Emergency oxygen: non-rebreather mask just as good as demand valve?

[Storker]

It's far cheaper to bring two cylinders, or a larger cylinder, or some combination.

Cheaper, sure. However, are you certain that Someone™ will bother to bring more than one tank? YMM(of course)V, but IME it's sometimes a PITA to schlep the O2 therapy kit. Making it bigger, heavier and more cumbersome to schlep by adding more tanks to it increases the risk that it won't be at the site when it's needed.

In the U.S., the standard cylinder for EMS use is an M15 or "D," which holds about 425 liters (15 cf) of oxygen.

That's about the same capacity as a metric 200 bar 2L (400 surface liters).

 

[DustyC]

I believe he's referring to % of saturation in the bloodstream as measured by a pulse oxymeter.

Yes.
But the ease of which we can get the saturation to 100% means we can push way beyond that to help with off gassing, while actually being able to help the patient breathe. Basically, I can push 95% of my patients to adequate blood sat with low flow, with the ability to multiply that flow by 12.5 as needed, for something like a dive accident where the PT needs help off gassing.

A simple demand valve can't do that.

People need to understand that Oxygen application in the medical field is an ever changing thing. We've gotten so good at field EMS that we now work full codes in the field. My system no longer even uses ET tubes, moving to a laryngeal mask style. We even monitor exhaled gas content and tailor our treatments to it. Even CPR still changes every couple of years. Stagnation, especially with 30 to 40 year old tech, isn't a good thing.

All that being said, I don't know what research is behind the current protocols for the dive agencies. It's quite possible that all the data was examined and it was determined staying with current ways is the best option. My views are biased, having almost 20 years in an EMS system with a large medical school in the city, and a very dangerous city, so we've always been able to quickly assemble a great deal of data, and implement changes, then assemble a great deal of data on the changes, repeat, repeat, repeat. So we're pretty forward thinking, all the way down to the fire departments providing initial street care.

The effect of that has been a strong disdain for the old ways that we know can be improved on, or were never very good in the first place.

 

[Beau640]

Where to start. I'm an emergency medicine physician but not a dive physician. I work regularly with oxygen delivery devices.

1) % sat does not equal partial pressure of oxygen in the blood or FiO2 of inspired air. Sitting here right now at the computer, breathing room air, i'm at 100% sat (just put a pulse ox on me for fun). If I put a non rebreather on me, I'll still be at 100% sat. If i use a demand device, I'll still be at 100% sat. If I have a patient in respiratory distress and has a saturation of 80%, and I place an oxygen delivery device on them, I can increase their sat to 100% potentially. That increase does not equal the fiO2 of air given however. A patient with a saturation of 80% can jump to 100% with 1L of nasal cannula. Or depending on their ventilation/perfusion mismatch and the severity of what's going on, then may require a non rebreather. The fiO2 delivered doesn't directly determine the sat %.

The reason it's important to think more about the ppO2 in the blood and the make up of the gas we are breathing when treating DCS is because a sat of 100% doesn't relate to decompression speed or effectiveness. What we actually want to do when we have the patient out of the water and are attempting to treat prior to EMS is deliver the closest FiO2 we can to 100% to help with off gassing. Think of it like deco at 10-20ft with a 100% O2 mix. We are attempting to make the ppN2 of our inspired gas 0 to help with off gassing. We can't tell what the actual FiO2 of what we are delivering to the patient is or what the ppO2 is by looking at sat. Once you get to a ppO2 of 100, you will be at 100% sat (near it) and giving a 100% O2 mix could potentially increase your ppO2 into the hundreds, which would help deco but is not changing the sat # of 100% (look up an image on google of the oxygen/hemoglobin dissociation curve to further see how %sat doesn't directly relate to FiO2/ppO2 at high numbers)

2) So our goal is to get as close to 100% delivered as possible to the patient. What delivery device should we use? A non rebreather mask is designed with a reservoir. The goal of the mask is to have valves on it to keep ambient air from being sucked it, and to have all the inspired air come from the reservoir which is filled with 100% O2. Theoretically and ideally, all air should be breathed from that reservoir bag, which would be 100% FiO2 delivered to the patient. In reality, what actually happens, is that the plastic mask sitting on the face, even when you attempt to bend the nose part to make a seal, doesn't actually form a seal. When you breathe in, room air/ambient air is sucked in around the mask mixing with the 100% O2 from the reservoir and mixes to form a lower FiO2. There is no way to measure easily how much the patient is actually getting. The varying estimates people have been posting reflects this because it all depends how much room air gets sucked in. Ideally close to 100% would be what we aim for, realistically it is probably closer to 80%. Just depends.

A BVM (bag valve mask) forms a seal around the face assuming you are using it right, and with a reservoir bag would deliver 100% FiO2.

The demand devices people are discussing I'm not familiar with because they are not used really anymore in hospitals or with EMS but I would assume their goal is to deliver 100% FiO2.

In reality, use whatever you got to try to deliver as close to 100% as you can.

