Pure oxygen not good for you!?!

[BEM]

Here is part of a new study:

"Pure oxygen can reduce blood flow to organs and tissues by increasing ventilation," Dr. Iscoe explains. "The increase in ventilation, which is almost never considered, 'blows off' carbon dioxide, and this fall constricts blood vessels. When carbon dioxide is added, however, the blood vessels dilate, increasing blood flow and causing more oxygen to reach tissues in key areas like the brain and heart."

O2 Study

If the results of this study are valid, how does this affect giving pure O2 for diving injuries?

 

[cool_hardware52]

Here is part of a new study:

"Pure oxygen can reduce blood flow to organs and tissues by increasing ventilation," Dr. Iscoe explains. "The increase in ventilation, which is almost never considered, 'blows off' carbon dioxide, and this fall constricts blood vessels. When carbon dioxide is added, however, the blood vessels dilate, increasing blood flow and causing more oxygen to reach tissues in key areas like the brain and heart."

O2 Study

If the results of this study are valid, how does this affect giving pure O2 for diving injuries?

I just read a study, or more correctly an article that cites a study, the current issue of the Dan magazine "Alert Diver" that correlates the outcomes of DCS cases and the administration of O2.

Early administration was better than late, the benefits of late administration was pretty close to the outcomes where no O2 was provided, IIRC. Sorry the articles at home, I don't remember the definition of early vs late, maybe 6 hours?

Pretty clear evidence that O2 early was a good thing.

This is only one study, the evidence for O2 as first aid for diving injuries is extensive, and well documented.

Tobin

 

[BigJetDriver]

This study could only be described most charitably as "controversial at best".

In divers with DCS we are dealing with the separate mechanism of having actual bubbles occluding blood flow, and therefore oxygenation, as far down as the cellular level.

Providing pure oxygen creates the steepest possible gradient between the inert gases in solution and bubble form, and the inspired gas (i.e. zero inert gas). This is obviously a good result.

The use of pure oxygen increases the oxygen saturation to the maximum possible in the patient's blood stream, therefore providing as much oxygen as possible to those areas in the patient's body where perfusion may be limited by the bubble blockage.

It is "possible" that inclusion of some slight fraction of CO2 in the medical oxygen being administered "might" increase the patient's breathing rate, and therefore help in over-all ventilation, thereby increasing the blood to atmosphere gas exchange.

There are quite a few other factors to consider, and until this has been studied in depth, I would caution against making any rash changes in our current procedures.

 

[Doc Intrepid]

If the results of this study are valid, how does this affect giving pure O2 for diving injuries?

Very little.

There are few medical remedies that do not cause _some_ adverse impact to other parts of the system. For example, in response to fluid in the lungs diuretics may be prescribed. Taken long enough, these can result in kidney damage...but they get the fluid out of the lungs.

Divers decompressing on pure O2 often perform "backgas breaks" in a ratio of X minutes off pure O2 for every Y minutes on pure O2. Such breaks are intended to address some of the issues involved with breathing pure O2 for lengthy periods.

For the reasons BJD noted, pure O2 is extremely efficient at removing nitrogen bubbles from the circulatory system.

Therefore, in response to your question "...how does this affect giving pure O2 for diving injuries?", the answer is "it doesn't". Despite the theoretical impacts of breathing pure O2 for lengthy periods, a bent diver is primarily concerned with immediate relief and preserving the greatest potential for complete recovery. This is currently accomplished most effectively and efficiently by providing pure O2 treatment to the bent diver.

At least for now...

 

[Dive-aholic]

To add to this, people who have been exposed to carbon monoxide are treated by being placed on 100% O2 (actually about 95% now that the NRBs have changed a little) for 12 or more hours, even if they don't exhibit any symptoms. 100% O2, in itself, is not a good thing to breath for long periods of time. However, if there is some metabolic or physiological issue at hand (like nitrogen uptake), then it is definitely helpful.

 

[babar]

When using hyperbaric oxygen there is a demonstrated constriction of arteries. This reduces the blood flow to certain areas. However there is so much more oxygen dissolved in the blood that that it more than makes up for the lesser total blood flow. This is also true with normobaric (normal pressure) oxygen.

Babar

 

[freediver]

Wow! Would you believe I just read a study which stated 50% of studies will be contradicted by a future study!

 

[BigJetDriver]

Wow! Would you believe I just read a study which stated 50% of studies will be contradicted by a future study!

:rofl: :lol:

 

[Dr Deco]

Hello readers:

Oxygen

I had a chance to look over this question. What the authors are referring to is tissue oxygenation in quit subjects (patients). I have advised divers to move about somewhat (sitting and moving arms and legs) while on the surface. This generates local, tissue CO2.

For patients with poorly healing wounds, CO2 in oxygen could well be of use and would need to be tried.

Dr Fisher

As an aside, one of the authors, Dr Joe Fisher, first mentioned this effect to me about ten years ago as suggested it as a method to reduce oxygen prebreathe time. It would probably take uncomfortable amounts of CO2 in the breathing mix, but we have not really tried it out.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology is September 10 – 11, 2005 :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[BigJetDriver]

Hello readers:

Oxygen

For patients with poorly healing wounds, CO2 in oxygen could well be of use and would need to be tried.

Dr Fisher

As an aside, one of the authors, Dr Joe Fisher, first mentioned this effect to me about ten years ago as suggested it as a method to reduce oxygen prebreathe time. It would probably take uncomfortable amounts of CO2 in the breathing mix, but we have not really tried it out.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology is September 10 – 11, 2005 :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

So, Doc, in essence this is an idea that has not really been studied properly, and we are not ready to modify our O2 procedures for DCS patients yet?

Rob