Tracheostomy fire risk

[waterbottle10]

I had a case a few days ago where prior to them entering the trachea, the surgeon asks what the oxygen level is. I told them the EtO2, but they specifically wanted FiO2 not EtO2. I can see how the FiO2 would be useful but wouldn't both be important?

Has anyone ever seen a fire with tracheostomy? We always lower it to room air, around 21% but what are actually the chances of fire if O2 was lets say 40%? I've had a few times where they took a while to get the trach in and the SaO2 went down to pretty low numbers because we start at room air so there no reserve.

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[pgg]

You can (and should) turn the FiO2 down to 25 or 30 for dissection and exposure using electrocautery, then turn it up again before the tube is exchanged for the trach.

 

[Twiggidy]

You can (and should) turn the FiO2 down to 25 or 30 for dissection and exposure using electrocautery, then turn it up again before the tube is exchanged for the trach.

Ditto this.

 

[ProtonPump]

Also don't use Nitrous Oxide

 

[Iso4ane]

Also don't use Nitrous Oxide

Save it for the race track.

 

[ProtonPump]

Save it for the race track.

A little bit of knowledge is a dangerous thing!

 

[Psai]

Why would eto2 matter? It's the highest oxygen concentration that makes a difference and the higher you go, the bigger the risk of fire.

 

[Iso4ane]

One more thing to add as many CA1s don't realize this, but the set FiO2 and the actual FiO2 in the circuit can differ by quite a bit, when FGF<MV as is often the case. And FiO2 is nearly always going to be higher than etO2 at equilibrium.

 

[ProtonPump]

Why would eto2 matter? It's the highest oxygen concentration that makes a difference and the higher you go, the bigger the risk of fire.

There is some nuiance to appreciate here: FiO2 represents the delivered O2 concentration. EtO2 will represent the O2 in the circuit in the expiratory limb which will will involve an admixture with the gas in the circuit. The nuiance here is that the other factor is gas flow. If the fresh gas flow is low and FiO2 is low and the EtO2 is high then the expired O2 would be contributing a lot to the O2 in the circuit. If the fresh gas flow is high in the circuit then FiO2 is contributing a lot to the O2 in the circuit.

 

[ProtonPump]

One more thing to add as many CA1s don't realize this, but the set FiO2 and the actual FiO2 in the circuit can differ by quite a bit, when FGF<MV as is often the case. And FiO2 is nearly always going to be higher than etO2 at equilibrium.

Oh Snap

 

[waterbottle10]

Why would eto2 matter? It's the highest oxygen concentration that makes a difference and the higher you go, the bigger the risk of fire.

Like what people above have said. Both matter but looking at etO2 tells you things have equilibrated. You can quickly turn FiO2 down to 21% but your EtO2 is still close to 100%.

 

[POW16]

I had a case a few days ago where prior to them entering the trachea, the surgeon asks what the oxygen level is. I told them the EtO2, but they specifically wanted FiO2 not EtO2. I can see how the FiO2 would be useful but wouldn't both be important?

Has anyone ever seen a fire with tracheostomy? We always lower it to room air, around 21% but what are actually the chances of fire if O2 was lets say 40%? I've had a few times where they took a while to get the trach in and the SaO2 went down to pretty low numbers because we start at room air so there no reserve.

Are you a first year resident ? Asking based on other threads you have started.

 

[waterbottle10]

Are you a first year resident ? Asking based on other threads you have started.

No, almost an attending. Why? These are very complicated questions. I usually ask the questions I ask to get general opinions with explanations

 

[Iso4ane]

etO2 is only important if it greater than your FiO2, which means you changed your FiO2 setting too late. This goes into the idea of time constants, the obvious being high FGF equals faster equilibrium.

If you are really ballsy you can get FiO2 below 21%. Your alarms will be going off, but its possible.

 

[waterbottle10]

etO2 is only important if it greater than your FiO2, which means you changed your FiO2 setting too late. This goes into the idea of time constants, the obvious being high FGF equals faster equilibrium.

