Asthma and nitrox

[blacknet]

Hello,

This should be an interesting thread to say the least. I was wondering if there was any beneficial use to an asthma patient while diving nitrox. It seems to me that the increase in o2 would be more beneficial to an asthma person than a non-asthma person.

The only thing I can find on scuba and asthma beats on the dead issues of "can I dive with asthma".

Ed

 

[nitroxbabe]

Hi Blacknet -
I'm no doctor, but I am a diver with a mild (and controlled!) case of asthma.

I suppose that if I were having some degree of asthma trouble, more O2 in my mix might help my lungs absorb more oxygen. However, that's not really the issue when underwater with asthma. The problem is really that asthma clogs the lungs and bronchial tubes with excess mucus and narrowed, inflamed airways.

As far as I've learned, the primary risk of diving with active asthma is air embolism, which in the case of active asthma, is caused by expanding air trapped in lung tissue when air cannot escape through narrowed, mucus-clogged bronchial tubes. I don't see how a change in gas composition could help that problem.

I would think that extra O2 would be most helpful after the afflicted person surfaces as they're rushed to the hospital.

 

[Snowbear]

The guy who has done most of my PADI instruction revealed to me that he has a mild form of asthma. He told me he noticed that while on a live-aboard trip diving Nitrox (EAN 36 I think?- but may have been 32) 4-5 dives a day that he was coughing excessively and was using an inhaler quite frequently. He switched to air and the problem went away. Turns out the higher O2 exposure over so many dives was irritating his lungs and INDUCING asthma.
As Nitroxbabe noted - Asthma is NOT a condition of not enough oxygen being inhaled, but rather a condition of inadequate air exchange. Basically what happens is, something irritates the airways (can be from allergens, dry air, excersize which increases air movement, whatever), causing the airway (bronchi) to spasm. The asthmatic person can generally breathe IN just fine, but cannot exhale very well. The problem that results is that when it's time for the next inhalation - there's less room in the lungs for the next breath, but the person inhales anyway. On the NEXT breath, there's even LESS room - and so the cycle continues. Yeah, with enriched air there is more O2 with the inhaled gas, but there's also LESS end gas exhaled....so.....As a paramedic, I'm thinking my instructor was dang lucky he didn't end up with a serious entrapped gas situation and embolize himself...

 

[Scuba_Vixen]

and the intendant risks that come from that? And do the moisturizers gadgets I see in the advertised in mags actually help?

 

[Snowbear]

Scuba_Vixen once bubbled...
Is there an additional buildup of CO2...and the intendant risks that come from that?

Yes. We have a fancy new tool on some of our ambulances that measures exhaled CO2. In patients having an active asthma or emphysema episode, the reading tends to be quite high. If I remember correctly (which is *always* in question ), the CO2 buildup is what causes the feeling of "air hunger" or shortness of breath. Patients with chronic asthma or emphysema actually adapt to this chronically higher CO2 buildup by changing their respiratory drive from CO2 to O2 driven. In other words, the urge to breathe is driven by low oxygen levels rather than increased CO2 levels. Clear as mud?

Scuba_Vixen once bubbled...
And do the moisturizers gadgets I see in the advertised in mags actually help?

I imagine they would reduce the airway irritation caused by dry tank air?

 

[large_diver]

I asked a very experienced technical instructor this exact question back in July. He was recommending that I take a Nitrox course -- I was blunt with him in saying that I have mild allergen-induced asthma and was rather concerned about the impact that Nitrox would have on my breathing underwater. I also said that I didn't see a big "bang for the buck" since I do a lot of relatively shallow shore diving.

His response involved the following information that recommends switching to Nitrox, even for shallower diving where there is no bottom time gain from using Nitrox due to long air shallow water NDL times:

- Air is more dense than Nitrox, increasing the work of breathing and increasing CO^2 levels

- CO^2 is over 100 times more narcotic than Nitrogen

- Your breathing capacity on air decreases significantly at depth (40% decrease at 50 feet; 50% at 100 feet). Research has shown that Triox significantly impoves these numbers (0% at 50 feet; 14% at 100 feet). Nitrox would likely be somewhere in the middle. He did not give me specifics on why this is true (or if he did, I can't remember them). If true, obviously someone who suffers from any sort of breathing restriction would be interested in these Nitrox

I also mentioned the same issues that Snowbear brings up above although in a slightly different context -- I brought up coucerns about instances where tech divers experience irritated lungs when breathing high oxygen content mixtures during deco. The instructor's response was that this was usually with 100% oxygen. Using EAN 32% would not result in this type of problem.

I haven't seen any sources that discuss Nitrox, diving and asthma -- it would be nice to see one of the medical regulators weigh in here or at least refer us to some useful online information. The jury is still out on this issue as far as I am concerned -- the arguments provided by the instructor did not really convince me one way or the other.

-Chris

 

[nitroxbabe]

Your instructor REALLY ought to take better care of himself. You're right: he's dang lucky he didn't end up injured, diving with active asthma.

I have my problem under control: my lung function exceeded predicted levels when I had it tested a couple months ago.

I would absolutely not dive if I was having a problem that required using a rescue inhaler repetitively.

I did not know that high concentrations of O2 could aggrevate asthma. I have not personally had that experience. Of course, I don't dive when having a reaction, so that doesn't mean anything.

CO2 is narcotic? That's a new one on me.

