Asthmatics - Do they use more air?

[gsclarke]

Question for those of you that have breathing problems.

Do you use more air than normal?

My first dive went well and I barely used any more air than my instructor. I'm 54 (female) and she's in her twenties. My husband used considerably more which I'm told is typical of novice divers (and also as he's male;) )

Apart from suggesting I was quite relaxed about it, do you feel it indicated that my breathing was pretty sound, which is what I think?

Although I have poor lung function test results which I clearly need to get sorted out, my breathing is fine and I'm trying to understand the mechanics of any risk I may run.

I know I need to get my FEV1/FVC ratio to 70% to be able to dive (It's 66% at the moment) but it's not quite so black and white is it?

Suppose I have 69%, you have 70%. Comparing us with a norm of let's say 80-85%, you would have to say that the 1% difference doesn't overnight remove the risk surely?

I'd like to understand more about what actually happens in these scenario's:

1. I get to 70% and I am allowed to dive. My breathing is fine.
2. Next day it drops to 69%
3. Day 3 it drops to 66%

Assuming no breathing problems, what do I expect to happen as I surface and need to release the extra air I've taken on? If I'm breathing well does any air in the little airways cause more problems as the days go on and the ratio drops?

[TerryH]

I'm sure some more knowledgable docs will be along in a mo, but AFAIK
the main problem is the restriction of the airways.

Dust house mite alergy etc. not an issue. Air is triple filtered anyway,
but what if it's cold or stress induced?

Diving can be cold and we all know that it's stressful at times.

What happens if you are starting an ascent and you have a problem?
You start to ascend and as the stress/asthma takes over, the now
expanding air cannot escape from your lungs fast enough via your
decreasing airways.

It still expands though and you end up with barotrauma and a whole
range of problems, many of which are fatal.

So although the lung capacity and good funcion is obviously important,
having a clear airway is very inportant in diving and anything that affects
that is, well bad.

HTH, but as I say there will be some medical boffs along in a mo :)

TerryH

[gsclarke]

Thanks for the reply Terry

I'm hoping that I won't get any reponse to cold, exercise, stress etc. but no doubt that will be tested soon.

What I'm actually trying to get my head round is the scenario where I don't have any changes under water, in other words I'm coming back up in the same state as I went down, breathing well.

Is there then a risk?

I seem to be a bit thick understanding whether it's the low fev1/fvc ratio in iteself that puts me at risk or whether BECAUSE of that the implication is that I could have some sort of breathing problems putting me at risk.

Also, if I don't experience breathing broblems, a slow ascent would be in order thus causing no little or no risk? I guess I'm a bit odd in that people would normally have breathing problems with a poor lung function test but I don't! :rolleyes:

Before anyone jumps on me :o , I do understand that I have to allow for emergencies. I'm only talking hyperthetically here in an effort to understand what risk I would be taking. Even if I get signed off, which would be great, I'd still like to have a good grasp on the physiology. I'm not about to go diving without knowing as much as I can even if I get past the medical.

[Paul Morris]

The problems around impaired lung function and diving are multi-faceted.

You're right to say what goes in must come out, if you come up breathing well (for you).

With impaired function, a quick (but perfectly normal) ascent may overcome your personal ability to get rid of the expanding air quick enough from all the tiny alveoli within the lungs. This might result in local overpressure, and possible rupture of these tiny air sacs causing air to enter your bloodstream (an embolism - very nasty, often fatal).

A rapid uncontrolled ascent which is a fair possiblity especially in early shallow dive training, may well cause you problems even if you breathe out all the way up, for the same reasons.

I haven't even mentioned decompression problems, but if your gas exchange ability (lung function) is impaired, it may also affect your ability to shift Nitrogen bubbles out of your bloodstream quick enough, making you more prone for decompression illnesses (the bends). Unlikely to be the main risk on shallow training stuff, but a big risk later on.

Its not simple. The doctors know what they're doing, and they're only acting in your best interests. If you get three opinions and two say no, one says yes - which is correct?

