Abstracts

Abstract

Increase in Alveolar Nitric Oxide in the Presence of Symptoms in Childhood Asthma; Mahut, B., Delacourt, C., Zerah-Lancner, F., et al. Chest 2004; 125:1012–1018.Background. Asthma is defined as an inflammation encompassing both the proximal and distal pulmonary airways. Exhaled nitric oxide is regarded as a non-invasive surrogate of airway inflammation. There is evidence of cellular inflammation in the very small airways and alveoli that result in an increase in nitric oxide (Qno) output. There is documentation using bronchial alveolar lavage of cytokine expression, eosinophil presence, and nitric oxide synthetase expression in the distal airways. The authors hypothesized that increased nitric oxide output could result from distal airways and/or alveoli in asthmatic individuals.Objective. The objective was to assess the contributions of alveolar and proximal airway compartments in exhaled nitric oxide (NO) output (Qno) in children with asthma and to determine their correlation with mild symptoms of bronchial obstruction.Methods. The subjects in this study included 15 children with asthma with recent onset of mild symptoms, 30 asymptomatic asthmatic children and 15 healthy children. The investigators measured exhaled nitric oxide concentration at multiple expiratory flow rates (V) allowing the determination of alveolar and proximal airway contributions in Qno. Spirometric measurements and flow volume curves were obtained, as well.Results. The asymptomatic and recently symptomatic individuals were not significantly different with regard to spirometry measurements. The maximal airway nitric oxide output was more elevated in recently symptomatic versus asymptomatic asthmatics, and in asymptomatic asthmatics versus healthy children. Variables that impacted airway nitric oxide output were symptoms and distal airway obstruction as assessed by MEF (25-75). The nitric oxide determination from the distal airways was significantly higher in individuals with MEF (25-75) less than 50% of predicted as compared with children whose MEF (25-75) was greater than 50% of predicted. Alveolar nitric oxide was significantly elevated in recently symptomatic children as compared with children who were asymptomatic, whereas it was not significantly different between asymptomatic and healthy children.Conclusions. An increase in alveolar nitric oxide concentration was observed in correlation with increased symptoms of asthma and proximal airway nitric oxide was correlated with distal obstruction during asthma.Reviewer's Comment. This is a useful prospective study, having healthy children as control subjects, which indicates the increased sensitivity and specificity of nitric oxide determination in the assessment of airway inflammation and correlating with the results of pulmonary function tests. It further extends our knowledge of airway inflammation to include the smallest airways and alveoli and indicates that even with mild or no symptoms, airway inflammation can be present distally as detected by nitric oxide, although it is not detected by conventional pulmonary function testing. It would be of interest to determine the correlation of nitric oxide with increasing levels of symptoms to provide parameters that might parallel the NHLBI Guidelines for mild, moderate, and severe asthma. Nitric oxide determination, particularly of the distal airway, may be useful as a marker of recent symptoms and of increasing loss of asthma control.Christopher Randolph, M.D.Waterbury, CT