Abstract Rationale Chronic Obstructive Pulmonary Disease (COPD) and Obstructive Sleep Apnea (OSA) are comorbid conditions that lead to compounded respiratory load and nocturnal hypoxemia. Apnea Time/Disordered Breathing Time (AT/DBT) is a surrogate of passive critical closing pressure (Pcrit), which reflects upper-airway collapsibility. Because individuals with COPD generally exhibit lower Pcrit and those with OSA have higher Pcrit, we examined how AT/DBT may vary across OSA severity and COPD severity to understand physiologic interactions along the comorbid spectrum. Methods We analyzed overnight polysomnography data from 483 participants in the Sleep Heart Health Study with available spirometry. Participants were stratified by tertiles of post-bronchodilator FEV1 (L) and by mild to severe categories of sleep-disordered breathing. AT/DBT was defined as total apnea duration divided by total apnea and hypopnea time. Multivariable linear regression models evaluated associations between OSA severity, FEV1 severity, and their interaction on AT/DBT, adjusting for age, body-mass index (BMI), and race. RESULST: Among 483 participants (mean age 68 ± 8.9 years, 30 % female, mean BMI 29.1 ± 5.3 kg/m²), predicted mean AT/DBT increased across OSA severity and differed by degree of airflow limitation (overall p 0.001). In the lowest FEV1 quartile, AT/DBT rose from 0.18 in mild OSA to 0.26 in moderate OSA (p = 0.04) and 0.44 in severe OSA (p 0.001). In the highest FEV1 quartile, corresponding values were 0.29, 0.34, and 0.54 (p 0.001 for trend). Conclusion Across all categories of ventilation impairment, upper airway collapsibility increased with increases sleep apnea severity. With increasing ventilation impairment, upper airway collapsibility was lower in mild and moderate stages of sleep apnea compared with severe, likely through well known mechanisms of tracheal tugging. Future studies should investigate whether AT/DBT can serve as a dynamic marker of evolving Pcrit to guide early detection, risk stratification, and targeted therapy in patients with comorbid obstructive lung and sleep disorders. This abstract is funded by: 1F32HL182345-01
Karmali et al. (Fri,) studied this question.