Comparison of fractional exhaled nitric oxide levels in chronic obstructive pulmonary disease, bronchial asthma and healthy subjects of Nepal

Abstract

Introduction: Fractional exhaled nitric oxide levels in exhaled breath can indicate ongoing eosinophilic airway inflammation, specifically in asthma. But its utility is being explored for central airway inflammations, including chronic obstructive pulmonary disease. Normal levels of fractional exhaled nitric oxide (FENO50) have been defined in different studies but not in Nepal. This study compares FENO50 levels in normal subjects, asthma and chronic obstructive pulmonary disease. Methods: Single breath estimation of FENO50 was measured by a handheld electrochemical sensor-based device in normal non-smoking adults (n = 106), clinically controlled asthma (n = 106) and stable chronic obstructive pulmonary disease (n = 106). Results: The geometric mean for FENO50 was 14 parts per billion (ppb) with a median of 16 ppb, first quartile at 11 ppb and third quartile at 20 ppb in normal non-smoking adults. The values were 31 ppb (geometric mean), 34 ppb (median), 17 ppb (first quartile) and 79 ppb (third quartile) in clinically controlled asthma. Similarly the values were 10 ppb (geometric mean), 11 ppb (median), 6 ppb (first quartile) and 17 ppb (third quartile) in stable chronic obstructive airway disease. The log-transformed data showed significantly higher FENO50 levels in the asthma group compared with the normal (p < 0.001) and chronic obstructive airway disease (p < 0.001). However, levels were similar between healthy and chronic obstructive airway disease groups (p = 0.08). Conclusions: FENO50 levels were higher in bronchial asthma (despite disease control) than in normal non-smoking adults and subjects with stable chronic obstructive pulmonary disease. Levels of FENO50 were similar between the chronic obstructive airway disease and normal groups.