Web Monkey:
OK, now how about if there's a gas switch? Say you're on EAN36 @95', then switch to air and drop to 130?
Is O2 Tox still a possibility?
Terry
I can't remember where I read this because I have done a lot of reading lately regarding mixed gas diving but I recall seeing something to the affect that CNS ox tox can still occur once the person has been moved to a lower ppO2. Apparently there is a bit of lag time until sufficient O2 has been removed from the system.
Been pondering your intitial scenario as it poses the typical moral dilemna of all rescue situations whether on land or in the water. That being, what level of risk is the rescuer taking if they decide to attempt a rescue?
Given your scenario, can one mitigate the risk of becoming an oxtox victim while attempting to rescue the already toxing diver at 130 feet? IMO--possibly. The thinking would have to go something like this
1.) The toxing diver is dead if you do nothing
2.) A ppO2 of 1.6 is acceptable for a "resting" portion of the dive.
3.) Attempt the rescue in a resting mode i.e exhale and dump some air from the BC to descend to the toxing diver using the absolute bare minimum of finning activity to place you at the toxing divers location. As you are arriving at the toxing diver add sufficient air to the BC to stop the descent and initiate an ascent while taking hold of the toxing diver.
4.) Continue a controlled ascent to the surface with the toxing diver and hope for the best.
As noted by the other repondents regarding the studies they have read, there is an increased risk to the rescuer of becoming a victim but what the actual probability would be is very hard to say.
Very good question and indeed a thought provoking one at that.