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nrobinson
02-27-2008, 19:08
Okay everyone so I am new to diving as is my brother and father-in-law. Being a former college soccer athlete I seem to be able to control my breathing really well and make a tank last forever. Unfortunately my father-in-law who is 48 years old can use up an 80cubic foot tank 3000psi in about 12 minutes at 60feet. I have no idea what to tell him. Please help.

fisheater
02-27-2008, 20:01
Have HIM discuss this with HIS instructor.

rye_a
02-27-2008, 20:22
Have HIM discuss this with HIS instructor.
...it is either nerves, or a little cardio could go a long way.

DarinMartell
02-27-2008, 21:14
buy him a 120

cummings66
02-27-2008, 22:06
Larger tanks are not a solution. Here's why.

Suppose his first stage quits. Now he's on your tank at depth, you're both nervous and you are sucking air faster because of it, and he's much faster. Who's going to run out of air now? You already had a tank that wasn't full, he's lost his air.

See, you can not, should absolutely not, never ever give an air sucker a larger tank and assume all is well. It is not, in a failure he's back to sucking down your smaller tank and that is the fatal error people miss out on.

cummings66
02-27-2008, 22:13
Here's the real solution, first tell me how many dives he has? Is he a good swimmer, does he feel comfortable on top of the water? When he dives is his trim horizontal or is he trying to constantly fin up to stay level? IE if he quits moving his fins what happens to his body? Does he sink or turn head up, or feet up, or stay horizontal? What happens? If we don't know we need to know to solve the problem. What are his arms doing? Are they trying to swim?

All those things add up.

Here's why, good air consumption is a direct result of being comfortable in the water, and more directly being in good trim. If you struggle to stay at a certain depth you use more air, if you struggle to maintain control you use more air. If you're moving too fast you use more air, and if...

The key is this, he needs most likely to fix his trim and buoyancy, then he needs to get comfortable around the water. I'm going to guess he's not a swimmer and thus not that comfortable on top of the water, he's fighting it and that makes him use more air. One of the signs is using his arms to swim with, if he is have him hold his hands together so he can't swim with them. If he's moving fast make him slow down. If he's finning a lot make him stop and then teach him neutral buoyancy by adding or removing air and moving weights to get his trim back to horizontal. If he's nervous, well, he's probably best off going to the Y and swimming every day until he knows he's drown proof. You've got to own the water so to speak, you've got to KNOW in your gut that you are completely safe in the water, you've got to believe it with every fiber of your being. Being a good swimmer does that. Perhaps he's nervous under water, then in that case practice the basic emergency skills, flood and clear the mask and share air. Show him there is nothing to worry about because training can overcome issues.

There is no need to get his instructor involved, just watch his body language. Tell me, what is his body telling you?

Lastly, not to pick on people out of shape, but how would you rate him physically? Can he run a block? How about a 1/4 mile? If he could do 1/4 mile he should be sound enough to have an average SAC rate.

WaScubaDude
02-27-2008, 23:08
18 Ways To Use Less Air
(one of many great training articles on:
18 Ways To Use Less Air - Scuba Diving Magazine (http://www.scubadiving.com/training/basicskills/18_ways_to_use_less_air)
Use these secrets of the air-sippers to stretch your next tank.
July 2007
By Selene Yeager
Photograph by Joseph Byrd

Do you consistently run through your gas supply faster than other divers on the boat? Do you frequently have to end the dive before the rest of the group? What's going on? And what can you do about it?

First, you can stop beating yourself up over it. People are different. Those with slower metabolisms will--other factors being equal--use less oxygen. Small divers have to use less energy than big ones to swim forward, so they also use less oxygen. Nature doesn't distribute her gifts equally, and you may never be the stingiest sipper of gas on the boat.

On the other hand, most of us can reduce our gas consumption and thereby extend our dives. We can be better, even if we can't be the best. Typically, divers waste air in one or more of these three ways:
By leaking it before it gets to their lungs, thanks to free-flowing octos and worn out O-rings.

By using more energy than necessary. Using energy means using air, because oxygen is necessary to burn the calories that make energy. Every bit of unnecessary exertion costs you psi.

By getting less than maximum benefit from each breath. When divers breathe inefficiently, they exchange less oxygen for carbon dioxide with each breath, so they need to take another breath sooner.

