Small airway function, exhaled NO and airway hyper-responsiveness in paediatric asthma

• Published in: Respiratory medicine Vol. 105; no. 10; pp. 1476 - 1484
• Main Authors: Keen, Christina, Olin, Anna-Carin, Wennergren, Göran, Gustafsson, Per
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2011; Elsevier; Elsevier Limited
• Subjects: Adolescent; Airway management; Allergies; Asthma; Asthma - diagnosis; Asthma - drug therapy; Asthma - physiopathology; Biological and medical sciences; Bronchial Hyperreactivity - diagnosis; Bronchial Hyperreactivity - physiopathology; Child; Chronic obstructive pulmonary disease, asthma; Cross-Sectional Studies; Exhalation; Female; Flow-independent exhaled nitric oxide; Humans; Lung clearance index; Lungs; Male; Mathematical models; Medical sciences; Multiple breath inert gas washout; Nitric oxide; Nitric Oxide - metabolism; Pediatrics; Pediatrik; Pneumology; Practice Guidelines as Topic; Pulmonary/Respiratory; Reproducibility of Results; Spirometry - methods; Treatment Outcome; Ventilation; Sweden; ATS; FENO; NO; cACT; D NO; RSD; MBW; S acin; ERS; Multiple breath inert gas washout; AHR; ACT; FVC; FEV 1; LCI; MMEFexpiratory flow; ULN; PNT; SF 6ur hexafluoride; Flow-independent exhaled nitric oxide; C W; S cond; Lung clearance index; forced vital capacity; sulph; residual standard deviation; childhood Asthma Control Test; European Respiratory Society; bronchial NO diffusion capacity; forced expiratory volume in 1 second; Asthma Control Test; nitric oxide; contribution to MBW phase III slope generated in the acinar lung zone; bronchial wall NO concentration; maximum mid; fraction of exhaled nitric oxide; pneumotachometer; American Thoracic Society; upper limit of normal; airway hyper-responsiveness; contribution to MBW phase III slope generated in the conducting airway zone; Lung disease; Multiple; Respiratory disease; Lung; Clearance; Asthma; Nitric oxide; Bronchus disease; Obstructive pulmonary disease; Pneumology
• ISSN: 0954-6111; 1532-3064; 1532-3064
• DOI: 10.1016/j.rmed.2011.04.004

Asthma is a chronic inflammatory airway disorder known to involve the peripheral airways. Current guidelines state that diagnosis and treatment should be guided by symptoms and spirometry. FEV 1 is, however, a poor marker of small airway function and correlates poorly with asthma control and airway inflammation. To assess the contribution of small airway dysfunction and inflammation in paediatric asthma. A secondary aim was to study the associations between small airway dysfunction, airway inflammation and airway hyper-responsiveness (AHR). Small airway function was measured as LCI, S cond and S acin, evaluated with the SF 6 multiple breath inert gas washout (MBW) technique, in 47 asthmatic children and 74 healthy controls. Exhaled NO at multiple exhalation flow rates including 50 mL/s (FENO 50) was assessed to calculate alveolar NO and bronchial NO flux (a surrogate for airway inflammation). AHR was evaluated with isocapnoic dry air hyperventilation challenge in the asthmatic children. S cond was elevated in 31 (66%) and S acin in 18 (38%) of the asthmatic subjects. LCI was increased and FEV 1 decreased in 7 (15%) of the subjects with asthma. Individuals with AHR had higher S cond ( p = 0.001) and FENO 50 ( p < 0.0001) than those without AHR. The levels of FENO 50 and bronchial NO flux were elevated in asthmatic subjects compared with healthy controls. In asthma, S cond correlated with FENO 50 ( r s = 0.42, p = 0.003) and alveolar NO ( r s = 0.40, p = 0.011), and S acin correlated with alveolar NO ( r s = 0.40, p = 0.015). Dysfunction of small conducting airways is associated with airway inflammation and hyper-responsiveness in paediatric asthma.