{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T03:09:28Z","timestamp":1781233768319,"version":"3.54.1"},"reference-count":32,"publisher":"Oxford University Press (OUP)","issue":"6","license":[{"start":{"date-parts":[[2026,3,20]],"date-time":"2026-03-20T00:00:00Z","timestamp":1773964800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["JP23K08466"],"award-info":[{"award-number":["JP23K08466"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,6,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Rationale<\/jats:title>\n                    <jats:p>Positive end-expiratory pressure (PEEP) balances recruitment against over-inflation in acute respiratory distress syndrome (ARDS). The early response to a PEEP step-down remains under-characterized. Four-dimensional computed tomography (4D-CT) can quantify within-breath mechanics with anatomy-specific resolution.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>Using 4D-CT to characterize the early (3-5\u2009minutes) effects of PEEP step-down (15 to 5 cmH2O) on tidal recruitment and over-inflation in ARDS patients.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In a prospective, single-center, physiological study, 40 patients with stabilized ARDS (77.5% with PaO2\/FIO2 \u2265150, median normalized respiratory system compliance 0.78\u2009mL\/cmH2O\/kg) received lung-protective volume-controlled ventilation with median PEEP of 8 cmH2O. 4D-CT was obtained at PEEP 15\u202fcmH2O and 3-5\u202fmin after a PEEP step-down to 5\u202fcmH2O. We quantified tidal recruitment (\u2212200 to +100\u202fHU) and over-inflation (\u22121000 to \u2212901\u202fHU).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Measurements and Main Results<\/jats:title>\n                    <jats:p>Tidal recruitment was low at high PEEP and minimally increased at low PEEP, from 1.15% to 1.84% of expiratory tissue weight (P\u2009&amp;lt;\u2009.001). End-inspiratory over-inflation decreased from 11.9% to 5.2% of end-inspiratory lung volume (P\u2009&amp;lt;\u2009.001), and tidal over-inflation decreased from 42.5% to 18.3% of tidal volume (P\u2009&amp;lt;\u2009.001). End-expiratory lung volume (EELV) substantially decreased (median \u2212787\u202fmL, 95%\u202fCI \u2212952 to \u2212743\u2009mL, P\u2009&amp;lt;\u2009.001), and the volume loss exceeded the passive elastic prediction, indicating substantial alveolar derecruitment. In exploratory analyses, the recruitment-to-inflation ratio did not modify the tidal recruitment response.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>At 3-5\u2009minutes after a PEEP step-down from 15 to 5 cmH2O, 4D-CT showed large EELV loss, substantial alveolar derecruitment, and reduced over-inflation, while tidal recruitment slightly increased and remained low. These results are compatible with a condition in which alveolar units prone to closure respond by closing and remaining closed.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial Registration<\/jats:title>\n                    <jats:p>UMIN000049583.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/ajrccm\/aamag137","type":"journal-article","created":{"date-parts":[[2026,3,21]],"date-time":"2026-03-21T10:14:48Z","timestamp":1774088088000},"page":"1253-1264","source":"Crossref","is-referenced-by-count":1,"title":["Early changes of lung mechanics after positive end-expiratory pressure reduction in acute respiratory distress syndrome: a four-dimensional computed tomography study"],"prefix":"10.1093","volume":"212","author":[{"given":"Shinshu","family":"Katayama","sequence":"first","affiliation":[{"name":"Division of Intensive Care, Department of Anesthesiology and Intensive Care Medicine, Jichi Medical University School of Medicine , Shimotsuke, Tochigi,","place":["Japan"]},{"name":"Department of Anesthesiology and Critical Care Medicine, Jichi Medical University Saitama Medical Center , Omiya, Saitama,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ken","family":"Tonai","sequence":"additional","affiliation":[{"name":"Division of Intensive Care, Department of Anesthesiology and Intensive Care Medicine, Jichi Medical University School of Medicine , Shimotsuke, Tochigi,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hisashi","family":"Imahase","sequence":"additional","affiliation":[{"name":"Division of Intensive