The importance of duration of respiratory events in the diagnosis and staging of patients with obstructive sleep apnea

Aim: The apnea-hypopnea index (AHI) is used to determine the presence and severity of the disease in PSG. AHI is calculated by summing apnea and hypopnea events per hour during sleep. Mean apnoea-hypopnoea duration (MAD) is the average duration of apnoea-hypopnoea during sleep. Intermittent hypoxemia is the primary cause of OSA pathophysiology. Therefore, the duration of respiratory events is as important as their number. However, MAD is still not used in the diagnosis and grading of OSA, and the number of studies investigating how MAD is reflected in the clinical parameters of patients and its relationship with other OSA risk factors are insufficient. The using of MAD parameters in addition to AHI in determining the severity of OSA in patients with OSA may facilitate better understanding of severity and taking precautions against possible additional diseases. The aim of this study is to compare clinical and demographic parameters, blood oxygenation, AHI and MAD use in patients diagnosed with OSA by PSG. Materials and Method: A total of 200 patients who applied to our clinic with OSA symptoms between 2014 and 2019 and were diagnosed with OSA (AHI≥ 5/h) over the age of 18 who underwent polysomnography in Ankara University Medical Faculty Chest Diseases Sleep Laboratory were included. According to the AHI value of the patients, the severity was classified as mild, moderate and severe OSA. The power of MAD values to differentiate patients with severe OSA was evaluated by the area under the ROC Curve (AUC). The best cut-off point was calculated using Youden's Index. The study is retrospective and cross-sectional. Results: In OSA patients included in the study, HT rate 47%, DM rate 32%, coronary artery disease (CAD) rate 17.5%, hyperlipidemia (HL) rate 17%, Heart Failure rate 1.5%, asthma rate 8%, chronic obstructive pulmonary disease rate disease (COPD) rate was 5.5%, hypothyroidism rate was 10.5%, depression rate was 13%, gastroesophageal reflux disease (GERD) rate was 11%, and arrhythmia rate was 6.5%. It was determined that 34% of the patients had mild OSA, 33% had moderate OSA, and 33% had severe OSA. There was no difference between the patients with OSA and the chronic diseases of the patients. The BMI values of those with severe OSA were higher than those with mild OSA. It was observed that the male ratio was higher in patients with severe OSA than in those with mild OSA. The MAD value was found to be higher in severe OSA than in mild OSA and mild+moderate OSA. The total ODI value was found to be higher in patients with severe OSA than in those with both mild and moderate OSA. Severe OSA's Avg. SpO₂, min. SpO₂ values were found to be lower than those with both mild and moderate OSA. Average+severe OSA SpO₂ and min. SpO₂ was found to be lower than those with mild OSA, and T.ODI was found to be significantly higher. AUC (Area Under the Curve) was found to be significant for MAD values in differentiating those with severe OSA, and the best cut-off point was found to be >16.86. MAD values of patients with moderate+severe OSA were found to be higher than those with mild OSA. AUC was found to be significant for MAD values in differentiating patients with moderate+severe OSA, and the best cut-off point was found to be >20.76. Chronic diseases, BMI, gender, Avg. SpO₂, Min. SpO₂, T.ODI were found to be similar. Conclusion: It is clear that the duration of respiratory events should be measured in addition to AHI when diagnosing and evaluating the severity of OSA and taking precautions against possible comorbidities.