If you are really ballsy you can get FiO2 below 21%. Your alarms will be going off, but its possible.

But that is what they are looking for right? It's not really a problem to them if you get it down EARLY (unless hypoxic). It's only a problem if you turn it down too late. The idea is hopefully you aren't going from FiO2 of 21% to 100% right when they are about to cut the trachea, since for most cases people have FiO2 of >21% and are turning it down during portions of the case. Therefore, EtO2 is a better predictor.

I have heard of several cases of laser tracheal surgery where the surgeon asks the oxygen to be turned down, the anesthesiologists does so, and the surgeon immediately start to laser, when the EtO2 is still significantly higher than 30%. Isn't that what the jet ventilator does when you press the Laser mode button, it turns FiO2 to 21% and wait for equilibrium to occur. Same for regular ventilation, we look at EtO2 to see if it has reached equilibrium.

 

[dannyboy1]

This is not that complicated. Turn the air on and the oxygen off and wait for both the inspiratory and expiratory O2 to be below 30%. As with all gasses the higher the flow the quicker you will get there....

 

[waterbottle10]

This is not that complicated. Turn the air on and the oxygen off and wait for both the inspiratory and expiratory O2 to be below 30%. As with all gasses the higher the flow the quicker you will get there....

Exactly! The first part of my question is just to confirm since the surgeon asked a weird question. I'm more interested about the 2nd part. Does anyone know of any studies (or Math) done in labs showing how likely it is to induce fire at certain oxygen concentrations? I believe knowing this information if it exists can help judge risk vs benefits for sicker patients. Eg if the risk of fire with cautery at 50% is 1 in 1000000, vs 1 in 10000000000 in room air, I may just take the risk of using 50% O2 for sicker people

 

[Iso4ane]

If they ask you for a number, just tell them the number that is higher, you don't have to them them if it's etO2 or FiO2. It's not like they are looking at your screen trying to trick you; even if the number that is higher is technically etO2. Cause in essence what they really are asking is, 'Is it safe to cut?"

Ex: "What is the FiO2?" Your answer is "We're good, we're below 30%" or "Give me one more minute, we are still a little high."

We're doctors, we can use our brains.

 

[deleted162650]

No, almost an attending. Why?

Umm, yeah - not buyin’ it dude. Somehow in just 7 years you went from pre-pharmacy cuz you couldn’t get in to med school to getting so many admissions you were wondering how to break the news to the schools you rejected, to asking if you should bother “going for AOA” to now being “almost an attending”???

It’s August, at best you would be a new CA-3 and no one in that position would say “I’m almost an attending”.

Get outta here monkey.

 

[Psai]

Umm, yeah - not buyin’ it dude. Somehow in just 7 years you went from pre-pharmacy cuz you couldn’t get in to med school to getting so many admissions you were wondering how to break the news to the schools you rejected, to asking if you should bother “going for AOA” to now being “almost an attending”???

It’s August, at best you would be a new CA-3 and no one in that position would say “I’m almost an attending”.

Get outta here monkey.

Agree, fa/fi is ridiculously basic question

 

[Psai]

Like what people above have said. Both matter but looking at etO2 tells you things have equilibrated. You can quickly turn FiO2 down to 21% but your EtO2 is still close to 100%.

Why would your eto2 ever be close to 100

 

[waterbottle10]

Why would your eto2 ever be close to 100

Dont take it too literally. I simply meant EtO2 is high.

As for the Fa/Fi question, I still do not have the answer I am looking for. I just haven't followed up on it cause I'm tired and I'm reading another textbook section of this topic

 

[pgg]

Exactly! The first part of my question is just to confirm since the surgeon asked a weird question. I'm more interested about the 2nd part. Does anyone know of any studies (or Math) done in labs showing how likely it is to induce fire at certain oxygen concentrations? I believe knowing this information if it exists can help judge risk vs benefits for sicker patients. Eg if the risk of fire with cautery at 50% is 1 in 1000000, vs 1 in 10000000000 in room air, I may just take the risk of using 50% O2 for sicker people

The wildfires burning down California right now (again) are doing quite well in 21% oxygen.

