[Significance of respiratory event duration in evaluating nocturnal hypoxemia and disease severity in adults with obstructive sleep apnea]

Abstract

Objective: To analyze the correlation between respiratory event duration and nocturnal oxygen saturation (SpO₂) in adults with obstructive sleep apnea (OSA), and to explore its significance in assessing nocturnal hypoxemia and OSA severity. Methods: A prospective study was conducted on adult OSA patients diagnosed via overnight standard polysomnography (PSG) at the Department of Otolaryngology, First Affiliated Hospital of Sun Yat-sen University from June 2019 to December 2023. Data collected included demographic information, PSG reports, scale scores, and comorbidities. Patients were first stratified by apnea-hypopnea index (AHI) severity. Relationships between respiratory event duration parameters,including total apnea-hypopnea time (TAHT), percentage of total sleep time with apnea-hypopnea (AHT%), total apnea time (TAT), total hypopnea time (THT), and mean apnea-hypopnea time (MAHT), and nocturnal SpO₂ parameters, including average SpO₂ (aSpO₂), minimal SpO₂ (mSpO₂), mean oxygen desaturation (MOD), and percentage of total sleep time with SpO₂<90% (CT90), were analyzed. Patients were then divided into two groups based on the median MAHT (27.6 s) for SpO₂ comparison. Finally, severe OSA patients were further subclassified using an AHI inflection point (50 events/h) identified via scatter plot analysis to compare nocturnal SpO₂. Statistical analysis was performed using SPSS 27.0. Results: Among the 250 study subjects, there were 201 males and 49 females, with ages ranging from 18 to 76 years (mean age: 41.6 ± 11.9 years).TAHT, AHT%, and TAT in OSA patients demonstrated significant negative correlations with aSpO₂(r=-0.698, -0.718, -0.646)and mSpO₂(r=-0.746, -0.746, -0.748), while showing positive correlations with MOD (r=0.783, 0.791, 0.823)and CT90 (r=0.868, 0.866, 0.852),P<0.05. When stratified by MAHT median (M=27.6 s), the "long-event" subgroup (n=125) displayed significantly lower mSpO₂ and higher MOD and CT90 compared to the "short-event" subgroup (n=125), Z=-3.319, 3.288, 2.242;P<0.05. No significant difference in aSpO₂ was observed (P>0.05). Subgrouping severe OSA patients at AHI=50 events/hour revealed significant differences in aSpO₂, mSpO₂, MOD, and CT90 between groups (Z=-5.011, -4.787, 5.142, 6.117, P<0.05). Conclusions: TAHT, AHT%, and TAT significantly correlate with nocturnal SpO₂ parameters in OSA patients and can supplement AHI in assessing OSA severity. MAHT independently reflects nocturnal oxygenation status beyond AHI.