 

[2airishuman]

Cheaper, sure. However, are you certain that Someone™ will bother to bring more than one tank? YMM(of course)V, but IME it's sometimes a PITA to schlep the O2 therapy kit. Making it bigger, heavier and more cumbersome to schlep by adding more tanks to it increases the risk that it won't be at the site when it's needed.

Situations vary. In my situation, I will generally only bring the kit on shore dives (because boat dives for me involve air travel and I can't bring the kit on an aircraft). In general the kit and the extra cylinder will stay in the car during the dive, along with extra diving cylinders and other spare gear. Under some circumstances the kit might come to the shore while the extra cylinder stays in the car. On shore dives I nearly always bring at least one extra diving cylinder and it's no big deal to throw a little O2 cylinder in alongside it.

If I had my own boat I'd leave a kit on board.

Where to start. I'm an emergency medicine physician but not a dive physician. I work regularly with oxygen delivery devices.

I would like to thank you and others with relevant professional experience for participating in the discussion. I find your perspective extremely valuable.

A BVM (bag valve mask) forms a seal around the face assuming you are using it right, and with a reservoir bag would deliver 100% FiO2.

The demand devices people are discussing I'm not familiar with because they are not used really anymore in hospitals or with EMS but I would assume their goal is to deliver 100% FiO2.

In reality, use whatever you got to try to deliver as close to 100% as you can.

So, here's a question. BVMs are cheap and readily available. I'm not interested in carrying one for the "bag" feature -- let's just say it's beyond my training and likely to stay that way -- but if the design of the mask is different than the design of the NRM mask, so that it seals better, that would be a reason to have one. Is the BVM design better able to seal than the NRM mask? Why?

 

[Beau640]

I'm busy and can provide a more robust explanation later but basically do not buy or use a BVM without the proper training as you need to be trained to make the seal properly and be trained to use it Correctly so you don't push air into the stomach And cause vomiting which will make a situation 10 times worse if you cause the patient to aspirate.

The BVM is more effective but it has to be used the right way to make the seal properly and Not hurt someone. Also you have to time it perfectly with the patients breathing or it will be very uncomfortable on an awake patient

Sorry typing quickly from phone

 

[uncfnp]

So, here's a question. BVMs are cheap and readily available. I'm not interested in carrying one for the "bag" feature -- let's just say it's beyond my training and likely to stay that way -- but if the design of the mask is different than the design of the NRM mask, so that it seals better, that would be a reason to have one. Is the BVM design better able to seal than the NRM mask? Why?

Short answer is the BVM has no method to secure it to the victim. It would have to be held in place and may be harder to get a good seal.

 

[PfcAJ]

A BVM is for ventilating an unconscious patient. It's bigger, heavier and more complicated than what you need for this application.

 

[CuzzA]

For what it's worth, my kit consists of M24 cylinder picked up off of Craigslist. Which my shop will fill as needed. A 0-15 lpm reg, 2 non rebreather masks and 2 bag valve masks. I maintain a Pro CPR/AED cert. I keep this kit on my boat along with other essential medical supplies, mostly to treat excessive bleeding and stings. This kit cost me about $80.

My next class (ART) will give me the ability to acquire 100% O2 fills and start increasing the risk of a serious dive accident far away from rescue. So due to that I plan on dedicating a couple steel 72's I already own as O2 tanks. I'll add a DIN to 1/4" pipe thread adapter, a coupling and a 1/4" pipe thread med O2 reg. Plus a cheap full face mask. This setup will give me a lot utility for both simple O2 delivery to IWR.

I also keep a spare AL80 full of air on the boat for emergencies and I want to add an AED. Of course the challenge always will be, is there someone else on the boat qualified to help me if I'm the one who goes down. I dive with a lot of medical professionals so that's good.

 

[Beau640]

Honestly if I had my own kit I would probably just use a non rebreather. I'd recommend it for the average person with no to minimal training. Important things to remember are when you first fire it up to hold down the valve above the bag to make sure the bag fills, then let it go. Then when you put it on someone bend the nose piece to try to make as good of a seal as you can.

We will never have a good study to compare dcs outcomes for 100% fio2 vs near 100% fio2. Who knows how much of a difference in outcome it makes. However you also have to consider time to getting things set up, time to applying o2, and ease of use/actually using the device correctly.

Non rebreathers are easy to use, quick to set up, and easy to apply. No one would fault someone for just having a NRB. The fact that you have something is going to help immensely until ems arrives. And honestly, ems will most likely switch them to a NRB anyways assuming they are conscious rather than keep them on a device they are not familiar with and is not in their protocol.

 

[2airishuman]

Short answer is the BVM has no method to secure it to the victim. It would have to be held in place and may be harder to get a good seal.

The demand valves from DAN that I've seen also have to be held in place.

And honestly, ems will most likely switch them to a NRB anyways assuming they are conscious rather than keep them on a device they are not familiar with and is not in their protocol.

Which speaks volumes.