The airway fire risk is never zero when there's an ignition source next to a plastic/hydrocarbon tube with a flow of gas containing oxygen and/or nitrous. All we can do is mitigate that risk by reducing the O2 concentration as much as possible.

It should be obvious that if you have a sicker person, you may need to compromise a bit and accept a higher risk of fire in return for delivering sufficient oxygen to sustain life. Don't fixate on decimal places in fire probability; that data doesn't exist and it's irrelevant anyway. Lower the FiO2 as much as you can without causing life threatening hypoxia, let the gases equilibrate, and tell the surgeon to proceed.

For high risk cases where you're the one placing the tube (vs the typical trach patient who's coming with a tube from the ICU) consider using an armored tube.

That's all.

 

[POW16]

No, almost an attending. Why? These are very complicated questions. I usually ask the questions I ask to get general opinions with explanations

I am of the opinion that the only stupid question is the one that doesn't get asked. That being said it helps to have an idea of your background/knowledge depth.

 

[daneeka]

This is pretty impressive on 100% O2 (with laser, but same deal). Convincing enough for me to dial the O2 down as far as I can.

Also, surely what you are trying to do with your etO2 can be done more usefully with a measured FiO2 (i.e. from the gas analyser, not what you dialled up)?

 

[sigrhoillusion]

The wildfires burning down California right now (again) are doing quite well in 21% oxygen.

The airway fire risk is never zero when there's an ignition source next to a plastic/hydrocarbon tube with a flow of gas containing oxygen and/or nitrous. All we can do is mitigate that risk by reducing the O2 concentration as much as possible.

It should be obvious that if you have a sicker person, you may need to compromise a bit and accept a higher risk of fire in return for delivering sufficient oxygen to sustain life. Don't fixate on decimal places in fire probability; that data doesn't exist and it's irrelevant anyway. Lower the FiO2 as much as you can without causing life threatening hypoxia, let the gases equilibrate, and tell the surgeon to proceed.

For high risk cases where you're the one placing the tube (vs the typical trach patient who's coming with a tube from the ICU) consider using an armored tube.

That's all.

Yeah like the 750lb guy who we trached today who desatted to the 80s if I ran him at less than 80%, and desatted to the 50s when we didn't ventilate him for like 5 seconds...

 

[fakin' the funk]

Umm, yeah - not buyin’ it dude. Somehow in just 7 years you went from pre-pharmacy cuz you couldn’t get in to med school to getting so many admissions you were wondering how to break the news to the schools you rejected, to asking if you should bother “going for AOA” to now being “almost an attending”???

It’s August, at best you would be a new CA-3 and no one in that position would say “I’m almost an attending”.

Get outta here monkey.

Was with you until the part where you didn't believe a new CA3 would self describe as almost an attending

 

[osumd]

This is pretty impressive on 100% O2 (with laser, but same deal). Convincing enough for me to dial the O2 down as far as I can.

The other part of this video shows 70% Nitrous / 30% O2, which is an even more impressive flamethrower.

 

[anbuitachi]

The other part of this video shows 70% Nitrous / 30% O2, which is an even more impressive flamethrower.

why did the fire suddenly go out?

 

[sigrhoillusion]

I'm assuming they shut off the N20/O2...

 

[anbuitachi]

I'm assuming they shut off the N20/O2...

but why doesn't the ET tube keep on burning??

 

[nimbus]

but why doesn't the ET tube keep on burning??

I think it is a less flammable fuel than a candle or gasoline or paper or dried up wood. It needs an oxygen or pressure enriched environment to continue burning.

 

[anbuitachi]

I think it is a less flammable fuel than a candle or gasoline or paper or dried up wood. It needs an oxygen or pressure enriched environment to continue burning.

i guess 21% isn't enough