Effect of spirometry and bronchodilation test in eNO levels

The ATS/ERS Recommendations for Standardized Procedures for the Online and Offline Measurement of Exhaled Lower Respiratory Nitric Oxide and Nasal Nitric Oxide, 2005, recommends measurement of eNO before spirometry (SP), due to the risk of transient reduction of eNO. We aim to assess the effect of SP with bronchodilation test (BD) in eNO levels of asthmatic patients. We enrolled all patients who perform spirometry with BD (400µg salbutamol) and eNO analysis as part of their routine evaluation during 6 weeks (2 Jan-10 Feb 2016). All subjects performed eNO analysis before initial spirometry according to our standard procedure and repeated eNO evaluation before post-BD spirometry. Simple paired t-test were used to assess the effect of spirometry and BD in eNO levels and a sub-group analysis were performed in order to test differences between gender, BMI, age, inflammatory status(ATS Clinical Practice Guideline 2011) and the result of BD. We included 149 patients (105 female, 70%), mean age(SD) of 28.2(18.1) years (40.3% with age <18) and a mean BMI of 24.2(5.9). Globally, spirometry yielded a mean (SD) FEV1 of 96.0%(17.4) and a positive BD in 21.6%. No significant differences between first and second eNO measurements were found considering, respectively: whole population (p=0.614), male (p=0.546) or female gender (p=0.164), BMI classes (normal weight p=0.556, overweight p=0.377 and obese p=0.201), age (>18 years, p=0.452 and <18 years, p=0.078), inflammatory status (normal eNO p=0.733, high eNO p=0.498 and very high eNO p=0.722) or BD results (negative p=0.774 and positive p=0.227). Exhaled NO levels are not significantly affected by spirometry and bronchodilation test when assessed 15 minutes later.