Oxygen Toxicity Discussion

[Tigerman]

Pseudoephedrine isnt really the "drug" in the terms its used about medicines, but the working component of a lot of differnt drugs..
It is the part of those drugs which is suspected of being an "o2 accelerant" though..

 

[AfterDark]

In PADI OW classes, divers are taught not to use nitrox without further training becaseu of the risks of increased oxygen exposure. They are also taught not to dive below 60 feet without further training. They are also taught that the depth limit for all recreational divers is 130 feet. PADI OW students may elect to use nitrox on their 4th training dive, and if they do, the risks associated with increased oxygen exposure are explained in more detail.

All of that has been true as long as I have been an instructor.

This is a long answer for no.

 

[uncfnp]

A little clarification.

Sudafed or pseudoephedrine, it's active ingredient, is a component of many allergy and cold medicines. It is the "D" in Allegra D, Claritin D, Zyrtec D, Mucinex D and others. It is the decongestant that must be signed for in the US. Because of this, some pharmaceutical companies changed the decongestant in their product to phenylephrine. Products with this ingredient are typically designated with PE, such as Sudafed PE.

As to Sudafed and addiction. Sudafed is used to manufacture methamphetamine which is addictive and the reason that quantities are limited and one must sign for it. But I am not aware of any studies that show Sudafed is addicting.

And DandyDon is correct that for many people, phenylephrine is not as effective. In fact, some studies suggest that it is no more effect for nasal congestion than placebo.

 

[Tigerman]

If it works, who cares if its just in your brains, right?

 

[uncfnp]

Regarding pseudoephedrine, oxtox and diving.

As in my earlier post, the only information with any credibility that I have access to for review is the article by DAN. The research study cited in that article that seems to support a connection between pseudophedrine and oxtox does not list the actual drug used. We only know that it is a sympathomimetric, as are many other drugs, including other decongestants. But the article only mentioned a potential link to sudafed/pseudoephedrine. Why is this? I can only assume it is because, unlike other decongestants, pseudoephedrine is also a stimulant, a CNS stimulant. This is the reason that pseudophedrine is "behind the counter" while others are not. It can be converted to methamphetamine. The others can not be used for this purpose. Given this fact. It is reasonable to assume that other decongestants, including oral and nasal phenylephrine, or nasal oxymetazoline (Afrin) would not pose the oxtox risk that is theorized with pseudoephedrine.

So ok, my pharmacology class was a long time ago. Any pharmacist, chemist, or others out there with better science?

 

[Rich Keller]

"Actifed" is too inexact a description, and it may cause unwanted drowsiness in a diver (or somebody operating heavy machinery ).


I use nitrox to maintain my safety margin and increase my bottom time.

As far as I know there is only one type of "Actifed" so that is as exact a description as there is. How can you increase the oxygen in your mix without reducing your safety margin? Adding oxygen can only increase your risk for oxygen toxicity.

 

[Tortuga68]

Adding oxygen can only increase your risk for oxygen toxicity

What depth/partial pressure do you consider air 'safe' to dive to? Whatever that depth/PPO2 is, why is it any less safe to dive EAN to the same EAD?

 

[vladimir]

As far as I know there is only one type of "Actifed" so that is as exact a description as there is.

You are wrong about that. There are multiple formulas, and not just in the States vs abroad, but probably side-by-side on the shelf of your neighborhood pharmacy. You should not be taking over-the-counter drugs without knowing what the actual chemicals they contain are, and googling those drugs separately so you know their effects. This is one of the few constructive applications of all that information at our fingertips (I no longer need a PDR cluttering my bookcase).

Here are the different formulas branded Actifed according to WebMD:

Actifed Allergy Daytime/Night Oral

Actifed Cold and Sinus Oral

Actifed Cold-Allergy Oral

Actifed Oral

Actifed Sinus Daytime & Night Oral

Actifed Sinus Oral

Actifed With Codeine Oral

How can you increase the oxygen in your mix without reducing your safety margin? Adding oxygen can only increase your risk for oxygen toxicity.

Oxygen toxicity is only one risk factor, and, for most recreational diving, a very minor one. To answer your question specifically, you could dive 32% in a quarry with a hard bottom at 90 feet. Alternatively, you could have control of your depth and buoyancy and dive within the MOD of your gas, using whatever PO2 you deem appropriately conservative.

 

[DCBC]

What depth/partial pressure do you consider air 'safe' to dive to? Whatever that depth/PPO2 is, why is it any less safe to dive EAN to the same EAD?

SurD O2 is often spent at PPO2 2.2 - 2.4 ATA with 5 minute Air brakes every 30 minutes (depending on the table). In OW, the highest PPO2 I've experienced has been 2.2 on Air. Obviously a Chamber provides much more protection in the case of CNS, but the ceiling is usually held at 2.4 for Chamber decompression.

At DCIEM we did some testing at PPO2 3.0 ATA. I was put on Air after 3 hours because of respiratory changes and almost the total loss of my peripheral vision. The affects of exercise (bicycle) were also tested with increasing intensity at 2.0 ATA. It's was felt that C02 contributes greatly to CNS O2 tox and may be an even greater factor than was originally thought.

As I mentioned previously, we each have marked differences in sensitivity and PPO2 tolerance that will vary between individuals and ourselves at different times. Because of this individual variability, it makes it difficult to set any O2 exposure limit that's safe and dependable. The safest PPO2 is 1.0, 1.4 or less is good and 1.6 (although it increases risk) is considered the maximum that's recommended.

Dr. Frank Butler (a ex-SEAL who served in Vietnam and who was Diving Medical Research Officer at the Navy Experimental Diving Unit in the early 80's) has done extensive research into OxTox. In-particular, the factor that time plays in dive duration (exposure) and time between dives which have high PPO2 exposures.

 

[Tortuga68]

Very good, and I've done PPO2 2.31 on air... but I was asking richkeller what he thinks is safe