{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,12]],"date-time":"2026-02-12T15:28:55Z","timestamp":1770910135120,"version":"3.50.1"},"reference-count":37,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"4","content-domain":{"domain":["lww.com","ovid.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2013,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n          <jats:sec>\n            <jats:title>Background:<\/jats:title>\n            <jats:p>During mechanical ventilation (MV), pulmonary shunt is cardiac output (CO) dependent; however, whether this relationship is valid during unsupported spontaneous breathing (SB) is unknown. The CO dependency of the calculated venous admixture was investigated, with both minor and major shunt, during unsupported SB, MV, and SB with continuous positive airway pressure (CPAP).<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Methods:<\/jats:title>\n            <jats:p>In seven anesthetized supine piglets breathing 100% oxygen, unsupported SB, MV (with tidal volume and respiratory rate corresponding to SB), and 8 cm H<jats:sub>2<\/jats:sub>O CPAP (airway pressure corresponding to MV) were applied at random. Venous return and CO were reduced by partial balloon occlusion of the inferior vena cava. Measurements were repeated with the left main bronchus blocked, creating a nonrecruitable pulmonary shunt.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results:<\/jats:title>\n            <jats:p>CO decreased from 4.2 l\/min (95% CI, 3.9\u20134.5) to 2.5 l\/min (95% CI, 2.2\u20132.7) with partially occluded venous return. Irrespective of whether shunt was minor or major, during unsupported SB, venous admixture was independent of CO (slope: minor shunt, 0.5; major shunt, 1.1%\u00b7min<jats:sup>\u22121<\/jats:sup>\u00b7l<jats:sup>\u22121<\/jats:sup>) and mixed venous oxygen tension. During both MV and CPAP, venous admixture was dependent on CO (slope MV: minor shunt, 1.9; major shunt, 3.5; CPAP: minor shunt, 1.3; major shunt, 2.9%\u00b7min<jats:sup>\u22121<\/jats:sup>\u00b7l<jats:sup>\u22121<\/jats:sup>) and mixed-venous oxygen tension (coefficient of determination 0.61\u20130.86 for all regressions).<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusions:<\/jats:title>\n            <jats:p>In contrast to MV and CPAP, venous admixture was independent of CO during unsupported SB, and was unaffected by mixed-venous oxygen tension, casting doubt on the role of hypoxic pulmonary vasoconstriction in pulmonary blood flow redistribution during unsupported SB.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1097\/aln.0b013e318283c81f","type":"journal-article","created":{"date-parts":[[2013,1,18]],"date-time":"2013-01-18T08:14:17Z","timestamp":1358496857000},"page":"914-923","update-policy":"https:\/\/doi.org\/10.1097\/lww.0000000000001000","source":"Crossref","is-referenced-by-count":5,"title":["Pulmonary Shunt Is Independent of Decrease in Cardiac Output during Unsupported Spontaneous Breathing in the Pig"],"prefix":"10.1097","volume":"118","author":[{"given":"Laszlo","family":"Vimlati","sequence":"first","affiliation":[{"name":"Department of Surgical Sciences, Anesthesiology and Critical Care, Uppsala University, Uppsala, Sweden; Consultant, Uppsala Cancer Clinic, Uppsala, Sweden."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anders","family":"Larsson","sequence":"additional","affiliation":[{"name":"Professor"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Goran","family":"Hedenstierna","sequence":"additional","affiliation":[{"name":"Professor, Department of Medical Sciences, Clinical Physiology, Uppsala University."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michael","family":"Lichtwarck-Aschoff","sequence":"additional","affiliation":[{"name":"Associate Professor, Department of Surgical Sciences, Anesthesiology and Critical Care, Uppsala University."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"276","reference":[{"issue":"4 Pt 1","key":"R1-20241219","first-page":"1241","article-title":"Spontaneous breathing during ventilatory support improves ventilation-perfusion distributions in patients with acute respiratory distress syndrome.","volume":"159","year":"1999","journal-title":"Am J Respir Crit Care Med"},{"key":"R2-20241219","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1097\/00000542-200308000-00019","article-title":"Spontaneous breathing improves lung aeration in oleic acid-induced lung injury.","volume":"99","year":"2003","journal-title":"Anesthesiology"},{"key":"R3-20241219","doi-asserted-by":"crossref","first-page":"1090","DOI":"10.1097\/01.CCM.0000163226.34868.0A","article-title":"Spontaneous breathing affects the spatial ventilation and perfusion distribution during mechanical ventilatory support.","volume":"33","year":"2005","journal-title":"Crit Care Med"},{"key":"R4-20241219","doi-asserted-by":"crossref","first-page":"856","DOI":"10.1213\/ane.0b013e3181aff245","article-title":"Pressure support ventilation and biphasic positive airway pressure improve oxygenation by redistribution of pulmonary blood flow.","volume":"109","year":"2009","journal-title":"Anesth Analg"},{"key":"R5-20241219","doi-asserted-by":"crossref","first-page":"1089","DOI":"10.1213\/ANE.0b013e31822ceef8","article-title":"Spontaneous breathing improves shunt fraction and oxygenation in comparison with controlled ventilation at a similar amount of lung collapse.","volume":"113","year":"2011","journal-title":"Anesth Analg"},{"key":"R6-20241219","doi-asserted-by":"crossref","first-page":"428","DOI":"10.1097\/00000542-198311000-00012","article-title":"Influence of mixed venous oxygen tension (PVO2) on blood flow to atelectatic lung.","volume":"59","year":"1983","journal-title":"Anesthesiology"},{"key":"R7-20241219","doi-asserted-by":"crossref","first-page":"291","DOI":"10.1007\/BF01708968","article-title":"Role of hypoxic pulmonary vasoconstriction in pulmonary gas exchange and blood flow distribution. 1. 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