Relationships between Fraction of Nitric Oxide, Airway Hyperresponsiveness, Blood Eoshinophil Counts and Serum Eosinophil Cationic Protein in Asthmatic Children

Abstract

Purpose:The measurement of fraction of nitric oxide (FeNO) is a noticeable tool that reflects airway inflammation in asthmatic patients. We wanted to find out the relationship between pulmonary function, bronchial hyperresponsiveness (AHR), blood eosinophilic inflammatory markers and FeNO level before and after methacholine bronchoprovocation test in asthmatic patients. Methods:Fifty-five children, who visited the Allergy Clinic of Korea University Anam Hospital from March 2011 to February 2012, due to asthmatic symptoms, such as history of episodic wheezing or dyspnea during the previous year and resolved after using bronchodilators, were enrolled. We performed the baseline pulmonary function and methacholine bronchoprovocation test in the enrolled patients. Blood eosinophil counts and blood eosinophil cationic protein (ECP) were measured. FeNO levels were measured before and after the methacholine bronchoprovocation test. Results:The mean FeNO levels (36.3 ppb) fell after methacholine bronchoprovocation test (25.7 ppb). Forced expiratory volume in one second (FEV1) %pred inversely correlated both with FeNO level before (R 2 =0.07, P=0.029) and after (R 2 =0.059, P=0.01) methacholine bronchoprovocation test. The provocative concentration, causing a 20% decrease in FEV1 to methacholine (methacholine PC20) inversely correlated both with FeNO levels before (R 2 =0.086, P=0.001) and after (R 2 =0.141, P=0.001) the challenge. FeNO level measured at bronchoconstriction state significantly correlated with blood eosinophil counts (R 2 =0.112, P=0.028). Serum ECP levels correlated FeNO level, neither before nor after bronchoprovocation. Conclusion:The baseline FeNO levels were higher in asthmatic children. However, FeNO levels rather decreased after methacholine induced bronchoconstriction. Repeated spirometry maneuver was considered to have an effect on reducing FeNO levels. FeNO correlated with pulmonary function, airway AHR and blood eosinophil counts. (Pediatr Allergy Respir Dis(Korea) 2012;22:282-291)