Susceptibility to Packing Blackout

[Mullins]

Just looking for some info or ideas on what factors make one more or less susceptible to packing blackouts.

This is becoming a bit of an issue for me - if I pack till I'm at or near my limit, as I do for all disciplines, there's a fair chance that I will BO or samba. And when I say BO I mean the whole deal: out like a light and taking a while to come round once my buddy picks me up. Sometimes I can catch it and come up myself, sometimes I have no warning.

It can make CB dives a bit scary too; a few times now I've regained consciousness at about 5-10m, after apparently having kicked myself down in a semi-conscious state but without recollection of so much as a duck dive!

My susceptibility seems to vary quite dramatically - some days I can pack heaps and have no problems, others (like earlier today) it's so bad there's not much point in doing statics. Fasting for too long beforehand seems to make it much worse, but that's the only factor I've been able to identify.

In all cases I'm doing a minimal warmup (snorkel breathing for a while then 2 very short exhales for statics) and no breatheup (by that I mean no forced breathing, just very slow and controlled breaths becasue I perform better with high CO2 as long as I can handle the 4+ minutes of contractions :vangry )

Diet? Temperature? Any ideas would be appreciated

Cheers in advance
Dave

 

[pat fish]

The hole phenomenon is still quite unclear to me, but there seems to be the following things going on.

1) blood pressure drop (reduced cardiac output due to pressure on chest)
2) stimulation of carotid sinus nerve (nervus vagus)
3) compression on carotid arterias
4) hormonal disbalance (blood pressure regulators, noradrenalin,etc.)
5) arterial tension through blood pressure (stability of vessels)

So factors making one more or less susceptible to blackout after packing could be

1) blood pressure niveau
2) predisposition to blood pressure variations
3) flexibility in diaphragma (hard limits for airspace)
4) stability of cardial/lung/arterial system
5) sensibility of nervus vagus
6) sensibility of adrenal glands
7) diet affecting blood pressure stability

some mind food...

yours
Pat

 

[Mullins]

Thanks Pat,

Actually I do have a history of weird BP readings - I'm very tall which might have something to do with it. They've generally been high rather than low though...
Just found this very helpful quote from Eric Fattah in an older thread:

It can be caused by both low CO2 and/or low blood pressure and/or being excessively alkaline (from diet or other reasons). Low blood pressure can be caused by being too hot (vasodilated), dehydration, eating vasodilating foods such as garlic, onions or pineapple; or it can even be somewhat genetic; it can also be caused by large amounts of cardio training.

In some people, taking a single very deep breath can lead to a blackout (it nearly happened to me once).

The problem will be worsened if you attempt to inhale while standing or sitting, rather than floating face down.

The problem can be reduced by:
- Cooling the body (vasoconstriction increases BP)
- Avoiding vasodilating foods
- Eating more salt and drinking more water (together!)
- Storing more water in the body by eating lots of starchy carbohydrates and drinking lots of water along with it
- Breathing less before the dive
- Pausing for 10-30 seconds with full lungs, right before the last breath
- Inhaling while floating face down, or better yet, float with your feet at a depth of 5 feet, with your ears barely above the water; the water pressure gradient forces blood from your legs to your head, improving the BP in your brain
- Eat more acid forming foods (meat, eggs, etc.), not necessarily the best solution
- Packing less or taking less air (not a good idea, not the best solution)

 

[pat fish]

Thanks to Eric we have a good base of practical measurements which can be taken to try to prevent blackouts from packing. Especially pack slowly and try experimenting with different positions to find out what works best for you. I do believe the phenomenon of packing blackouts is complex and does not only depend on the bp niveau. I would recommend to listen to your body and simply not pack to an absolute physiological maximum regarding airspace. Rather focus on relaxation and adaptation. Umberto has done 7min+ and has been down to 150m without any packing.

yours
Pat

 

[naiad]

I used to feel close to blackout when I first started packing, but now I am much more used to it and I don't have any problems.

One thing which makes me much more susceptible to blackouts and sambas is being cold, even if I am not actually shivering. I find it impossible to know my limits when I am even a bit too cold.

I agree with Pat that maybe it would be a good idea to pack a bit less.

Lucia