Any reported cases of Ox Tox between 1.4 and 1.6?

[flymolo]

yea, getting bent a few times a year sounds concerning. you might want to consider making some adjustments to try and prevent future incidents. i personally wouldn't accept 3 bends a year as the cost of doing business, i'd try and make changes to the way i dive

 

[rob.mwpropane]

I'm trying to extend my stops, be aware of my exertion level, generally move around during the stop, try to make sure we have oxygen on the boat, etc.

I'm not harping on you, we all need to start somewhere. I try to learn before I take the leap, but to each his own.

Get a better computer, get to know what gf's work for you. Take it easy, take it really easy in the last 20'. Pad your stop. Go see a doctor. Bent × 1 is an alarm to change some things let alone 3.

Other people beat me to a lot. I type slow, lol.

 

[Nick_Radov]

So to answer your question where does the 1.4 idea come from, my thoughts were always because of time (I am just assuming this). If you look are "XYZ" agencies CNS clock you will see that as you increase the PPO2 your CNS starts to rack up exponentially, especially between 1.6-2.0 its actually pretty crazy quickly it can sky rocket at these PO2's.

And if you dig into the scientific primary sources there is basically zero reliable experimental data for CNS% effects of pO2 above 1.6atm. The dive computer manufacturers are literally just making up numbers by extrapolating the curve out or applying arbitrary "safety" factors, and doing so in inconsistent ways. Like on your 20ft oxygen deco stop if you drop down to 21ft for a few seconds the computer's CNS% might spike way up, which probably doesn't reflect any physiological reality.

Garmin dive computers have a design flaw where they store the CNS% as an unsigned 8-bit integer (uint8). I've seen mine hit 255% on a dive and wrap around back to 0%, which is kind of hilarious.

 

[AeroSpartacus]

I'm trying to extend my stops, be aware of my exertion level, generally move around during the stop, try to make sure we have oxygen on the boat, etc.

If it's happening regularly, it could also be that you have a PFO, but you would have to see a cardiologist to confirm that. If that was the case it increases the risk of DCS considerably

 

[Duke Dive Medicine]

If it's happening regularly, it could also be that you have a PFO, but you would have to see a cardiologist to confirm that. If that was the case it increases the risk of DCS considerably

That depends on the symptoms and presentation. PFO is associated with severe, sudden-onset neurological DCS, inner ear DCS, and cutis marmorata. If @johndiver999 's bends were pain-only (I read "back hit" followed by pain relief with an attempt at IWR) then a PFO would be a red herring. It's more likely due to diving the computer to the edge of the no-stop limit, even if the computer says it's ok and clears deco. My old nurse manager used to say that we've never treated a bent computer.

Best regards,
DDM

 

[AeroSpartacus]

That depends on the symptoms and presentation. PFO is associated with severe, sudden-onset neurological DCS, inner ear DCS, and cutis marmorata. If @johndiver999 's bends were pain-only (I read "back hit" followed by pain relief with an attempt at IWR) then a PFO would be a red herring. It's more likely due to diving the computer to the edge of the no-stop limit, even if the computer says it's ok and clears deco. My old nurse manager used to say that we've never treated a bent computer.

Best regards,
DDM

Gotcha, thanks for the explanation, that makes sense!

 

[Kendall Raine]

And if you dig into the scientific primary sources there is basically zero reliable experimental data for CNS% effects of pO2 above 1.6atm.

Bingo. Can't imagine even the Navy doing controlled swimming tests with CNS toxicity as an endpoint. Ethics. Real world combat swimmer results certainly used to inform limits but not the same as controlled studies. Note Navy 100% CCR (e.g. LAR V) dosage limits are way above NOAA's. Navy has even dropped CNS TOX susceptibility testing as part of combat swimmer qualification because of variability.

 

[scubadada]

That depends on the symptoms and presentation. PFO is associated with severe, sudden-onset neurological DCS, inner ear DCS, and cutis marmorata. If @johndiver999 's bends were pain-only (I read "back hit" followed by pain relief with an attempt at IWR) then a PFO would be a red herring. It's more likely due to diving the computer to the edge of the no-stop limit, even if the computer says it's ok and clears deco. My old nurse manager used to say that we've never treated a bent computer.

Best regards,
DDM

Hi @johndiver999

Could you describe your 2 episodes of skin bends?

Besides the 3 episodes of DCS in the last year, have you had others?

 

[Kendall Raine]

As for ox tox, the O2 clock was never an issue despite 4 dives each day, but chronic O2 exposure issues were noticed on the return home. I had slightly blurred vision (corneal edema) and a dry cough (pulm ox effects) for about two weeks. With EAN we were exposed to PPO2 of 1.0-1.2 for much of our 52 total hours underwater. Much like a patient in the ICU on a ventilator requiring 100% oxygen due to an illness, we lightly toasted our lungs over the two week trip. All better two weeks later, though.

Hi Rob;

This is interesting. Whole body (pulmonary) Tox after recreational (essentially no deco) multi-dive multi-day on 32% (average depth ~55; P02's 1.0-1.2, w/ ~1-2 hour air breaks/SITs) is something I've never heard of. For that matter, outside of OxTox chamber tests, I've only heard of whole body Tox being an issue (cough, burning chest) in chamber treatments running consecutive T6's (max P02=2.8; cumulative time on 100% 02 6 hours per treatment).

The duration of your symptoms (two weeks), and delayed onset (they didn't manifest until you returned home), are also well beyond anything I've read about in either OxTox research or chamber treatments. Was pulmonary toxicity the conclusion of a hyperbaric doc/pulmonologist? Kinda spooky stuff.

 

[rsingler]

That's my conclusion as a former USAF hyperbaric doc and retired cardiac anesthesiologist.
Sequential T6's are not wholly unlike 47 repeated sessions at a PPO2 of 1.2, or spending several days on a high PO2 ventilator with dehumidified gas. There's a tiny bit of oxidative stress on the lungs, plus the repeated dry gas exposure. My slight dry cough was indicative of that. I'll concede that the whole symptom complex may just have been alveolar dessication since my mouthpiece bypassed nasal humidification, but I personally think the high PPO2 played a small role. Symptom onset may have been sooner, but not noticed since we were so active. But arriving home and lying about, the slight cough became more noticeable.

@Duke Dive Medicine ?