Posted by John Walker on October 28, 2000 at 23:38:45:
In Reply to: Re: What's to argue? posted by Ken Kurtis on October 28, 2000 at 01:31:56:
Ken this is not directed at you, I am just posting under you. One of the problems I see in the general diving community v.s. nitrox is that few either spend enough time trying to learn about it or that some just don't know that many resources are so readily available.
General anesthesiology study's have long promoted the belief that ALL gases will uptake and defuse from tissue groups at the same rate except in FATS.
One of the things that we know about nitrogen is that it is highly soluable in FATS and highly retentive in fats. This means that tissue groups with fats or higher amounts of fats will take longer to defuse nitrogen into the circulatory system where N2 can be transported to the filters (our lungs). Another problem seems to lay in how this diatomic gas (N2)defuses from tissue and the adema that is left in it's path. Since the tissue's don't store O2, which is molecurly heavier as they do N2 this is not an issue with O2 in my opinion. Mr. Huggins could surely alaberate.
Another theory is that N2 may possible cause red blood cells to become rigid. Red blood cells are required to oblongate themselves to pass through some very small capalaries which are actually smaller than the 4-6 micron RBC. This would obviously cause an acidic problem as well as a hypoxic tissue problem not to mention damage top the RBC it's self.
One the other side of the fence these fatty tissues are generally slower to absorb the gas that generally composes about 80% of our breathing medium. About 21% of our air is O2 in which about 4% to 6% of that is used for metabolic requirments. The rest (maybe 16%) is thought to travel via hemaglobin (Hb) and some of that will be defused back through the alveoli. This is one of the area's where nitrox can POSSIBLY inhibit the normal metobolic process by increasing the overall O2 load on Hb.
If most of the Hb are bound with molocules of O2 then Hb is less likely to have space to latch with Co2 which needs to be transported out of the body befoe we have an acidic problem.
Another problem with to much O2 (high PPO2) for extended periods is the vasal contrictive reaction that may in fact limit circulation thus creating another problem with the Co2 transportation as well as other offgassing processes.
Another is that higher levels of O2 at the cellular level may produce extra superoxide radicals which will be converted via superoxide distumase (SOD) into a toxic chemical to the brain, hydrogen peroxide. Although other reactive oxygen species are responsible for detoxifying hydrogen peroxidase they sometime become unbalanced and can actually assist the toxicity. Hydrogen peroxide is believed my several to be one of the key players in a hyperoxic siezure (CNS tox hit).
Anyhow there are pros and cons to Nitrox. I believe it has a valid role for divers weather recreational single tank divers to rad tad deep divers. Although the deep divers general use Nitrox to saturate tissues with higher pressures of O2 in order to push out stored inert gases, singles tank divers can choose to use it to limit the total NITROGEN load. Either way divers need to learn all thay can about either side of the fence.
Disclammer, I am not a doctor nor a physiologist. I try hard to learn about diving as well as share. Sometimes I don't spell so well. Please live with it for now and when I get bored learning about diving I will work on my english.
RAP