Obstructive sleep apnea (OSA) is a common but largely underdiagnosed condition. This study aimed to test the hypothesis that the oxygen desaturation index (ODI) obtained using a wireless high-resolution oximeter with a built-in accelerometer linked to a smartphone with automated cloud analysis, Overnight Digital Monitoring (ODM), is a reliable method for the diagnosis of OSA. METHODS: Consecutive patients referred to the sleep laboratory with suspected OSA underwent in-laboratory polysomnography (PSG) and simultaneous ODM. The PSG apnea-hypopnea index (AHI) was analyzed using the criteria recommended and accepted by the American Academy of Sleep Medicine (AASM) for the definition of hypopnea: arousal or X3% O 2 desaturation (PSG-AHI 3%) and X4% O 2 desaturation (PSG-AHI 4%), respectively. The results of PSG and ODM were compared by drawing parallels between the PSG-AHI 3% and PSG-AHI 4% with ODM-ODI 3% and ODM-ODI 4% , respectively. Bland-Altman plots, intraclass correlation, receiver operating characteristics (ROC) and area under the curve (AUC) analyses were conducted for statistical evaluation. ClinicalTrial.gov: NCT03526133. RESULTS: This study included 304 participants (men: 55%; age: 55±14 years; body mass index: 30.9±5.7 kg/m 2 ; PSG-AHI 3% : 35.3±30.1/h, ODM-ODI 3% : 30.3±25.9/h). The variability in the AASM scoring bias (PSG-AHI 3% vs PSG-AHI 4%) was significantly higher than that for PSG-AHI 3% vs ODM-ODI 3% (3%) and PSG-AHI 4% vs ODM-ODI 4% (4%) (9.7, 5.0, and 2.9/h, respectively; po0.001). The limits of agreement (2 ± SD, derived from the Bland-Altman plot) of AASM scoring variability were also within the same range for (PSG vs ODM) 3% and 4% variability: 18.9, 21.6, and 16.5/h, respectively. The intraclass correlation/AUC for AASM scoring variability and PSG vs ODM 3% or 4% variability were also within the same range (0.944/0.977 and 0.953/0.955 or 0.971/0.964, respectively). CONCLUSION: Our results showed that ODM is a simple and accurate method for the diagnosis of OSA.

Obstructive Sleep Apnea (OSA) is a syndrome characterized by episodes of airway obstruction, which causes oxygen desaturation events. These events can be identified by oximetry analysis and are used as one of the parameters to diagnose OSA. However, desaturation events have an inaccurate definition in manuals and in most of the literature. Thus, this work aims to evaluate whether different methodologies for the calculation of desaturation events impact the Oxygen Desaturation Index (ODI) and the diagnosis of OSA. The results indicated that the ODI values are significantly different from each other (p <0.001) and the methodologies provided variable performance for the diagnosis of OSA.