Monoxyde d'azote (NO) exhalé et fonction ventilatoire mesurée par pléthysmographie corporelle chez l'enfant

Abstract

Exhaled nitric oxide (NO) may be a marker of airway inflammation. Previous studies in adults have shown that the level of NO in exhaled air is influenced by several factors (breath holding, exercise, etc), or by several disease (asthma, congestive heart failure, diseases of the upper respiratory tract, cystic fibrosis, etc). However, few studies have been performed in children less than 3 years of age. The aim of this study was to determine endogenous NO levels in children with various diseases during lung volume measurements. Fifty-two children aged 18.3 +/- 9.5 months were studied. The population was divided in two groups, according to the underlying disease: a group of 39 children with cystic fibrosis (n = 7), bronchopulmonary dysplasia (n = 17), asthma (n = 7) or recurrent respiratory tract infections (n = 8) and a second group of 13 children without respiratory disease. Lung function was measured by whole body plethysmography and several respiratory parameters were calculated (functional residual capacity [FRC], compliance and resistances of the respiratory system, trapped volume). NO production was measured on a chemiluminescence analyzer from mixed exhaled air collected into a bag, over a period of 5 minutes. NO production was related to disease: exhaled NO levels were three times higher in bronchopulmonary dysplasia and cystic fibrosis, compared to NO levels in children without respiratory disease. They were higher in asthma. They were not altered in recurrent respiratory tract infections. No correlation was found between respiratory parameters and NO production. However, exhaled NO levels were correlated to trapped volume, which defined dynamic part of pulmonary hyperinflation. Levels of endogenous NO in infants were similar to those measured in adults with and without inflammatory respiratory disease. Lung distention influenced exhaled NO production.