Which is more important: the number or duration of respiratory events to determine the severity of obstructive sleep apnea?

Aim: Apnea-hypopnea index (AHI) take account only the number of apnea and hypopnea regardless of their duration and morphology. The aim of this study was to compare the mean obstructive apnea duration (MOAD), mean mixed apnea duration (MMAD), mean central apnea duration (MCAD), mean total apnea duration (MTAD) and mean hypopnea duration (MHD) with the demographic parameters, blood oxygenation and other polysomnographic sleep parameters in patients diagnosed with severe obstructive sleep apnea (OSA). Materials and methods: A retrospective study included 121 patients who had a diagnosis of severe OSA. The correlations between the MOAD, MMAD, MCAD, MTAD, MHD and patient demographic parameters, blood oxygenation and other polysomnographic sleep parameters were analyzed. Results: Severe OSA patients with longer MOAD and MTAD had shorter Stage N3. Longer MOAD, MMAD, MCAD, MTAD, MHD were related to lower mean oxygen saturation. Longer MOAD and MTAD were associated with higher oxygen desaturation index. MOAD, MMAD, MTAD were positively associated with a duration below oxygen saturation 85%. Conclusions: Respiratory events can have different characteristics even though the average number of events per hour would be similar. Novel parameters like MOAD, MMAD, MCAD, MTAD, MHD could enhance the evaluation and classification of OSA in addition to AHI.