{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T05:55:10Z","timestamp":1781502910818,"version":"3.54.1"},"reference-count":14,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T00:00:00Z","timestamp":1781481600000},"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. Cardiovasc. Med."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Perioperative hypoxemia during one-lung ventilation (OLV) is commonly managed by applying positive end-expiratory pressure (PEEP) to recruit the dependent lung. However, in rare instances, PEEP escalation may paradoxically compromise oxygenation. We describe a case in which a transient rise in right-sided pressures relative to left-sided pressures likely unmasked a pressure-dependent right-to-left intracardiac shunt.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case presentation<\/jats:title>\n                    <jats:p>\n                      A 55-year-old male underwent elective video-assisted thoracoscopic surgery (VATS) right upper lobe resection. During otherwise stable OLV, mild hypoxemia (SpO\n                      <jats:sub>2<\/jats:sub>\n                      88%\u201390%) prompted escalation of PEEP from 5 to 10\u2005cmH\n                      <jats:sub>2<\/jats:sub>\n                      O. Paradoxically, SpO\n                      <jats:sub>2<\/jats:sub>\n                      abruptly declined to 82% within 2\u2005min despite hemodynamic stability and no evidence of an acute mechanical or surgical cause. Suspecting a pressure-dependent shunt, PEEP was reduced to 2\u2005cmH\n                      <jats:sub>2<\/jats:sub>\n                      O, with rapid recovery of SpO\n                      <jats:sub>2<\/jats:sub>\n                      to 96%\u201398%. Emergent intraoperative transthoracic echocardiography was nondiagnostic owing to limited acoustic windows. Postoperative evaluation identified an anatomical PFO on transesophageal echocardiography and a small right-to-left shunt on contrast-enhanced transcranial Doppler, supporting the suspected pressure-dependent shunting mechanism.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>This case illustrates that PEEP can be a double-edged sword during OLV. Under certain conditions, escalating airway pressure may transiently reverse the interatrial pressure gradient and facilitate right-to-left shunting across a PFO. When oxygenation deteriorates following a recruitment maneuver, clinicians should resist reflexive PEEP escalation and consider an intracardiac shunt as a potentially reversible cause; in this context, PEEP reduction may serve as both a diagnostic probe and a therapeutic rescue.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fcvm.2026.1878145","type":"journal-article","created":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T05:33:53Z","timestamp":1781501633000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Case Report: Paradoxical worsening of hypoxemia with PEEP during one-lung ventilation: a case of pressure-dependent intracardiac shunting"],"prefix":"10.3389","volume":"13","author":[{"given":"Xinrui","family":"Yin","sequence":"first","affiliation":[{"name":"Department of Anesthesiology, Aerospace Center Hospital","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shijia","family":"Du","sequence":"additional","affiliation":[{"name":"Department of VIP Dental Service, Peking University Stomatological Hospital","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,6,15]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"898","DOI":"10.1016\/j.bja.2019.08.017","article-title":"Lung-protective ventilation for the surgical patient: international expert panel-based consensus recommendations","volume":"123","author":"Young","year":"2019","journal-title":"Br J Anaesth"},{"key":"B2","doi-asserted-by":"publisher","first-page":"324","DOI":"10.1016\/j.bja.2019.10.024","article-title":"Intraoperative ventilation strategies to prevent postoperative pulmonary complications: a network meta-analysis of randomised controlled trials","volume":"124","author":"Deng","year":"2020","journal-title":"Br J Anaesth"},{"key":"B3","doi-asserted-by":"publisher","first-page":"17","DOI":"10.1016\/S0025-6196(12)60336-X","article-title":"Incidence and size of patent foramen ovale during the first 10 decades of life: an autopsy study of 965 normal hearts","volume":"59","author":"Hagen","year":"1984","journal-title":"Mayo Clin Proc"},{"key":"B4","doi-asserted-by":"publisher","first-page":"e1","DOI":"10.1164\/rccm.201505-0967IM","article-title":"Weaning failure for disproportionate hypoxemia caused by paradoxical response to positive end-expiratory pressure in a patient with patent foramen ovale","volume":"193","author":"Tavazzi","year":"2016","journal-title":"Am J Respir Crit Care Med"},{"key":"B5","doi-asserted-by":"publisher","first-page":"2932","DOI":"10.1161\/STROKEAHA.124.046907","article-title":"Transcranial Doppler with microbubbles: screening test to detect and grade right-to-left shunt after an ischemic stroke: a literature review","volume":"55","author":"Palazzo","year":"2024","journal-title":"Stroke"},{"key":"B6","doi-asserted-by":"publisher","first-page":"e106","DOI":"10.1016\/j.bja.2022.06.037","article-title":"Driving pressure-guided ventilation and postoperative pulmonary complications in thoracic surgery: a multicentre randomised clinical trial","volume":"130","author":"Park","year":"2023","journal-title":"Br J Anaesth"},{"key":"B7","doi-asserted-by":"publisher","first-page":"3182","DOI":"10.1093\/eurheartj\/ehy649","article-title":"European Position paper on the management of patients with patent foramen ovale. 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