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

[2airishuman]

DAN has defined the "standard of care" for DCI first aid as the provision of oxygen using a demand valve. This relatively unusual piece of equipment consists of a first stage with a 50 PSI intermediate pressure, connected to a mask with a cushioned seal and a second stage functionally similar to a SCUBA second stage.

The purpose of this arrangement is to deliver 100% oxygen to the patient, less mask leakage losses.

There are two problems with this. The first is that the mask, demand valve, and hose assembly are expensive, both because of their complexity and because they are not widely used by EMS, medical facilities, or much of anyone else outside of highly specialized respiratory therapy. The second, related problem is that these things have to be kept clean and maintained and are not disposable.

It appears to me that the only advantage that these very expensive devices offer over a non-rebreather mask is that they conserve oxygen. Non-rebreather masks cost a few dollars each. They are easy to use, and deliver 100% oxygen to the patient, again less mask leakage losses.

It is far cheaper to carry somewhat (or even several times) more oxygen than it is to carry a demand valve.

Adjustable flow rate oxygen regulators are readily available and cheap. I just bought a bunch of U.S.-made ones on ebay for under $10 each including shipping. Non-rebreather masks in quantity are around $2. At these prices an emergency O2 kit can be assembled for under $100, including a used E cylinder, hydro, fill, and a bag to put it all in. E cylinders are widely used for home oxygen and are cheap and plentiful, and hold more than the various options in the DAN O2 kits.

The great thing about a $100 kit is that you don't care what happens to it. You can buy it, leave it on the shore, put it in your boat or car. If something happens, no great loss. You don't need to be an instructor or a dive op or a club to afford it.

 

[tursiops]

DAN has defined the "standard of care" for DCI first aid as the provision of oxygen using a demand valve. This relatively unusual piece of equipment consists of a first stage with a 50 PSI intermediate pressure, connected to a mask with a cushioned seal and a second stage functionally similar to a SCUBA second stage.

The purpose of this arrangement is to deliver 100% oxygen to the patient, less mask leakage losses.

There are two problems with this. The first is that the mask, demand valve, and hose assembly are expensive, both because of their complexity and because they are not widely used by EMS, medical facilities, or much of anyone else outside of highly specialized respiratory therapy. The second, related problem is that these things have to be kept clean and maintained and are not disposable.

It appears to me that the only advantage that these very expensive devices offer over a non-rebreather mask is that they conserve oxygen. Non-rebreather masks cost a few dollars each. They are easy to use, and deliver 100% oxygen to the patient, again less mask leakage losses.

It is far cheaper to carry somewhat (or even several times) more oxygen than it is to carry a demand valve.

Adjustable flow rate oxygen regulators are readily available and cheap. I just bought a bunch of U.S.-made ones on ebay for under $10 each including shipping. Non-rebreather masks in quantity are around $2. At these prices an emergency O2 kit can be assembled for under $100, including a used E cylinder, hydro, fill, and a bag to put it all in. E cylinders are widely used for home oxygen and are cheap and plentiful, and hold more than the various options in the DAN O2 kits.

The great thing about a $100 kit is that you don't care what happens to it. You can buy it, leave it on the shore, put it in your boat or car. If something happens, no great loss. You don't need to be an instructor or a dive op or a club to afford it.

Do some more research. You'll find the non-rebreather mask delivers a lot lower O2% than the demand valve.

 

[fmerkel]

It is a much simpler and less expensive system. As such if you HAVE and USE it you are much more effective than not having anything.
But......it is less efficient. When the patient is between breaths or breathing out the system is still delivering O2. Some will be placed in the bag reservoir but some will simply be exhausted and lost.

A properly used demand valve delivers near 100% with little waste. It will last longer and create a superior gradient for removing N2 when used with the same tank size.

You'll get varied estimations of non-rebreather mask delivery, but the reality is they will not deliver 100% and their waste will be higher.

Here's some textbook specs:
[Nonrebreather
6 – 10 LPM
FIO2 0.70 – 1.0
Flow must be sufficient to keep reservoir bag from deflating upon inspiration
With the exception of the Venti mask, the above are all low flow oxygen delivery
systems and therefore the exact FiO2 will be based on the patient's anatomic reservoir and minute ventilation]

[3. Non-Rebreather Mask (NRB): This is a mask that ideally will bring in 100% Fio2 so long as the liter flow is 15 and there is a good seal between the mask and the patient's face. And all three one-way valves are on the mask to prevent air entrainment.