Here are 18 tank-stretchers to try, starting with the obvious first step.

Fix the Small Leaks
Even a tiny stream of bubbles from an O-ring or an inflator swivel adds up over 40 minutes, and may be a sign of more serious trouble ahead anyway. You don't think you have leaks? Do you have eyes in the back of your head? Ask your buddy to look behind you to be sure. A mask that doesn't seal is another kind of leak in that you have to constantly blow air into it to clear out the water. It's also a source of stress, which needlessly elevates your breathing rate and thereby reduces your breathing efficiency. Does your octo free-flow easily? That can dump a lot of air quickly. Detune it or mount it carefully so the mouthpiece points downward.

Dive More
Inexperienced divers are famous for burning through their air supply at a furious rate. The reason is anxiety. A new diver is understandably nervous, and his body's automatic response to danger is to raise his metabolism, his heart rate and his breathing rate. It's hard-wired, the body revving its engine to be ready for fight or flight, though the result is a lot of air cycled through his lungs but never used, just dumped into the ocean.

You may not be a new diver, but unless you dive almost every week it's still an unnatural activity, and your body isn't as happy as you are about putting its head under water. Dive more--your body will get used to the idea, and you'll breathe less.

Take a Class
Any class, almost, will reduce your gas consumption just by making you feel more accomplished and therefore more comfortable. But the best bet is probably a class to improve your weighting and buoyancy control. When you get that dialed in, you can control your altitude mostly with your lungs, so you're not squirting that valuable gas into your BC and then venting it to the ocean. Most important, you can now forget (nearly) about the mechanics of diving, drift like a fish, and relax.
Sleep More, Party Less
Be well rested on dive day. Fatigue is stress. If you start the dive already tired, your body has to work harder to overcome the extra burden, so you breathe harder. A hangover is stress too. You may think you're sober in the morning, but in fact alcohol and other drugs affect your physiology the next day. As SSI instructor Jim Bruning puts it, "Your body does what your mind tells it to. If you had a good night of sleep, your body and mind are going to be much more relaxed, much calmer."

Be Early
If you're late to the boat, running to get your gear on board, worried about the hard looks of divers who were on time, stuck with the least-convenient gear station and generally playing catch-up all day, you're giving yourself unnecessary fatigue and mental stress. You start the day breathing hard and never have a chance to calm down. On the other hand, if you're early to the boat, early to gear up and early to the dive briefing, you'll conserve your energy, feel confident and relaxed, and your breathing will remain slower.

Swim Slowly
The energy cost of speed is even more than you might think because it's an exponential function proportional to the square of the speed. So swimming twice as fast requires four times as much energy and air. But the reverse is true, too: Swim half as fast as you do now, and you'll use only one-fourth as much air.

Stay Shallow
It's physics again. Because your regulator has to deliver air at the same pressure as the water, a lungful at 33 feet (two atmospheres) takes twice as much out of your tank as does the same breath at the surface. At 99 feet (four atmospheres) it takes twice as much as at 33 feet.

There's absolutely nothing you can do about that except to avoid being deeper than you have to be. If you're making a transit over an uninteresting sand flat to get to the edge of the drop-off, do it at 15 feet instead of at 40 feet, and you'll save air.

Minimize the Lead
If you're overweighted, you have to put more air into your BC to float it and be neutral. The inflated BC is larger and requires more energy and oxygen to push it through the water.

An extra eight pounds of lead means your BC is one gallon bigger when inflated enough to make you neutral. Imagine the extra effort of having to push a gallon-sized water jug through the water.

Adjust Your Trim
If your body is horizontal in the water, when you swim forward, your legs and fins will pass through the "hole" in the water made by your head and shoulders. You'll disturb less water and expend less energy and air.

Many divers, however, swim with their feet lower than their torso and their head higher. Adjust your trim by moving some lead from your hips to your back--to trim pockets on your BC or to your tank.

Seek Neutral Buoyancy
Always being exactly neutral is the key. If you're not, if you're slightly heavy or light, you're constantly using fin power (and air) to maintain a constant depth. If you're not neutral, you can't glide between fin strokes and you can't hang effortlessly.

Streamline Your Gear
All fast-swimming fish have smooth skins with few or no protuberances. That minimizes drag so they can swim with the least energy and oxygen consumption. Divers, by contrast, have rough, convoluted surfaces with all sorts of attachments from scuba tanks to whistles. Anything disturbing the flow of water past your body creates drag and wastes air.

