Headaches & PFOs

"Jen" wrote

> It is difficult to overcome what is default behaviour. I suppose for me
> the
> long exhalation is at least making me more aware of my default breathing
> behaviour underwater so is going some way to reducing the CO2 build up,
> enough it seems to prevent the headache on surfacing.

It can be difficult, but, in my personal opinion, what you are doing
requires about the same degree of attention. If you're going to develop new
habits, why not the best ones. Still, if what you are doing works for you,
then it works for you. 8^)

> I was talking about this to a guy on my livaboard last week who swore the
> Nitrox was the solution for him. His consumption was astonishing, always
> coming out with at least twice the gas of anyone else. I did wonder
> whether
> CO2 build up was his problem too as there were comments of 'he just
> doesn't
> breathe' from anyone who buddied him. But then I wasn't sure what role the
> Nitrox played in reducing his headaches cos an eggspurt on gases I aint.

You provided me with all sorts of opportunities to speak on things I like to
speak on.

I'm one of those guys that has low consumption. One of my favorite stories
is about a trip to Cozumel. We were a group of about 30 divers from all
over the world and with all levels of diving experience. Four of us,
including my wife, a German technical diver and a relatively new, but very
talented BSAC diver kind of hit it off and tended to dive as a sub group of
the larger group. Various subgroups booked their own diving according to
their preferences, but on two days, we scheduled a trip with a shop that had
boats large enough to accommodate all of us. The first day, the DM went
through his pre dive briefing. We listened attentively both because it's
polite and because you never know when a DM will say something worth
hearing. The rules of the dive were set out, every body nodded, and then,
as usual, the 4 of us headed off to do what we wanted rather than what the
DM wanted. We did nothing dangerous for us, but it wasn't what the DM
expected. We came up on schedule, but our common low consumption levels
allowed us to go deeper during that time than others and still return with a
reasonable reserve. The second day, there were two DMs on the boat, one
specifically for us.

Our DM started off with his canned speech and stopped only a short way into
it. He turned and looked at me and said are you going to do what I say this
time or do whatever you want like you did yesterday. You had to be there to
understand how well he did it. It was not criticism, or a lecture, just an
honest question. I looked at the other divers, who nodded their agreement
and told the DM that was would behave. He then asked if 120 feet (I think
it was 120, I'd have to check my log), was deep enough. Again, I checked
with the group who indicated their agreement. I said that 120 was fine. He
then asked us how long we wanted to dive. Without checking, I responded,
about an hour. He looked at me a bit funny and said, no, really, how long.
I again responded, about an hour. He looked at my wife and she also
responded, about an hour sounds good. He gave up and we all went over the
side of the boat. How much alike the four of us was quickly became
apparent. Every one of us descended to exactly 120 feet and began a slow
ascent, monitoring our time, depth and gas supply frequently. While we had
done a dive to 120 feet, our average depth was considerably less. We all
timed our dive to return to our safety stop just before an hour had passed
and all of us extended our stop as much as was necessary to meet or exceed
our hour projection.

When we were back aboard the boat, my wife turned to the DM and said, "I bet
you thought we were kidding when we said about an hour." The DM laughed and
admitted that he had and went on to say that it was a good thing that we had
surfaced when we had, because he was just about out of gas. Our UK buddy
turned to him and, said, "no problem, mate. You could have come to any of
us if you needed some." Everybody laughed at the joke, but on the way back
to shore, the four of us confirmed the accuracy of his statement. Each of
us had at least 1,000 psi remaining of our original 3,000 psi. Not
everybody gets to out dive a Cozumel DM.

I love telling that story.

At any rate, I have low consumption. I probably didn't always have low
consumption, but after more than 40 years of diving, I don't remember when I
didn't. My consumption was low when I only used air and it's true now that
I most often use nitrox. It's not as true when I use trimix simply because
I'm new to, and less comfortable with, trimix. Most of my diving is no
decompression diving. I use nitrox because I get more no decompression time
at a given depth and surface interval time than I do with air. Even on the
first dive of the day, it's an advantage to me, and probably for the guy you
met. Our low consumption rates make it not only possible, but easy to get
into a decompression obligation on the first dive of the day with a standard
single tank (an aluminum 80 cubic foot tank everywhere I dive.) Nitrox
makes it harder. Most divers, even those that do not have very low
consumption rates, find nitrox to be an advantage for second or at least
third dives in the same day. For me, the relationship between nitrox and
consumption is reversed. I use nitrox because I first used nitrox because I
have a low consumption rate, not the other way around.

An added benefit of nitrox, at least according to many that use it, is
feeling better, more energetic at the end of a dive. Many report this
effect. I don't notice it. It may be that I'm diving for long enough to
get the same load of nitrogen while on nitrox that others get when diving
air. Whatever, they seem to experience it. I don't. You might. If/when
you try nitrox, let me know.

