bit late to this game, but am redoing my emergency O2 stuff right now, and the thread isn't that old.
@Beau640 the demand valves in question are typically used with pocket masks, so they plug into the same hole that the bag would. They come out of the DISS port on oxygen regulators. Three types as mentioned. Standard demand, no purge button. Purge button *not in use anymore*, and the MTV-100 which doesn't actually have an OPV, but it will actually shut off the flow of gas if it sense backpressure. It doesn't take a whole lot to get it to cut off. The demand valve/MTV-100 is nice for conscious patients because they are a lot smaller and less awkward than a non-rebreather for short uses, but do have to get held in place which is slightly annoying.
Part of the reasons hospitals don't use them is because it's typically much more convenient to just have the O2 lines run around at lower pressures than the 50psi that the regulators need and have it come out of the barbs with flow meters on them. Much cheaper and more convenient to just plug a new soft hose onto the barb than screwing regulators around and maintaining them for minimal benefit. They are also on massive o2 bank systems so you aren't really concerned about wasting it. On a dive boat or even in a vehicle, you are limited in how much you can take with you. People will typically be breathing between 7-12 liters/minute, so to save that amount of O2 can be pretty significant in extending the time that they are on O2.
@DustyC for the demand valves being banned, it's important to differentiate which ones are really not safe. The standard purge button ones that aren't MTV-100's really do need to be banned due to over-expansion injuries, and I haven't seen one in use. They are far too easy to overinflate someones lungs and cause serious damage.
The standard demand valves are fine because you can only trigger them by inhaling. The inconvenience here is if the patient stops breathing, you have to remove that and switch to a BVM so the benefit isn't really there.
The MTV-100's have the shut-off, and I find are much better than the bag valves, just not cheap. The auto-shutoff triggers really fast and with hardly any backpressure. If you have someone in your area with one in a DAN kit, go try it out, it's pretty slick. It's probably impractical in an EMS situation since BVM's are very inexpensive and they're trained to use them properly, but I truly believe the risk of a lung overexpansion injury is much lower with an MTV-100 vs a BVM, especially in marginally trained O2 administrators.
For most divers, I really have to say that having medical O2 kits is just not worth it. I'm 99% with
@PfcAJ on this one. The odds of you having someone that isn't breathing and needs to be resuscitated is extremely small, so better to have a setup ready to go. For divers, I think every diver that is serious should really get AN/DP and DAN O2 admin. Even with DAN O2 admin, you should be able to get dive cylinders filled with O2 with most shops.
Whether you plan on doing decompression dives or not, the knowledge gained in that class as well as the ability to get O2 is well worth it. With this, you can keep an AL40 of O2 around and if the diver is conscious, have a demand valve to breathe on at the surface, or do your safety stops on O2. If you put an LPI on there and invest in something like the RescuEAN ($95) you can also use a non-rebreather mask or BVM and have a continuous flow of O2 for hands free use/unconscious diver use. The added benefit with the RescuEAN is even if you exhaust your O2 supply, you can keep them on Nitrox which is always better than air.
@CuzzA That setup above is about $300, and the masks are the same as you'd need on any O2 kit. The difference here is you have a setup that you can take in the water with you and is scalable without needing any special tanks/regulators or adapters. The RescuEAN is going to be much better for what you have talked about compared to having a DIN-NPT-CGA540/870 valve adapter contraption. Just take your O2 regulator, put a LPI on it and call it a day.
