{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T12:45:57Z","timestamp":1785761157708,"version":"3.56.0"},"reference-count":30,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2026,8,1]],"date-time":"2026-08-01T00:00:00Z","timestamp":1785542400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Background: This study evaluated the use of circulation time (Tcirc) calculated from polysomnogram (PSG) with pulse oximetry to identify poor cardiac function with low left ventricular ejection fraction (EF). Methods: Subjects over 18 years of age with sleep apnea (apnea-hypopnea index (AHI) &gt; 5\/h diagnosed by PSG who had transthoracic echocardiography (TTE) within 1 year of PSG were included in this retrospective study. Tcirc of each sleep stage (N2, N3, and REM) were measured and averaged and EF was recorded. Statistical analysis was carried out using the Wilcoxon rank sum test, logistic regression and Youden index. Results: There were 89 subjects who met the inclusion criteria, 14 with EF \u2264 45% (Group A) and 75 with EF \u2265 50% (Group B). The normal Tcirc is &lt;20 s, but Group A subjects had a prolonged overall Tcirc with a median time of 27.8 s (range 14.1\u201339.6 s), compared to Group B subjects with a median Tcirc of 23.5 s (range 14.3\u201337.6 s), p = 0.311. The optimal cut-point for overall sleep Tcirc with moderate discrimination (AUC = 0.6) was 28.6 s. Those with total sleep Tcirc \u2265 28.6 s were 2.5\u00d7 more likely to have low EF with OR = 2.56 (95% CI, 0.55\u201311.16). Conclusions: In sleep apnea patients, total sleep Tcirc &gt; 28.6 s is associated with low ejection fraction with specificity = 0.78.<\/jats:p>","DOI":"10.3390\/s26154849","type":"journal-article","created":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T11:50:21Z","timestamp":1785757821000},"page":"4849","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Sleep Circulation Time from Pulse Oximetry and Polysomnography: Predictive Value in Patients with Heart Failure with Reduced Ejection Fraction"],"prefix":"10.3390","volume":"26","author":[{"given":"Wei Jung","family":"Hsia","sequence":"first","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90023, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jack","family":"Rodman","sequence":"additional","affiliation":[{"name":"Southern California Clinical and Translational Science Institute, University of Southern California, Los Angeles, CA 90089, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Benjamin","family":"Cantrill","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90023, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3502-4558","authenticated-orcid":false,"given":"Richard J.","family":"Castriotta","sequence":"additional","affiliation":[{"name":"Division of Pulmonary, Critical Care and Sleep Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90023, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/S0272-5231(21)00051-4","article-title":"Respiratory disturbances during sleep","volume":"1","author":"Remmers","year":"1980","journal-title":"Clin. 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