Do your best to imitate the fish. If you don't need a light on this dive, for example, don't take it. If you do need something, try to hide it in a pocket instead of dangling it from a D-ring. Take the snorkel off your mask and strap it to your leg or tuck it under your BC or get a folding snorkel that fits into a pocket. Shorten hoses that are too long. Clip your console close to your body. Suit your gear to conditions: You don't need the bulk of a BC with 40 pounds of lift in the tropics.

Streamline Your Movements
Keep your arms close to your body. Straighten your legs and keep them as close together as your fins will allow. Kick with short strokes so your fins stay within the slipstream of your body. Some fins do require a wider stroke so you have to compromise between efficient propulsion and streamlining. But usually you're better off finning faster instead of wider.

Breathe Deeply
Any oxygen taken from your tank but not absorbed into your bloodstream is wasted. That's the case when you take short, shallow breaths. A large part of the air you take in fills your throat and bronchia, but doesn't reach your lungs before it is expelled again. You have to take another shallow breath sooner because you didn't get much benefit from the first one, and a lot of air is wasted.

Instead, try to inhale deeply, filling your lungs completely with each breath. A deeper breath brings air to more of your lungs' tiny "air sacs" (the alveoli) where gas exchange takes place. It also adds more fresh air to the volume of "dead air" that remains in your lungs, throat and mouth from the previous breath, so the mix is richer. When more alveoli are more fully inflated with fresher air, gas exchange is more efficient: More oxygen is extracted from the incoming air and more carbon dioxide is released. Although each breath uses more air, you will take fewer breaths, and the net effect will be that less air is used. Short, shallow breaths are more frequent and less efficient.

Exhale fully too, so you expel as much carbon dioxide as possible. Anything not exhaled is carbon-dioxide-heavy "dead" air. On your next inhale, that dead air--instead of fresh air--partially fills your lungs. The urge to take the next breath is triggered not by lack of oxygen but by excess of carbon dioxide, so you find yourself inhaling again sooner. On the other hand, a deep exhale extends the time before you feel the need for another breath.

Breathe Slowly
You consume considerable energy just by breathing, by sucking the air in and pushing it out again. To inhale, you have to suck open a demand valve in your second stage and pull gas down your throat and into your lungs. Each inch along the way and each corner the gas stream turns mean friction and turbulence. Both increase the effort you put out in just breathing and decrease the amount of gas that actually gets to your lungs. Friction and turbulence are unavoidable, but the amount goes up dramatically when you try to breathe quickly--just as a faster-moving boat creates a bigger wake. The problem gets worse as you go deeper because the gas is thicker--it's like trying to suck a milkshake instead of water through a straw.

So don't force it. Try for a long, slow inhale until your lungs are full, then a long, slow exhale until they are empty. More air will get to your lungs, it will spend more time there exchanging "good" for "bad," and you will use less energy pushing the air back and forth.

Upgrade Your Gear
Overhaul your regulator on schedule and consider one with lower work of breathing, especially if you often dive deep. ScubaLab tests have shown that the work of breathing demanded by some regs can be three times as much as others, even more. A "hard-breathing" reg not only demands more energy and therefore oxygen just to operate it, your difficulty breathing through it increases your anxiety level and elevates your breathing rate. So it wastes gas two ways.

Get in Shape
Two people climb a flight of stairs. At the top, one is huffing and puffing and the other is breathing normally. The heavy breather is getting more oxygen, but he's wasting a lot of what he inhales because he's breathing so rapidly there isn't much time for gas exchange. It's an adaptation that makes sense only on land where the air supply is unlimited.

Diving can be surprisingly strenuous because water is so much denser than air. Swimming into a current, it's not difficult to elevate your breathing to the very wasteful rate of huffing and puffing. But even much lower levels of exertion will cause your breathing rate to rise. How much it rises and how soon depend mostly on your aerobic conditioning. A diver in better condition will have less increase when the workload goes up, so he will use less air. The other part of getting in shape is to lose fat and achieve a more streamlined shape.

Stay Warm
Even warm water is cold when you're immersed in it, because if it's cooler than about 95 degrees, it takes heat out of your body at a surprising rate. Heat is energy that has to be replaced by metabolism, using oxygen to make it. Getting cold also creates mental stress which, often without your noticing it, increases your breathing rate.

