Extending dive time

[GotAir]

I was driving back from my LDS today after getting some supllies for my save a dive kit. I think im pretty prepared for anything that might happen during a dive next week . except for things I cant control like nuclear war, sar's, MadCowfish, 20ft Lost, Hungry, Menapausal, Hormonal Great White and a postal DandyDon etc.. So I was thinking how come i use up my air so fast?. I'm comfortable UW I dont excert myself but I still go thru air like there's no tomorrow. so i thought i know why! on practicly all my dives i fiddle around with my BC alot so everytime i hit the inflator button there's no telling how much air i'm losing thru that right there. so from now on i'm really going to pay attention to that. so if i want to tickle a fish's belly with some air its going to be out of my reg not my BC. I'm writing this not because I have a question so much, but for others that cant figure out why they go thru so much air also.


Mike

 

[DennisS]

Tickling the fish's belly with the long hose is DIR using the BC is not.

 

[Padipro]

Cold can affect air consumption in a big way. The body is trying to keep warm and that requires extra O2 which of course means that you'll be breathing harder to get the extra oxygen using up your gas supply. Make sure you have adequate thermal protection for the area you are diving in and stay warm before, during and inbetween dives.

This is only one of the things that can affect your gas consumption but it's a common one.

 

[DivesWithTurtles]

Cold can affect air consumption in a big way. The body is trying to keep warm and that requires extra O2 which of course means that you'll be breathing harder to get the extra oxygen using up your gas supply.

I know, of course, that the benefits of NITROX are based on the reduction of N2, not on the increased O2, and that the body only metabolizes about 6%-8% of the inhaled O2 per breath. But, I wonder if the increased availability of O2 has any effect in staying warm. If there were any relevant studies, I guess it would be common knowledge and a popular claim.

 

[bedazzle410]

The increase amount of O2 helps the bodie absorb O2 in that you do nto get as tired while breathing compressed air so it would seem that the larger percentage of O2 should help in other ares of a persons metabolism.

 

[DandyDon]

I know, of course, that the benefits of NITROX are based on the reduction of N2, not on the increased O2, and that the body only metabolizes about 6%-8% of the inhaled O2 per breath. But, I wonder if the increased availability of O2 has any effect in staying warm. If there were any relevant studies, I guess it would be common knowledge and a popular claim.

The few studies I've seen would say no way. And really, the BC is not the culprit here. While the BC does use some air, less than you'd think. The real factors are usually:
(1) Relaxation - which starts before gearing up; prayer & meditation help; and
(2) Learning how to breath slowly, without "skip breathing".

Rondales magazine has its own agenda - profitable business and all, but I think they do much to promote the sport and industry. This article covered efficient breathing...

http://www.scubadiving.com/article/0,7424,3-39-42-71-3-4X6-3,00.html

From that article in particular... (emphasis mine)

Exhale completely. This reduces the "dead air" volume and eliminates as much carbon dioxide as possible, thus delaying the urge to take another breath.

Pause after inhaling. Use your diaphragm to hold air in your lungs a few extra seconds while keeping your throat open. This allows even more time for gas exchange. Your breathing pattern should be: Exhale, inhale, pause. Exhale, inhale, pause.

Note: Every time we describe this breathing pattern, someone writes us, "Isn't this skip breathing?" It's not. Skip breathing involves holding your breath by closing your epiglottis (like when you grunt) and holding it for much longer. Closing your throat creates a closed air space that is vulnerable to embolism if you ascend. Keeping your throat open avoids that risk.

Besides, skip breathing doesn't work. Holding your breath too long means retaining too much carbon dioxide, triggering the urge to breathe sooner than necessary and resulting in rapid shallow breathing. The net result: You use more air by skip breathing, not less.