Don't worry too much about the physiology aspects, you will get a fair grounding on the issues involved during your ocean diver lectures which cover the basics of diving physiology, and decompression (Nitrogen management). If you already have your 'Diving manual', take a look in there, its covered. If not, if you're interested now ask about in the club - someone will have a copy.

[PeteM]

Thanks for the reply Terry

I'm hoping that I won't get any reponse to cold, exercise, stress etc. but no doubt that will be tested soon.

What I'm actually trying to get my head round is the scenario where I don't have any changes under water, in other words I'm coming back up in the same state as I went down, breathing well.

Is there then a risk?

I seem to be a bit thick understanding whether it's the low fev1/fvc ratio in iteself that puts me at risk or whether BECAUSE of that the implication is that I could have some sort of breathing problems putting me at risk.

Also, if I don't experience breathing broblems, a slow ascent would be in order thus causing no little or no risk? I guess I'm a bit odd in that people would normally have breathing problems with a poor lung function test but I don't! :rolleyes:

Before anyone jumps on me :o , I do understand that I have to allow for emergencies. I'm only talking hyperthetically here in an effort to understand what risk I would be taking. Even if I get signed off, which would be great, I'd still like to have a good grasp on the physiology. I'm not about to go diving without knowing as much as I can even if I get past the medical.

Asthma is a restriction on breathing out, not in. Any restriction on breathing in is caused by residual air in the lungs.

So you are on the surface and breathing, no problem as you are not breathing heavy enough to cause an discomfort.

You drop down to 10m, the restricted air in you lungs has halved in volume so new air you are breathing goes in to fill up the restricted areas in your lungs.

As you come up the restricted air now doubles in volume, if the restriction is minor then as the volume increases you just breath it out. However if the restriction prevent the gas escaping from the lungs (or more correctly the alveoli) then the expanding gas will expand the lungs until it has the same result as an over expaned baloon (Pop!). This is what is known medically as Bad News

You do not have to rise quickly for this to happen but obviously the chances are higher if you do, and with the best will in the world you can not guarantee a correct ascent rate you might be caught by an up current, swell, bubbles from divers below you, etc. etc. all of which are going to have thier biggest effect close to the surface where the expanding gases have thier biggest effect and you have the shortest time to sort it out.

All of the tests and restrictions are designed to prevent anyone with a substantial risk from this sort of injury diving.

[gsclarke]

Thanks Paul and Pete

I'm begining to get a better understanding (slowly) of what I'm facing. :)

What do you feel about this magical cut off point of 70%?

Ultimately it may come to me just scraping by if I can get from 67% FEV/FVC to the required 70% but it seems a bit too black and white to me. At 67% my lung function is comparable to that of an 86 year old (I'm 54). If I can improve my FEV so I reach 70% that still equates to an 81 year old. Not so good uh? :mad:

The risks don't just disappear do they? They've just reduced a little.

Let's suppose I get to 70% and get signed off. I think I will decide to carry on diving but would like to be fully aware of what I can do to decrease any chances of problems, eg slower ascents etc.

Again, just playing devils advocate here. I've made arrangement to see a respiratory specialist Monday to try and get it sorted. In the meantime I'm gathering as much background as I can so I at least know what questions to ask about how it affects both my health and my diving.

[Nick Kay]

A number of (unrelated) points:

1. There are quite a few asthamtics who dive. Yes, they may have restrictions placed upon them: depth, temperature of water, no-stop dives, nitrox mandatory... but they do dive

2. I know of at least one active instructor who is asthmatic and teaches at club & regional level

3. Be careful of cold water. My understanding is that cold water may cause problems with the airways contracting (not talking about an asthmatic "attack" here) and therefore ANY abnormal/fast/yoyo ascent can cause greater problems in a susceptible asthmatic than other divers

Nick

[gsclarke]

Thanks for that Nick.

Any of you reading this that are asthmatic - do you know if you use more air than your buddies?

Another question.

