Is oxygen a medicine?

[Dr Deco]

Dear Readers:

Spontaneous Remission

Below is an abstract (edited for clarity) that speaks to the problem of what to do in the case of spontaneous remission on neurological DCS.

Arterial gas embolism with spontaneous recovery: rationale for therapeutic compression.

Clarke D, Gerard W, Norris T. Pulmonary barotrauma-induced cerebral arterial gas embolism with spontaneous recovery: commentary on the rationale for therapeutic compression. Aviat Space Environ Med 2002 Feb;73(2):139-46

Cerebral arterial gas embolism (CAGE) continues to complicate diving activities. Inadvertent breath holding or rapid buoyant ascent can quickly generate a critical state of lung over-pressure.

Bubbles are then free to embolize the systemic circulation via the pulmonary vasculature and the left heart. The brain is a common target organ. Bubbles that enter the cerebral arteries coalesce to form columns of gas as the vascular network narrows. Small amounts of gas frequently pass directly through the cerebral circulation without occlusion. Larger columns of gas occlude regional brain blood flow, either transiently or permanently, producing a stroke-like clinical picture.

In cases of spontaneous redistribution, a period of apparent recovery is frequently followed by relapse. The etiology of relapse appears to be multifactorial, and chiefly the consequence of a failure of reperfusion (= blood to start flowing again after the bubble has gone). Prediction of who will relapse is not possible, and any such relapse is of ominous prognostic significance. It is advisable, therefore, that CAGE patients who undergo spontaneous recovery be promptly recompressed while breathing oxygen.

Therapeutic compression will serve to antagonize leukocyte-mediated ischemia-reperfusion injury; protect against embolic injury to other organs; aid in the resolution of component cerebral edema; reduce the likelihood of late brain infarction reported in patients who have undergone spontaneous clinical recovery; and prophylax against decompression sickness in high gas loading dives that precede accelerated ascents and omitted stage decompression.

Dr Deco :doctor:

 

[MikeFerrara]

Dr Paul Thomas once bubbled...
It would seem to me that denial played a major part in this incident and the failure of the dive marshall or skipper to put Pos-tech on oxygen is worrying. Had I been present I think I would have treated this incident very differently but minor violations are very, very common as is denial and to my mind the this is simply because of the legal status of oxygen administration as "medical treatment".

Maybe I'm showing my ignorance but...
Based on my understanding of the benefits of O2, the DAN recommendations and my legal risks as an instructor...

If a recreational diver who in any way, shape of form would be considered under my charge (this could make for a long debate in itself because instructors have been found partially liable even when not acting in a proffessional capacity) feels the need for O2 then I call for help (figuratively). I will at least call DAN and maybe EMS. This diver will be examined by a doc unless he refuses. If the diver refuses treatment It is then between him and medical pro's. Now is this a perfect solution. No, I think there have been some very valid points made here.

Here is something else to thing about...If minor violations are so common, IMO, we need to get back to basics and teach these folks to dive or just keep them out of the water.
IMO, if dives are conducted dives conservatively within recreational limits they are statisticly "safe" and there is no real need for O2 to be used for decompression and this debate becomes moot (or near to it). Recreational divers are tought not to conduct such profiles. If we're doing dives that require O2 to control the risk we need to back off on the depth and/or bottom time not breath more O2.
Pos-tech's profile seems obsurd to me. So i guess from where I stand any rec diver who needs O2 also needs a follow-up exam. All things considered I don't see how I could recommend otherwise.

 

[The Iceni]

MikeFerrara once bubbled...
. . . IMO, if dives are conducted dives conservatively within recreational limits they are statisticly "safe" and there is no real need for O2 to be used for decompression and this debate becomes moot (or near to it). Recreational divers are taught not to conduct such profiles.

Clearly there is considerable difference in what is considered "recreational limits" in the US and the UK, where accellerated decompression is commonplace. In addition, sadly, it would seem, many in both the UK and th US do dive beyond their competence.

This was a thread, the subject of which can have no universally acceptable definitive answer but I think it was an interesting debate.