I pause a bit with full lungs, keeping my throat open, to get just a little more O2 / CO2 exchange in my lungs, and it helps. I would not suggest it to a newbie, but for someone who feel comfy in the dive - sure!

don

 

[RiverRat]

I'm comfortable UW I dont excert myself but I still go thru air like there's no tomorrow. so i thought i know why! on practicly all my dives i fiddle around with my BC alot so everytime i hit the inflator button there's no telling how much air i'm losing thru that right there.
Mike

You may be overweighted. I just came back from a trip with a new setup, BP/W I was diving. I started out heavy, 15# but that was way too much lead as I had a heavy backplate. Anyway, I logged all details of my dives, kept dropping 3#'s and got down to 3# on the belt. Remarkably, as the weight came off my SAC came up dramatically! I'm sure I was getting more relaxed as I got comfy with the gear but it was weight mostly that killed my air consumption. When I was heavy I had to keep pumping and dumping air, not too much, but enough to waste some to stay neutral. Noticed I was finning quite a bit when stationary, a sign of overweighting. Toward the middle of my trip when I was truly diving neutral I was using NO air in my wing (BC) and neutral throughout the water column. Once I hit that "sweet spot" the diving seemed so much more relaxing and enjoyable, exactly what I was looking for.
Trim is critical also, that's why I like a back inflate setup.

 

[GotAir]

Not to go without mentioning everyone else's great points also. that said let me breakdown my last dive. fresh water spring in Fl I had on the full 6.5mil farner john and booties 1 AL80 And I guessed at the weight i needed was 18lbs of lead and Skye let me use 2 soft weights of 2lbs each that i stuck in my BC pockets I'm 6" 2" 210lbs. my BC was a new dacor talan At vest. I was all over the place! as I went down to 40+ ft I started sinking like a rock. once i got down to the bottom at 54ft i got neutral no prob. then as i made my accent Here we go all over the place. just cruising at a depth of 35ft was a chore. I'm sure practise and time will cure a lot of this. But the weight thing is a very good point i never considered. i thought i could use as much lead as I wanted and make-up for it with my BC :bonk: Anybody what would be your recomended weight for this dive ?

The day I stop learning I'm a deadman anyway! Confusous Said :japanese:

 

[DandyDon]

Yep, I think RiverRat hit the main point here. 22# with a 6.5 mil F-John in Freshwater for a 210# guy sounds very overweighted. I'd think 16-18#.

Except, it can take more when one is new at some aspects. Was 18# not enough at first?? Were you maybe a little nervous at first?

What happens when you're over weighted like that is - you'll add more air to your BC to compensate for the weight - too much at times, then as you ascend, the air expands under reduced pressure - creating run-away bouyancy.

When you're over weighted, and carrying extra air in the BC, swimming will take more work to push your expanded profile through the fluid, burning more air. And if you start bouncing "all over the place," you'll breathe fast, buring air.

don

 

[RiverRat]

GotAir,
When I did my open water dives I was in freshwater, 7mmm full wetsuit, 7 mm hood, 5 mm gloves, 5mm booties and Jet Fins which are negative. I was in a Scubapro rental BC. AL tank. I was weighing in at the time around 228 or so. I needed 28# to sink (keep in mind OW dives, nervous etc.) I tried some dives at 26 but could not re-ascend with 1000 psi. My trim was way off. Head high, feet dragging. The problem was mostly trim and attitude in the water and I was probably overweighted to overcome poor technique, nervousness etc. I made the decision to get the weight off my belt, whether BP/W, Jacket with weight pockets, whatever. With the vest I was using there was probably some air bubble trapping, extra buoyancy from vest material etc. Like a see-saw, lots of weight on the belt weight, one end, lots of "hidden buoyancy" on the lung end, lungs, BC padding, air trapping etc. I was not able to hover, when I stopped forward motion, my feet would drop and I found myself finning alot. Another sign of overweighting. With the right BC and as much trim weight over the my back I would have done much better. With the right Jacket and trim weights, or BP/W setup, you should be able to move the weight "over the top of your lungs", where it balances out the buoyancy. If you find yourself constantly adding and releasing air in your BC you're probably not close enough to being neutral. When I got close I was able to exhale, sink at a controlled rate and stop anywhere in the water column. Inhale and rise, fin a little and ascend if I wanted all without ANY air in the BC. If you're truly neutral you should only need maybe a little air at most to compensate for suit compression etc. at depth and only need more air in the BC for emergency, flotation at surface etc.