For legal purposes, however, one flap is always removed just in case the oxygen gets shut off. And therefore the highest FiO2 you can get from an NRB is 75%. The bag acts as a reservoir for oxygen, and therefore allows device to provide higher FiO2s to the patient.]

Yep, more expensive, and requiring maintenance...which is more expense. This is not entirely a trivial barrier. These kits are expensive. I've been carrying a kit around for over 10 years and it's only been used once. It was in a large city with the chamber ~ 15-20" drive away so maximum efficiency was not a big deal. OTOH, it's not too hard to be a fairly long way from the nearest hospital facilities.
In a hospital if you don't need intubation and ventilation you will likely just be put on a non-rebreather mask while they sort out what to do with you. You will not be put on a demand valve system while conscious, breathing spontaneously, and not in respiratory distress.

OTOH, those first few minutes of O2 can really make a big difference. The sooner and harder you jump on a real case of DCI the more effective you are, which can lead to a better outcome.

 

[PfcAJ]

Normal scuba regulator works pretty well for delivering oxygen.

 

[2airishuman]

Do some more research. You'll find the non-rebreather mask delivers a lot lower O2% than the demand valve.

I haven't been able to find a reliable source that actually confirms that, and I don't believe it's true. There's no reason I can see why a demand valve should be able to deliver a higher amount of O2 that a non-rebreather mask when both are used properly. The main problem with either is getting the mask to seal completely.

 

[2airishuman]

Normal scuba regulator works pretty well for delivering oxygen.

I don't hold the certs to get oxygen fills in scuba cylinders, and I don't have any oxygen clean gear. The cost of gearing up for oxygen service for scuba -- even if I leave out the training -- would approach the cost of one of the DAN kits.

 

[2airishuman]

[3. Non-Rebreather Mask (NRB): This is a mask that ideally will bring in 100% Fio2 so long as the liter flow is 15 and there is a good seal between the mask and the patient's face. And all three one-way valves are on the mask to prevent air entrainment.

For legal purposes, however, one flap is always removed just in case the oxygen gets shut off. And therefore the highest FiO2 you can get from an NRB is 75%. The bag acts as a reservoir for oxygen, and therefore allows device to provide higher FiO2s to the patient.]

FWIW, demand valves have the same hazard -- the patient cannot breathe if the mask is affixed in place and the oxygen supply is exhausted or interrupted, unless there is a leak in the mask, deliberate or otherwise.

With a NRB mask that isn't modified (has all the valves in place), the FO2 should approach 100%, right?

Generally when planning for emergency care of DCI patients, if the patient is unconscious at the dive site in the immediate aftermath of the accident, the prognosis is so poor that O2 administration is unlikely to help.

 

[tursiops]

I haven't been able to find a reliable source that actually confirms that, and I don't believe it's true. There's no reason I can see why a demand valve should be able to deliver a higher amount of O2 that a non-rebreather mask when both are used properly. The main problem with either is getting the mask to seal completely.

From the DAN O2 Instructor Guide, Version 1.3:

You are correct; the problem is the lack of a good seal with the non-rebreather mask.....even when used as it is supposed to be used, and that is not likely. Just getting the nose piece bent properly is an art form.

 

[PfcAJ]

I haven't been able to find a reliable source that actually confirms that, and I don't believe it's true. There's no reason I can see why a demand valve should be able to deliver a higher amount of O2 that a non-rebreather mask when both are used properly. The main problem with either is getting the mask to seal completely.

NRBs aren't great. The "one way valves" don't seal (if they're even present), and they don't seal well to the face because of how they're made.

A demand valve actually seals and doesn't leak oxygen when the patient isn't breathing. Both will work on an unconscious person.

 

[2airishuman]

I suppose the first question is whether the figures in the DAN table reflect what happens in the real world. Perhaps they do.

The second question would be whether the relatively small difference in FO2 makes a difference in outcome. We may never know for sure -- how would anyone design an ethical study?