Do not ignore mouth breathing syndrome: respiratory functions are affected in early childhood.

INTRODUCTION Impulse oscillometry (IOS) is a useful test for measuring pulmonary resistance and reactance from the early ages. We aimed to investigate the etiological factors of mouth breathing syndrome (MB), its effects on respiratory functions, and to compare the results with those of children with nasal breathing (NB). METHODS This prospective cross-sectional study investigated children aged 3-7 years with MB (n=202) and NB (n=127) admitted to the pediatric allergy clinic between January 2023-2024. The MB group was evaluated for etiological factors by means of otorhinolaryngological examination. Respiratory function tests were evaluated using IOS and were repeated two months after appropriate treatment. RESULTS Adenoid hypertrophy (AH-44.0%), allergic rhinitis (AR-11.3%) and AH co-existent with AR (34.6%) were the principal causes of MB. Entire airway resistance was higher, upper and lower airway reactance were lower in the MB group compared to the NB group. No difference was detected in terms of IOS parameters between the first and second visits of MB group. Upper and entire airway resistance parameters were higher in children with AH and AH co-existent with AR groups compared to the non-obstructive group. Entire airway resistance was higher, upper and lower airway reactance were lower, in children with adenoid size>50% compared to those with adenoid size mouth breathing, allergic rhinitis, adenoids, respiratory function test, pediatrics.