Is oxygen a medicine?

[The Iceni]

Alban once bubbled...
Dr T I have not voted in your poll because I feel it is slightly missleading for the following reasons :

"Yes, it must only be used for established DCI"
It is not necessary to wait for symptoms of dcs quite the opposite.

Hi Alban, Unless the violation was obvious this is what occurs in practice, as pos-tech's example confirms. I thought very carefully about the wording of the poll. Shame you will no commit yourself! The poll is anonymous!

O2 will not prevent or cure dcs. I think you are suggesting that O2 will prevent a hit .While I understand there are many degrees of dcs will breathing O2 really prevent a HIT.

You appear to be saying you do no believe accelerated decompression with rich Nitrox mixes works. Surely this is "prevention of of dcs". You cannot have it both ways.

"If the nitrogen dose were sufficient, all decompressions would develop into a case of DCS (assuming that micronuclei were present). " Dr Deco.

Would anyone like to give details when they would administer O2 and not notify the coast guard ( depth , bottom time , missed stops ) ? Yours Alban

I think this can be answered by the application of a bit of common sense. When do you call an ambulance for chest pain?

 

[Dr Deco]

Dear Readers:

Preventing Hits

Alban has raised the question, “Can oxygen really prevent a hit?” Indeed, it can. This is because the growth of tissue gas bubbles by inward diffusion of dissolved inert gas is in competition with the loss of inert gas into the circulatory system.

The dissolved inert gas molecules are not “drawn” to the bubbles or capillaries as if these were magnets; they are not attracted as is a moth to a flame. A nitrogen molecule will just as well diffuse from the capillary to the tissue as the other way around – if dissolve nitrogen quantities were equal. The lower the concentration of nitrogen in the capillary blood, the less is the chance that this outward diffusion process will occur.

Here is the point with oxygen breathing. The concentration of inert gas (nitrogen) in the capillary will be lowest if you are breathing pure oxygen. The ratio of nitrogen molecules entering the capillary verse the number leaving it will be least. This is the [statistical mechanics] meaning of the “gradient.” It is the ratio of dissolved nitrogen molecules (or whatever) going one way or the other.

Clearly, the more nitrogen carted off in the capillary, the less will remain to possibly find its eventual way into the gas bubble. The growth process of the gas phase is thus cut off. We can actually prevent DCS before it occurs (it remains “silent”).

Silent Bubbles

Are “silent bubbles” really present? Most would believe that concept today, but it was not always so. This early visual detection and observation of bubbles in asymptomatic rats was one of my first scientific papers in the barophysiology field. {MR Powell. Gas phase separation following decompression in asymptomatic rats: visual and ultrasound monitoring: Aerospace Med., 43, 1240-1244, 1972}

Dr Deco :doctor:

 

[The Iceni]

Dr Deco once bubbled...
Dear Readers:

Preventing Hits

Here is the point with oxygen breathing. The concentration of inert gas (nitrogen) in the capillary will be lowest if you are breathing pure oxygen. The ratio of nitrogen molecules entering the capillary verse the number leaving it will be least. This is the [statistical mechanics] meaning of the “gradient.” It is the ratio of dissolved nitrogen molecules (or whatever) going one way or the other.

Clearly, the more nitrogen carted off in the capillary, the less will remain to possibly find its eventual way into the gas bubble. The growth process of the gas phase is thus cut off. We can actually prevent DCS before it occurs (it remains “silent”). . . Dr Deco :doctor:

This is precisely why I think a "hidden stop" is such a good idea, Dr Powell, but I believe there is even more to this.

Breathing oxygen results in little or no nitrogen dissolved in arterial blood. As has so often been pointed out most now believe that micronuclei are formed in the blood when the diver performs isometric exercise such as climbing the ladder, for example, and some may arise in, or be small enough to pass into the arterial tree whether a PFO is present or not. If these form or lodge and persist in the capillaries they reduce perfusion (and offgassing) in the affected area.

These arterial bubbles will contain the same gasses that are dissolved in the blood and if this is oxygen alone this will all be rapidly used by metabolism at tissue level, following the diffusion gradient. No so if they contain nitrogen at 0.79 bar.

