Question about Oxygen

[Drew Sailbum]

How it's handled...

I've been on that boat, about 45 minutes away from the nearest dock, when stuff happens. There are many things which must be done quickly so as to reach help promptly. It helps to have more than one person involved in getting the boat moving.

All divers must be recalled. You only make a bad thing much worse by leaving someone behind. While this is happening, primary assessment of the patient is occurring, and oxygen delivery is initiated.

Initiate a VHF or cell phone call to summon EMS as soon as possible. This way help can be standing by when you arrive to the dock. Provide as much information as possible to EMS.

Double check that everyone is aboard and all lines are stowed and then get the boat moving.

Monitor patient, and supply supportive care as best as possible.


In all of the suspected Type 1 DCS cases I have seen, the patient was easily able to maintain breathing on a demand regulator oxygen delivery system. This comprises a large majority of the emergency response cases I have expereinced on the water. In these cases, a single D cylinder was sufficient to supply the oxygen needed. In a majority of those cases, the treating physician ultimately does not diagnose DCS.

In all of the suspected Type 2 DCS cases I have seen, the patient required oxygen by continuous flow via a non-rebreather mask. Depending upon distance from the dock, this oxygen was provided by either one or two D cylinders.

I have yet to personally see a suspected pulmonary barotrauma. I would suspect that such a patient would not tolerate a demand mask and thus oxygen would be provided via continuous flow via a NRB mask.


Upon arrival at the dock, hopefully the EMS are already on scene, though we maintain several additional oxygen cylinders on shore. Shore staff are gathering these cylinders while the boat is on the way in to dock.


Our established protocol is to maintain the patient on the highest concentration of oxygen available, without regard to supply. Should all available 100% O2 be depleted, supplemental oxygen can be provided by having the patient breath nitrox at teh highest available concentration.

 

[HammerNoMore]

Excellent writeup Drew.

 

[padiscubapro]

OK, all of you are probably aware, I am the one who threw the flashbang grenade into the hornet's nest that was "The Oxygen Administration" debate. I shot my mouth off before and stepped on some toes in my attempt to balance what I learned in regular clinical settings and what is the "norm" for dive accidents. I have a simple question for the dive medicine docs (I am no longer debating the points were brought up in the previous forum):

If you are far out (say 45 minutes from shore) and you only have a single D tank, is it preferable to give as high concentration of oxygen as possible for a short time (assuming that that is going to burn through the O2 tank faster) or maintain the patient on a lower concentration (say 70%) for a longer period of time?

What are the risks involved with potentially running out of O2 on a DCS patient (that is are they gonna crash or worsen because of a sudden drop in FiO2)?

I can't seem to get anyone to look at this question for me and look beyond the "JUST GIVE AS MUCH O2 AS YOU CAN" response. I'm new to dive medicine (but not to other forms of medicine) and I am trying to learn. Can any of the MD's on here give me honest answers (non-sarcastic) to this?

-Steve

Don't worry about running out of oxygen or trying to extend it.. A diver with SUSPECTED DCS (remember you are not qualified to diagnose) should immediately be put on the highest oxygen available. if you run out and the diver is capable of using a demand reg go for the highest nitrox available..

If you are running recreational trips 36% is most likely the highest you will see, if it happens with tech divers there is probably more high fo2 mixes than you could shake a stick at..

a 50% nitrox mix will increase offgassing and in many cases works as well as oxygen for releaving some of the symptopms.
many masks even when fed with 100% oxygen unless the flow rate is very high dont supply much more than 70% (extra gas is taken from opend up vents)

A surface rebreather is a good choice for those with expected long response times.. Dan supposedly has a new design to replace the REMO, at ANDI we sell the SOR which is a simple surface rebreather that can stretch a small cylinder out quite far.. The scrubber is a disposable cartridge and is about $25 (I dont remember the exact cost).

The SOR is set up to rebreathe most of the gas and is similiar in function of an scr to maintain the highest FO2 possible with good gas efficiency and ease of breathing.

