wetvet
Guest
Hi DIR folks;
I was diving a couple of weeks ago with a DIR outfit a couple of weeks ago. The dive was to ~85 feet, and because of a problem my buddy had, we cut the dive short with a bottom time of about 15 minutes. I surfaced and asked the captain to unzip my drysuit so I could get out of it. My neck seal is fairly tight, and I can feel the pressure in my head go up when I'm in my suit for a bit. The captain told me that the reason I felt this discomfort had to do with the fact that I was breathing AIR, and that this gas was inappropriate to breathe on ANY dive. I got the "good for flat tires" speech, and I asked him if that was strictly a narcosis issue, or if there was another reason why I should never dive on air. I wasn't worried about narcosis at 85 feet, and had no intention of even approaching NDL times since the water was cold, and I was diving with a guy on an AL80.
I was told that CO2 retention was causing my headache, and that air made it much worse. He warned me of the dangers of passing out, and vastly increased narcotic effect of CO2 vs N, but it didn't make sense. He couldnt give me an answer that made me understand, thus this post.
I understand how CO2 retention can result from work underwater, shallow or skip-breathing, or poor supply of gas due to badly serviced gear, but air does not contribute to any of these.
CO2 is produced by the body under work...it is a byproduct of respiration....the amount in air is negligible, and the normal production of Nitrox means that the majority of gas in my tank is air anyway.
The theory of increased work of breathing doesn't wash with me for 2 reasons....1- the diaphragm and intercostal muscles are so small in comparision with the muscles used for swimming or working that the increase in workload would have to be severe to make a noticible difference in the body's total CO2 production, and 2- since oxygen has a higher molecular weight than Nitrogen, air should be less viscous than the EAN32 he was telling me to use.
I appreciate the vasodilation effect of Oxygen on the brain, and thus the reports of some divers of feeling better, but I have never noticed this response in myself. Is the DIR credo of "never dive on air" just a way to gain that extra bit of narcosis safety, or is there something I am missing??
Thanks for any information..
Wetvet
I was diving a couple of weeks ago with a DIR outfit a couple of weeks ago. The dive was to ~85 feet, and because of a problem my buddy had, we cut the dive short with a bottom time of about 15 minutes. I surfaced and asked the captain to unzip my drysuit so I could get out of it. My neck seal is fairly tight, and I can feel the pressure in my head go up when I'm in my suit for a bit. The captain told me that the reason I felt this discomfort had to do with the fact that I was breathing AIR, and that this gas was inappropriate to breathe on ANY dive. I got the "good for flat tires" speech, and I asked him if that was strictly a narcosis issue, or if there was another reason why I should never dive on air. I wasn't worried about narcosis at 85 feet, and had no intention of even approaching NDL times since the water was cold, and I was diving with a guy on an AL80.
I was told that CO2 retention was causing my headache, and that air made it much worse. He warned me of the dangers of passing out, and vastly increased narcotic effect of CO2 vs N, but it didn't make sense. He couldnt give me an answer that made me understand, thus this post.
I understand how CO2 retention can result from work underwater, shallow or skip-breathing, or poor supply of gas due to badly serviced gear, but air does not contribute to any of these.
CO2 is produced by the body under work...it is a byproduct of respiration....the amount in air is negligible, and the normal production of Nitrox means that the majority of gas in my tank is air anyway.
The theory of increased work of breathing doesn't wash with me for 2 reasons....1- the diaphragm and intercostal muscles are so small in comparision with the muscles used for swimming or working that the increase in workload would have to be severe to make a noticible difference in the body's total CO2 production, and 2- since oxygen has a higher molecular weight than Nitrogen, air should be less viscous than the EAN32 he was telling me to use.
I appreciate the vasodilation effect of Oxygen on the brain, and thus the reports of some divers of feeling better, but I have never noticed this response in myself. Is the DIR credo of "never dive on air" just a way to gain that extra bit of narcosis safety, or is there something I am missing??
Thanks for any information..
Wetvet