Quote: (Originally Posted by
Brad_Horn)
G'Day,
From 'Oxygen and the diver: Kenneth Donald, pg 67' there is mentioned an 'Off Effect'.
Namely "The 'Off Effect' on returning to air breathing after exposure to toxic tensions of carbon dioxide is well known. there is a sudden exacerbation of symptoms often associated with headache, nausea and vomiting." "In one or two cases it appeared that convulsions were precipitated by reverting to air breathing"
Whilst, this appears to support either a good FFM or a BOV (& gag strap) that you can vomit into (& clear) and/or at least retain the ability to breathe from whilst convulsing post getting off the loop after/during a CO2 hit.
It doesn't appear to delve further into the subject with regard to air breathing, apart from that the effect is well known, does anyone know any further references/reading on the subject of the 'Off Effect'?
Have any studies been done, comparing going onto Trimix/Heliox as opposed to Air after a Co2 hit?
Regards
Brad
I have seen it a couple of times in chamber subjects. In both cases the subject was exhibiting symptoms suggestive of oxygen toxicity, which is why the oxygen was removed. Soon afterwards the convulsion started.
As Samuel Johnson once said: "It is incident to physicians, above all other men, to mistake subsequence for consequence."
My guess is that these people were going to convulse anyway. They merely had some concerning symptoms that resulted in the oxygen being removed shortly before the convulsion, which was going to happen anyway, started.
I am not aware of any research on the subject. I can't think of a mechanism by which a sudden reduction in PO2 might produce a seizure, but that doesn't mean much.
Andy