Care, Department of Anesthesiology and Intensive Care Medicine, Jichi Medical University School of Medicine , Shimotsuke, Tochigi,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shunsuke","family":"Saito","sequence":"additional","affiliation":[{"name":"Division of Cardiovascular Medicine, Department of Internal Medicine, Jichi Medical University School of Medicine , Shimotsuke, Tochigi,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ryuichi","family":"Nakayama","sequence":"additional","affiliation":[{"name":"Division of Intensive Care, Department of Anesthesiology and Intensive Care Medicine, Jichi Medical University School of Medicine , Shimotsuke, Tochigi,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giorgio Antonio","family":"Iotti","sequence":"additional","affiliation":[{"name":"Hamilton Medical , Bonaduz,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Atsuko","family":"Shono","sequence":"additional","affiliation":[{"name":"Division of Intensive Care, Department of Anesthesiology and Intensive Care Medicine, Jichi Medical University School of Medicine , Shimotsuke, Tochigi,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,3,20]]},"reference":[{"key":"2026061104164782700_aamag137-B1","doi-asserted-by":"crossref","first-page":"1301","DOI":"10.1056\/NEJM200005043421801","article-title":"Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network","volume":"342","year":"2000","journal-title":"N Engl J Med"},{"key":"2026061104164782700_aamag137-B2","doi-asserted-by":"publisher","first-page":"312","DOI":"10.1186\/s13054-017-1905-9","article-title":"Regional physiology of ARDS","volume":"21","author":"Gattinoni","year":"2017","journal-title":"Crit Care"},{"key":"2026061104164782700_aamag137-B3","doi-asserted-by":"publisher","first-page":"3","DOI":"10.1097\/MCC.0000000000000579","article-title":"Bedside respiratory physiology to detect risk of lung injury in acute respiratory distress syndrome","volume":"25","author":"Beitler","year":"2019","journal-title":"Curr Opin Crit Care"},{"key":"2026061104164782700_aamag137-B4","doi-asserted-by":"publisher","first-page":"327","DOI":"10.1056\/NEJMoa032193","article-title":"Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome","volume":"351","author":"Brower","year":"2004","journal-title":"N Engl J Med"},{"key":"2026061104164782700_aamag137-B5","doi-asserted-by":"publisher","first-page":"20","DOI":"10.1097\/MCC.0000000000001121","article-title":"Setting positive end-expiratory pressure: does the \u2018best compliance\u2019 concept really work?","volume":"30","author":"Menga","year":"2024","journal-title":"Curr Opin Crit Care"},{"key":"2026061104164782700_aamag137-B6","doi-asserted-by":"publisher","first-page":"2125","DOI":"10.1007\/s00134-024-07695-y","article-title":"Personalized positive end-expiratory pressure in spontaneously breathing patients with acute respiratory distress syndrome by simultaneous electrical impedance tomography and transpulmonary pressure monitoring: a randomized crossover trial","volume":"50","author":"Mauri","year":"2024","journal-title":"Intensive Care Med"},{"key":"2026061104164782700_aamag137-B7","doi-asserted-by":"publisher","first-page":"762","DOI":"10.1007\/s00134-024-07397-5","article-title":"Positive end-expiratory pressure optimization in ARDS: physiological evidence, bedside methods and clinical applications","volume":"50","author":"Battaglini","year":"2024","journal-title":"Intensive Care Med"},{"key":"2026061104164782700_aamag137-B8","doi-asserted-by":"publisher","first-page":"178","DOI":"10.1164\/rccm.201902-0334OC","article-title":"Potential for lung recruitment estimated by the recruitment-to-inflation ratio in acute respiratory distress syndrome: a clinical trial","volume":"201","author":"Chen","year":"2020","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B9","doi-asserted-by":"publisher","first-page":"1775","DOI":"10.1056\/NEJMoa052052","article-title":"Lung recruitment in patients with the acute respiratory distress syndrome","volume":"354","author":"Gattinoni","year":"2006","journal-title":"N Engl J Med"},{"key":"2026061104164782700_aamag137-B10","doi-asserted-by":"publisher","first-page":"e70","DOI":"10.1164\/rccm.202201-0120IM","article-title":"Four-dimensional computed tomography of paradoxical motion of eventrated diaphragm