The link between exhaled NO and bronchomotor tone depends on the dose of inhaled steroid in asthma
Received 28 September 2009; accepted 3 February 2010. published online 02 March 2010.
Summary
Background
Exhaled NO (FENO) is a steroid dose dependent eosinophilic inflammometer, but also a mediator of bronchomotor tone, but statistically significant relationships have infrequently been obtained with pulmonary function tests (PFT). The aim was to test the hypothesis that the relationships between FENO and PFT could be uncovered by inhaled corticosteroid (ICS) treatment, namely that a link between FENO and bronchodilator response (an index of bronchomotor tone) would appear under ICS.
Methods
Exhaled NO, forced expiratory flows and lung volumes were measured in atopic asthmatic children without recent (one month) respiratory symptoms.
Results
Two hundred and thirty children (mean±SD, age: 11.2±2.5 years, 69 girls) were included (% predicted, FEV1: 100±14; FEF50%: 76±23; RV: 107±29). The relationship between ICS dose (GINA classification) and FENO plateaued in children with an ICS dose higher than 200μg beclomethasone equipotent daily dose: FENO (median [25th–75th percentiles]), 43ppb [15–105] (no treatment, n=65), 33ppb [15–77] (low dose, n=70), 23ppb [12–57] (medium dose, n=57) and 26ppb [9–49] (high dose, n=38). Statistically significant relationships between FENO and PFT were only observed in children receiving more than 200μg/day ICS: with FEV1 (medium ICS dose: ρ=0.43, p=0.001; high dose: ρ=0.32, p=0.052) and bronchodilator (400μg salbutamol) response (medium dose: ρ=0.54, p=0.001; high dose: ρ=0.65, p=0.002).
Conclusions
A positive correlation between FENO and bronchomotor tone appears with increasing ICS doses in atopic children with clinically controlled asthma, which further suggests that children depicting the highest FENO values may have lesser steroid sensitivity.
fCIC 9201 Plurithématique, Hôpital Européen Georges Pompidou, Paris, France
Corresponding author. Service de Physiologie – Clinique de la Dyspnée, Hôpital Européen Georges Pompidou, 20, rue Leblanc; 75015 Paris, France. Tel.: +33 1 56 09 34 88.
ABSTRACT