Would I be right in thinking that risks like nitrogen narcosis and decompression problems (not specifically related to what I was asking about) are more of a quantitive risk, ie a question of degree where as the sort of risk I am looking at is more statistical? I don't actually know what affect poor lung function has on these things but I'm not proposing to dive deep so I will forget that for the moment.

What I mean by that is, assuming I get signed of to dive, the main point is not that my lungs will function a little better or a little worse, more that I at slightly more or less at risk of having a serious or fatal problem.

I'm not sure if I'm expressing myself very well. I kind of see it a bit like the difference between angina and heart attack in that angina you can get to varying degrees but a heart attack either happens or not. Does that make sense or have I missed the plot?

[Paul Morris]

Any of you reading this that are asthmatic - do you know if you use more air than your buddies?
Yes, I'm asthmatic and I usually use less air. I'd like to attribute that to my fitness, but alas its down to experience (6 years regular diving) and the fact I dive regularly a few times each month, and I'm sure has nothing to do with my asthma.

Would I be right in thinking that risks like nitrogen narcosis and decompression problems (not specifically related to what I was asking about) are more of a quantitive risk, ie a question of degree where as the sort of risk I am looking at is more statistical? I don't actually know what affect poor lung function has on these things but I'm not proposing to dive deep so I will forget that for the moment.
Nitrogen narcosis - no. Thats different.
Decompression problems, yes possibly. Any problem that affects the rate of gas exchange in the lungs may load the statistical risk of a problem occuring. Knowledege is power, you can use this information to reduce the underlying base risks e.g. Use nitrox, dive within no-stop limits, make safety stops.

[PeteM]

Decompression problems, yes possibly. Any problem that affects the rate of gas exchange in the lungs may load the statistical risk of a problem occuring.

And the load could be in either direction, we simply do not know enough

[Paul Morris]

Decompression problems, yes possibly. Any problem that affects the rate of gas exchange in the lungs may load the statistical risk of a problem occuring.And the load could be in either direction, we simply do not know enough

Absolutely. Hence the liberal use of 'possibly' and 'may'. Anyone talking about decompression illnesses that starts quoting hard facts or hard evidence should be treated carefully. That whole area of science is lacking hard facts.:(

[Andy Wade]

A number of (unrelated) points:

1. There are quite a few asthamtics who dive. Yes, they may have restrictions placed upon them: depth, temperature of water, no-stop dives, nitrox mandatory... but they do dive

2. I know of at least one active instructor who is asthmatic and teaches at club & regional level

3. Be careful of cold water. My understanding is that cold water may cause problems with the airways contracting (not talking about an asthmatic "attack" here) and therefore ANY abnormal/fast/yoyo ascent can cause greater problems in a susceptible asthmatic than other divers

Nick

So... a CCR with it's nice warm gas circuit might be worthwhile? :D

[gsclarke]

Thanks Paul

Good to hear you say knowledge is power. I know I can't dive till I get my problems sorted but at least I can listen to anything you guys have time to talk about and hopefully by the time I can dive I will have more idea about what risks I may run.

So do you feel you you use less air DESPITE the asthma rather than because of it. I guess if you're asthma is well controlled that would perhaps be the case. I'm wondering what a poorly controlled asthmatic would be like with air usage.

As far as I know most asthmatics overbreath as they are always feeling they need more air although I suppose anyone feeling like this probably doesn't dive?

BUPA are paying for me to see Professor Pavord on Monday. I'm told he's one of the best respiratory consultants in the field so I am quite hopeful I will at least know what I'm up against soon. I will be so diappointed if I can't dive at all :(

Yes, I'm asthmatic and I usually use less air. I'd like to attribute that to my fitness, but alas its down to experience (6 years regular diving) and the fact I dive regularly a few times each month, and I'm sure has nothing to do with my asthma.

Nitrogen narcosis - no. Thats different.
Decompression problems, yes possibly. Any problem that affects the rate of gas exchange in the lungs may load the statistical risk of a problem occuring. Knowledege is power, you can use this information to reduce the underlying base risks e.g. Use nitrox, dive within no-stop limits, make safety stops.