Polysomnography (PSG)
All patients underwent full-night polysomnography in a sleep laboratory (Compumedics Grael). Oronasal airflow was measured by a thermistor, and oxyhaemoglobin saturation was recorded using a finger pulse oximeter. The same registered sleep technologists performed polysomnograms, and the study investigators validated polysomnography manually to ensure the quality of interpretation. The PSG data collected included the obstructive sleep apnea hypopnea index (OAHI), longest time of apnea, oxygen desaturation index (ODI), and lowest oxygen saturation (LSaO2).
Diagnostic criteria of OSAHS in children[12]: The obstructive apnea hypopnea index (OAHI) was defined as the sum of all apnoeas (≥90% decrease in airflow for a duration of ≥2 breaths) plus hypopneas (≥30% decrease in airflow and either ≥3% desaturation or electroencephalographic arousal, for a duration of ≥ 2 breaths). OAHI > 1 events/h is recommended as the standard diagnosis of OSAHS in children. Mild OSAHS was defined as 1 events /h< OAHI ≤5 events /h; moderate OSAHS was defined as 5 events/h < OAHI ≤10 events/h; and severe OSAHS was defined as OAHI > 10 events/h.