SWB: Reducing the Risk

[trux]

Sounds like you might have moved to avoiding the anxiety Sebastien but maximising the temperature difference?.

Moderate levels of stress are actually beneficial for good DR, so I doubt Seb is trying to avoid anxiety (though it may be difficult to have any if you are diving as much as himself). The no-preparation approach and the temperature shock adds to the stress and helps so with early DR.

There are at least three different (though related) effects of cold water:

1. Facial immersion - quite crucial for the DR
2. Increased stress due to the temperature shock and consequent releasing of stress hormones
3. Cold water on extremities helps with the vasoconstriction

 

[sebastien murat]

Is the reflex (actually reflex responses) related to diving per se or the deprivation of breathing, and hence oxygen, and the build-up of waste products?

Diving = deprivation of breathing
Cost-effective diving requires CO2 storage ability + O2 conservation


By the way, bradycardia = slow heart = oxygen conservation


Seb

Therefore, I think it's ok to call it a dive reflex, especially considering that its accentuated by diving.

 

[johnny]

Bad Day: Say it never happened
Good Day: Say it never happened
Every Day: Clean slate & carry no good or bad luggage

Seb

Hi Seb and everyone.

Great thread thanx for all the input.

 

[Jon]

In the transcript they went into specific detail that simply lowering heart rate is not dive reflex- although the slowing of the heart will help to conserve 02.

They did mention the other aspects that Trux said, vasoconstriction, blood shunt, elevated hematocrit, spleenic contraction, ect. These things were attributed to other things than just facial immersion. These are the things that kick into place after pressure being exerted upon the body.

Jon

 

[sebastien murat]

Getting extra O2 to be released through splenic contractions has the same effect as as peripheral vasoconstriction, all but varying in magnitude. Therefore, if the premise is that splenic contraction is the dive reflex than so too must vasoconstriction, i.e., same difference.

Both these responses can be achieved by simply breath-holding.

Seb

 

[naiad]

I have experienced that - after doing pool training (static or dynamic) I am sometimes very pale for up to two hours afterwards. I don't feel ill or unusually cold, so I think it must be peripheral vasoconstriction caused by the dive reflex. When I do dry statics, I notice that my hands and feet become colder, particularly if I do repeated apnea, such as tables.

 

[trux]

They did mention the other aspects that Trux said, vasoconstriction, blood shunt, elevated hematocrit, spleenic contraction, ect. These things were attributed to other things than just facial immersion. These are the things that kick into place after pressure being exerted upon the body.

I just restate what I already wrote - diving reflex/response is not a single physiological effect, but a complex combination of several physiological mechanisms. And the same goes for the trigger - there are diverse conditions contributing to the DR, and I would not limit it to only facial immersion (or cooling), although it is definitely one of the strongest triggers. Other conditions influence the DR - the simple effect of stopping to breath, PaCO2, PaO2, pH chemoreceptors, pressure/depth, temperature, stress, psychical state, training, ... So telling that DR is not bradycardia but rather splenic contraction, or not initiated by facial immersion but rather by the depth is all nonsense and truth in the same time. DR is all of it.

 

[ADR]

Great thread guys!

Good grief, is somebody paying him by the word?

A common training session for me is:

- Get in
- Swim 70% dynamic (150m)
- Rest 5 mins
- Repeat another 2-4 times
- Get out

or, for variety:

-Get in
-Swim 95% dynamic
-Get out

Dave, by my calculations that would have your max dynamic pegged at 214m....are you telling porky pies ??

 

[Jon]

Trux,

The lastest little bit that I have been reading has the Doc's arguing over what the difference is between a "diving reflex" and a "diving response". They are trying to break different parts of it down into specific catagories- with little concensus.

The part that got my attention with the whole thing was when one questioned the fact of bradycarida being a diving response or simple 02 conservation- which I had always thought it was.

Facial imersion doesn't always coincide with breath hold- when it does they DO consider it diving response. There are times when divers simply float on the surface, without a mask on, and breath through a snorkel to slow their heart rate down. I used to do this a LOT before my deep air dives to get in the "zone"- this was before I started trimix diving. Breathing on the surface this way will slow things down, but, as the one doctor argued, it's not a full diving response.

When the breath hold is used the response kicks in (spleen, blood shunting,ect) and this was even greater when the apnea is combined with facial imersion. Of course spleen contraction can be caused by other things- running and exercise. There was also some argument as to whether or not spleen contraction should be considered a seperate time altogether different from the dive reflex.

It goes on to state that you can train yourself, through many of the ways that have already been mentioned, to slow your pulse on command but that spleen contratction can't be trained this way.

So, I'm not doubting what your saying, just commenting on some new stuff that I read and thought it was interesting to throw in the mix.

Jon

 

[trux]

Yes, Jon, that's in fact very close to what I wrote - diving reflex/response is not any of the isolated effects, but the total complexity of all of them. It is also true that for full, profound, and strong DR you best have the maximum of conditions present (facial immersion, apnea, hypercapnia, cold, pressure/depth, stress, ...). And also for the training it is certainly better having most of them. However, it is not true that you cannot simulate splenic contraction (or most of other DR effects) by plain facial immersion combined with apnea. If you read the first document I linked to (a very interesting one), you can see that it is exactly what they did. Facial immersion alone (with snorkel) is likely not sufficient for that, but when it is combined with breath-hold, there is no problem, and no deep dive is necessary (though I definitely do not dispute that it would not lead to a faster/stronger reaction).

 

[freedivinmike]

This has been a great thread. The spleen keeps coming up in this conversation and there is chance I may have mine removed (keeping my fingers crossed this doesnt have to happen). I am wondering what kind of effect this would have on my freediving. I certainly hope I would not have to give it up!