And Just Chill Out
The competition over who uses less air can itself be a problem when divers associate low gas consumption with diving skill, virtue and the right to take up space on the boat. It's one of those self-fulfilling prophecies: You worry about using more air than your buddy, which causes stress, which elevates your breathing so you do, in fact, use more air.

In fact, a higher rate of air consumption can be caused by many things, some of them fixable and some not. In itself it means little or nothing and is nobody's business but yours and arguably your buddy's--who, we hope, is not out to ruin your day. So if you'd like to reduce your gas consumption, work gradually on reducing your lead, controlling your buoyancy, improving your shape and posture in the water, going slowly, breathing slowly and relaxing. Then forget about it. That alone will help.

Kingpatzer
02-28-2008, 06:47
Larger tanks are not a solution. Here's why.

Suppose his first stage quits. Now he's on your tank at depth, you're both nervous and you are sucking air faster because of it, and he's much faster. Who's going to run out of air now? You already had a tank that wasn't full, he's lost his air.


Wrong answer here. That only happens if you fail to plan your dive. If you've planned your dive, and actually have an idea of what your rock bottom air is, then when it is time to go, it's time to go.

Larger tanks can be part of the solution.

The other thing is that if he is a newer diver, he'll get better with practice.

Since you're a soccer guy, you probably have pretty good leg muscles, are you swimming off at 30 knots while he's trying to keep up or are you lazily swimming slowly through the water? If he's trying to keep up with you, you might be part of the problem as well.

cummings66
02-28-2008, 07:30
Wrong answer here. That only happens if you fail to plan your dive. If you've planned your dive, and actually have an idea of what your rock bottom air is, then when it is time to go, it's time to go.


Nope, partially wrong but I'll qualify my answer. If we use rock bottom it does not solve this guys problem who reported it. He wants longer dive times and that's why he's trying to fix the problem with his buddy.

If you use rock bottom which is a depreciated term now, you must plan on the cf needed, which I do by the way for my diving. So even if he's got the 120 he still has to plan the dive but will discover that he's still limited by the AL80 because he's using air out of it as he dives, that still gives us maybe a little more than 12 minutes of dive time but not much more, not what the guy wanted I think. To be honest it'd probably give us less than 12 minutes if we're being honest about rock bottom because I'm certain that they have not been diving with a large reserve of air, most likely coming back up with 500 psi. If that dive time was based on his sucking his tank empty and not carrying a reserve for his buddy he'd be lucky to get 10 minutes if we use rock bottom, irregardless of his having a larger tank.

A large tank only fixes the problem for the diver, it does little for rock bottom calculations because to an extent we're still limited by the smallest tank in the group. A large tank can not fix this problem but identifying the trouble can.

For those that don't get rock bottom, in simple terms it's the amount of gas needed to get you and your buddy to the surface in the event of an emergency, plus do it safely which might mean doing the safety stop. It's an amount of gas that you never use because it belongs to somebody else. For example, you may turn a dive at 100 feet with 1400 psi of air in the tank because that's how much you have decided you need to get both of you breathing off the tank to the surface. It doesn't mean you need to hit the surface with 1200 psi because the rock bottom figure changes as your depth decreases. Using rock bottom is a good idea and an excellent example of planning a dive.

It's figured by how much your air consumption is and your buddies added together (and if we're using different size tanks cf is the easiest way to do that) so it's the SAC rate times the ATA times the time spent at depth of about a minute to try and fix said problem, then the average ATA back to the surface multiplied by the time it takes to return to the SS times the SAC rate of both of you added up, plus the ATA of the SS multiplied by the time multiplied by the SAC rate for the two of you.

