Is it important to know the predominant respiratory event in AHI for the management of patients with OSA?

Introduction: Obstructive sleep apnea (OSA) is a heterogeneous disorder. The apnea-hypopnea index (AHI) cannot fully reflect this heterogeneity on its own. In this study, the OSA patients were analyzed by grouping them based on the predominant type of respiratory event, and the distinctive findings of each group were evaluated.

Materials and methods: The records of 213 patients with OSA were evaluated retrospectively and the patients were divided into three groups as Group 1 (apnea-predominant OSA; apnea index (AI)≥ 2x hypopnea index (HI) and HI≤ 15/hour), Group 2 (hypopnea-predominant OSA; HI≥ 2xAI and AI≤ 15/ hour), and Group 3 [No Respiratory Event-Predominant OSA (NREP OSA)].

Result: There were 65 patients in Group 1, 58 patients in Group 2, and 90 patients in Group 3. There was no difference between the groups in terms of sex, age, body-mass index, the distribution of symptoms, and concomitant diseases (p> 0.05). Only witnessed apnea was more frequently described by Group 1 patients (p= 0.042). Except for the higher N2 percentage and arousal index (p= 0.009, p= 0.011, respectively) in those with apnea-predominant OSA compared to those with hypopnea-predominant OSA, there was no difference in sleep architecture. In the apnea-predominant group, while the AHI, apnea durations (p= 0.000, 0.000, 0.000, respectively), total oxygen desaturation index (tODI), NREM ODI and REM ODI were higher (p= 0.000, 0.000, 0.047, respectively), nocturnal minimum oxygen saturation (SpO2) was lower (p= 0.001).

Conclusions: This study concluded that apnea-predominant OSA patients had more severe OSA in terms of AHI, respiratory event durations, and problems in oxygenation. These differences may guide the management of OSA.