Why does packing lungs cause dizziness?

[pekelo01]

Is it recommended that we pack our lungs with air before diving?By packing I am referring to sucking in extra gulps of air after taking a full deep breath for a static apnea breath hold.

I tried doing this this and noticed that I can get momentarily really dizzy for a few seconds around the 5th pack. After a few seconds the dizziness passes away and I'm ok.

Q1. Is this similar to hyperventilating?

Q2. Why does packing the lungs with extra air cause dizziness?

Mahalo,
Peter

[Cliff Etzel]

I am going to speculate here, but I am going to guess that it is due to a sudden increase in blood pressure. The same kind of feeling can be experienced if your inhale deeply, then hold that breath and "bear down".

Hope this helps...

[snorklebum]

Dizziness is like death or psychosis: it doesn't have a specific cause, it occurs when you don't have it together enough not to experience it.
A lot of breathing variations cause lightheadedness and dizziness. Sudden sprints, sudden deep inhale or hyperventilation, asphyxiation, even venous pressure drop when you stand up too quick.
It's rumored that being blonde can be a causitive factor.

[Erik]

I am not an authority on packing, but I have had a few blackouts after a lot of packs, especially earlier in the day, and if I haven't got my reflex kicked in. I just learned how this year from an earlier post by Eric Fattah. Laminar will be able to elaborate more, but it has somethimg to do with the extra presuure on the heart and carotid arteries I believe. If your CO2 level is especially low, ie after a long breathe-up, and you pack a lot of times, then you are more subsceptible to dizziness and blackout. If you start to hear ringing in your ears, tingles, warmth, and perceptual narrowing, then you are getting a warning that blackout may be imminent. At least that's what I experience. I ride it closely, but am learning where to back off.
It's not hyperventilating, and I don't think it's dangerous in itself; there is no evidence that lung expansion injuries can result, as far as I've read.
I would reccomend that you learn how to do it, and slowly keep building up to a substantial amount. If you want to dive extremely deep, then you will have to, just to able to equalize at depth. Some static competitors use packing as well; the time it takes to pack the extra air is outweighed by the gain in breath-hold, but you have to be stretched out enough to be able to do it reasonably comfortably.
Hopefully Eric F., Laminar, or Peter Sheard will reply with a better explanation of the process.
Cheers,
Erik Y.

[pekelo01]

Thanks everybody on the usefull comments on why packing can cause fainting.

I recently found the other older and longer set of emails on "Does shallow water blackout really exist?" that also covered this subject. It was extremely informative. (This set of emails should be moved over to those for easier viewing and reading.)

I've since learned to prevent myself from passing out (happened only once) while packing. In my case, it occurred because I was packing too quickly and my body hadn't had a chance to adjust to the sudden increase in lung pressure (but decrease in blood pressure to my brain).

I was at work standing in an area where there weren't too many others and suddenly found myself lying on the floor. Good thing no one saw me. Ha-ha-ha!!!

Mahalo,
PeterE.