FRV / FRC / Exhale diving

[Ben Gowland]

Following a few recent threads, I'd like to start a poll to gauge popular opinion on the above method of diving.

Hopefully the categories I've given will make sense and allow people to place themselves accurately. Although, I'm sure any discussion will request more cats!

Deep freediving is inherently a PB-chasing activity for most people and thus switching to this technique exclusively is not in many people's interest. Since I don't have easy access to deep water, it has given me a 'new lease of life' that perhaps it wouldn't have done if I did have access to deep water. However, now that I have been using it for a year and a half or so, I'm absolutely hooked and see little reason to go back to full-lung diving even when I am in deep water. I'm also not very PB driven anymore, compared to what I used to be, which may have also played a part.....

so.....how do others see it?

 

[JasonWelbourne]

I have experimented with diving to depths beyond the depth at which it becomes possible for me to push air out of my lungs, mainly via exhale diving. I am still very confused about the sensations I experienced and whether they were normal or bad. It has not dettered me from this technique, but I would regret to find out years from now, dying of pulmonary edema, that I was infact wrong.

What I experince doing exhale diving is that once I pass a specific depth, slightly beyond the depth at which I find it possible to empty my lungs at, I begin to feel the pressure being exerted on my lungs. It is a strong pressure, but not painful. It builds as i descend, and upon ascent, it does not diminish until I hit the surface and start breathing again. Breathing is normal, and without any indication of pain, residual pressure, or blood / fluids. The experiment is repeatable with the same effects dive after dive.

I have coughed up specks of blood before, but it has always come from my throat after breathing heavily through a snorkel for extended periods. I am confident that when it happens, it is not as the result of a lung squeeze.

I would like to know if my experiences are consistant with positive exhale diving.

 

[JasonWelbourne]

I think this is vital info for the community. From reading some of the posts regarding exhale diving, it seems that there is a lot of confusion on the matter. I think that knowledge is paramount in making personal safety decisions, and if there is not enough public knowledge on the matter, then it makes sense that there would be so much confusion on the issue.

 

[Ben Gowland]

It seems unlikely that there will be any differences to the pulmonary system between FRV diving to 40m and inhale diving to 80m. Since many people have done many dives to those depths using those techniques with little or no ill effects - it suggests that you should be safe too. Alternatively we might all snuff it in 10 years time in strange and mysterious circumstances.

The risk is indefinable, and thus ours to take or avoid as we see fit.

Ben

 

[efattah]

Ben,

How did you build that graph? Experimentally?

 

[Ben Gowland]

Eric - You mean the one on the other thread ?

I drew that graph to represent the hypothesis that Simon's experiment would test. I can see that it may be considered inappropriate for such things to be posted here, so I've removed it.

Ben

 

[subaquaticus]

Following a few recent threads, I'd like to start a poll to gauge popular opinion on the above method of diving.

Hopefully the categories I've given will make sense and allow people to place themselves accurately. Although, I'm sure any discussion will request more cats!

Deep freediving is inherently a PB-chasing activity for most people and thus switching to this technique exclusively is not in many people's interest. Since I don't have easy access to deep water, it has given me a 'new lease of life' that perhaps it wouldn't have done if I did have access to deep water. However, now that I have been using it for a year and a half or so, I'm absolutely hooked and see little reason to go back to full-lung diving even when I am in deep water. I'm also not very PB driven anymore, compared to what I used to be, which may have also played a part.....

so.....how do others see it?

Would you be so kind as to pity those who do not master freediving jargon ?

What do you understand under FRC - FRV ???

I guess it might have something to do with empty lungs, mightn't it ?

 

[Decca]

I've fluctuated from thinking it was too dangerous to consider to being excited about its possibilites. All my diving is serial diving (spearing). I've found the method an enjoyable way to dive.

I guess it will take time for its benefits and drawbacks to become known. I'm glad to have discovered this method. For the time being I am keen to practice and learn more about the method.

subaquaticus
While breathing normally, the amount of air remaining in your lungs after you exhale is your residual volume, also called functional residual capacity or functional residual volume. Hence the TLA's FRV, and FRC.