 

[cornfed]

If you are far out (say 45 minutes from shore) and you only have a single D tank, is it preferable to give as high concentration of oxygen as possible for a short time (assuming that that is going to burn through the O2 tank faster) or maintain the patient on a lower concentration (say 70%) for a longer period of time?

I think it is preferable to carry enough oxygen to get your patient back to shore. I can't think of a good reason to knowing travel significantly further offshore then your oxygen supply will last. If space or cost is an issue consider this: a Jumbo D cylinder holds 24 cu ft of oxygen while an AL80 holds three and a half times this much.

 

[Saturation]

I'd second Drew's write up. I think your concern is to reduce the Fi02 to preserve your 02 supply to increase the duration of 02 therapy.

The sooner you desaturate the blood and shrink the bubbles, the faster the response of treatment can be. As DCI can range from joint bends to neurological bends, depends on the inert gas load of the dive and the volume of bubbles, its not possible to guestimate a lower Fi02 that will be sufficient.

You can avoid wastage ... the demand valve is preferred on all instances, and any 02 on deco bottles on an OC reg is as efficient or better, than a demand valve. Continuous flow should be avoided whenever possible in remote settings, as its most wasteful of gas, such as 100% rebreather masks. If the patient is not breathing, then an ambu pocket mask or an ambu-bag is a recourse with supplemental continuous flow 02 ... wasteful but few alternatives, in such cases only intubation and additional support is often necessary and survival on just 02 alone is low probability.

In general, the more 02, the better, in fact hyperbaric is tons better than normobaric, the only limiting factor is 02 toxicity. Thus, success is more likely the higher your Fi02 is.

Note I mention Fi02 here because the maximum 02 at 1ATA is ~ to the percentage of inspired 02 in air.

 

[medic_diver45]

I talked to the doctor who runs the Scubadoc.com website and he said to blow the O2 into the patient at as high an FIO2 as possible and not to worry about running out. He did caution me however that no one has ever studied the effects of suddenly stopping O2 administration in a DCS/AGE patient. He is going to check with some colleagues of his and ask. But that basically answered my question. I really appreciate everyone's help on this subject. Thank you.

If you want to carry more O2, and don't mind paying more for the tank (A LOT MORE ACTUALLY)....check this out- http://www.buyemp.com/dept.asp?dept_id=1020602

I'd like to start seeing SCUBA cylinders made out of carbon fiber....I mean they make SCBA cylinders out of it (and my back thanks the person who invented them) I can't see why a SCUBA tank would be any different.

-Steve

 

[HammerNoMore]

I'd like to start seeing SCUBA cylinders made out of carbon fiber....I mean they make SCBA cylinders out of it (and my back thanks the person who invented them) I can't see why a SCUBA tank would be any different.

-Steve

You can get them now, however there are a lot of disadvantages. A search here should sort those out for you.

James

 

[Saturation]

You may want to estimate how much 02 to carry thus:

Determine the most wasteful use of 02 onboard, say continuous flow;
Determine the soonest arrival of a medivac or the boat making port for advance treatment;
calculate the amount of 02 cuft needed to sustain the 02 until rescue.

As you'll see, in remote locales, it can be quite a bit, even with the most frugal 02 user. Weight savings on large vessels is less an issue than raw gas storage.

 

[Peo]

You may want to estimate how much 02 to carry thus:

Determine the most wasteful use of 02 onboard, say continuous flow;
Determine the soonest arrival of a medivac or the boat making port for advance treatment;
calculate the amount of 02 cuft needed to sustain the 02 until rescue.

As you'll see, in remote locales, it can be quite a bit, even with the most frugal 02 user. Weight savings on large vessels is less an issue than raw gas storage.

And multiple the amount with the total number of divers on board. ;-)

 

[Saturation]

And multiple the amount with the total number of divers on board. ;-)

Yes, you are so right. It can be a boggling amount of gas to contemplate bringing. One can take solace knowing in recreational dives, its very uncommon to have over 2 accidents at the same time, usually its the buddy pair. One victim is typical.