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

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.