 

[subaquaticus]

I've fluctuated from thinking it was too dangerous to consider to being excited about its possibilites. All my diving is serial diving (spearing). I've found the method an enjoyable way to dive.

I guess it will take time for its benefits and drawbacks to become known. I'm glad to have discovered this method. For the time being I am keen to practice and learn more about the method.

subaquaticus
While breathing normally, the amount of air remaining in your lungs after you exhale is your residual volume, also called functional residual capacity or functional residual volume. Hence the TLA's FRV, and FRC.

thanks ! Functional Residual Volume... such a beautiful expression...

 

[Decca]

thanks ! Functional Residual Volume... such a beautiful expression...

It gets around the bad press caused by calling it exhale diving.

 

[Will]

Decca, you are right about the definition of FRC, but RV is not the same thing. Freedivers talk about passive exhales (i.e. an exhale during normal unmonitored breathing) and forced exhales (breathing out all you can). A passive exhale will give you Functional Residual Capacity, FRC, (functional in the sense that it is what you use every day), while a forced exhalation will give Residual Volume, RV.
FRV isn't a recognised term, and will just confuse matters.
I don't know what TLA is supposed to mean, but TLC is Total Lung Capacity.

 

[Alun]

"A passive exhale will give you Functional Residual Capacity"...

if i exhale passively on land my lung volume reudces to FRC. if i exhale passively in water my lung volume reduces to RV. i'm sure that's true for most people. if i want to dive on FRC then i have to control my exhale and judge the right amount air to take down with me. i find this easier to do when horizontal breathing through a snorkel, because there's less pressure on the lungs.

 

[sebastien murat]

Capacity = dynamic, functional, measures

Volume = static



The aim of exhale diving is to initiate a passive descent. It is a common mistake to assume that a diver needs to exhale to FRC to 'sink.' Some do, some don't. Some need to exhale more, other less. FRC is a good starting point for most. More recently, I've been experimenting with the idea of undertaking a couple of strokes to initiate descents. This did not affect the overall outcome to any great significance.


Seb

 

[Decca]

TLA stands for three lettered acronym.

 

[sebastien murat]

Dear all,

For those whove asked me for some preliminary info. on the dive experiments:

For interest only (not statistical extrapolation to the general population), I've attached a heart-rate (energy expenditure index) curve for 3 'inhale', followed by 3 exhale dives. The data is not representative of the greater sample but is specific to to my case. Dives were shallow (i.e., 15m) and carried out wholly unassisted, i.e., no mask, no fins, no wetsuit, no ballast. Exhale dives were undertaken with 1-2 downward strokes (unassisted). 'Inhale' dives required stroking down all the way to ensure reaching the bottom.

Dives on inhale were consistantly 1'32" duration. Dives on exhales were exactly 3" longer and accounted for by the greater -ve buoyancy during the exhales during ascent. Also note, tachycardia (rise in heart rate) did not occur during ascent, during exhales; the tachycardia occured in all cases 5-10" post dive. A lack of tachycardia during ascent is most probably associated with a reduced arterial oxygen desaturation rate. Pre-dive heart rate was more elevated with the 'inhale' strategy, implying an anticipatory exercise tachycardia. This does not necessarily imply greater oxygen consumption, however. Post-dive heart rate was more elevated with the 'exhale' strategy, accounted for by either greater shift to anaerobic metabolism caused by cold-induced vasoconstriction at the end of the dive bouts. Subsequent experiments will aim to control for this confounding variable since previous, preliminary experiments indicated that carbon dioxide levels 20-30" post-dive were actually less elevated than with the 'inhale' strategy. Relatively reduced carbon dioxide levels 20-30" post-dive would indicate reduced shift to anaerobic metabolism and hence, fatigue.

I've attached the expired, end-tidal oxygen and carbon dioxide concentrations. Clearly, these were higher with 'exhales', which indicates not only greater oxygen conservation but reduced risk of blackout for equivalent dive durations. Carbon dioxide levels were also lower, suggesting a reduced respiratory drive.

Cheers,
Seb
Aust.

 

[Decca]

Some questions:

1. Was the oxygen testing done on the first expired breath?

2. Why does elevated heart rate at the end of the dive imply anaerobic metabolism?

3. What was the water temperature?

4. If the diver was to swim along the bottom for say 20 seconds, what affect would this have on the final oxygen levels. Would you expect the amount of oxygen used to be about the same for both inhale and exhale.