That tells you how many cf of air you need, then you figure turn pressures by a tank conversion factor for each tank. This is why the larger tank won't solve the problem, one guy still has the AL80, the turn is based on the guy who has the smallest tank volume no matter how you slice it because keep in mind he's breathing down that tank the entire dive. You might get a bit longer dive times but you've got to keep in mind that rock bottom means there is so many cf of air left in EACH tank, enough to get both people back to the surface. So, the small tank still controls the dive, even if it's on the buddy. You will gain a small amount of time but not enough to do a 30 minute dive. So IMO the larger tank is not the answer, fixing his issue is and we do not know at this point if this is just an old out of shape broken down old man who simply will never have a good SAC rate. It could also be a new diver, we don't know if improvement is possible without more data.

skdvr
02-28-2008, 08:47
For those that don't get rock bottom, in simple terms it's the amount of gas needed to get you and your buddy to the surface in the event of an emergency, plus do it safely which might mean doing the safety stop. It's an amount of gas that you never use because it belongs to somebody else. For example, you may turn a dive at 100 feet with 1400 psi of air in the tank because that's how much you have decided you need to get both of you breathing off the tank to the surface. It doesn't mean you need to hit the surface with 1200 psi because the rock bottom figure changes as your depth decreases. Using rock bottom is a good idea and an excellent example of planning a dive.

It's figured by how much your air consumption is and your buddies added together (and if we're using different size tanks cf is the easiest way to do that) so it's the SAC rate times the ATA times the time spent at depth of about a minute to try and fix said problem, then the average ATA back to the surface multiplied by the time it takes to return to the SS times the SAC rate of both of you added up, plus the ATA of the SS multiplied by the time multiplied by the SAC rate for the two of you.

That tells you how many cf of air you need, then you figure turn pressures by a tank conversion factor for each tank. This is why the larger tank won't solve the problem, one guy still has the AL80, the turn is based on the guy who has the smallest tank volume no matter how you slice it because keep in mind he's breathing down that tank the entire dive. You might get a bit longer dive times but you've got to keep in mind that rock bottom means there is so many cf of air left in EACH tank, enough to get both people back to the surface. So, the small tank still controls the dive, even if it's on the buddy. You will gain a small amount of time but not enough to do a 30 minute dive. So IMO the larger tank is not the answer, fixing his issue is and we do not know at this point if this is just an old out of shape broken down old man who simply will never have a good SAC rate. It could also be a new diver, we don't know if improvement is possible without more data.

WOW, thanks for the explanation. I really need to get better about keeping track of my SAC and planning my dives like this. I guess I need to get my normal buddies to do the same. He is the one who usually goes through air pretty fast. So I guess the worry would be if I had a problem and to make sure that he has enough air for the two of us. It helps that both of us are now using 40cf pony's.

Thanks again for all that info...

Phil

caroln
02-28-2008, 10:05
WOW, thanks for the explanation. I really need to get better about keeping track of my SAC and planning my dives like this.



I agree---great info--thank you again

For the heavy breathing buddy---one thing that I found kinda helpful was something I learned in my underwater photo class. Everyone always hears 'slow down your breathing, take your time' etc, but as a new diver, what does that exactly mean? In our photo class, our instructor told us to practice on the surface--while driving to work, or whatever, taking regular inhales, but stretching out the exhales to last a count of 8. That was pretty helpful in learning what 'slow down' meant, and after a while of doing it everyday on the surface, I didn't even have to think about it while diving.

Of course with more practice diving, I learned plenty of other ways of managing my breathing, but that was really useful early on because it gave me something concrete to do.

cmburch
02-28-2008, 10:18
Thanks for the info - I am printing it out for myself.
I suck a lot of air compared to my buddies, but I have a larger tank to compensate. The original poster though - 12 min at 60 feet sounds like some major problem that a professional should look into.

cummings66
02-28-2008, 12:23
If you do the math he comes close to a SAC of 1.7. Here's my guess work and keep in mind it's based on a lot of assumptions which the OP hasn't yet answered. 1.7 while worse than average is something I've seen in new divers, I dive with them a lot so I have seen it. He could easily drop that down to a 1 if he's doing what I think he is.

60' is 2.8 ATA ((60/33)+1). Assume a rapid drop to 60 feet and a SAC of 1.7 cf per minute at the surface, that gives us a consumption rate of 4.76 cf per minute at depth (1.7*2.8). Multiply that times 12 minutes ((1.7*2.8)*12) and that tells us he used 57.12 cf of gas at depth, leaving 20 cf. From 60 feet to 20 feet (60-20=40) )(close enough to 30 fpm ascent) would take you about 30 seconds, and you'd use about 1.6 cf doing it (60/2) gives us average depth of 30 feet who's ATA is 1.9, so (1.9*1.7)/2 because it's 30 seconds in happening. That now gives us 18.4 cf of air left. 3 minutes at 20 feet gives us 8.19 cf of air, leaving us with 10.21 cf of air, or a SPG reading of ~400 psi. Tank conversion factor for the AL80 is .0258.

