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Discussion Starter #1
Having been a lifelong smoker I quit to help my air consumption. After six years I (foolishly) started again. This was 2 years ago. Since then I have seen my air consumption rise rapidly. I have quit again since my last dive trip in April. My air consumption had gone up from around 18 litres/min to around 27 litres/ min. (equated to surface).

My question is, does anyone know wether, because of this excess consumption, am I discarding the nitrogen as well as the oxygen, or am I taking up the nitrogen despite not using the oxygen. In which case, my computer's predictions are pretty useless. My computer is on my wrist and has no idea how much air I use, although I do use a conservative personal setting.
 

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Nigel Hewitt
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Your breathing rate is totally based on CO2 removal.
Nitrogen take up and removal is almost independent of breathing rate just on the difference of gas levels.
You are either running ineffective lungs and are needing more breaths of low CO2 gas to flush out the stuff in your blood or you have become less tolerant of CO2 generally.

My father died of Emphysema which is bunged up lungs taken to its sad conclusion down, in his case, to smoking. I hope you're not on that track.
 

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....
Nitrogen take up and removal is almost independent of breathing rate just on the difference of gas levels.
...
Our science expert is, as ever, on the money. Smokers are generally at risk of heart attack as well as the obvious lung cancer. Heart attack while diving is almost certainly fatal, while on dry land can often be sorted. Other diving related problems include fluid build up (like Nigel's dad) which can result in pulmonary barotrauma. I'd worry more about these issues than a bend.

Diving and smoking is fairly stupid IMHO.
 
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Discussion Starter #4
I totally agree with your HO, but the number of professional divers who do smoke despite their knowledge of the problems, is astounding. Back to Nigel: Yes I do believe my lungs are far less efficient, I am pretty certain it is not emphysemia despite 17 years as a coal mining engineer. My excessive air use seems directly linked to my resumption of smoking. I know all the other associated smoking risks, but I am still not certain of your answer. Am I, in your opinion, exhaling unabsorbed nitrogen with the rest of the unused gas in each breath?
 

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A short fat well off crap cave diver. Likes wrecks
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I used to smoke and my OC consumption averaged 12 on the bottom 8-10 on deco.

Now i don't smoke and my consumption is about the same.

When i first started diving my consumption was avg 20lpm. After i became relaxed and learned a few tricks it staid sub 15. My wife who's tiny (5stone under 5ft tall) has a SAC of 25.

Theres no odsing it. Some people just breath less.

A buddy of my'n a few years back had a SAC of 8 and had to force himself to breath more because he was getting C02 headaches. He smoked as well

ATB

Mark
 
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There were reports some years ago of an increased risk of DCI in smokers. This was said to be due to smokers having an increased level of platelets in their blood which formed a seed for nitrogen bubbles.

I've never smoked and have a SAC in single figures most of the time. However, I'm sure this is due to having started diving many years ago when cylinders were only small and we learned not to waste energy and hence air. I still move as little as practical when I'm diving - why swim against the current when you can drift with it. Have you thought that the way that you act underwater can be having a big effect on your consumption? Has your style of diving or your equipment configuration changed. A friend of mine noticed a big increase in consumption after switching to a twinset. I've had dives where I've dived a single 12l and come up with a higher pressure in my cylinder than my buddy who was diving twin twelves.
 

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This is my first year as a non smoking diver after many as a smoking diver, I do feel better in myself, have noticed no difference in my SAC but don't cough up as much phlegm after a dive so thats a good thing.......

As for Nitrogen uptake....not got a clue
 

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Nigel Hewitt
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I totally agree with your HO, but the number of professional divers who do smoke despite their knowledge of the problems, is astounding.
The Alkaloids got you back into their clutches so why are you surprised that others are just as unfortunate?
Back to Nigel: Yes I do believe my lungs are far less efficient, I am pretty certain it is not emphysemia despite 17 years as a coal mining engineer. My excessive air use seems directly linked to my resumption of smoking. I know all the other associated smoking risks, but I am still not certain of your answer.
I am more concerned that your air consumption is going up. This is not the way it usually goes. This rings my warning bells.
Smokers don't tend to use more or less gas so we are not looking at something good here. Over the years my gas consumption has dropped to the point that I have to mentally check myself to see that I am breathing enough.
Am I, in your opinion, exhaling unabsorbed nitrogen with the rest of the unused gas in each breath?
Obviously yes. Most of the nitrogen you inhale you exhale again. You are absorbing and releasing nitrogen all the time but if the blood levels are higher than the air level the net slow is outward and vice versa. My concern is that lungs that are not removing CO2 efficiently are just moving breath into and out of dead space so moving more than required.

