Infants with recurrent lower respiratory tract symptoms – who benefits of extensive investigations?

Abstract

There is limited information on lung function and exhaled nitric oxide fraction (FeNO) in infants with recurrent lower respiratory tract symptoms. In 2000–2003, 201 recurrently symptomatic infants were referred to a tertiary center for further investigation. As part of the clinical investigation, whole-body plethysmography, tidal FeNOmeasurements, and skin prick tests were performed. In addition, 77 (38%) of the children underwent bronchoscopy. Increased work of breathing in clinical examination (in 22%), and abnormal chest radiograph (in 30%), were associated with decreased airway conductance (sGaw z-score ≤−1.65) (p<0.001 and p = 0.048, respectively) and hyperinflation of the lungs (FRC z-score ≥1.65)(p = 0.004 and p = 0.038, respectively). Exposure to environmental tobacco smoke (ETS) was associated with FeNO≥40 ppb (p = 0.009). Increased work of breathing, sGaw z-score ≤−1.65, and FRC z-score ≥1.65, were associated with low FeNO(p = 0.002, p = 0.005, p = 0.026, respectively). A definitive diagnosis was made in 184 (92%) children; asthma was diagnosed in 149 (74%), infection in 23 (11%), and a structural abnormality in 12 (6%). Abnormal findings in clinical examination predicted the diagnosis of asthma or a structural abnormality in 96% of cases, whereas in children with underlying respiratory infection or no definitive diagnosis, clinical examination was normal in 92% (p<0.001). In conclusion, clinical findings of bronchial obstruction predict well lung function and the diagnosis of asthma in recurrently symptomatic infants. FeNOis affected by ETS exposure, clinical state of the child, and the used methods, and the information obtained should be interpreted with care.