induced by reverse triggering","volume":"206","author":"Tonai","year":"2022","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B11","doi-asserted-by":"publisher","first-page":"e41","DOI":"10.1164\/rccm.202303-0413IM","article-title":"Intercostal recession and bulging during pendelluft detected in four-dimensional computed tomography","volume":"208","author":"Katayama","year":"2023","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B12","doi-asserted-by":"publisher","first-page":"490","DOI":"10.1164\/rccm.202208-1545IM","article-title":"Upward diaphragm motion on four-dimensional computed tomography in severe diaphragm weakness","volume":"208","author":"Tonai","year":"2023","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B13","doi-asserted-by":"publisher","first-page":"592","DOI":"10.1164\/rccm.202309-1659LE","article-title":"Can four-dimensional computed tomography assess dynamic changes in lung volumes in mechanically ventilated patients?","volume":"209","author":"Katayama","year":"2024","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B14","doi-asserted-by":"publisher","first-page":"336","DOI":"10.1186\/s13054-024-05130-8","article-title":"Regional ventilation dynamics of electrical impedance tomography validated with four-dimensional computed tomography: single-center, prospective, observational study","volume":"28","author":"Katayama","year":"2024","journal-title":"Crit Care"},{"key":"2026061104164782700_aamag137-B15","doi-asserted-by":"publisher","first-page":"410","DOI":"10.1164\/rccm.202405-0956IM","article-title":"Vigorous diaphragm movement captured by four-dimensional computed tomography in quadriplegia patient","volume":"211","author":"Shono","year":"2025","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B16","doi-asserted-by":"publisher","first-page":"1573","DOI":"10.1007\/s00134-012-2682-1","article-title":"The Berlin definition of ARDS: an expanded rationale, justification, and supplementary material","volume":"38","author":"Ferguson","year":"2012","journal-title":"Intensive Care Med"},{"key":"2026061104164782700_aamag137-B17","doi-asserted-by":"publisher","first-page":"1444","DOI":"10.1164\/ajrccm.163.6.2005001","article-title":"Computed tomography assessment of positive end-expiratory pressure-induced alveolar recruitment in patients with acute respiratory distress syndrome","volume":"163","author":"Malbouisson","year":"2001","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B18","doi-asserted-by":"publisher","first-page":"1571","DOI":"10.1164\/ajrccm.158.5.9802101","article-title":"A lung computed tomographic assessment of positive end-expiratory pressure-induced lung overdistension","volume":"158","author":"Vieira","year":"1998","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B19","doi-asserted-by":"publisher","first-page":"160","DOI":"10.1164\/rccm.200607-915OC","article-title":"Tidal hyperinflation during low tidal volume ventilation in acute respiratory distress syndrome","volume":"175","author":"Terragni","year":"2007","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B20","doi-asserted-by":"publisher","first-page":"1211","DOI":"10.1097\/ALN.0000000000005677","article-title":"Evaluation of the potential for lung recruitment with the recruitment-to-inflation ratio during general anesthesia","volume":"143","author":"Ros\u00e0","year":"2025","journal-title":"Anesthesiology"},{"key":"2026061104164782700_aamag137-B21","doi-asserted-by":"publisher","first-page":"1254","DOI":"10.1164\/rccm.201507-1413OC","article-title":"Lung recruitment assessed by respiratory mechanics and computed tomography in patients with acute respiratory distress syndrome. What is the relationship?","volume":"193","author":"Chiumello","year":"2016","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B22","doi-asserted-by":"publisher","first-page":"732","DOI":"10.1097\/CCM.0b013e3182711b6e","article-title":"Bedside estimation of nonaerated lung tissue using blood gas analysis","volume":"41","author":"Reske","year":"2013","journal-title":"Crit Care Med"},{"key":"2026061104164782700_aamag137-B23","doi-asserted-by":"publisher","first-page":"292","DOI":"10.1164\/rccm.200703-484OC","article-title":"Relation between shunt, aeration, and perfusion in experimental acute lung