Validity of Fractional Exhaled Nitric Oxide and Impulse Oscillometry in Patients With Cough Variant Asthma

FeNO level was evaluated according to the American Thoracic Society (ATS)/ERS recommendations using a NIOX MINO analyzer (Aerocrine, Solna, Sweden) .Subjects were informed to deeply inhale NO-free air and immediately exhale in full via a mouthpiece at a constant flow rate (50 ml/s) for 10s.

The patient take seats, body relax, make sure the mouthpiece is fully covered by mouth, then clip nose with both hands to cover both sides of the cheek, and then calm breathing 1 minutes, the computer is automatically collected data calculation and print out the measurement results.