Normal Variability of Tidal Breathing Flow-volume Curves During Sleep in Healthy Children

Inclusion Criteria: * Age 12 months-71 months, both sexes * Healthy at the time of inclusion * Signed informed consent Exclusion Criteria: * Preterm birth * Recurrent bronchitis or recurrent hospitalizations because of a respiratory illness * Nasal congestion, adenotonsillar hypertrophy, signs and symptoms of sleep apnea or sleep disordered breathing * Acute respiratory infection or hospitalization because of an acute illness within 4 weeks prior to inclusion * Personal or family history of asthma * Recurrent wheezing without respiratory infection * Allergic rhinitis, chronic rhinosinusitis, or other chronic respiratory disorders * Atopic dermatitis * Diagnosed allergic sensitization * Use of asthma rescue or maintenance medication within 4 weeks prior to inclusion * Any major chronic illness as judged by the investigators * Implanted or external active medical devices such as pacemakers