Study population
Infants aged between 2 and 18 months diagnosed with noisy breathing, either clear wheezing or clear rattling, were recruited at a paediatric clinical practice in Hasselt, Belgium after parents provided informed consent. Exclusion criteria were preterm birth (gestational age < 37 weeks), congenital or genetic disorders, chronic respiratory diseases. All participants were treated according to standard clinical practice given that treatment did not depend on the study and vice versa. Two follow-up visits were planned three and six weeks after the first consult. At all three visits the paediatrician scored the intensity and duration of rattling and/or wheezing heard during auscultation. Based on the paediatrician’s rattle and wheeze scores, patients were classified into mild, moderate or severe rattling or recovered. Additionally, exhaled breath was collected at every visit. The study has been approved by the ethical review committee of the Jessa Hospital in Hasselt and with the advice of the medical ethics committee of the University of Hasselt (nr. B243201837634).