Quote: (Originally Posted by Nick uk.)
If you get off your high horses, and read what has been writen we might be able to get somewhere. Mavericks and Quacks..........i'm neither, and unless you are an expert on hyperbaric medicine, my guess is your guessing, and if a concept is new to you doesn't nesecerally make it wrong!
The fact is that hight PpO2 for a prolonged time do cause 'capilaries' to restrict on a polmonary level and therefore inhinit the gas exchange at this level, not in the arteries, and blood stream, but in the lungs where the gas exchange takes place....during deco, for example, which is why we/i take air breaks to combat this and re-open, if you like the efficiency levels, or the all famous Oxygen Window, but there is a benefit on any deco profile from lets say 30mins + not just for the CNS but for the restriction of the capillaries.
Believe it or not.
Nick,
I am a hyperbaric physician and so is Gasman. Pulmonary oxygen toxicity is not due to pulmonary capilary vasoconstriction but due to direct damage to the lung cells. Air breaks have been shown to prolong the time to measurable decreases in various lung volumes - no question - but it's not got much to do with blood flows.
Air breaks underwater are mostly to do with a (presumed) CNS toxicity benefit. You would have to do a lot of diving in a day to get to a level of exposure that you would even begin to see measureable pulmonary toxicity (about say 700 UPTD - over 8 hours at a setpoint of 1.4) Even at this level there would not be a significant decrease in gas exchange in someone with normal lungs.
There is a thing called hypoxic pulmonary vasoconstriction where blood flows to areas of the lung are not well ventilated are reduced, to help maintain good gas exchange. There may be circumstances (in diseased lungs) where high concentrations of oxygen may abolish hypoxic pulmonary vasoconstriction and paradoxically worsen gas exchange but this doesn't have much to do with diving medicine.
The question being debated in this thread (as I understand it) is "Is it wrong to use 100% O2 for the treatment/first aid for DCI"? The answer to this question is NO, absolutely and emphatically.
Dave T