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Just to add: what does 1% of 10m really mean? This is 10cm. This is even challenging for the calibration of dive computer pressure sensors. And on top of that, even in very good trim, the vertical extent of most divers will be several 10s of cm ;) So where to measure? Decompression anyhow is...

Of course I was not there. And actually, I have never seen a person with PAME. Just saying what I read is that it normally is a rapid onset of really severe physical symptoms, with which afflicted persons surely will not be able to dive, suicidal intent or not. Additionally, the diseases is so...

I did not know that story, but honestly, it sounds not really realistic (to me at least): PAME, the meningitis caused by N. fowleri, is as far as I know a disease with quite rapid onset, and manifests with heavy fever, severe headaches, vomitting, this type of symptoms. Surely nothing that would...

The thing that in effect sometimes makes table-dives quite „conservative“ is that one is motivated to assume a box-style profile even if it is a multi-level dive. This can result in effectively short NDLs. Exaggerated example: Diver briefly goes to 30m to check on a nice gorgonia. After 4...

Do not want to state anything that may be obvious, but: it is after a single DCS incident simply not possible to pinpoint "the cause" with absolute certainty. Sure, sometimes there may be a strong suspicion, e.g. a very aggressive profile (just to name something where there will be little...

First, let me say that what we are discussing at the moment, percent-level inequalities, does not even depend on metric units. Those issues also are there when using imperial units. Just often ignored. Which is OK. It is actually not even a given that pressure sensors measure to percent...

The EN13319 salinity (precise: density at a fixed temperature) is so that 10m column result in 1bar pressure. However, 1 physical atmosphere is also a bit more than 1bar, and the salinity of ocean water often enough is a bit higher than in the EN. In the SI, actually, neither is the [kg] any...

The unit [atm] was not based on a column of water, but rather on the pressure of the air column at sea level. This is roughly 1.013bar, equivalent to a salt water column of about 10m, or a fresh water volumn of about 10.3m. The TDI / SDI material has it correct.

I would guess if that is indeed DCS (very hard to really tell, as you are also saying), it may be an indication that you are pushing the boundaries of what your body will tolerate. So while those very same bubbles that cause the hurt will go nowhere critical, a future dive may still be by...

Indeed. Looking into our heritage, this is very normal! A human that is suddenly submerged (e.g. from a fall into water) has to immediately and effectively hold his or her breath. Full lungs mean life in that situation. Our reflexes do not inutitively know that there is a very ample supply of...

Fully agreed. And that is different from static breath holding, where, as Simon Mitchell and others already noted here, basically everyone sees much longer times with O2. Although part of that effect is the hyperventilation part that to some extent also would work with air, O2 adds on that.

Gelirfella, you mean me? Then maybe postings crossed. I was talking about a regime existing where high inspired fO2 moves backward the urge.

Gelirfella, well, one regime has been named here already, it is apnea times. But in general, as said many times, I do agree; I also do not expect to see a notable effect in scuba diving air consumption.

Would indeed be interesting to check! "Urge to breathe" is a bit unspecific. It can be a rather psychological urge, that would then not change with fO2. Or it can be driven by CO2 and the need to eliminate that, which is quite similar for air and nitrox. A notable difference in gas consumption...

Sorry but that is diverging now! The question was not "How can a diver practically reduce air consumption?", and also not about gas densities, at least not to my reading. The question was for an explanation whether breathing pure oxygen (or nitrox) -- both happens inevitably e.g. during most...

Well we were considering the question in a scientific context, not if that is a good idea from a practical vewpoint. It does come up from time to time, and I personally think it has a rather clear answer: "In theory, yes that happens, but in practice normally one will not notice".

Well that goes into the direction I am talking about. Just compare your breathing pattern right now, fully relaxed on land, with your pattern while fully relaxed during a dive. Very probably the two will be different. For a number of reasons. A lessened urge to breathe will only matter for gas...

There surely are several effects. In the end, the "experiment" that was suggested above (static apnea time after pre-breathing O2) results in very significantly longer apnea times. Of couse in scuba diving we very often breath much higher ppO2 than on dry land, even when using air. My basic...

It is not only the "purging" of CO2 from the lungs; pre-breathing O2 results in generally longer apnea times than doing the same pre-breathing pattern with air. The higher O2 concentration in effect also lessens the chemoreceptor response to the rise of the CO2. But I would like to comment on...

Putting aside for the moment that of course there are many other factors involved, including training and experience: it may even be! Many seasickness meds are actually H1 antagonists. Those are centrally acting and can influence both heart rate and breathing. I know of no solid data to even...