Association between acute tobacco exposure and fractional exhaled nitric oxide in patients with chronic obstructive pulmonary disease: National health and Nutrition Examination Survey (NHANES) 2007-2012.

Background: Fractional exhaled nitric oxide (FeNO) is a marker of type 2 airway inflammation. Tobacco exposure can lower FeNO levels. However, the effect of acute tobacco exposure on FeNO in patients with chronic obstructive pulmonary disease (COPD) is unclear.