The results certainly back up much of what you have been saying. I look forward to seeing other results.

In the mean time, I'll keep up the exhale diving. Thanks for posting the information.

 

[sebastien murat]

1. Was the oxygen testing done on the first expired breath?
Yes, Divers were instructed to blow past the the syringe to ensure that samples would not be contaminated. Secondly, only the latter part of the breath was sampled to ensure we obtained only alveolar as opposed to dead space air.

2. Why does elevated heart rate at the end of the dive imply anaerobic metabolism?
Post-dive, a relatively more elevated heart-rate to well beyond pre-dive baseline levels would tend to indicate elevated CO2 levels due to lactate metabolism. Lactate from anaerobic processes is metabolized to produce considerable amounts of CO2. This will result in an elevated cardiac output and venous return achieved in part through increases in heart-rate.
The paradox, however, from preliminary analysis of results on my person and involving taking alveolar gas samples 20" post-dive revealed lower CO2 tensions with the 'exhale' method than with the 'inhale' method. I'm currently trying to interpret thise seemingly conflicting situation

3. What was the water temperature?
Water temp ~27-28 degrees C.

4. If the diver was to swim along the bottom for say 20 seconds, what affect would this have on the final oxygen levels. Would you expect the amount of oxygen used to be about the same for both inhale and exhale.
I would expect the same results but with more severe hypoxia and hypercapnia. Off to Sydney soon to do some more sampling with this in mind.

The results certainly back up much of what you have been saying. I look forward to seeing other results.

Cheers,
Seb

 

[Decca]

Sebastien,

Thanks for your responses.

Heard from a fellow in church today who was a missionary in PNG. He said the natives over on one of the PNG islands were very good divers, with a breath hold of around three minutes. As far as I know this fellow knows little about diving, but he made the point that the natives exhale so they sink.

Apparently they train from a young age. Uncle pushes their head under water, and they're allowed up for air when uncle is ready. I thought this was a pretty aggressive training method.

Not sure how much of this is urban myth, but it made for an interesting story.

 

[sebastien murat]

Hi Decca,

Very interesting, as I've been searching for some time for some Indo-Pacific islanders diving in this way. Haven't found any as yet. If you're able to find out from which particular island that would be helpful as I'll be returning there soon again.

On the other hand, I also remember a couple of years ago when this PNG national was trying to convince me that the local on Manus Is. would casually dive around for 10' at a time. I told them they must be very good as I was flat-out doing what I was doing and if that was indeed the case perhaps I should take-up ice-hockey instead!


Cheers,
Seb

 

[migs]

The paradox, however, from preliminary analysis of results on my person and involving taking alveolar gas samples 20" post-dive revealed lower CO2 tensions with the 'exhale' method than with the 'inhale' method. I'm currently trying to interpret thise seemingly conflicting situation

Interesting results. I assume your resting heartbeat is about 85 in water (rate at the beginning of the measurement period)? If that's the case then it's interesting to see three inhale and three exhales averages out your resting heart rate. Whereas if the graph is split in two then the inhales would result in a higher average and exhales a lower average.

Why the elevated heart rate post dive?
No idea but the same thing happens for me (on two occasions I was diving to just 5 m and measuring my heart rate before during and post passive exhale dive).

One thing not shown on the graph is exactly when the heart rate elevates post dive and how c02 levels alter during this phase. Perhaps they stay flat for a bit longer than expected? Your first breath out (assuming a blood shunt) is about CO2 around the heart lungs and brain, then you breath in and I guess there would be the opposite of the blood shunt (not fully because you're still immersed). It could be balance, both in terms of vaso blood volumes in respect the rest of the body or balance in terms of CO2, your first breath increasing oxygen to the heart, lungs and brain (which says 'ok i've got enough now where's the rest of the body at?'). So perhaps it's a way of balancing the blood throughout the body?

Whereas inhale, with the high heart rate, you might expect less of a shift in blood, more balance throughout the body during the dive.

have you thought about serial CO2 level measurements (multiple breaths post inhale/exhale dive)? Or is this irrelevant for other reasons?