Breathing rate and volume

[Sludge]

I've been told Edd Sorenson's SAC rate is lower than mine, and he outweighs me by probably sixty pounds.

[GeorgiaDoc]

Your SAC rate is of course determined by the volume of gas inspired per breath and the number of breaths per min. Your lung volume is fairly static. You can change the amount of each breath to an extent but each of us has a comfortable volume of each breath we take while diving.
People who have smaller lung volumes are females, shorter people, smokers, non-athletes, and people who live at low altitudes. It takes and extended period of time to change your lung volumes to any extent.
This leaves just your rate per min that you can appreciably change to change your SAC rate. If you fill your lungs to your comfort level each breath, and your lung size is static you can only change the rate you breath.
Several factors affect your drive to breath but the most powerful is CO2 levels. As CO2 rises from a normal of about 40mmHg to 50mmHg the drive to breath takes over and you WILL breath. You can change this set point over time by exposing the chemoreceptors to increasing amounts of CO2. This takes prolonged regular exposure to increasing CO2. It probably doesn't matter if you do this by breath holding or using a paper sack. If you practice breath holding by first hyperventilating you are most likely defeating the purpose.

[cavediver256]

does anybody remember a guy named Rob who used to work at Cave Excursions? He was a good sized man and his SAC rate was unbelievable!

Hehe as big as that boy was, he breathed like a girl !!!!!

[jeandiver]

oooh, a breathe-off! i wanna be the chick with the scarf at the start!

ROFL !!!!!

[TommyB]

TJ hates it that I smoke.. Tried to quit a couple times, etc, etc. Same 'ole story --
Bad Habits are hard to break.

5'9" , 158 lbs, SAC = 0.567 - 0.498 on most dives.

Now, if I could just give up that habit, prolly could stay under for days on end

[bullfrog]

A thought no one else has mentioned is dead space. Each breath you take ( average for 150 lb.male) has about 150 cc of dead space because of the volume of your trachea and oral phaarynx. this is wasted as far as respiration (gas exchange) is concerned. It stands to reason that slow deep breaths would be more efficient. 5 400 cc breaths would waste (5x150=750 cc) as opposed to 10 200 cc breaths (10x150=1500 cc) being relaxed would allow this. 400 ccs is not a deep breath I just used the easy numbers to visulize.

[tomhauburn]

TJ hates it that I smoke.. Tried to quit a couple times, etc, etc. Same 'ole story --
Bad Habits are hard to break.

5'9" , 158 lbs, SAC = 0.567 - 0.498 on most dives.

Now, if I could just give up that habit, prolly could stay under for days on end

Tommy
I know a few divers that gave up smoking or at least gave up for awhile and all of them told me their sac rates went up. Seems like it would be the other way or maybe they were just having a fit because they needed a smoke to calm them down? Who knows ? Folks please do not think I endorse smoking as I do not but that just what I have heard.