Kind Regards

 

[Laurence Stein DDS]

Hi Dr. Paul and Dr. Powell,

A few months ago, I had to refill, and hydro all my O2 cylinders used at my office and for diving. I was told something rather interesting by Puritan Bennett/Airgas.

While O2 normally requires an Rx to obtain for medical purposes (for non medical personel), any cylinder with a DAN sticker will be filled without the Rx. I have purchased double D cylinders from DAN and was never required to present my credentials as a doctor nor was I asked if I had taken an O2 administration course.

So, appearantly, you can purchase an O2 cylinder and fill it without Rx as long as it has a DAN sticker.

I was also told that any dive shop would be allowed to swap O2 cylinders for dive emergency use without the need to be a medical practice--as long as they all had DAN stickers.

I think the current rules governing medical grade oxygen and it's administration are rather ambiguous.

To make matters worse, Aviator's grade oxygen which is supposed to be slightly "dryer" than medical grade oxygen is, in fact from the same source--liquified oxygen (LOX).

The liquified oxygen is "gassified" and used to fill all cylinders from welder grade, reagent grade, medical grade(USP) and aviators grade (Aviator's Breathing Oxygen-ABO) (I've probably left something out). All oxygen derived from LOX is actually the same grade. Only the label makes it different.

Now it is possible for oxygen to be condensed from air and thus have different grades, however, most sources of O2 use LOX and if you purchase Aviator's grade, you have oxygen the is as least as pure as USP (medical grade).

So a person may legally purchase Aviator's grade O2 without an Rx or Medical grade without an Rx but with a DAN sticker on the cylinder. But they can't purchase Medical grade without an Rx if there is no DAN sticker. Silly, don't you think?

If used on a boat for emergencies, the outcome for Aviator's or Medical grade O2 should be the same.

I'm not sure what the FDA or other governing body for medicines is trying to accomplish by limiting O2 purchase to those with an Rx while the same quality of O2 is readily available. The only roadblock to the purchase of oxygen for use as a decompression tool by self administration would be legally filling a bottle with oxygen that has a fitting for a clean scuba regulator.

None of this addresses the liability issue. Emergency administration would be covered by the Good Samaritan laws. I don't think that being O2 trained or not is going to matter if the victim is unconscious and should have oxygen adminsitered. It would be pointless for a non trained person or a non medical person to state to an unconsious person that that oxygen administration is thought to be of benefit in such a situation....as a disclaimer.

Regards,

Larry Stein

 

[The Pirate]

I just joined this forum and saw this message thread. It is a common misconception among divers and some gas suppliers that divers need a prescription to purchase medical grade O2. I buy several thousand dollars worth of USP O2 and USP He every year from a medical gas supplier. The supplier knows that I use the gas to partial pressure blend breathing gas for diving. The supplier also knows that a prescription is only needed if the person is using the O2 for medical purposes. I have never had a prescription for USP O2 or USP He and don't need one because I'm not using it for medical purposes.

The Pirate

 

[The Iceni]

Hi Pirate,

Thanks you for your post.

I think we all accept that divers can purchase oxygen for blending without prescription but

1. Do you use high concentrations for accelerated deco?
2. Do you use 100% from 6 metres
3. Do you occasionally use 100% oxygen post-dive prophylactically?
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[The Pirate]

[*]Do you use high concentrations for accelerated deco?

Yes! All tech dives are done using 100% from 24' - 20' to the surface.

[*] Do you use 100% from 6 metres

Yes, always, unless recreational diving in some remote tropical location.

[*]Do you occasionally use 100% oxygen post-dive prophylactically?

I will occasionally continue to breath O2 upon surfacing for awhile, but I don't recall ever going beyond 5 minutes or so. I only do this on extreme dives, i.e. long exposure 3+ hours at 100 to 120' or deep, 270' - 300' for longer exposures (40 min +). This is only to help wash out the remaining bubble shower from the last 10' of ascent.

The Pirate

 

[The Iceni]

The Pirate once bubbled...
. . . This is only to help wash out the remaining bubble shower from the last 10' of ascent.

The Pirate

That's what I would have expected from our current understanding.

Thanks for the clarification.

Regards,