I don't think I've seen a discussion on whether nitrox reduces CO2
retention. It makes sense that it would. The exchange of gases in the
system is directly proportional to the concentration of the gas in the
breathing mix and body tissues. CO2 is a very small part of the air you
breathe, but it's an even smaller part of nitrox. The lower concentration
should allow CO2 to exit body tissues a bit faster, but I suspect it would
be such a small difference that it would not be significant or noticeable,
but I might be wrong.

The answer, for the guy you met, is more likely to be slow, deep breathing.
This is not only better from a CO2 perspective, but also from a consumption
perspective. There's a lot of agreement that the most significant factor in
low gas consumption is comfort in the water. This means more than just
being physically comfortable. I also means being calm, relaxed and at home
in the water. The way I often like to describe it is by saying that my
average dive is less strenuous than a nap on the couch. The water is
supporting me completely. My buoyancy and trim are so precise that I exert
no energy at all to maintain position, depth or rotational (I'm usually
horizontal, but I'm equally comfortable in any position). The only energy
I'm expending is what little it takes to sustain life and, perhaps to move
forward a bit. I'm in no hurry to get anywhere. I am using very little
energy, when means I'm not converting a lot of oxygen to CO2 and, because
CO2 is the primary trigger for the need to breathe, am breathing slower.
I'm not getting CO2 buildup both because I'm breathing slowly and completely
and because I'm not generating as much as most other divers.

All else being equal, women usually use less gas than men. I don't know
why, but it's pretty clear that it's true. Inexperienced divers, whether
men or women, rarely reach a high level of comfort and a comparably low
level of consumption until they've been diving for quite a while. The first
roadblock is nervousness. Most new divers are at least a little nervous
during a dive. For most, it takes time to relax. Another roadblock to low
consumption is familiarity with equipment. New divers have to think about
where everything is, thinking about what their fins are doing and who or
what they might be kicking, fuss with things in their pockets (I have no
pockets) or constantly check gauges, computers, etc. They're burning a lot
of energy for little or no real return. Buoyancy is also a big issue. If
you're constantly adding and venting gas from your buoyancy control system,
you're not only losing gas, you're using energy and, as a result, more gas.
Trim is possibly the most overlooked element of low consumption. Watch
other divers. Some, probably most, will be finning continuously simply to
stay level. You probably are too. They can not easily stay in one place
because they are using energy to maintain trim rather than distributing
weight to accomplish the same thing. You may also note that most of them
are feet down (may not apply to drysuit diving), even when kicking
continuously.

Comfort and relaxation come with time. Good buoyancy and trim usually take
a bit of work, first to reduce weight, thereby reducing gas expansion and
necessary buoyancy adjustments and second to balance your configuration,
including your body, so that it take energy to change position instead of
taking energy to maintain it. Move weight until you are as balanced as
possible in every direction. Slow, deep breathing takes a bit of practice,
but, when everything else is in order, will become quite natural. Your body
knows how to do it. It's how you breathe when you are asleep and how you
should breathe when you are awake. You too, will expend about as much
energy as a nap on the couch, breathe about the say way, and make others
suspect that you're hiding your gills.

Lee

In article <0QAZd.1702$dE.615@news.cpqcorp.net>,
Jen <jen@the-computer.co.uk> wrote:
>"Lee Bell" wrote
>> I was going to let this thread go without comment, but since you brought
>it
>> up, I'll add my few pence worth.
[snip 5p]
>> Lee
>>
>Thanks for the advice Lee,
>
>It is difficult to overcome what is default behaviour. I suppose for me the
>long exhalation is at least making me more aware of my default breathing
>behaviour underwater so is going some way to reducing the CO2 build up,
>enough it seems to prevent the headache on surfacing.
>
>I was talking about this to a guy on my livaboard last week who swore the
>Nitrox was the solution for him. His consumption was astonishing, always
>coming out with at least twice the gas of anyone else. I did wonder whether
>CO2 build up was his problem too as there were comments of 'he just doesn't
>breathe' from anyone who buddied him. But then I wasn't sure what role the
>Nitrox played in reducing his headaches cos an eggspurt on gases I aint.

The medics I have been talking to has this as a case for further study.

There are some people that do not respond normally to CO2; where the O2
has a stronger effect on breathing response. The medics call them
CO2 retainers. It is normally a symptom of severe lung or metabolic
disease, but has been shown in long-time _heavy_ dope-smokers. [1]

The SAC rate for such people is extremely low, sometimes down to 6-7
liters/minute, and one of the primary indicators is that breathing
stimulus is significantly reduced when the oxygen content of the gas
is increased.

Normally people in this group are not fit to walk, much less dive.


-- mrr




[1] like 10 a day for a decade, except we are not talking about tobacco

Captain's log. On StarDate Tue, 15 Mar 2005 15:54:56 GMT received comm from "Lee
Bell" <leebell@ix.remove.netcom.com> on channel uk.rec.scuba:

: You provided me with all sorts of opportunities to speak on things I like to
: speak on.

[ snip on a very interesting post ]

Greatly appreciated info/insight (especially for a newbie like me) -- thanks.

martin törnsten

--
martinot@gmail.com