injury","volume":"177","author":"Musch","year":"2008","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B24","doi-asserted-by":"publisher","first-page":"109","DOI":"10.1148\/radiol.2421052066","article-title":"Multi-detector row CT attenuation measurements: assessment of intra- and interscanner variability with an anthropomorphic body CT phantom","volume":"242","author":"Birnbaum","year":"2007","journal-title":"Radiology"},{"key":"2026061104164782700_aamag137-B25","doi-asserted-by":"publisher","first-page":"903","DOI":"10.1097\/CCM.0b013e318236f452","article-title":"Tidal recruitment assessed by electrical impedance tomography and computed tomography in a porcine model of lung injury","volume":"40","author":"Muders","year":"2012","journal-title":"Crit Care Med"},{"key":"2026061104164782700_aamag137-B26","doi-asserted-by":"publisher","first-page":"e2419374122","DOI":"10.1073\/pnas.2419374122","article-title":"Mechanical ventilation energy analysis: recruitment focuses injurious power in the ventilated lung","volume":"122","author":"Gaver","year":"2025","journal-title":"Proc Natl Acad Sci U S A"},{"key":"2026061104164782700_aamag137-B27","doi-asserted-by":"publisher","first-page":"25","DOI":"10.1164\/rccm.202212-2300OC","article-title":"Lung recruitment assessed by electrical impedance tomography (RECRUIT): a multicenter study of COVID-19 acute respiratory distress syndrome","volume":"208","author":"Jonkman","year":"2023","journal-title":"Am J Respir Crit Care Med"},{"key":"2026061104164782700_aamag137-B28","doi-asserted-by":"publisher","first-page":"340","DOI":"10.1186\/s13054-015-1044-0","article-title":"Dynamics of end-expiratory lung volume after changing positive end-expiratory pressure in acute respiratory distress syndrome patients","volume":"19","author":"Garnero","year":"2015","journal-title":"Crit Care"},{"key":"2026061104164782700_aamag137-B29","doi-asserted-by":"publisher","first-page":"1377","DOI":"10.1007\/s00134-013-2969-x","article-title":"Time to reach a new steady state after changes of positive end-expiratory pressure","volume":"39","author":"Chiumello","year":"2013","journal-title":"Intensive Care Med"},{"key":"2026061104164782700_aamag137-B30","doi-asserted-by":"publisher","first-page":"100579","DOI":"10.1016\/j.eclinm.2020.100579","article-title":"Evaluation of PEEP and prone positioning in early COVID-19 ARDS","volume":"28","author":"Mittermaier","year":"2020","journal-title":"EClinicalMedicine"},{"key":"2026061104164782700_aamag137-B31","doi-asserted-by":"publisher","first-page":"995","DOI":"10.1097\/01.ccm.0000163402.29767.7b","article-title":"Time required for equilibration of arterial oxygen pressure after setting optimal positive end-expiratory pressure in acute respiratory distress syndrome","volume":"33","author":"Tugrul","year":"2005","journal-title":"Crit Care Med"},{"key":"2026061104164782700_aamag137-B32","doi-asserted-by":"publisher","first-page":"76","DOI":"10.1186\/s13613-017-0299-9","article-title":"Bedside selection of positive end-expiratory pressure by electrical impedance tomography in hypoxemic patients: a feasibility study","volume":"7","author":"Eronia","year":"2017","journal-title":"Ann Intensive Care"}],"container-title":["American Journal of Respiratory and Critical Care Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/ajrccm\/advance-article-pdf\/doi\/10.1093\/ajrccm\/aamag137\/67454165\/aamag137.pdf","content-type":"application\/pdf","content-version":"am","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/ajrccm\/article-pdf\/212\/6\/1253\/67454165\/aamag137.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/ajrccm\/article-pdf\/212\/6\/1253\/67454165\/aamag137.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,11]],"date-time":"2026-06-11T08:16:58Z","timestamp":1781165818000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/ajrccm\/article\/212\/6\/1253\/8532517"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,20]]},"references-count":32,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2026,3,20]]},"published-print":{"date-parts":[[2026,6,1]]}},"URL":"https:\/\/doi.org\/10.1093\/ajrccm\/aamag137","relation":{},"ISSN":["1073-449X","1535-4970"],"issn-type":[{"value":"1073-449X","type":"print"},{"value":"1535-4970","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2026,6]]},"published":{"date-parts":[[2026,3,20]]}}}