Lung function measurements and FeNO
IOS was performed in accordance with established
guidelines.16The difference of the respiratory
system resistance (Rrs) at 5 Hz and 20 Hz (Rrs5-20) has a high
sensitivity for detecting small airway dysfunction.17Airway resistance was also measured at 1, 2, 3, 5, 10, 15, and 20 Hz for
calculation of area of reactance (AX) as a function of frequency. The
signals were analyzed for 30 s at each frequency. Oscillometric tests
were performed using a Jaeger MasterScreen device (Jaeger Co., Wurzburg,
Germany).
The FeNO concentration in exhaled breath in parts per billion (ppb) was
measured using a portable nitric oxide analyzer (NIOX MINO®; Aerocrine,
Solna, Sweden) according to the American Thoracic Society (ATS)
guidelines.18