Nitrox and Sudafed

[CD_in_Chitown]

Here's an article by Dr. Eddie Brian which addresses some of the why's behind the anectodal claims.

Dr. Brian doesn't make anything more than anecdotal claims regarding the use of Sudafed, notice this statement on

Although not studied, it is possible that pseudoephedrine may contribute to hyperoxic seizures by elevating brain catecholamines

However before this he details how brain catecholamines vary from body catecholamines, and how sudafed targets the bodies catecholamines.

Now that is alot of $5 words but what I took from it was that it was purely conjecture based upon how pseudophedrine works in the body and what were possible should it ever react in the brain. Notice, however that this was not studied specifically. Dr. Brian does go into some detail in the earlier pages regarding the differences between body and brain catecholamines. This only works to make me question his statement on pseudophedrine though.

The article by Dr. Thalman that Dandy Don has posted for us on the other hand, comes from one of the most prestigious names in diving medicine (DAN) and includes a case-by-case summary of the original incidents that led to the "No pseudofed for Nitrox diving" mentality that we all grew up listening to. In fact detailing out the five criteria for a causal relationship;

"Statistical association" means that there is statistical evidence that symptoms that occur when pseudoephedrine is taken in association with certain types of dives are not a random occurrence. Mount did not provide enough information to establish a statistical association.

"Strength of association" means that very frequently, when the drug is taken before a dive, some sort of untoward effect usually occurs during or after the dive: that is, the incidence of effects when pseudoephedrine is take in association with a dive is very high.

Conversely, if no pseudoephedrine is taken, similar types of dives almost never produce side effects. Since we don't know how many individuals take pseudoephedrine before diving with no effects, like those reported above, we can't measure the incidence.

"Timing of association" means that the reported side effects usually occur if the drug is taken before a dive, and not if it is taken afterward. Since only incidents in which the drug was taken before the dive were reported, we can't invoke this criteria.

"Consistency of response" means that the same effect is seen when the drug is taken, although the incidence may be rare. There does not seem to be any consistency in the symptoms reported above.

"Biological plausibility" means that there is some identified mechanism by which the drug could cause an undesirable side effect. In particular, we are interested in whether it may enhance susceptibility to oxygen toxicity. Here, we do have some evidence. In 1962, none other than DAN's Chief Executive Officer, Dr. Peter Bennett, while working as a research physiologist at the Royal Navy Physiological Laboratory in England, published a paper (Life Sciences; 12:721-727, 1962) testing the hypothesis that oxygen toxicity and nitrogen narcosis were caused by similar mechanisms.

But the DAN doc goes one further in his conclusion saying that not only is pseudophedrine fine for air diving, but details his thoughts on EAN diving as well;

...and it seems reasonable to avoid the drug entirely if diving while using oxygen-nitrogen mixes where the PO2 during a dive might exceed 1.4 ata, the current recommended "safe" open-circuit scuba limit.

Now my reason for inquiring is based on the OW class that I have to dive with in a few hours, sinuses giving me all heck yesterday making it nearly impossible to equalize and I'm looking for something to open my head up. I will be well below the 1.4 PO2 limit utilizing EAN36 for these dives, I certainly appreciate everyone posting here and linking articles on the subject. I guess if you don't hear back from me get my computer to Dr. Thalman so he can update his research.

 

[babar]

Aside from that article I don't think I've ever heard it referred to as "antecdotal" before. Here's an article by Dr. Eddie Brian which addresses some of the why's behind the anectodal claims.

Anecdotal refers to the fact that some episodes of hyperoxic seaizures have been reported in association with pseudophed use. However no controlled studies have been done to determine wether people who take pseudoephedrine seize earlier or at lower PO2's. Dr. Brain states that in the article. Just to put things in perspective, many of our patients in hyperbaric treatments take pseudophed to facilitate equalization, this is at po2 of 2ATA for 2 hours plus. I have yet to see anyone seize from taking pseudophed at an appropriate dose. Pseudophed overdose can cause seizure even in surface air.
Other chemicals are also known to lower seizure threshold. The most commonly used one being caffeine. Also not specifically studied with diving or hyperbaric medicne, it's known to lower seizure threshold. We do not know if it lowers the threshold for hyperoxic seizures. It seems reasonable to assume that it does. Caffiene in overdose also causes seizure even in surface air.

One thing that has been studied a fair amount is the effect of CO2 on seizure threshold. Increased CO2 DEFINATELY lowers hyperoxic seizure threshold. It seems to me that diving with congestion or a cold, and maybe having increased work of breathing and CO2 retension, could be seen to be more dangerous than taking an APPROPRIATE dose of pseudophed. Especially if one is willing to forgo there morning coffee that day.

Babar

 

[BillP]

Other chemicals are also known to lower seizure threshold. The most commonly used one being caffeine. Also not specifically studied with diving or hyperbaric medicne, it's known to lower seizure threshold. We do not know if it lowers the threshold for hyperoxic seizures. It seems reasonable to assume that it does.

In rats at least, caffeine seems to reduce the chance of hyperoxic seizures. The same may be true for humans.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8574677&dopt=Abstract

Bill

 

[babar]

In rats at least, caffeine seems to reduce the chance of hyperoxic seizures. The same may be true for humans.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8574677&dopt=Abstract

Bill

That's very interesting. I hadn't seen that before. Cloud's the water even more.

babar

 

[Rick Murchison]

That's very interesting. I hadn't seen that before. Cloud's the water even more.

babar

It doesn't address Sudafed.
I know that in some people Sudafed can torch off nerves in odd ways. When I was 17 I found out that in me, a single Sudafed (or Teldrin or other similar decongestant) can cause an irregular heartbeat for two or three days! And while it doesn't affect most folks as dramatically as it does me, that's enough evidence for me to discourage its use on dives where oxygen exposure is a concern. (anything above about 1.1 ATA PPO2)
Rick

 

[BillP]

It doesn't address Sudafed.

