Evaluation of airway hyperresponsiveness and exhaled nitric oxide as risk factors for airway remodeling in patients with stable asthma

Abstract

Chronic eosinophilic airway inflammation, airflow limitation, and airway hyperresponsiveness (AHR) are distinctive features of bronchial asthma. Exhaled nitric oxide (eNO) is a marker of eosinophilic airway inflammation. Airway remodeling due to chronic airway inflammation results in fixed airway obstruction. Asthmatic patients have been reported to have greater declines in forced expiratory volume in 1 second (FEV(1)) over time than nonasthmatic patients. This longitudinal observational study aimed to elucidate outcomes and risk factors for the decline in FEV(1) in patients with stable asthma. Postbronchodilator FEV(1) was measured in 30 outpatients with stable asthma every 6 months for 5 years. We calculated the rate of decline in postbronchodilator FEV(1) (deltaFEV(1)/year) in each subject and adjusted deltaFEV(1)/year with predictive FEV(1). Patients were examined while their asthma was well controlled. In the first observation period, we measured AHR to methacholine (the provocative concentration of methacholine causing a 20% fall in FEV(1) [PC(20)]). In the second observation period (defined as the period over 2 years from start of observation), we measured methacholine PC(20) and eNO. The mean deltaFEV(1)/year (SEM) was -36 +/- 4 mL/year and the adjusted deltaFEV(1)/year (SEM) was -0.015 +/- 0.001/year. Adjusted deltaFEV(1)/year did not correlate with eNO measured during the second observation period or methacholine PC(20) measured during the first observation period. On the other hand, methacholine PC(20) measured during the latter period was correlated significantly with adjusted deltaFEV(1)/year. Persistent AHR may be a risk factor for longitudinal decline in FEV(1) in asthma patients even if their asthma is stable and well controlled by inhaled corticosteroid.