BTW Largediver: OK, you said: "Your breathing capacity on air decreases significantly at depth (40% decrease at 50 feet; 50% at 100 feet). Research has shown that Triox significantly impoves these numbers (0% at 50 feet; 14% at 100 feet). Nitrox would likely be somewhere in the middle. He did not give me specifics on why this is true (or if he did, I can't remember them). If true, obviously someone who suffers from any sort of breathing restriction would be interested in these Nitrox"

Do you mean that your lung capacity itself decreases? I never heard that before. I was under the impression that the capacity of a diver's lungs remains constant (as long as you're not ascending or descending with held breath, which obviously can kill ya quick). If a person's lungs were actually compressed as he descended, he would "dry drown".

And obviously he couldn't be talking about "capacity" related to gas absorption, since the greater partial pressures cause far greater absorption, which leads to nitrogen narcosis, O2 toxicity, etc.

I don't understand about "decreased capacity". Anybody shed some light on that?

Snowbear once bubbled...
The guy who has done most of my PADI instruction revealed to me that he has a mild form of asthma. He told me he noticed that while on a live-aboard trip diving Nitrox (EAN 36 I think?- but may have been 32) 4-5 dives a day that he was coughing excessively and was using an inhaler quite frequently. He switched to air and the problem went away. Turns out the higher O2 exposure over so many dives was irritating his lungs and INDUCING asthma.
As Nitroxbabe noted - Asthma is NOT a condition of not enough oxygen being inhaled, but rather a condition of inadequate air exchange. Basically what happens is, something irritates the airways (can be from allergens, dry air, excersize which increases air movement, whatever), causing the airway (bronchi) to spasm. The asthmatic person can generally breathe IN just fine, but cannot exhale very well. The problem that results is that when it's time for the next inhalation - there's less room in the lungs for the next breath, but the person inhales anyway. On the NEXT breath, there's even LESS room - and so the cycle continues. Yeah, with enriched air there is more O2 with the inhaled gas, but there's also LESS end gas exhaled....so.....As a paramedic, I'm thinking my instructor was dang lucky he didn't end up with a serious entrapped gas situation and embolize himself...

 

[BRW]

All,

Just want to pass on some field data points from C & C
on asthmatic issues. Statistics of course are not existent
to my knowledge, but are definitely needed.

We have 2 asthmatics who have dived well over 1000
dives on nitrox, heliox, helitrox, and trimix (plus air on rec
sojourns). They are world class tech divers (scientists too).

No problems, additional discomfort, nor worries for them
on different bottom gases.

Nor for many in C & C with allergies. No probs and
just the usual sinus/ear clearing ritual.

As stated elsewhere, the prob may not be mix at all, but
CO2 levels which reported vary little with mix but certainly
change with diver health, mind set, stress, regulator function,
etc.

If diving nitrox gives you goose bumps, that is some kind of
contraindication? Plus any other mix?

Just some info to pass on -- plus speculation which is always
cheap. We pay more attention to general health always.

Bruce Wienke
Program Manager Computational Physics
C & C Dive Team Leader
ut:

 

[large_diver]

I sent a question to DAN about this -- I posted their response below. They seem to confirm the breathing capacity facts I presented above. I sent them a follow-up e-mail today asking what effect, if any, Nitrox has on breathing capacity underwater. I'll post the response here when I get it.

-L_D

---------------------------------------------------------------------------------

Chris

Thanks for the inquiry

The concerns with asthma are not the percentage of Oxygen in the mix but the fact that breathing any air mix at depth with a potential for air trapping and then ascending could create a lung expansion injury.

Scuba diving can be dangerous for asthmatics for two reasons. First, during scuba diving there is normally a reduction in breathing capacity due to immersion and an increase in breathing resistance caused by the higher gas density at depth. At 33 feet, the maximum breathing capacity of a normal scuba diver is only 70% of the surface value, and at 100 feet it is only one half. If a diver's breathing capacity is already reduced because of asthma, there may be insufficient reserve to accommodate the required increase demanded by exertion. Second, both narrowing of the bronchi and excessive mucus production can inhibit exhalation of air during ascent, and could predispose to pneumothorax, pneumomediastinum or air embolism.

For these reasons, almost all physicians trained in diving medicine previously recommended that people with asthma should never dive. However, a consensus of experts at a 1995 workshop held under the auspices of the Undersea and Hyperbaric Medical Society (UHMS) proposed more liberal guidelines. A range of medications is available for asthma treatment, and can often return lung function to normal. Specific breathing tests (often referred to as "pulmonary function tests" or "PFTs") can be used to determine the response to therapy. The UHMS workshop panel felt that the risk of diving with asthma is probably acceptable if, both before and after a provocative test such as exercise, the diver has normal PFTs. Even if divers with asthma fulfill this criterion, they must also be free of respiratory symptoms before each dive.

[The consensus at the UHMS Workshop on diving and asthma was that the provocative test should be exercise, rather than histamine/methacholine inhalation. I would highly recommend obtaining the full workshop report entitled: Are Asthmatics Fit to Dive (DH Elliott, Ed), 1996, Undersea and Hyperbaric Medical Society, Kensington, MD. The book can be obtained via the UHMS web site: www.uhms.org. ]

So the concerns are not the mix but the fitness to dive for asthmatics.

I hope this is helpful.

Laurie Gowen, NREMT-B, DMT
DAN Medical Services
Department of Anesthesiology
Duke University Medical Center

Visit DAN's website at: http://www.DiversAlertNetwork.org