• Eric Staykov, Dwayne L Mann, Brett Duce, Samu Kainulainen, Timo Leppänen, Juha Töyräs, Ali Azarbarzin, Thomas Georgeson, Scott A Sands, and Philip I Terrill.
• School of Electrical Engineering and Computer Science, The University of Queensland, Brisbane, QLD, Australia. Electronic address: e.staykov@uq.edu.au.
• Chest. 2024 Apr 1; 165 (4): 9901003990-1003.

BackgroundImpaired daytime vigilance is an important consequence of OSA, but several studies have reported no association between objective measurements of vigilance and the apnea-hypopnea index (AHI). Notably, the AHI does not quantify the degree of flow limitation, that is, the extent to which ventilation fails to meet intended ventilation (ventilatory drive).Research QuestionIs flow limitation during sleep associated with daytime vigilance in OSA?Study Design And MethodsNine hundred ninety-eight participants with suspected OSA completed a 10-min psychomotor vigilance task (PVT) before same-night in-laboratory polysomnography. Flow limitation frequency (percent of flow-limited breaths) during sleep was quantified using airflow shapes (eg, fluttering and scooping) from nasal pressure airflow. Multivariable regression assessed the association between flow limitation frequency and the number of lapses (response times > 500 ms, primary outcome), adjusting for age, sex, BMI, total sleep time, depression, and smoking status.ResultsIncreased flow limitation frequency was associated with decreased vigilance: a 1-SD (35.3%) increase was associated with 2.1 additional PVT lapses (95% CI, 0.7-3.7; P = .003). This magnitude was similar to that for age, where a 1-SD increase (13.5 years) was associated with 1.9 additional lapses. Results were similar after adjusting for AHI, hypoxemia severity, and arousal severity. The AHI was not associated with PVT lapses (P = .20). In secondary exploratory analysis, flow limitation frequency was associated with mean response speed (P = .012), median response time (P = .029), fastest 10% response time (P = .041), slowest 10% response time (P = .018), and slowest 10% response speed (P = .005).InterpretationIncreased flow limitation during sleep was associated with decreased daytime vigilance in individuals with suspected OSA, independent of the AHI. Flow limitation may complement standard clinical metrics in identifying individuals whose vigilance impairment most likely is explained by OSA.Copyright © 2023 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

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