Exhaled nitric oxide monitoring in COPD using a portable analyzer

BackgroundThe exhaled nitric oxide (FeNO) is a non-invasive marker of airway inflammation in asthma. A very recent statement has suggested FeNO as potential outcome in chronic obstructive pulmonary disease (COPD). Recently, a new hand-held FeNO analyzer (NIOX MINO) has been developed.Patients and methodsWe have evaluated the NIOX MINO in COPD patients and monitored FeNO levels during 1-year assessment in the outpatient setting. Short-term variability in FeNO was compared using a NIOX MINO and a stationary chemiluminescence analyzer (NOA, Sensormedics) in healthy volunteers and COPD patients on two consecutive months. Long-term FeNO variability was assessed on a cohort of 70 COPD outpatients measuring FeNO for 1 year. The intra-individual FeNO coefficient of variation (eNOCoV) was taken as index FeNO long-term variability.ResultsIn COPD there were no significant differences between NIOX MINO and NOA FeNO values recorded at baseline and 1 month later. Ninety five percent limits of agreement between NIOX MINO and NOA were—2.7 and 1.9 ppb with significant reliability (r=0.96, p<0.0001). Mean FeNO at baseline was 15.0±9.5 ppb. Over the 1-year period the overall mean FeNO was 15.5±10.1 ppb. The long-term eNOCoV was 33.9±16.4% (range 8.1–83.1%), and it was significantly associated with exacerbation rate (r=0.57, p<0.0001).ConclusionFeNO electrochemical hand-held analyzer is feasible in COPD showing good agreement with stationary chemiluminescence analyzer. COPD patients exhibit a wide range of FeNO levels and a high variability of FeNO over time, which was positively associated with the number of exacerbations.