Neurally Adjusted Ventilatory Assist vs Pressure Support Ventilation: Short-Term Effects on Shunt and Dead Space after Cardiac Surgery

Neurally Adjusted Ventilatory Assist vs Pressure Support Ventilation: Short-Term Effects on Shunt and Dead Space after Cardiac Surgery | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Neurally Adjusted Ventilatory Assist vs Pressure Support Ventilation: Short-Term Effects on Shunt and Dead Space after Cardiac Surgery Andreas Martinsson, Carl Lundholm, Sven-Erik Ricksten, Jonatan Oras, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7502329/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 21 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted 13 You are reading this latest preprint version Abstract Background: Postoperative pulmonary complications, particularly atelectasis, are common after cardiac surgery and may contribute to impaired gas exchange or acute lung injury (ALI). Neurally Adjusted Ventilatory Assist (NAVA) delivers ventilatory support proportional to the patient’s respiratory drive, offering theoretical advantages over Pressure Support Ventilation (PSV), including improved synchrony, enhanced diaphragmatic efficiency, and reduced risk of ventilator-induced lung injury. However, comparative data on gas exchange, dead space, and regional ventilation during weaning after cardiac surgery remain limited. Methods: This prospective crossover study evaluated 12 mechanically ventilated patients with mild ALI following cardiac surgery across three ventilation phases: two PSV phases (PSV1 and PSV2) separated by a phase of NAVA. Intrapulmonary shunt fraction was calculated from measurements obtained via a Swan-Ganz catheter. Physiological dead space fraction (V D /V T ) was assessed using three methods: the Bohr–Enghoff equation, end-tidal CO₂-derived alveolar dead space fraction (AVDSf-ET), and a novel time-to-volume converted capnographic approach (V CAP−CALC ). Regional ventilation was assessed using electrical impedance tomography (EIT), and neuroventilatory efficiency (NVE) was calculated from diaphragmatic electrical activity (EAdi). Data were analyzed using linear mixed-effects models to account for repeated measures and within-subject variability. Results: V D /V T was significantly lower during NAVA compared with PSV1 and PSV2 when assessed by V CAP−CALC (58.5% vs. 63.8% and 61.3%, respectively; p < 0.001). The PaO₂/FiO₂ ratio and NVE were significantly higher during NAVA ( p = 0.01 and p = 0.039, respectively). No significant difference in pulmonary shunt fraction was observed. EIT revealed a modest increase in dorsal end-expiratory lung volume during NAVA, without redistribution of tidal volume or Center of Ventilation. The V CAP−CALC method showed strong agreement with established dead space measures (R² = 0.77–0.82) and demonstrated high repeatability (mean coefficient of variation 3.5%). Conclusion: NAVA is a safe and feasible ventilatory mode following cardiac surgery, associated with reduced dead space fraction, improved oxygenation and enhanced neuroventilatory efficiency. Given that shunt fraction remained unchanged, the observed improvement in ventilation–perfusion (V/Q) matching reflects a reduction in V D /V T . These findings suggest that NAVA may facilitate respiratory recovery following cardiac surgery. ClinicalTrials.gov: NCT03217305. Initial Release 21/06/2017. Health sciences/Cardiology Health sciences/Diseases Health sciences/Medical research Biological sciences/Physiology Full Text Additional Declarations No competing interests reported. Supplementary Files TheNAVAPSVstudySupplements.docx Cite Share Download PDF Status: Published Journal Publication published 21 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 12 Oct, 2025 Reviews received at journal 29 Sep, 2025 Reviews received at journal 28 Sep, 2025 Reviews received at journal 23 Sep, 2025 Reviewers agreed at journal 18 Sep, 2025 Reviewers agreed at journal 17 Sep, 2025 Reviewers agreed at journal 15 Sep, 2025 Reviewers agreed at journal 15 Sep, 2025 Reviewers invited by journal 15 Sep, 2025 Editor assigned by journal 15 Sep, 2025 Editor invited by journal 03 Sep, 2025 Submission checks completed at journal 02 Sep, 2025 First submitted to journal 02 Sep, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7502329","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":518183033,"identity":"aaf941ab-19fb-471b-9431-78a3191770fe","order_by":0,"name":"Andreas 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Surgery","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7502329/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7502329/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePostoperative pulmonary complications, particularly atelectasis, are common after cardiac surgery and may contribute to impaired gas exchange or acute lung injury (ALI). Neurally Adjusted Ventilatory Assist (NAVA) delivers ventilatory support proportional to the patient’s respiratory drive, offering theoretical advantages over Pressure Support Ventilation (PSV), including improved synchrony, enhanced diaphragmatic efficiency, and reduced risk of ventilator-induced lung injury. However, comparative data on gas exchange, dead space, and regional ventilation during weaning after cardiac surgery remain limited.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis prospective crossover study evaluated 12 mechanically ventilated patients with mild ALI following cardiac surgery across three ventilation phases: two PSV phases (PSV1 and PSV2) separated by a phase of NAVA. Intrapulmonary shunt fraction was calculated from measurements obtained via a Swan-Ganz catheter. Physiological dead space fraction (V\u003csub\u003eD\u003c/sub\u003e/V\u003csub\u003eT\u003c/sub\u003e) was assessed using three methods: the Bohr–Enghoff equation, end-tidal CO₂-derived alveolar dead space fraction (AVDSf-ET), and a novel time-to-volume converted capnographic approach (V\u003csub\u003eCAP−CALC\u003c/sub\u003e). Regional ventilation was assessed using electrical impedance tomography (EIT), and neuroventilatory efficiency (NVE) was calculated from diaphragmatic electrical activity (EAdi). Data were analyzed using linear mixed-effects models to account for repeated measures and within-subject variability.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eV\u003csub\u003eD\u003c/sub\u003e/V\u003csub\u003eT\u003c/sub\u003e was significantly lower during NAVA compared with PSV1 and PSV2 when assessed by V\u003csub\u003eCAP−CALC\u003c/sub\u003e (58.5% vs. 63.8% and 61.3%, respectively; \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001). The PaO₂/FiO₂ ratio and NVE were significantly higher during NAVA (\u003cem\u003ep\u003c/em\u003e = 0.01 and \u003cem\u003ep\u003c/em\u003e = 0.039, respectively). No significant difference in pulmonary shunt fraction was observed. EIT revealed a modest increase in dorsal end-expiratory lung volume during NAVA, without redistribution of tidal volume or Center of Ventilation. The V\u003csub\u003eCAP−CALC\u003c/sub\u003e method showed strong agreement with established dead space measures (R² = 0.77–0.82) and demonstrated high repeatability (mean coefficient of variation 3.5%).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNAVA is a safe and feasible ventilatory mode following cardiac surgery, associated with reduced dead space fraction, improved oxygenation and enhanced neuroventilatory efficiency. Given that shunt fraction remained unchanged, the observed improvement in ventilation–perfusion (V/Q) matching reflects a reduction in V\u003csub\u003eD\u003c/sub\u003e/V\u003csub\u003eT\u003c/sub\u003e. These findings suggest that NAVA may facilitate respiratory recovery following cardiac surgery.\u003c/p\u003e\n\u003cp\u003eClinicalTrials.gov: NCT03217305. 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