Tissue stress associated with bubble formation; potential benefits of diving enriched air

[tursiops]

As a scientist, you should be well aware of the placebo effect.

LOL. You can't think of a better counter argument to the hypothesis presented? Try again.

 

[Diver-Drex]

@MaxBottomtime - two points...

Lowering the rate from .1% to .05% seems like nothing, but it's cutting the rate in half. That's a huge improvement.

I don't think that the benefit will ever be fully realized because of diver behavior. Regardless of breathing gas, if you stay to the NDL for that gas at that depth the result in terms of inert gas loading will be the same.

 

[MaxBottomtime]

.01, not .1
DAN estimates the risk of DSC using air between one in 7500 to 10,000 dives. Nitrox may lower that risk, but not necessarily by half. It is really not any safer than diving air.

 

[uncfnp]

.01, not .1
...It is really not any safer than diving air.

Are you really saying there is no benefit in safety? Period?

 

[DevonDiver]

As I asked earlier... what actual figure do those risk ratios represent?

It's all to easy to be dismissive of risk when dealing with risk ratios... or not applying individual risk factors to the mix.

For instance, how do those ratios account for individual factors (that may be known by the diver) or the existence of DCS susceptibility factors?

If an individual diver notes a personal issue with post-dive fatigue... and also notes that EANx use rectifies that issue... should we dismiss it as 'placebo' or 'zealotry'... or can we intelligently consider that DCS presentation (clinical or otherwise) is highly influenced by a multitude of variable individual physiological factors?

It should be noted that 'post-dive fatigue' isn't listed as a symptom of decompression stress / sub-clinical DCS.

The actual named symptom is "Unusual post-dive fatigue".

Who is actually best placed to define and recognise if their post-dive vitality is usual or not? The diver themselves...

It's a very unique issue to each individual ... and attempting to discredit or dismiss divers for their unique experiences and symptoms is very short-sighted.

 

[MaxBottomtime]

Are you really saying there is no benefit in safety? Period?

No, as I said earlier it is negligible. Of course there are some who are more susceptible to DCS due to their weight or other factors, but many posters here use blanket statements that nitrox is safer without realizing to what degree it is. For the average diver there is a 1 in 10,000 chance of getting DCS breathing air. If those odds seem too risky to you, by all means use nitrox.
As for post-dive fatigue, try making a slower ascent and/or swimming less during a dive while breathing air. I'm sure most will find little to no fatigue if they slow down.

 

[Diver-Drex]

I am curious as to why? Some possibilities maybe.
- Some divers are predisposed to get bent behaviorally. They commonly push dives to NDLs, have deliberately decreased the conservatism of their DC to gain dive time, ascend rapidly or have poor buoyancy control.
- Some divers are predisposed due to their physiology. Body composition, chronic dehydration, underlying medical condition, poor physical condition.
- The availability of 'tec' dive computers and information on the web promote divers attempting dives beyond their capabilities. More often these are EAN dives, thus scewing the data.
- There is no way to determine how many EAN dives would have resulted in DCS had they been done on air.

I don't know if these are actual reasons why there is little difference in the rates, maybe DAN has data on this?

 

[BRT]

The third factor is rather obvious here: the diver.

There is a group of divers who feel better after breathing nitrox 100% of the time and so the based on that number the third factor can be statistically removed. And thus we can say with increasing certainty that correlation between nitrox and feeling better is real. Very common motif in arguments for existence of god (various), as I recall.

I feel better after diving nitrox, but I'm not sure it isn't all in my head.

 

[BRT]

No, as I said earlier it is negligible. Of course there are some who are more susceptible to DCS due to their weight or other factors, but many posters here use blanket statements that nitrox is safer without realizing to what degree it is. For the average diver there is a 1 in 10,000 chance of getting DCS breathing air. If those odds seem too risky to you, by all means use nitrox.
As for post-dive fatigue, try making a slower ascent and/or swimming less during a dive while breathing air. I'm sure most will find little to no fatigue if they slow down.

I'm guessing that the chance of getting DCS gets higher if you only consider divers who dive at max NDL's.

 

[archer1960]

I am curious as to why? Some possibilities maybe.
- Some divers are predisposed to get bent behaviorally. They commonly push dives to NDLs, have deliberately decreased the conservatism of their DC to gain dive time, ascend rapidly or have poor buoyancy control.
- Some divers are predisposed due to their physiology. Body composition, chronic dehydration, underlying medical condition, poor physical condition.
- The availability of 'tec' dive computers and information on the web promote divers attempting dives beyond their capabilities. More often these are EAN dives, thus scewing the data.
- There is no way to determine how many EAN dives would have resulted in DCS had they been done on air.

I don't know if these are actual reasons why there is little difference in the rates, maybe DAN has data on this?

One big one you left out of predisposition is a PFO (though I guess that could be grouped under "underlying medical condition", but a PFO has been very strongly correlated with a susceptibility to DCS.