Asthma is characterized by reversible airway obstruction and bronchial hyperresponsiveness result from airway inflammation. Fraction of nitric oxide in expired air (FeNO) has recently been investigated as a noninvasive measure of airway inflammation. FeNO has been reported to correlate with induced sputum eosinophilia and methacholine challenge test that it is represent severity of asthma. The purpose of this study was to analyze the relationship of FeNO with pulmonary function tests in patients with intermittent asthma.

Eighty children included in this study were diagnosed as asthma from April through August, 2005 in Department of Pediatrics, College of Medicine, Kyunghee University. They aged from 4 to 15 years who were able to conduct spirometry and FeNO monitoring. They did not have upper respiratory tract infection and did not use an asthma controller which contain corticosteroids within 4 weeks. Pulmonary function test was done and FeNO was measured with online tidal breathing method using a chemiluminescence NO analyzer (CLD 88 sp, Eco Medics, Duernten, Switzerland). The correlations between pulmonary function test and FeNO were analyzed using Spearman correlation coefficient method.

The mean of FeNO of subject was 16.88 parts per billion (ppb). The mean of forced expiratory volume in 1 second (FEV₁) was 0.890±0.455 L and forced vital capacity (FVC) was 1.071±0.630 L. The mean of predicted FEV₁% (FEV₁%pred) was 98.39±34.27% and FEV₁/FVC was 88.53±19.49. FeNO was significantly correlate with FEV₁ (r=0.345, P <0.01) and FVC (r=0.244, P <0.05). FeNO did not correlate with FEV₁%pred or FEV₁/FVC.

The measurement of FeNO could be a useful marker in the management of childhood asthma and it is evolving to provide a complementary role alongside existing pulmonary function test. We propose that measuring technique and establishment of normal reference range are important area for future research.