2nd Percentile SAC Rate

[joebob24]

then why the heck do you care about your sac?

If you read the original post, I am asking about medical conditions that could cause high sac rates based on the assumption that my sac rate was higher than 98% of divers. The question is out of curiosity of why it is so high, not about trying to lower it. I have already accepted that I will never be able to carry enough air to keep up with my buddy diving hp100s sidemount with a sac of 0.5 if someday we decide to advance into tec diving.

Are there any medical conditions that could cause this?

The original question still hasn't been answered, but I think my assumption that I was something special might have been wrong.

 

[Beau Holden]

I'm not a doctor, but this a gauge you can use to evaluate your condition first. This is what I did.

Can you walk up at least 3 flights of stairs without being out of breath?
Should be able to answer Yes.
Can you walk at a brisk pace and still have a conversation after a 1/2 mile?
Should be able to answer Yes.
When you get your heart rate up to 75% max, how long does to take to drop 20bpm while resting?
Should be between 1 and 2 minutes
Are you shallow breathing or deep breathing with diaphragm when diving?
No shallow breathing. Exhale all the way out.

If you answer the affirmative to these, then get more dives in. At 25 to 49 dives most likely you just have not got things dialed in yet. Drop all the weight you can from gear. Learn how to trim out. Learn how to frog kick. Slow down. Forget about your SAC rate for now and just enjoy the dives. It will come.

Also being cold will make you breath more. Cold water can suck it out of you.

 

[hammet]

Try using an air integrated dive computer that displays your SAC rate. Here’s how I find it helpful….

I know from experience my rmv is typically between 0.4 to 0.5 cf per min for warm water drift dives. I know I can get a full hour dive at about 65ft with an hp100 if I keep my breathing in that range so I monitor my SAC rate on my teric constantly. (Note you have convert your target rmv to sac for the size tank you are using…. For an hp100 the sac rate works out to be about 17psi/min and for an al80 about 19psi/min for an rmv of .5)

If you find the sac is higher than your target number you can zen out by slowing your breathing and movement. It has become a habit to glance at my wrist after every time I exert myself like finning against the current, grabbing a lobster, catching up w buddy, etc.

 

[Blackcrusader]

I have had pretty consistent SAC rate of 1.2 cu ft/min over my first 25 dives or so. Occasionally it is as high as 1.6 if I am crabbing. I am relatively active and 6'1", 230lb. According to the thread on Average Gas Consumption, only 2% of people have a SAC rate above 1. Are there any medical conditions that could cause this? I checked my weighting and trim, tried jogging for a few months and tried to just relax under water and nothing seems to really change it much. Starting to wonder if my lungs just don't work like they should.

Hi Joebob, I am 6'1" and weigh near 300 pounds. Large fat 62 year old dude. Generally active taking mountain walks with my dog in the mornings. I last dived in June last year. I am off to Bali for 3 weeks next week then off to Bohol Cebu 2nd half of October thru 1st week of November.

Now I have posted in the average sac rate thread and yes I am quite good on air but use diving and breathing techniques. I have been diving since 1986 and before covid hit for the previous decade I was doing around 200 - 250 dives a year on diving vacations. I will often do 12 days straight diving with 3 - 4 dives a day. By the end of these vacations I am so zoned in I get people tugging on my fins thinking unresponsive diver cause I move like a corpse. When I was new to diving I certainly used far more air than my dive buddies.

Perhaps go back to a single 100 tank and just try to do dives where you really do not move around, let the water currents carry you.
In Bali we will be doing some fast drift dives... In this video you see lots of divers flailing around except the diver at the back barely moving his fins. He is the one in control and perhaps using less gas.
I think your lungs work just fine. It's diving techniques that you need to learn to reduce gas consumption.

I get lots of people who have never dived with me thinking this fat guy will be done in 20 minutes.

 

[arew+4]

If you read the original post, I am asking about medical conditions that could cause high sac rates based on the assumption that my sac rate was higher than 98% of divers. The question is out of curiosity of why it is so high, not about trying to lower it. I have already accepted that I will never be able to carry enough air to keep up with my buddy diving hp100s sidemount with a sac of 0.5 if someday we decide to advance into tec diving.

The original question still hasn't been answered, but I think my assumption that I was something special might have been wrong.

I would not be worrying about a medical condition, it's most likely inexperience and large lung volume. I'm 5'11" currently 240, typically run around .65 at the start of a vacation and end up around .55 I've gotten under .5 once or twice on a drift dive with no camera. Back when I started diving I was lighter with the same lung volume and probably averaged about 1.2. both of my son's started out in the 1 to 1.2 and are now usually in the .75 to.85 range as they close in on 100 dives. Getting comfortable and limiting extra effort is the key to longer dives.

 

[joebob24]

Drop all the weight you can from gear

I think I am pretty well weighted. I don't carry any lead, just a steel backplate, HP100 doubles and all the manifolds are plenty. I could probably get away with an aluminum backplate, but I would be pretty light if I ever ran the tanks all the way down.

Try using an air integrated dive computer that displays your SAC rate. Here’s how I find it helpful…

I would like to try one sometime. I always wonder if there are certain parts of the dive that I have higher consumption, or if it is just continuous. I usually dive from shore with at least a bit of a surface swim and we usually drop down past 100' for the deepest part of the dive within the first few minutes. If my consumption is still high from the exertion of the surface swim, I could still be using a lot of air at that depth.

do dives where you really do not move around, let the water currents carry you

I do tend to do dives where I do quite a bit of moving around. I might try that sometime just to see how big of a difference it makes. I have heard of a few good drift dives here, but I don't know if I am experienced enough for them yet.

then why the heck do you care about your sac?

The cost of fills was also really starting to add up.

 

[boulderjohn]

I don't carry any lead, just a steel backplate, HP100 doubles and all the manifolds are plenty.

OK, so we are talking steel doubles. Are you using a drysuit, too?

Put me in doubles and a drysuit and my SAC rate will be far higher than with a single tank and light wetsuit. That chart you reference is pretty much filled out with input from divers in single tanks and wetsuits.

 

[joebob24]

I am in a 6mm wetsuit right now. The last 10-15 dives have been with doubles, but before that was all single tank. It might be interesting to switch back for a few dives to see if there is a big difference. I could see a scenario where it would have gone down more over time if I hadn't switched to doubles. My single tank setup is a jacket style though.

 

[johndiver999]

Cool video, Doesn't look like fun to me. DM has no inflator hose it looks like. huh?

 

[formernuke]

I was just diving double hp100's. Steel plate, bands and manifolds in a drysuit with a 40 deco bottle, was overweighted in my drysuit.

I'm going to agree with everyone else. Your still new to diving as you get more dives in your comfort and control will get better and your sac goes down.

Also being overweighted will have drastic effects on SAC.

For now go back to single tank, forget about sac and just dive, Dive, dive.