LMA vs ETI

Hey team,

OK how did you go with this week’s questions?

EGD (Extraglottic device) include various types of LMA and iGel.
iGel is popular and is viewed as ETI alternative by some EMS.

Obvious problem for LMA is that overzealous bagging often seen by adrenaline driven hands resulting in gastric insufflation causing vomit so once again don’t forget the universal rule for PPV…

Squeeze small and slow!

≈˙∆˚ƒ¬≈∂©˚…˜ˆ¬¬!

Tidal volume

Typical Vt (Tidal volume) is 7ml/kg*
* 6~8ml/kg depending on the book you read).

20kg child = approx 150ml
70kg adult = approx 500ml (1/3 of adult bag)

In case of ventilation, the weight calculation is supposedly based on the ideal weight for the height rather than the actual (or estimated) weight, as obese does not mean they have huge lungs. The calculation formula for the ideal weight used in the hospital is too complicated to remember and we don’t have to (can’t) be that precise. We just need to understand the concept and use common sense to avoid over inflation resulting in the KFC vomit all over ambulance.

* Obese (including pregnancy) patients are very tricky to ventilate with LMA due to its relatively low seal pressure, and obese patients also desaturate very quickly.

Ventilation rate

During cardiac arrest = 10 breaths / min (every 6 seconds)
Cardiac arrest secondary to asthma = 6 breaths / mins (every 10 seconds)*
Post cardiac arrest = start with 1 breath every 5~6 seconds and titrate to EtCO

* Waiting for 10 seconds feels like eternity but it takes long time for the air to come out of the broncho-constricted lungs. In this setting, we also allow high level of CO2 = permissive hypercarbia.

I don’t think we need to go through how to insert LMA here but here is the difficult EGD predictor RODS by Walls et al. and here is that great video again.

R = Restricted mouth opening
O = Obstruction
D = Distortion
S = Stiff (poor compliance)

You’ve noticed some of the predictors overlap between MOANS, RODS, and LEMON . I use combined approach looking at all those elements together by looking at the patient i.e. obese? beard? small mouth? hard to bag? etc.

Endotracheal intubation (ETI)

So…the EGD vs ETI debate…

As you know, this debate continues around the world but the recent trend appears to be in favour of ETI by paramedics when it’s done well.
St John is obviously supporting this evidence based practice and I’m pleased our medical directors have confidence in our ability.

Old studies showing low ETI success rates by paramedics have been found to be less convincing due to paramedics receiving inadequate training and the equipment.
And there was the Australian landmark study bernard2010_tbi that had a major influence on the prehospital airway management in New Zealand (and other countries).
Recent meta-analysis also found patients with OHCA (Out of Hospital Cardiac Arrest) who receive ETI by EMS are more likely to obtain ROSC, survive to hospital admission, and survive neurologically intact when compared to SGA.

Reference: Endotracheal intubation versus supraglottic airway placement in out-of-hospital cardiac arrest: A meta-analysis

Additionally, EGD may impair carotid blood flow may be harmful in cardiac arrest, although more studies are required to change our practice at this stage.

Reference: EMCrit “Are Extraglottic Airways Harmful in Cardiac Arrest?”

When it’s done well, ETI certainly is advantageous in protecting airway and provides continuous chest compression in case of cardiac arrest. 

* There is also a NZ study done on an early ETI in OHCA, and people doing the Advanced Resuscitation paper can possibly elaborate on this. (Thanks Shane and Shelly).

Well…this post is getting long again so will leave the rest of the debate, particularly the adverse effects of ETI, to the C & C as well as please share your thoughts via blog comments for those cannot attend C & C.

Ja matane (see you later) : )

Tatsu

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