You're right. It doesn't. I was simply addressing Babar's comments on caffeine- not pseudoephedrine.

But then, what seems "reasonable to assume" doesn't always prove to be true. For example, it seems perfectly resonable to assume that the Sun circles the Earth. You can see it happen every day with your own eyes, and you certainly can't feel the Earth turning around the Sun, you foolish heretic. But if you actually test a hypothesis, sometimes you find that your assumptions might be misleading. Copernicus, Galileo, and others clouded things up pretty good at first- until it became clear that earlier reasonable assumptions were wrong.

Sympathomimetics (drugs like pseudoephedrine in the adrenaline family) stimulate the central nervous system (CNS). At least some sympathomimetics have been found to increase the risk of hyperoxic seizures. Caffeine is also a CNS stimulant (although it is in the xanthine family of drugs- not a sympathomimetic), so, hey, maybe it increases the risk of hyperoxic seizures too! Well, maybe not. Maybe caffeine works on the CNS by a different mechanism from the sympathomimetics, and maybe, just maybe, it protects against hyperoxic seizures. And maybe, juuuusssst maybe, we need to look at some of our assumptions about the effects of other drugs.

Personally I would like to see more studies on various CNS stimulants (like pseudoephedrine and caffeine) and their effects on hyperoxic seizure threshold. I found that rat study intriguing.

 

[Quero]

It doesn't address Sudafed.
I know that in some people Sudafed can torch off nerves in odd ways. When I was 17 I found out that in me, a single Sudafed (or Teldrin or other similar decongestant) can cause an irregular heartbeat for two or three days! And while it doesn't affect most folks as dramatically as it does me, that's enough evidence for me to discourage its use on dives where oxygen exposure is a concern. (anything above about 1.1 ATA PPO2)
Rick

Rick states what we all know about drugs affecting different people in different ways. I recently experienced days of rapid heartbeat and tremors in the extremities, and even migraine-type headaches, when I underwent simple medicinal inhalation treatments at a clinic to get me past chest congestion exacerbated by smog (so I'd be fit for an upcoming dive trip). I was told that these side effects occur in some people, though certainly not in most, and that I'm not a good candidate for that particular treatment.

On the other hand, pseudoephedrine has caused me no easily discernable problems, at least on dives within no-stop limits, even using Nitrox blends (but then, I have never been the subject in a rigorous scientific study to check it out for certain). Having said that, I have recently completed the "basic training" for tech diving (IANTD Deep Air and Advanced Nitrox), and as a precautionary measure, I won't use pseudoephedrine on deep dives, especially not on decompression dives with 50% O2 deco gas.

Still, I'd like to find out if there *is* a suitable long-acting decongestant out there which would be less risky than pseudoephedrine.
Anybody have an insight?

 

[Doc Intrepid]

No insight at all. Several trips, however, to an ENT specialist in Kennewick, WA who is also an active diver, with my son who has some problems clearing easily. The ENT recommended using a nasal mist and Afrin before diving, and indicated that these were entirely appropriate for recreational diving. It comes down to a question of who you believe.

 

[padiscubapro]

Rick states what we all know about drugs affecting different people in different ways. I recently experienced days of rapid heartbeat and tremors in the extremities, and even migraine-type headaches, when I underwent simple medicinal inhalation treatments at a clinic to get me past chest congestion exacerbated by smog (so I'd be fit for an upcoming dive trip). I was told that these side effects occur in some people, though certainly not in most, and that I'm not a good candidate for that particular treatment.

On the other hand, pseudoephedrine has caused me no easily discernable problems, at least on dives within no-stop limits, even using Nitrox blends (but then, I have never been the subject in a rigorous scientific study to check it out for certain). Having said that, I have recently completed the "basic training" for tech diving (IANTD Deep Air and Advanced Nitrox), and as a precautionary measure, I won't use pseudoephedrine on deep dives, especially not on decompression dives with 50% O2 deco gas.

Still, I'd like to find out if there *is* a suitable long-acting decongestant out there which would be less risky than pseudoephedrine.
Anybody have an insight?

personally I think its an individual choice that should be made with a discussion with your physician.. There is not enough data out there... If you don't use it normally I wouldn't use it when diving, If you know how your body reacts in normal situations you should have a better feeling as time goes by how you can use it..

I know for me PERSONALLY, I have never experienced any problems with "sudafed", I have been using it since I started diving in the 80s.. I usually take the 12 hour release pills, and a normal dose before the dive and have never suffered any ill effects (I am not saying this will be true for everyone, I just know it is true for me)..

I also do very high po2 exposures (all my dives these days are on a ccr) so my minimum po2 exposure is a 1.3, with my decos higher than this.. I have done dives with oxygen exposures several times over the daily nOAA limits without any problems as well(and I accepts the risk associated with these exposures).. I have also done deco where I went on oxygen at 30fsw (1.9 po2) using a FFM as a precaution, again with no ill effects.. The highest exposure that comes to mind is 3 hours on o2 for my 30fsw and 20 fsw stops.. I definately do not recommend this without the proper trainng, support and safety precautions..

 

[StSomewhere]

This was stressed in my IANTD Nitrox class, topical decongestants (nasal mists) for diving in general and esp. with Nitrox.