nitrox downsides

[gamon]

what?

I meant that the advantage of trimix over nitrox for recreational divers cannot be verified if there are no verifiable aka measurable outcomes that demonstrate what those studies are suggesting. It's all theoretical, or at least, the effects of those gases on divers both positive and negative may have no practical application for divers in that particular group (recreational divers in depths of 100-130') if there are no serious/permanent effects

 

[crofrog]

I meant that the advantage of trimix over nitrox for recreational divers cannot be verified if there are no verifiable aka measurable outcomes that demonstrate what those studies are suggesting. It's all theoretical, or at least, the effects of those gases on divers both positive and negative may have no practical application for divers in that particular group (recreational divers in depths of 100-130') if there are no serious/permanent effects

While your call for measurable outcomes to justify trimix over nitrox at recreational depths is understandable, the argument overemphasizes the need for practical, observable data when existing research already confirms trimix’s physiological benefits. We know that helium reduces gas density, work of breathing, and narcosis compared to nitrox, directly mitigating risks like CO₂ retention and cognitive impairment that affect every diver on deep dives. These aren’t theoretical. They’re measurable physiological improvements, even if their impact on incident rates (e.g., immersion pulmonary edema or CO₂ toxicity) isn’t fully quantified in recreational contexts.

Requiring “serious/permanent effects” to validate trimix ignores how subtle impairments, like decreased mental capacity or error propensity can escalate into cascade failures.

 

[gamon]

While your call for measurable outcomes to justify trimix over nitrox at recreational depths is understandable, the argument overemphasizes the need for practical, observable data when existing research already confirms trimix’s physiological benefits. We know that helium reduces gas density, work of breathing, and narcosis compared to nitrox, directly mitigating risks like CO₂ retention and cognitive impairment that affect every diver on deep dives. These aren’t theoretical. They’re measurable physiological improvements, even if their impact on incident rates (e.g., immersion pulmonary edema or CO₂ toxicity) isn’t fully quantified in recreational contexts.

Requiring “serious/permanent effects” to validate trimix ignores how subtle impairments, like decreased mental capacity or error propensity can escalate into cascade failures.

Ok, well then I suppose we can agree that for those recreational divers who want to experience subtle, measurable (in studies only) positive physiological effects of trimix that remain unquantified when diving over 100' they're welcome to pay the additional cost of tri-mix if they can even find it.

 

[crofrog]

Ok, well then I suppose we can agree that for those recreational divers who want to experience subtle, measurable (in studies only) positive physiological effects of trimix that remain unquantified when diving over 100' they're welcome to pay the additional cost of tri-mix if they can even find it.

How many trimix dives do you have?

 

[bardass]

@bardass

I can't find a single reference to a person experiencing symptoms such as the ones you describe with this lady, anywhere.

Some sort of odd placebo effect simply cannot be ruled out.

I suggest you do the following:

1- double blind study where the lady in question alternately dives a few tanks of air and a few tanks of nitrox, and reports her symptoms to a person who records them, that same person does not know which tank holds which blend.

2- In the event there is a definite statistical correlation to back up her claims the next step would be to have her dive a 22% blend, increasing the 02 percentage over a series of dives to determine at what level the symptoms begin, again doing this as a "double blind" study with the lady diver and the person recording any symptoms not knowing what she's actually breathing.

That way you can not only verify that her claims are real and valid but also determine at what level she can enjoy the benefits of nitrox without experiencing symptoms. I'm sort of surprised that a trimix and nitrox instructor wouldn't have thought of that.

Come on...
This lady isn't some monkey we can experiment on...
Her pulmonologist advised her to stop diving with nitrox or to limit her exposure to nitrox because she has been diagnosed with pulmonary weakness (I don't know the details, medical confidentiality).
She is still allowed to dive to 20m but less often.
That's why she dives less.

The irritating effects of oxygen are well known; rebreather divers who make long stops are familiar with them.
On an other hand, oxygen therapy sessions consist of alternating oxygen and air breathing (25 min oxygen - 5 min air - 25 min oxygen - 5 min air, etc.). Because of irritating effects, among other things.

Admittedly, this is the first time I have encountered such a case
But stop talking about placebo when we hear dry coughing fits after diving...

 

[Living4Experiences]

Getting a little narcosis actually feels good so why avoid it?

TROLL!! He's going on the "ignore" list.

 

[lowwall]

You're talking **** ...
You don't know this diver, yet you're imagining what she might be like, what she might believe...

I am a nitrox and trimix instructor in France, Oc and CCR.
My colleagues and I encourage all divers to use nitrox and trimix as much as possible.

We trained this lady in nitrox diving given her age and physical condition. She is enthusiastic and request about nitrox when the shops couldn't supply it.

Several months after her training, we noticed her hoarse cough when she came up from her dives.
She also told us about a burning sensation in her lungs and dry mucous membranes.
These are known effects of oxygen therapy.
But I had never encountered such cases with the use of nitrox in diving.
It is a fact that some divers are much more sensitive than others to oxygen inhalation.
Unfortunately, this diver now dives much less than before (she has gone from 30-40 dives to less than 15 dives per year) because she still wants to dive with nitrox and not use air.

The partial pressure of O2 (pO2) rather than the fraction should be the relevant measure. If she wants to keep diving nitrox, I would explore the pO2 level where her discomfort begins. Once established, it should be simple enough to tailor the mix and/or the depth with that limit in mind.

 

[crofrog]

@bardass

I can't find a single reference to a person experiencing symptoms such as the ones you describe with this lady, anywhere.

"While there are theoretical models that predict the expected level of pulmonary function deficit because of prolonged exposure to raised PiO2 that are based upon the expected decline in FVC, there is considerable individual variation in susceptibility to a uniform degree of pulmonary oxygen poisoning [3,4,5]. Currently, there are no methods to predict individual susceptibility to PO2tox. Furthermore, a sensitive non-invasive biomarker that can detect changes in lung pathology at an early stage in the oxygen toxicity process has remained elusive."

Fothergill, D.M.; Gertner, J.W. Exhaled Nitric Oxide and Pulmonary Oxygen Toxicity Susceptibility. Metabolites 2023, 13, 930. https://doi.org/10.3390/metabo13080930

 

[gamon]

Come on...
This lady isn't some monkey we can experiment on...

Why not at least try lower percentage blends to see where her trigger point is?

Once you find it, give her a banana and call it a day.

 

[gamon]

Currently, there are no methods to predict individual susceptibility to PO2tox.

I accept this and have posted as much. That much said, I've never ever heard of pulmonary toxicity symptoms due to breathing recreational nitrox blends nor can I find a single other reference to it here on this forum nor anywhere else online.

Furthermore, I've suggested 2 effective ways of further diagnosing and dealing with it which were immediately rebuked by a trimix/nitrox instructor who is perfectly ok with this woman continuing to dive nitrox despite the serious symptoms which may very well be associated with permanent lung damage.