Wednesday, January 11, 2012

FEVone and FVC for Pot Smokers

Ah ha - got your attention on that last part didn't I?

You may recall from past posts, several of them, that I am a advocate for spirometry testing in smokers - in fact, I find it much more important and necessary than CT scans.  A spirometer is the device used in a lung function test.  It is relatively simple and straight forward.  The patient takes a deep breath and then blows into a tube which measures the volume you expire (blow out) in one second (FEVone) and your full expiration or FVC.  Read more here.
Certain values are indicative of lung problems and the diagnosis of Chronic Obstructive Pulmonary Disease.  Pulmonary means lungs.  COPD is very common in cigarette smokers and involves lung enlargement, air sac destruction and loss of elasticity.  It can feel like one is drowning and unable to breathe.  Emphysema is a type of COPD.
When I was doing presentations on the medical complications of tobacco use, the audience would sometimes ask about marijuana use.  I would say, "Anything that you light on fire and breathe into your lungs will cause them harm."  I still stand by that statement, however, research reported in the Journal of the American Medical Association this month, shows that marijuana smokers do NOT have the same decline in lung function, based on FEVone and FVC as cigarette smokers do.
This was not a lung cancer study, but it was a study that followed many people over 20 years.  The people in the study were classified as either 1) non users of both cigarettes and marijuana, 2) cigarettes users only, 3) marijuana users only and 4)users of both.  
The marijuana only group did not fair as well as the nonusers of both but certainly better than the smokers or both group.
Some thoughts put forward by the researchers include 
  •  Cigarette smokers consume several cigarettes every day whereas marijuana users might have a whole marijuana cigarette or two only once per week.  Most marijuana users do not use every day or even every week.  
  • Marijuana smokers breathe in very deep and hold their breath before exhaling - similar to what one does with spirometry (so they practice what the test requires and they may strengthen their lungs in the process) 
  • THC, which is found in marijuana may actually soothe or heal lung tissue.
Interesting study - it does not imply that marijuana use is safe nor that we should add THC to our cigarettes, but it is evidence that marijuana smoking does not damage lungs to the same extent as cigarettes do.  This study does confirm the severe, adverse effect that cigarette smoking has on lung function.

Association Between Marijuana Exposure and Pulmonary Function Over 20 Years
 Mark J. Pletcher, Eric Vittinghoff, Ravi Kalhan, Joshua Richman, Monika Safford, Stephen Sidney, Feng Lin, Stefan Kertesz JAMA. 2012;307(2):173-181.

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