Tidal breathing flow volume loops (TBFVL) can indicate the site/severity of upper airway obstruction (UAO). The authors did a pilot study to determine 1) the correlation between TBFVL and obstructive sleep apnea (OSA) as well as its severity and 2) the validity of TBFVL in determining OSA and desaturation during sleep in young children with adenotonsillar hypertrophy (ATH). A cross sectional analytical study was performed in 10 patients with ATH (age 4.2+0.4 yrs; 40% female) at King Chulalongkorn Memorial Hospital during January-June 2004. All had polysomnography and TBFVL performed during sleep. Median apnea/hypopnea index (AHI) was 3.4/hr. Eight (80%) patients had OSA. The TBFVL was normal in 2, variable UAO in 3, and fixed UAO in 5 patients. Among these 3 groups, the number of OSA patients (2, 3 and 3, respectively; ns) and the number of those who had desaturation (2, 3 and 3, respectively; ns) were not different. There was no correlation between mid tidal expiratory flow rate/mid tidal inspiratory flow rate (Me/Mi) ratio and AHI (r=0.5; ns) or lowest arterial oxygen saturationduring sleep (r=-0.4; ns). The accuracy of Me/Mi>1.5 for diagnosing
OSA and desaturation was 50% and 60%, respectively. The abnormal TBFVL also had the same accuracy in defining these
2 conditions. In conclusion, TBFVL did not correlate with OSA and its severity and had low accuracy in determining either
OSA or desaturation in young children with ATH.

Keywords: Obstructive sleep apnea, Tidal breathing flow volume loops, Adenotonsillar hypertrophy