Dry BlackOut - why?

[TLoonie]

Hi,

I recently discovered FreeDiving.
I started to exercise 6/7 days in order to prepare for my trip to Thailand.
morning : empty lungs (10mn) + quick breathing (yoga 6mn)
night : hypercapnia 3days/w + hypoxia 3days/w

Today i blackout during a dry hypercapnia training. I was going for 2:30s when I BO and "woke up" with my head in my feet at 30s
During the first 6 holds (1' / 1'15" / 1'30" / 1'45" / 2' / 2'15") I felt dizzy from 15-30s. I didn't worry much as it happens sometimes and because it's a funny feeling. My pulse was particularly high tonight 60-100 when it's usually 40-70. My PB is 3mn and my resting heart rate around 45.

Do you have any ideas why I did a BO?

 

[MarcinB]

Was it on empty or full lungs? What was the position of your body? (sitting, lying?)

 

[TLoonie]

Full lungs
Sitted with my legs crossed

 

[MarcinB]

It definitely was a combination of full lungs+sitting position+some hyperventilation. Holding breath on full lungs while sitting can cause black out in 30 seconds. It happened to me at least twice. Increased pressure in the chest resulting from maximal inhale strongly impairs the ability of the heart to pump blood. Moreover, in the sitting position blood pressure in brain vessels is much lower compared to supine position. Combination of these two factors causes transient brain ischemia. I would strongly advice you not to hold your breath while sitting or at least don't do it on full lungs.

 

[TLoonie]

Ok thanks for the explanation and info about sitting ischemia.
I didn't know that sitted position was bad for blood flow.
When I'm full breath I feel a pressure on my chest. Is this the diaphragm being stretched or something else?
I've been training for a bit now and my thorax size has gotten bigger already by a few cm. I do stretch my chest, sitted "opening" it with my arms in my back. How can is it possible to do this exercise laying down?

Thanks in advance

 

[MarcinB]

Pressure or tension in the chest after maximal inhale is normal at the beginning. I think it's rather related to the rib cage. If you continue with stretching this feeling will diminish with time.
My advice considered breath holds (tables etc.). It's impossible to stretch the chest in supine position. You just need to be careful and release the air if you feel dizzy or notice other unusual symptoms. I do much chest stretching in standing position on full lungs. If I hold air too long (more than ~15s) while stretching I start to hear ringing in my ears, I got tunnel vision and then everything gets dark. From this point blackout is just a matter of few seconds if I don't release air immediately. Some people (usually the tall ones) are more prone to this.

 

[TLoonie]

wow interesting
Aren't you worried that you may fall and hurt yourself?
I thought the ears whistling was just me ^^ I don't get tunnel vision so much but I have like blurrish spotted vision and a staggering feeling (which I do enjoy, I must admit)

Other question for you, you seem to know so much it's exciting
When I do empty lungs after 5-10s of contraction (about 30s for me) I start to get stronger ones that are hard to hold in. It's like my blood is getting squeezed and when I release the tension it feels really good. But it's a totally different feeling from full lung release. Do you know why? (I'm sure you do)

 

[MarcinB]

I fell once, from that time I'm more careful and release air as soon as I start to feel the symptoms I've mentioned above.

During empty lung static CO2 builds up in blood really quickly which causes massive diaphragm contractions and very strong dive response. Lung volume makes much difference. On full lungs pressure in the chest is higher as compared to the rest of your body which lowers blood volume in the pulmonary circulation and reduces blood shift when the diving response kicks in. On empty lungs pressure in the chest is lower than in the rest of your body which strongly enhances blood shift to the pulmonary circulation. Moreover strong diaphragm contractions lower the pressure even more. I think this feeling when you release air is caused by large volume of blood flowing quickly from pulmonary circulation back to your extremities.

 

[Azrael3000]

What you describe above is also not hypercapnia but a hypoxia table as only in O2 tables the hold times are supposed to be increased. In CO2 tables the hold times are supposed to be constant with the rest times in between being reduced. This also explains why together with the rest of the circumstances you BO'ed.
As usual it is advisable to take a course to learn about all these things and have a buddy by your side. If you BO dry and your tongue blocks your airways you will not be talking to us later on.

 

[TLoonie]

@MarcinB
Thanks again

@Azrael3000
Indeed it was on a hypoxia table.
I plan to take a class about when I'm in Thailand (Koh Samui). As of the buddy, I cannot have someone with me whenever I'm practicing, that's just the ultimate luxury.
Anyhoo, if I had a buddy what should he have done once he saw me blackingout?
(your tongue-swallow story is scary)

 

[Azrael3000]

Okay I asked a friend of mine (apneaboy here on the forums) who has much more experience than me and his take on the tongue block is the following:
It is most certainly possible that the tongue relaxes and blocks your airways. This is for example something that also occurs in sleep apnea. However, that said, he reckons that chances of this happening are extremely slim and he does not know any cases of dry apnea deaths due to this. Also your body will try and start breathing again once you have blacked out, so it is likely that the body will solve this issue itself. So to conclude, it's miles safer to do dry holds than wet ones on your own. There is a remaining chance that things might go bad, but you could also get hit by a car next time you leave the house.

 

[mrjomac]

Hi TL,
I've just started doing 3 big breaths before hold again after taking an apnea course and one thing I've noticed is that there's one stretching exercise that will immediately tell me if I'm going over my limit. This is the third apnea stretch I'm doing, rotating the shoulders to the side in relation to the rest of the upper body. If I'm doing anything like a purge/forced exhalation at the end of the 2 slow whistling exhalations between the 3 big breaths I'll get immediately dizzy/roaring in ears/BO warnings as soon as I rotate my shoulders to one side.
If I don't force an exhale this doesn't happen.
Haven't noticed any of this when doing dry static sitting on the couch or diving or during the other stretches, just during this particular stretch but methinks it might be a positive thing as it's showing me if I'm overdoing it, in particular that I shouldn't purge when breathing in so deep. So now I'm concentrating on exhaling without actually pushing any air out forcibly.

I've stopped doing O2 tables for the moment and am just doing a Co2 table, more radical than the one I was doing before based on the one we were doing on the course.

If you're getting dizzy on all your static breath holds I think that's your body telling you you're breathing wrong for your particular body and level. In my case I'm pretty sure it was a slight purge on each exhalation while taking in a lot of air and squeezing/twisting the full lungs while stretching.
As far as I can tell, if I'm breathing in a way that's OK for my body and level, I'll get no dizziness and contractions will kick in nice and easy about halfway through the hold. If I'm doing things wrong, I can get dizzy and/or late contractions, neither of which I want to have underwater.

 

[TLoonie]

@Azrael3000
Thanks for checking with your buddy

@mrjomac
Thanks for the feedback on your experience. It's always valuable to know what others do


So I changed the way I do my static. I now do them on my back and I haven't had any dizziness since. It actually helps to relax and I save O2 from my back not being tensed.
Doing empty lungs + O2 / CO2 tables for 4w got me +45s on my PB static ^__^

 

[Azrael3000]

Congrats mate. Keep going and enjoying.