Carbon Monoxide Conundra
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CO Conundra of FDA

GIVEN that FDA’s mission is to regulate all medical drugs and devices used to diagnose, treat or prevent disease ...

WHY does FDA regulate oxygen and nitric oxide gases but not CO, despite the widespread use of CO by respiratory therapists in a lung function test called DLCO, which stands for Diffusing Capacity of the Lung for Carbon Monoxide.  This test involves repeatedly inhaling a gas mixture containing CO and  holding your breath for 10 seconds each time before exhaling.  (A DLCO instrument then measures how much CO you exhaled as a way of calculating how much CO you absorbed through your lungs into your blood, which allows doctors to estimate the capacity of your lungs to diffuse oxygen.)    

DLCO testing is commonly done without informed consent on patients of all kinds with respiratory disease.  If patients ask about any  potential risks, respiratory therapists are taught to say that there are none because the amount of CO involved is so small, only 0.3%.  

Unfortunately, 0.3% = 3000ppm, which is more than twice the 1200 ppm level that NIOSH deems “Immediately Dangerous to Life & Health,” 15 times the 200ppm at which NIOSH recommends the immediate evacuation of any workplace, and 333 times the EPA limit of 9ppm for public exposure.    FDA has never required that  DLCO equipment manufacturers submit any studies on the safety of DLCO testing, and no one has ever published any such study. 
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