Should oxygen desaturation time be used to determine disease severity in patients with obstructive sleep apnea?

Introduction: Obstructive Sleep Apnea Syndrome (OSAS) is a disorder characterized by recurrent narrowing or complete obstruction of the upper airway during sleep. If not treated effectively, it can lead to significant health problems such as cardiovascular diseases, hypertension, and excessive daytime sleepiness. Therefore, its treatment is of utmost importance. One of the most critical steps in the treatment process is undoubtedly the diagnosis and determination of disease severity. In current accepted protocols, the severity of OSAS is determined solely based on the apnea-hypopnea index (AHI). However, it should not be overlooked that the AHI score may not always correlate with disease severity and that oxygen desaturation parameters may be related to the severity of the disease. Aim: This study was conducted to investigate the role of oxygen desaturation in determining disease severity in patients diagnosed with OSAS. Materials and Methods : In this study, which aimed to investigate the role of oxygen desaturation severity and the duration of desaturation in determining the severity of OSAS, a total of 120 participants with an AHI value of 5 or higher, who underwent PSG tests at the Van YYU Dursun Odabaş Medical Center Polysomnography Unit within the last six months, were included. Among the participants, 30 had an AHI value of 5≤AHI<15, 30 had an AHI value of 15≤AHI<30, and the remaining 60 were randomly selected with an AHI value of ≥30. All participants were administered the Epworth Sleepiness Scale questionnaire. For the evaluation of metabolic syndrome, waist circumference and blood pressure measurements were taken, and plasma triglyceride, cholesterol levels, and fasting blood glucose values were analyzed. The diagnostic criteria for metabolic syndrome recommended by the International Diabetes Federation were used to determine the presence of metabolic syndrome. All overnight PSG reports were evaluated, and parameters including the duration of oxygen saturation below 90% (D90), the lowest oxygen saturation, and the mean oxygen saturation were recorded. Similar studies have frequently demonstrated that as OSAS severity increases, the Epworth score and the prevalence of metabolic syndrome also increase. In this context, the Epworth Sleepiness Scale score and the presence of metabolic syndrome were used as reference criteria. The participants' D90, lowest oxygen saturation, and mean oxygen saturation parameters were compared based on their Epworth Sleepiness Scale scores and the prevalence of metabolic syndrome. Results: Of the total 120 participants, 30 were randomly selected with an AHI value of 5≤AHI<15, 30 with an AHI value of 15≤AHI<30, and 60 with an AHI value of ≥30. Metabolic syndrome was found to be positive in 14 participants with an AHI of 5≤AHI<15, in 19 participants with an AHI of 15≤AHI<30, and in 40 participants with an AHI of ≥30; however, no significant difference was found between the groups in terms of metabolic syndrome. In the Pearson correlation analysis performed for all participants without separate evaluation within AHI groups, the AHI score showed a significant positive correlation with the Epworth Sleepiness Scale score. Among the participants, the duration of oxygen saturation below 90% (D90) ranged from a minimum of 0 minutes to a maximum of 210 minutes. The mean D90 was found to be 34.4 minutes in participants with metabolic syndrome and 12.6 minutes in those without, showing a significant difference between the groups [34.4 min (15.4–76.4) vs. 12.6 min (1.3–42.3); p=0.002]. D90 was also significantly correlated with the Epworth Sleepiness Scale score (r=0.449, p<0.001). The lowest oxygen saturation among participants was recorded as 53%. In participants with metabolic syndrome, the lowest oxygen saturation was significantly lower [78 (69–83) vs. 82 (78–85); p=0.001]. The lowest oxygen saturation was significantly correlated with the Epworth Sleepiness Scale score (r=–0.576, p<0.001). Among all participants, the mean oxygen saturation ranged from a minimum of 76.6% to a maximum of 94.7%. The mean oxygen saturation was lower in the group with metabolic syndrome [89.9 (87.4–90.9) vs. 91.1 (88.8–92.5); p=0.001]. Furthermore, mean oxygen saturation was significantly correlated with the Epworth Sleepiness Scale score (r=–0.511, p<0.001). Conclusion: Our study, titled "Should the Duration of Oxygen Desaturation Be Used to Determine Disease Severity in Patients with Obstructive Sleep Apnea?", was conducted to evaluate the necessity of using oxygen desaturation parameters in determining disease severity among OSAS patients. Although current accepted protocols recommend using only the AHI score to determine disease severity, the data obtained from our study indicate that the AHI score may not always correlate positively with disease severity and may not fully reflect it on its own. When evaluating the relationship between oxygen desaturation parameters and disease severity, which constituted the main focus of our study, a strong association was found between these parameters and disease severity. Our study demonstrated that the use of parameters such as mean nocturnal oxygen saturation and the duration of oxygen saturation below 90% may provide benefits in determining the severity of the disease. Key words: Obstructive Sleep Apnea (OSA), Oxygen desaturation parameters, Severity of OSA