It seems axiomatic that the stability of tissue bubbles containing oxygen alone is much less and they are far more likely to reduce and completely disappear in comparison with those containing any inert gas. In fact, the latter are more likely to grow by taking on more of that inert gas at high pressure diffusing from the tissues. This results in blockage of the affected capilliaries, a reduction in perfusion and a consequential reduction in localised offgassing (RGBM).

I do not know how stable oxygen bubbles are but it seems entirely logical to me that if I breath 100% oxygen during the phase when micronuclei formation is the greatest - in the immediate post dive period - I will be preventing the formation of stable bubbles at the level of the tissues and thus maximise offgassing at all subsequent stages of the post dive period. :doctor:

 

[Alban]

Hello Dr T

I am still not convinced enough to vote either way ( yet )
May I ask Dr Deco or yourself ,:doctor:

Could O2 delay the symptoms of dcs ?
Could a diver suffering from dcs have his judgement impaired ?
Is it true the diver is at the greatest risk in the 60 mins after surfacing ?
Is it true a diver suffering dcs may not feel pain ?
If a diver waits until pain irreversible damage may have occurred ?
Will O2 alone prevent dcs in all but mild cases ?

The response to treatment depends upon the severity of symptoms and the delay to recompression. This is from the DAN site I think you would agree it to be correct.

Doctors often talk of "the golden hour" by administering O2 and waiting for pain you will compromise successful treatment . If a diver is sat on the boat breathing O2 how long should he breath it ? the responsibility of deciding to launch a rescue would normally rest with the Hyperbaric doctor this now rests firmly with the dive master who may only have 50+ dives and very limited knowledge of decompression procedures. Should all further diving on the boat be suspended because part or all of the O2 has been used ?
I think I am trying to balance the benifit of giving O2 as a prevention against a delay in recompression . I do not think I could shoulder the responsibility of a diver sat on the boat breathing O2 who has messed up without notifying the emergency services ;-0 Legally I would be hung out to dry !

Yours Alban

 

[Dr Deco]

Dear Alban:

Here are some quick answers to your questions. Sorry to be so brief at this time.

Could O2 delay the symptoms of DCS?

Most definitely oxygen could not only delay the appearance of DCS. If it were delayed long enough, all nitrogen would diffuse away and DCS would not appear.

Could a diver suffering from DCS have his judgment impaired?

It the diver had neurologic decompression sickness (in the brain, not the spinal cord), it is definitely possible to have cognition (= judgment) problems.

Is it true the diver is at the greatest risk in the 60 minutes after surfacing ?

Most problems associated with decompression sickness will appear within sixty minutes.

Is it true a diver suffering DCS may not feel pain ?

If it is joint-pain DCS, the diver will feel it. If it is neurological DCS, there is generally not any pain associated with it (although there might be numbness or itching). This form manifests itself in difficulties in moving arms and legs, balance, speech, and facial muscles.

If a diver waits until pain, might irreversible damage have occurred ?

If it is pain-only DCS, there is not any irreversible damage. Unfortunately, there might be nerve injury in addition to the joint pain. In this case, there could be "neurologic residuals."

Will O2 alone prevent DCS in all but mild cases ?

No, oxygen is not an all-purpose cure. The balance between nitrogen moving to the capillaries and moving towards to bubbles is what initially causes the DCS process. Naturally, the greater the dose of nitrogen, the larger will be the bubbles. Oxygen changes the equation by allowing no nitrogen at all to “back flow” into the tissue from the arterial system.

Dr Deco :doctor:

 

[The Iceni]

Alban once bubbled...
Hello Dr T

I do not think I could shoulder the responsibility of a diver sat on the boat breathing O2 who has messed up without notifying the emergency services ;-0 Legally I would be hung out to dry !

Yours Alban

Hi Alban, I couldn't agree more with your very last statement.

However, can I ask if you are being deliberately obtuse?

Are you, perhaps a politician?

May I clarify (again).

1. If you are the dive marshal/skipper, who will tell you the diver has "messed up?"; - either the diver or his buddy. For the reasons I gave earlier, at least for minor violations there is considerable pressure to deny anything is wrong until symptoms develop.
   
2. Divers often "get away with it" even for major violations and wait for symptoms to develop or not - "just like before". I have seen it!
   