I could even stretch it and say that he has a 1.6 based on how long it would take him to descend, he's got to use around 1 to 1.5 cf during the descent so he might have a slightly lower SAC and 1.6 could be argued for as well. You guys can refigure it if you want to, I've got to get back to work and don't have time to muck with the figures, but I would say that on this guy I'd plan on a consumption rate of 4 for rock bottom figures.

In a dive plan I do count the gas to depth. Here I would say he's got about 1.5 cf of gas consumed by the time he gets to 60 feet or about 59 psi drop on the SPG.

Using rock bottom at 4 for the combined SAC rate that means you must return with 23 cf of air in your tanks as a reserve just in case. That's 900 psi for the AL80 and about 700 psi for the HP120. That means both tanks would be empty when you hit the surface if you had to share air. I'd personally add 300 psi to the figures so the tank wouldn't be empty and gives a margin for error. So that's 1200 psi in the AL80 and 1000 psi in the HP120.

That's a lot of air, huh? But, you don't need to surface with it because the values change at 30 feet, I work up a dive plan based on the ascent and know what pressures I need at various depths. We'll play until we hit that and then up some more.

Kingpatzer
02-28-2008, 12:41
Wrong answer here. That only happens if you fail to plan your dive. If you've planned your dive, and actually have an idea of what your rock bottom air is, then when it is time to go, it's time to go.


Nope, partially wrong but I'll qualify my answer. If we use rock bottom it does not solve this guys problem who reported it. He wants longer dive times and that's why he's trying to fix the problem with his buddy.

It addresses part of the problem but does not solve it, I agree.

I don't fully agree that rock bottom is determined by the guy with the smallest tank. Rock bottom is computed for each member of the team if you're diving different gear. So if I'm in a 120 and you're in an 80 and we both have the same SAC rate, you'll be calling the dive most of the time because you'll hit rock bottom before I do, so we'll plan on that.

But if I have twice the SAC rate that you do, and I'm in a 120 and you're in an 80, I'll be the one to hit rock bottom first.

This is where I think it is part of the solution. But only part. I actually see two issues here.

First problem: big breather doesn't have rock bottom pressure and is calling the dive on a basically empty tank, so he should be either turning the dive sooner or getting a bigger tank just to keep up.

Second problem, down time, and this is a little bit trickier. If the big breather gets a bigger tank, maybe (and you have to do the math to see if it works in each case -- it will vary by the specifics of each dive) you can squeeze a few more minutes of dive time. It would work like this.

Suppose, for sake of argument, that rock bottom for both of you comes out to 20 cf. For an 80 that would be a little less than about 800 psi. So you have to conduct the dive on 2200 psi of the 80.

Now if our deep breather burns through the remaining 2200 psi at twic the rate of the shallow breather, say 10 minute and 20 minutes repectively, then the dive is over in 10 minutes if they are both diving 80s.

However, let's give our deep breather a 120. Now, the rock bottom doesn't change. For our hypothetical dive it is still 20 cf and that is 800 psi on an 80. But on a 120 at 3300 psi, it is 560 psi. So now, our deep breather has more gas and a lower rock bottom on his tank.

Assuming the same rate of breathing, he'll squeeze out a few more minutes of bottom time.

cummings66
02-28-2008, 12:49
Your 20 cf was pretty close, I guessed at 23 cf for rock bottom per my post. You can see it's not going to extend the dive that much though and to be honest, if you skip rock bottom all together and just go by empty tanks it's not much. Say he's got 40 cf more gas (to make math easier) that means his 12 minute dive is now 18 minutes. That's 6 minutes more and he's got to carry a tank that weighs 20 lbs more for it.

Frankly, 6 extra minutes sucks.

Hopefully my prior post about the cf of air needed addressed your concerns about what I was saying about the smaller tank being a deciding factor. What I was getting at is that the 120 only gives a few more minutes time, is it enough to worry about spending $400 for 6 minutes or are we going to address the real issue here and not just stick a bandaid on it.

Kingpatzer
02-28-2008, 12:53
Your 20 cf was pretty close, I guessed at 23 cf for rock bottom per my post. You can see it's not going to extend the dive that much though and to be honest, if you skip rock bottom all together and just go by empty tanks it's not much. Say he's got 40 cf more gas (to make math easier) that means his 12 minute dive is now 18 minutes. That's 6 minutes more and he's got to carry a tank that weighs 20 lbs more for it.

