Surface interval after a trimix dive...

[kierentec]

Not to long ago, a buddy of my got a spinal DCS hit on a 100 ft non-deco air dive about 24 hours after a 245ft trimix dive. His chamber operator and doctor both suggested a minimum of 48 hours before diving air/nitrox after a trimix dive. What do you guys recommend/practice?

 

[anytime]

We usually wait at least 1:30 mins after a deeper dive. But if was 48 hours... alot more people would be bent.

 

[Dive-aholic]

Never heard of that and never practiced it. I've done nitrox dives less than 24 hours after a trimix dive. You state it was a air NDL. What was his actual profile?

 

[GrimSleeper]

Not to long ago, a buddy of my got a spinal DCS hit on a 100 ft non-deco air dive about 24 hours after a 245ft trimix dive. His chamber operator and doctor both suggested a minimum of 48 hours before diving air/nitrox after a trimix dive. What do you guys recommend/practice?

I've been told the same thing, although no-one had any real explanation for why, other than the empirical one: they'd seen people get bent for no other apparent reason. After a series of trimix dives, if I'm going to go straight onto recreational dives I generally top off my remaining back gas with air or nitrox, use that, top it off again... If there is some sort of problem with diving air/EAN after trimix, the topping off seems to work, and if there isn't a problem, well, I'm just using gas that's in my tanks anyway.

 

[Cave Diver]

Not to long ago, a buddy of my got a spinal DCS hit on a 100 ft non-deco air dive about 24 hours after a 245ft trimix dive.

Doesn't make sense to me. At 24 hours, I would expect tissues to be sufficiently washed out that 100' air dive wouldn't be a problem. My guess would be either something about his physiology, something about the dive, or both caused the hit. For example, previous back injury that may have scar tissue or something or a rapid ascent that led to bubble formation.

His chamber operator and doctor both suggested a minimum of 48 hours before diving air/nitrox after a trimix dive. What do you guys recommend/practice?

Was this a general suggestion, or specific to him for some reason?

I also wonder if he might have sustained a minor, unnoticed DCS injury during the trimix dive that was exacerbated during the air/nitrox dive.

 

[amascuba]

90 minute SI and I'm good to go.

 

[rjack321]

Jack the helium content on the trimix dives so you load less nitrogen. Nix the air dives for nitrox.

But really the "basis" for the recommendations are flimsy.

 

[kierentec]

Thanks for you input everyone. I had never heard it before, and didn't seem to make a whole lot of sense. I'm not 100% sure on whether it was a specific recommendation for him or not, i know he does have some preexisting back issues, but they have now made it a rule at their dive center, no air or nitrox dives for 48 hours.

 

[danvolker]

Sounds like he was likely bent from the trimix dive, and just did not really present symptoms till he did the nitrox dive....
For an athletic tech diver, with good cardio, good perfusion etc., and hour after the first dive is ended should have you pretty cleaned out. The 48 hours is based on a lack of knowledge.

 

[Ste Wart]

What was the deco profile for the TMX dive?