3. If they opt for denial (rightly or wrongly) and do not have their own oxygen they have little choice other than to sit it out with fingers (and toes!) crossed.
   
4. When and if their DCI develops it will be worse that it would have been had the diver used oxygen right from the start. (I do not think, even you, can argure with that!)
   
5. There will be occassions when oxygen was all that was needed and if not it will certainly have reduced the diver's residual nitrogen load for subsequent dives.
   
6. You main objection would be solved if a second non-medical oxygen bottle were made available on the boat to those who request it, for whatever reason.
   
7. Do you believe in the dissolved gas/bubble theory of DCI? If so I find it hard to see what genuine objections you can have.[/list=1]
   The original question was intended to clarify whether it is oxygen itself that is a medicine or whether this this governed by the circumstances of its use? Dr Deco gave water as an example.
   
   Clearly bottled water is not a medicine but water is if it is given intravenously, (or by mouth in the treatmant of DCI) in these circumstances it's use is very much medical. Perhaps there will come a time when intravenous fluids are given by diver medics but that day has yet to come, if ever.
   
   Quite honestly, I do not understand your confusion, Alban.
   
   :doctor:

 

[Alban]

Your idea would work very well IF a diver could have O2 with no drama attached to it unfortunately this will not happen..Which ever way you dress it up O2 is not a drink of water.
I would agree with all of your points and would agree in principal to the idea. But diver denial is the biggest problem and that is because of the stigma attached to it. Your idea is well intentioned but would not work in to-days society ( maybe 10 years ago ) .I believe the only way forward now is to change attitudes, there is no shame in addmitting a fault or to ask the emergency services for advise that is what they are there for and what they are trained to do. It is possible to change attitudes as the cave divers did when they suggested :
Any person can call a dive for any reason no questions asked.

The benifits of what you suggest would remain unseen there would be no way to tell if the diver would have sustained injury or not , as such it would be balanced against the worst case scenario. It would only take one case where a diver went on to develop full blown dcs and it was proven there was a delay in recompression because you decided to administer O2 and NOT notify the emergency services straight away. Then alas they would be queing up to take you to court .
The idea is hypothetical but is against the recomendations of ALL training agencies , to ignore the correct procedures will invalidate your insurance and a civil claim for damages would be considerable ££££

Have you run the idea past your D.O. ? I bet it would make him cough.

Yours Alban

 

[The Iceni]

Hi Alban,

I won't ask him but I feel pretty confident that my DO would not readily grasp the concepts I detailed in my earlier post regarding tissue bubbles and the hidden stop.

A club DO will, by the nature of his post, be required to follow established guidelines as you suggest.

I have spent enormous amounts of energy persuading BSAC of the undoubted benefits of surface oxygen following an oxygen incuded convulsion underwater leading to near drowning and hypoxia. The official position is still confusing and unclear.

For some, it would seem oxygen remains the devil gas!

I am somewhat gratified from the results of the poll that they are in a very small minority.

 

[TwoBitTxn]

Using the scenario where a diver makes a mistake great enough he feels he needs O2 just to be safe. He also wishes to wait a period of time an see if he developes symptoms of DCS.

At 15LPM on a non rebreather a standard size boat O2 bottle goes very quickly. Even if he doesn't drain the bottle the boat is now deficient on one very important peice of safety equipment.

It is my opinion that the diving day for the boat is now finished due to this lack.

Thoughts?

TwoBit

 

[Alban]

Hello TwoBitTxn

I would agree with you if there was only one cylinder the day would be over so there would still be the pressure there for denial.
Dr T did suggest in a previous post that there could be two O2 cylinders available , although I think the matter could get confusing if the Dive Master carried on with a second dive leaving the skipper ? to monitor the distressed diver.

There would also be a concern over any after care would the Dive Master carry out a neurological examination then state in his opinion it would be safe for the diver to drive home but as a precaution he should visit his local Doctor ?

A Dive Master could possibly prevent numerous hits but he has only to get it wrong once.
Perhaps technical divers could treat themselves with there stage bottles but if you hand that bottle to someone else you enter a grey area that a smart Lawyer will exploit !

Dr T I don't think it is a case of the devil gas more a case of litigation in the event of an accident the suits will disect the incident look at the hard facts and apportion blame where ever they can.

Yours Alban