Frankly, 6 extra minutes sucks.

Yeah, I agree there's something else going on here with his sac rate. My guess is basic experience and trim.

I also agree that a bigger tank isn't a great, or whole solution! I don't think we're really disagreeing. We both agree that the dive can be extended by a larger tank, and we both agree that it won't extend it by much.

They could always go with surface supply :)

cummings66
02-28-2008, 13:19
There is one advantage to a poor rate like that. I've got a buddy very similar and I get 4 dives per his one, so I don't need to bring 8 tanks to do a dive, 2 will suffice for 8 dives with him.

You're right in that we're not really disagreeing, and it's funny but I never thought I'd get into this kind of discussion in the Fitness area.

rfb3
02-28-2008, 13:21
buy him a 120

:smiley36:

doczerothree
02-28-2008, 13:56
Tell us something about him eg. lifestyle, is he active? what kind of work does he do? If he sits at a desk all day or is he physically active at work. Is scuba his only activity? or does he go to the gym "sometimes". It may be that he is only reacting to his new water enviorment and he will get better "gas" usage as he become more comfortable. Keep him diving. His comsumption is not the worst i've seen. Remember: always check your gauges!!!!

nrobinson
03-01-2008, 20:52
Here's the real solution, first tell me how many dives he has? Is he a good swimmer, does he feel comfortable on top of the water? When he dives is his trim horizontal or is he trying to constantly fin up to stay level? IE if he quits moving his fins what happens to his body? Does he sink or turn head up, or feet up, or stay horizontal? What happens? If we don't know we need to know to solve the problem. What are his arms doing? Are they trying to swim?

All those things add up.

Here's why, good air consumption is a direct result of being comfortable in the water, and more directly being in good trim. If you struggle to stay at a certain depth you use more air, if you struggle to maintain control you use more air. If you're moving too fast you use more air, and if...

The key is this, he needs most likely to fix his trim and buoyancy, then he needs to get comfortable around the water. I'm going to guess he's not a swimmer and thus not that comfortable on top of the water, he's fighting it and that makes him use more air. One of the signs is using his arms to swim with, if he is have him hold his hands together so he can't swim with them. If he's moving fast make him slow down. If he's finning a lot make him stop and then teach him neutral buoyancy by adding or removing air and moving weights to get his trim back to horizontal. If he's nervous, well, he's probably best off going to the Y and swimming every day until he knows he's drown proof. You've got to own the water so to speak, you've got to KNOW in your gut that you are completely safe in the water, you've got to believe it with every fiber of your being. Being a good swimmer does that. Perhaps he's nervous under water, then in that case practice the basic emergency skills, flood and clear the mask and share air. Show him there is nothing to worry about because training can overcome issues.

There is no need to get his instructor involved, just watch his body language. Tell me, what is his body telling you?

Lastly, not to pick on people out of shape, but how would you rate him physically? Can he run a block? How about a 1/4 mile? If he could do 1/4 mile he should be sound enough to have an average SAC rate.

The big thing is that he isnt comfortable in the water. Yes he can tread and swim a little ways but that is about it. His trim is suprisingly good so I don't think that is the issue. I talked to him and he said he has been taking big deep breathes and trying to let them out slowly whats everyones outlook on that type of breathing? Any other ideas?

newways
03-01-2008, 21:14
A wealth of great info in this thread. thank you.

cummings66
03-02-2008, 11:24
A diver should always try to breathe fully, what he's doing doesn't sound out of line. In fact divers that breathe deeply often have lower air consumption.

If he can only swim a bit I'll bet he's just very nervous under water and that's the big issue for him. Does he have many dives?

nrobinson
03-04-2008, 09:28
Okay so I am getting some really good information out of this, but what really is getting me is that he is in pretty decent shape he is a construction superintendent and runs up and down flights of stairs all day. This said his eating habits could use some help. I personally think the issue lies in the way he is breathing any advie there?

rfb3
03-04-2008, 09:34
Good health, staying calm and MORE DIVE EXPERIENCE will be all that is needed.... The dive experience is key. A healthy person without experience will not be calm and will therefore breath more heavily.

