{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T05:52:08Z","timestamp":1791525128087,"version":"4.3.4"},"reference-count":39,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T00:00:00Z","timestamp":1791504000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Med."],"abstract":"\n Background<\/jats:title>\n \n Arterial oxygen content (CaO\n 2<\/jats:sub>\n ) combines hemoglobin-bound and dissolved oxygen. A time-weighted CaO\n 2<\/jats:sub>\n deficit could capture changing anemia and desaturation that a hemoglobin-only summary misses. We examined its association with hospital mortality and its added value beyond hemoglobin.\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n In this retrospective cohort study, we included mechanically ventilated adults from the Medical Information Mart for Intensive Care IV (MIMIC-IV) and eICU Collaborative Research Database (eICU). The MIMIC-IV 25th percentile of the first matched CaO\n 2<\/jats:sub>\n value (12.48\u2005mL O\n 2<\/jats:sub>\n \/dL) was prespecified as an empirical cutoff and was applied unchanged to eICU. The first-24-h burden integrated the time-weighted deficit below this cutoff. Models were adjusted for demographics and diagnosis-derived case mix. We compared CaO\n 2<\/jats:sub>\n burden with hemoglobin burden calculated at the same blood-gas time points and performed landmark, measurement-coverage, severity, and\n post hoc<\/jats:italic>\n peripheral oxygen saturation (SpO\n 2<\/jats:sub>\n )-stratified analyses.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Burden was available for 14,050 MIMIC-IV and 20,780 eICU stays. CaO\n 2<\/jats:sub>\n was strongly correlated with hemoglobin (\n r<\/jats:italic>\n \u2009=\u20090.965 and 0.949, respectively), which explained\n R<\/jats:italic>\n 2<\/jats:sup>\n \u2009=\u20090.932 and 0.901 of first-measurement CaO\n 2<\/jats:sub>\n variation, respectively; median dissolved-oxygen contributions were 2.9% and 2.5%, respectively. Per 1-SD higher burden, adjusted odds ratios for hospital mortality were 1.33 (95% confidence interval 1.28\u20131.39) in MIMIC-IV and 1.29 (1.24\u20131.35) in eICU. Additional Acute Physiology and Chronic Health Evaluation adjustment attenuated the eICU estimate to 1.14 (1.10\u20131.19), while 24-h landmark estimates were 1.26 (1.21\u20131.32) and 1.19 (1.14\u20131.25), respectively. Cross-validated area under the receiver operating characteristic curve (AUROC) gains over matched hemoglobin burden were 0.006 and 0.010, respectively, and calibration was similar. In\n post hoc<\/jats:italic>\n analyses, hemoglobin explained less CaO\n 2<\/jats:sub>\n variation when first SpO\n 2<\/jats:sub>\n was &lt;90% (\n R<\/jats:italic>\n 2<\/jats:sup>\n \u2009=\u20090.787 and 0.682, respectively) than when it was \u226595% (\n R<\/jats:italic>\n 2<\/jats:sup>\n \u2009=\u20090.973 and 0.978, respectively); corresponding AUROC gains were 0.045 and 0.044 versus 0.002 in both databases.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n \n In cohorts dominated by preserved oxygen saturation, low CaO\n 2<\/jats:sub>\n was predominantly an anemia-related signal, and its association with mortality was substantially attenuated by illness-severity adjustment. The burden is best viewed as a compact observational summary of the depth and duration of low arterial oxygen content, not as an independent measure of tissue oxygenation, a superior prediction model, or a treatment target.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fmed.2026.1935082","type":"journal-article","created":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T05:34:55Z","timestamp":1791524095000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Low arterial oxygen-content burden during the first 24\u2005h and hospital mortality in mechanically ventilated adults: analyses of MIMIC-IV and eICU"],"prefix":"10.3389","volume":"13","author":[{"given":"Xiaoyan","family":"Gao","sequence":"first","affiliation":[{"name":"Department of Pulmonary and Critical Care Medicine, The Sixth Hospital of Wuhan, Affiliated Hospital of Jianghan University","place":["Wuhan, Hubei, 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China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cheng","family":"Jiang","sequence":"additional","affiliation":[{"name":"Department of Pulmonary and Critical Care Medicine, The Sixth Hospital of Wuhan, Affiliated Hospital of Jianghan University","place":["Wuhan, Hubei, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juan","family":"Li","sequence":"additional","affiliation":[{"name":"Community Health Service Center of Minquan Street, Jianghan District","place":["Wuhan, Hubei, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shi","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Pulmonary and Critical Care Medicine, The Sixth Hospital of Wuhan, Affiliated Hospital of Jianghan University","place":["Wuhan, Hubei, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cong","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Pulmonary and Critical 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