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Squirrel’s Theory on Smoking With Asthma

March 22, 2004

I’ve had a lot of people tell me over the years that ever since they started smoking, their asthma has gotten better. I’ve developed a theory on this, which requires a little background in order to fully explain, so bear with me.

When I was in high school, I worked for Baylor College of Medicine’s Pulmonary Diagnostic Lab. Basically the lab was an offshoot of the Asthma clinic at Texas Children’s Hospital. While I was only doing basic secretarial stuff, I still learned a lot about asthma, mainly because I’m an asthmatic myself and I’m a little compulsive about such things. Part of the equipment at the lab was this really nifty little machine where you would blow into a mouth piece and it would track your flow. There’s a standard deviation that shows up in asthmatics which shows up as a little dip in the graph. The techs liked to use me to demonstrate the equipment because they had an actual asthmatic on hand to show people how it all worked. This is, incidentally, the first time I had ever seen actual physical proof that I was an asthmatic. That came in handy later when my crack smoking allergist tried to claim I wasn’t asthmatic, but that’s another story. This is also the first time we had physical proof that my lung capacity was larger than normal. All obvious puns aside, it meant that while I had moderate to severe asthma problems, I wasn’t showing signs of it because I was still getting plenty of air into my system.


In the case of smokers, there’s also a standard deviation in the chart. It’s similar to, but not identical, to the deviation one sees in an asthmatic. In both cases, there is a problem with the lung function, and that problem can be charted by one’s output of air. One of the major differences in the two is how one reacts to medication. For asthma, the problem is that the lungs aren’t functioning properly. The air passages have become constricted and need to be opened. “Key” medications, or medications which are designed to unlock air passages, can fix this. Some medications can even repair the problem, although this takes time and proper care. However with smokers, the lungs are actually damaged. There is no key to unlocking the airways because the airways are blocked. Think of it as the difference between a hallway with a locked door blocking it verses a hallway where the ceiling has collapsed. Both can be opened up, but the second one takes a lot more time and effort.

Here’s where the numbers come in. Peak flow is the maximum amount of air one can expel in a single breath. It’s a great way to figure out if you’re having an asthma attack if you’re not sure, but in general the “Oh God, I can’t breathe!” reaction is more accurate. Imagine that we have a patient who is an average male, age 20-25, about 6’1″. He is a non-smoker, but an asthmatic, though in fairly good health. His average peak flow is about 635 liters per minute. A good, or Green, peak flow for him is 80-100% of his average, or 508-635 lpm. While having an mild asthma attack, his peak flow may drop down to 50-80% of his average, or 318-508. He has entered his Yellow zone. Not serious, but definitely worth taking some medication for. A severe attack is when his peak flow drops below 50% of his average into the Red zone, or 317.

A smoker’s peak flow readings are on average 100 lpm less than a non-smoker. There are two ways of looking at that bit of information, both of which lead to similar conclusions. The first method is to remove the 100 lpm completely from the equation and reevaluate one’s zones. After all, this is an average At 535, the Green zone is 535-428, the Yellow zone is 428-268, and anything below that is a severe attack. Now, while the numbers seem to mathematically support the idea that smoking is better for you (after all, the severe attack range is much lower), it should be noted that the ranges are much smaller. A factor which would only cause a slight drop to the non-smoker may cause a smoker to push more quickly into the Red zone.

The second method is to compare this drop using the lung capacity our patient would have, were he a non-smoker. If our imaginary patient’s lung capacity as a non-smoker is 635, a drop in 100 lpm puts him at 535. Still not in the yellow range, but not by much. A drop into the yellow range would require only a 27 point decrease. A bare 4% of the total lung capacity. A deviation of that little would very likely not be noticed in the average person, especially since it takes a deviation of 20% before entering the Yellow zone for an average person.
We’re almost done, stay with me now!

Now imagine a situation where our patient’s lung capacity drops to 400 lpm. Low enough to be in the Yellow zone no matter how one calculates it. In the case of our non-smoker, that’s a 37% drop! More than enough to be noticeable. In the first case of our smoker, that’s a 25% drop. Still pretty bad, but not as noticeable. In the last case, it’s only 21%. In both cases of the smoker, the difference in change is smaller. And that’s where my theory comes in.

It is my belief that smoking is bad for you, that it does damage to your lungs, and that damage is very similar to an asthma attack when it comes to one’s airflow. It is my theory that all of the smokers who claim that they didn’t have as many asthma attacks after they started smoking were simply not noticing that their output levels were dropping into a range that could be considered an attack. They simply didn’t notice enough change in their lung capacity to mark it mentally, so in their mind, they are having fewer attacks. However, the reality is that they are very likely having more attacks and just not realizing it.

Le Fin (for now).

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