lumen.

- This increases airway resistance and also limits the size of fiberoptic bronchoscope used to facilitate positioning

- Narrow age range where this method is the preferred: 6–8 yrs

4- Double Lumen Tubes

Considered Gold standard in ages > 8 yrs

The equation of Size =Age×1.5+14 can help to estimate the sizing needed

Smallest DLT size is a 26 Fr, which is generally suitable for children 8–10 yrs of age

Recommended method for each age group

A table listing the preferred method for lung isolation in each age group can be found in the Info sheet at the bottom of this page

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