Packing
Peter,
To say that a diver gets 22-39% more air from packing may be true for those who are just learning the technique. Spirometer experiments have shown, for example, the following differences:
Me: No packing (7.89L max, 7.50L avg), with packing (10.52L max, 10.35L avg)
Herbert Nitsch: No packing (7L), with packing (10L)
Hubert Maier: No packing (10L), with packing (14L)
Further, if you do the math on the air packed per second, and substract metabolic O2 consumption, you'll see that you gain, no matter how long you pack for, based solely on the fact that the O2 store increases at a greater rate than O2 consumption, even allowing for the high BP and high HR which occur from the stress during packing.
However, care must be taken. I don't believe you can cause an embolism from packing (some scientist tried to prove it was impossible, and I agree), however the intercostal (and other muscles) are at risk of hyperstretching unless you proceed gradually. I have gradually worked up over the years, but in Florida I showed Karoline Dal Toe how to pack an extra liter by changing her body position. She got the extra liter, and her apnea improved along with it, but she suffered sore chest muscles for several days.
When deep diving in constant weight, I pack through my snorkel, about 70 times, and it takes about 20-30 seconds.
Packing can cause a blackout under certain circumstances. I take great care to ensure my physiology is balanced before attempting a huge pack. The body must be well hydrated, BP must be good or better, all vasodilators must be avoided (i.e. garlic, onions), the electrolytes must be balanced, and the adrenals must be in top shape (i.e. avoid simple sugar, caffeine, alcohol).
Eric Fattah
BC, Canada