Just keep getting wet! :)

cummings66
03-04-2008, 12:05
The way you described his breathing is fine, there is nothing wrong with how he's doing it. How FAST is he breathing ie how many cycles per minute and how large is his lung volume?

To be honest those questions are not really that important, I think it's not how he's breathing so much as how nervous he is.

How many dives does he have? Does he dive often?

cummings66
03-04-2008, 12:11
I would hasten to add, one breathing style some people think they should use to decrease their SAC rate is very dangerous, and that is to inhale, hold the breath and then exhale.

The best way to do it is breathe deeply and exhale slowly, try to avoid shallow breaths as that will give you headaches and might make you pass out under water.

Rockhound76
03-04-2008, 20:25
I'm a big guy and have a good sac rate, but one of my long term buddy's has a terrible rate. He has logged hundreds of dives all over the world, but he just happens to be an air hog.

He's not a perfect physical specimen (hey, that looks funny spelled out), but he's not a slouch either; he's just old like me. Some folks, I'm afraid, are natural "breathers".

He dives with a 120 to my 80 and it does help on certain dives.

mm2002
03-15-2008, 14:18
To be honest those questions are not really that important, I think it's not how he's breathing so much as how nervous he is.

How many dives does he have? Does he dive often?


In my opinion, how many dives, and how often, are probably the best questions here. I don't know about most new divers, but my air consumption decreased tremendously over the first 10 or so dives. Being relaxed, confident, and comfortable under water is what it's all about. After that, work on the other factors such as trim, etc.

mitsuguy
03-15-2008, 20:01
reading the op's posts tells me that this person is not a natural water person... even though I'm not in the greatest shape of my life, I have pretty darn good air consumption compared to others my size (6', 200 lbs) I attribute the majority of this to the fact I'm naturally comfortable in the water... I move around efficiently, and probably have a lower heart rate and breathing rate lightly swimming under water than I do walking around on solid ground... if he does nothing other than get in a pool and swim around, his breathing rates will increase - as he becomes more comfortable in the water...

RoyN
03-16-2008, 20:09
I can't really offer any breathing tip, but the only one I could offer is just relax, enjoy the water, and have fun. :)

Thats what I did and my sac rate decreased to the point where I could stay longer since I'm diving nitrox.

USF_Diver
04-21-2008, 18:26
I would guess he hasn't had many dives.

Alot of great info in this thread.

Panchita
04-24-2008, 11:49
but I figure my two cents might as well be spent here! I was very good on air consumptions from certification, and after some quizzing from the dive crew we narrowed it down to the fact that I've done a little yoga and take what they called 'complete' breaths. You don't have to indulge in any heavy-duty meditation or pretzel-like contortions to learn this method - just get yourself a good beginner tape (I use yoga zone), do what you can and pay attention. Not only does it feel good to regain flexibility and build strength, it really does help your air consuption.

cummings66
04-24-2008, 12:10
I have never heard of complete breaths, describe how you do them if you would please. In other words, what are they?

cummings66
04-24-2008, 12:18
I found a link.

How To Do The Complete Breath In Yoga | eHow.com (http://www.ehow.com/how_2054390_do-complete-breath-yoga.html)

That is a fancy name for Skip breathing. From a page on that.

Skip Breathing is a controversial technique to conserve breathing gas (http://en.wikipedia.org/wiki/Breathing_gas) when using open-circuit (http://en.wikipedia.org/wiki/Open-circuit) scuba, which consists of briefly holding one's breath between inhalation and exhalation (i.e. "skipping" a breath). It leads to CO2 not being exhaled efficiently. There is also an increased risk of burst lung from holding the breath while ascending.

To others reading it, be careful if you choose to do this.

Panchita
04-24-2008, 12:27
put your hands around your lower ribcage, thumbs around the back. Inhale slowly and feel the ribcage rise as you do so. When your ribs stop rising, slowly inhale and feel your stomach pull in. Complete each breath before rushing into the next. Try to keep shoulders down and breastbone up as you breath. When you breath through your nose, you should hear a little echo-y sound, but that's not going to happen with a regulator for obvious reasons... Doing this with yoga exercises helps make it more habit and you don't have to think about it so much.

Edit: Okay, I just read the above link - funny how it says to raise your shoulders. Not the way I learned, but whatever floats the boat... :) For the record, I never skip or hold - just steady, slow in-and-out.