 

[Jon]

It's the combinging it with apnea that's the key- and we both agree on that. Dry apenas alone will also stimulate the dive reflex.

BTW: Isn't it like 3am your time right now? :friday

Jon

 

[trux]

This has been a great thread. The spleen keeps coming up in this conversation and there is chance I may have mine removed (keeping my fingers crossed this doesnt have to happen). I am wondering what kind of effect this would have on my freediving. I certainly hope I would not have to give it up!

As I wrote, the spleen is not at all that important in DR - it contains only 8% of total body red blood cells, and not even all gets released during the contraction, so in the worst case you lose around 5% of your max time. So if your max is 5 minutes, you'll loose around 15s (assuming you have very good DR with strong splenic contractions), which is rather minor - the influence of psychics and other factors is much higher than that. Read the document I linked - it also compared test persons with and without spleen. However, it is a question if and how the body handles the removed spleen and compensates for it - it is quite possible that the difference will be even less after some period of adaptation.

 

[trux]

BTW: Isn't it like 3am your time right now? :friday

No, it around 5AM. I came late from the pool today :friday

 

[freedivinmike]

Thanks Trux! I appreciate the quick response as I will sleep easier now tonight knowing I will still be able to dive. I will check the link you mention.

 

[Bill]

"...As I wrote, the spleen is not at all that important in DR - it contains only 8% of total body red blood cells, and not even all gets released during the contraction, so in the worst case you lose around 5% of your max time. So if your max is 5 minutes, you'll loose around 15s...."

I won't argue with the first part but if I remember right, the blood holds less than half of the useable O2 at the start of the dive/hold. I'd wager that the spleen contributes even less than 5%.
Aloha
Bill

 

[Mullins]

Dave, by my calculations that would have your max dynamic pegged at 214m....are you telling porky pies ??

Nope. Actually that percentage is rounded up slightly.

 

[trux]

I won't argue with the first part but if I remember right, the blood holds less than half of the useable O2 at the start of the dive/hold. I'd wager that the spleen contributes even less than 5%.

@ Bill: Yes, that's right. The 8% of red blood cells (RBC) from the spleen increase the stock and transport capacity of hemoglobin by those 8% (or less - depending on the strength of the contraction). And since the splenic contraction releases the RBC (at best) only during the first apnea, it actually helps to pre-stock oxygen only at consequent breath-holds. It is correct, that the O2 in blood is roughly only half of the volume consumed during apnea (hint: compare your full and empty lungs breath-holds), and the rest continues to get bound and transported from the lungs during the apnea. So, theoretically, in the hypothetic case of 8% of RBC increase, and 50% of initial oxygen stock in blood, the stocked O2 would add 4%. However, the increased RBC make also the consequent binding and transfer of O2 from lungs more efficient. Theoretically it would improve the transfer by 8% too, but is is probably much less, because there are more factors playing role, and because the O2 transfer by hemoglobin becomes less and less efficient with increasing CO2. So, I think that the 5% would be about OK (better told the theoretical maximum might be even slightly higher), but I agree that in praxis it is quite likely even (very) much less.

@ freedivinmike: Additionally, if you are having problems with spleen and it needs to be removed, it is likely that it does not contribute to your apnea at all already now, so the operation wan't change your performance at all. Wishing you good luck with the operation, quick recovery, and early return to diving!

@ Seb and all others: Sorry for bringing this thread little bit away from the original topic of reducing the risk by initiating a strong DR, but because it is still about DR, I hope it does not mind too much.

 

[sebastien murat]

I think its a little more complex than that.

Trux, you say: "It is correct, that the O2 in blood is roughly only half of the volume consumed during apnea (hint: compare your full and empty lungs breath-holds), and the rest continues to get bound and transported from the lungs during the apnea....................O2 transfer by hemoglobin becomes less and less efficient with increasing CO2"


The consumption of lung O2 vs. blood O2 stores works differently. Until, you get to about 80% Hb desat, lung O2 stores are predominantly used, with essentially next to little effect on blood O2 stores. Also, CO2 production will also affect the relative proportions. CO2 production with empties compared to fulls is entirely different. Lastly, I would argue the converse: O2 transfer by hemoglobin becomes more (not less) efficient with increasing CO2.

E. Shagatay looked at splenic removal on BHD (breath-hold duration) several years ago, well before the Croatians extended the resarch. Her findings: remove the spleen -> essentially no improvement in BHD duration, i.e., the benefits of warm-ups in delaying the urge to breathe would have no effect on persons with no spleen. This of course deos not mean you can improve your breath-hold, only that there's be less difference between a BH to max between the first rep and any subsequent rep.


I think we're straying now!

S
PS: Here's another one for you, if you like challenges: do contractions (not splenic contractions but the ones that make you want to breathe) increase the rate of O2 consumption, thus reducing BHD and increasing the risk of a blackout? (Hint: its a trick question). I'll copy and past it to another thread, under safety.

 

[trux]

I think its a little more complex than that.
... Lastly, I would argue the converse: O2 transfer by hemoglobin becomes more (not less) efficient with increasing CO2.

Yes, indeed it is more complex, but since this thread is about something else, I did not go into details. However, you'll certainly agree that the effect of CO2 is a double-edged sword: on one hand it helps releasing O2 from hemoglobin there where it is needed (in the place where it is consumed) - hence it improves the transport. But on the other hand, in the moment the level of CO2 in alveolus becomes critically high, and the gradient between the CO2 in blood and in the alveolus becomes too small, hemoglobin will no more be able to bind and transfer oxygen from lungs efficiently although there is still plenty of it. And that's what I meant.