In simple terms the net gas flow is directly proportional to the difference between the blood tension and the Alveoli partial pressure. You just need to be breathing fast enough to keep the pp in the Alveoli from changing enough to slow things down. Poor lungs aren't going to make you gas on or gas off faster or slower
 
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..... My concern is that lungs that are not removing CO2 efficiently are just moving breath into and out of dead space so moving more than required....
It might be possible (if the smoking is chronic enough) that the base breathing rate is different. Badly damaged lungs tend to make you pant a little - this is bad for diving obviously. Cigarette smoke causes fluid build up as the cillia stop working properly. Shallow breathing results as only the top part of the lungs now function. My mum (just before she died of lung cancer) used to puff like a train as she tried to get the last working part of her lungs to work. You could hear her breathing a kilometre away. I very much hope the OP is not in this state. My recollection of my mum in the year or so before she died was of a woman standing in front of the kitchen sink coughing up tar and spitting it into the sink. Sometimes the coughing fit would be so severe she would fart uncontrollably at the same time. My childhood friend who lived across the street watched his grandad die the same way. I really wish I had had a video camera (not around in those days) and I could show you a video of my mum coughing and farting and dying every time you light up. I'm sure it would help you quit. I wish you every success in giving up - from the bottom of my heart I truly do.
 

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Discussion Starter #11
My equipment hasn' changed. My age has, although I know divers just as old and older who do not use as much air. None of these have ever smoked. I told myself I wouldn't book another trip until I had been stopped for 3 months. Another 2 to go and then I will check if stopping has helped.

When my consumption was around 18 lpm, my buddy (40 year old son) and I would be air matched with me on a 15ltr and him on a 12ltr. Worked well. Obviously my increased consumption shortens his divetime unnecessarily. I am concerned about this.
 

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Your SAC is what your SAC is, just as the lead on your belt weighs what it weighs, there are no hard and fast rules or cures, it is what it is
 

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Discussion Starter #13
Yes I know that, but when it increases by around 50% it makes you take notice.
 

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Aquanauts tea boy & GUE instructor
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Yes I know that, but when it increases by around 50% it makes you take notice.
As pointed out a SAC has many variables,but some of things I have looked at with students with similar changes to SAC have been the following. The fitter you are, generally the better your SAC. I would look there for changes first. Increased CO2 whatever its cause will drive up your SAC so factors on the dive itself will have an impact. Swimming resistance due to poor or demished technique and equipment drag, reduced in water comfort if you hadn't dived for a while.
If you are concerned about smoking in relation to Nitrogen uptake and release also remember that in addition to lung damage the Carbon Monoxide will reduce efffective perfusion. Prehaps not enough on its own but take a broad view of all the variables and you might find some of your missing bottom time!
 

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The worlds slowest sailor.
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Yes I know that, but when it increases by around 50% it makes you take notice.
my sac goes from about 10 to 20 depending on the amout of work i do on a dive.
a change of 100%?

smoking and fitness dont seem to factor much.
 

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Do we assume you are a 20 a day salad dodger?
i smoke-i dont smoke.
my weight is around 90 kgs but goes up or down by 5kg depending on work and xmas at my mums.
my diving doc tells me i am as fit as an average 38 year old guy.(i'm 47)
my latest nhs doc tells me i'm overweight.
the last time i did oc was for 45 mins and i got out with 140bar on a shite fill.

i like salad.

sac is related to the amount of diving you do and if you are a girl or not.
 

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Discussion Starter #19 (Edited)
Thank you all anyway, but I do know most of what has been said. When I say 18 ltrs per min, quite obviously that can go up or down depending on the current and how inquisitive those silkies were. Lets look at this from my computers point of view for a minute. It knows my dive time, it knows all my depths and the time spent there. It does not know my air intake, hence it does not know my nitrogen intake. Is it lying about my 'No deco' time because it doesn't know how much I am breathing? What I am asking is, because my lungs are obviously less efficient, is the nitrogen exhaled, along with the gas I need, before absorption into the blood stream or not? Difficult one I know.
 

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It might be possible (if the smoking is chronic enough) that the base breathing rate is different. Badly damaged lungs tend to make you pant a little - this is bad for diving obviously. Cigarette smoke causes fluid build up as the cillia stop working properly. Shallow breathing results as only the top part of the lungs now function. My mum (just before she died of lung cancer) used to puff like a train as she tried to get the last working part of her lungs to work. You could hear her breathing a kilometre away. I very much hope the OP is not in this state. My recollection of my mum in the year or so before she died was of a woman standing in front of the kitchen sink coughing up tar and spitting it into the sink. Sometimes the coughing fit would be so severe she would fart uncontrollably at the same time. My childhood friend who lived across the street watched his grandad die the same way. I really wish I had had a video camera (not around in those days) and I could show you a video of my mum coughing and farting and dying every time you light up. I'm sure it would help you quit. I wish you every success in giving up - from the bottom of my heart I truly do.
that has to be the best post you have ever made.
 
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