{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T14:36:04Z","timestamp":1787150164967,"version":"build-2736575974"},"reference-count":23,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T00:00:00Z","timestamp":1787097600000},"content-version":"unspecified","delay-in-days":18,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100022617","name":"Fisher and Paykel Healthcare","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100022617","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open Resp Res"],"accepted":{"date-parts":[[2026,6,24]]},"published-print":{"date-parts":[[2026,8]]},"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>\n                      Non-invasive ventilation (NIV) interface can generate carbon dioxide (CO\n                      <jats:sub>2<\/jats:sub>\n                      ) rebreathing, potentially contributing to NIV failure. The impact of leaks and mask design remains unclear. This study evaluates how these factors influence CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing in oronasal face masks.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design, settings, participants<\/jats:title>\n                    <jats:p>\n                      A bench study was followed by a physiological study. The bench study used a mannequin head connected to a breathing simulator exhaling CO\n                      <jats:sub>2<\/jats:sub>\n                      . Six oronasal face masks designed for single-limb circuits with varying exhalation port positions were tested with three levels of fit. A CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing index was calculated, along with intentional and unintentional leaks. The best-performing mask was then compared with two clinically used masks in healthy volunteers. Ventilatory ratio (VR, reflecting dead space) was derived from transcutaneous CO\n                      <jats:sub>2<\/jats:sub>\n                      (PtcCO\n                      <jats:sub>2<\/jats:sub>\n                      ) and ventilation was assessed by electrical impedance tomography. Analyses used Friedman test and linear mixed-effects model.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      The bench study showed (1) mask design as a whole, rather than intentional leak flow rate, was the main determinant of CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing: exhalation ports situated on the mask body had lower CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing; (2) unintentional leaks decreased CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing only with poor mask design and (3) a new under-nose mask with nasal nozzles had the lowest CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing index. The latter was compared with two other masks in ten volunteers, median aged 32 (IQR 29\u201334): PtcCO\n                      <jats:sub>2<\/jats:sub>\n                      decreased from 37.3 (33.7\u201339.5)\u2009mm Hg at baseline to 32.5 (28.9\u201335.4) with the new mask (p=0.023). VR with the new mask (0.96 (0.93\u20131.12)) was lower than with the classical masks (1.40 (1.20\u20131.50)\u2009and 1.38 (1.19\u20131.45); p&lt;0.001 for both).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>\n                      Mask design significantly influences CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing during NIV, with leaks\u2019 effects dependent on exhalation port position. A novel under-nose hybrid mask with embedded nozzles reduces CO\n                      <jats:sub>2<\/jats:sub>\n                      rebreathing and dead space when compared with classical masks.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial registration number<\/jats:title>\n                    <jats:p>\n                      <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"clintrialgov\" xlink:href=\"NCT03902639\">NCT03902639<\/jats:ext-link>\n                      .\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjresp-2026-004135","type":"journal-article","created":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T14:20:29Z","timestamp":1787149229000},"page":"e004135","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Influence of leaks and mask design on CO\n                    <sub>2<\/sub>\n                    clearance during non-invasive ventilation: a combined bench and physiological study"],"prefix":"10.1136","volume":"13","clinical-trial-number":[{"clinical-trial-number":"nct03902639","registry":"10.18810\/clinical-trials-gov"},{"clinical-trial-number":"nct03902639","registry":"10.18810\/clinical-trials-gov"}],"author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2502-2217","authenticated-orcid":false,"given":"Nattapat","family":"Wongtirawit","sequence":"first","affiliation":[{"name":"Keenan Centre for Biomedical Research, Unity Health Toronto, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada"},{"name":"Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada"},{"name":"Department of Critical Care, St Michael\u2019s Hospital, Unity Health Toronto, Toronto, Ontario, Canada"},{"name":"Division of Critical Care, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rosie","family":"Butterworth","sequence":"additional","affiliation":[{"name":"Keenan Centre for Biomedical Research, Unity Health Toronto, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fernando","family":"Vieira","sequence":"additional","affiliation":[{"name":"Keenan Centre for Biomedical Research, Unity Health Toronto, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada"},{"name":"Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada"},{"name":"Fisher & Paykel Healthcare Ltd, Auckland, New Zealand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Annia","family":"Schreiber","sequence":"additional","affiliation":[{"name":"Keenan Centre for Biomedical Research, Unity Health Toronto, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada"},{"name":"Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada"},{"name":"Department of Critical Care, St Michael\u2019s Hospital, Unity Health Toronto, Toronto, Ontario, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matthew","family":"Ko","sequence":"additional","affiliation":[{"name":"Keenan Centre for Biomedical Research, Unity Health Toronto, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada"},{"name":"Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada"},{"name":"Department of Critical Care, St Michael\u2019s Hospital, Unity Health Toronto, Toronto, Ontario, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laurent","family":"Brochard","sequence":"additional","affiliation":[{"name":"Keenan Centre for Biomedical Research, Unity Health Toronto, Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada"},{"name":"Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada"},{"name":"Department of Critical Care, St Michael\u2019s Hospital, Unity Health Toronto, Toronto, Ontario, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,8,19]]},"reference":[{"key":"2026081907202367000_13.1.e004135.1","first-page":"1126","article-title":"CO2 rebreathing during BiPAP ventilatory assistance","volume":"151","author":"Ferguson","year":"1995","journal-title":"Am J Respir Crit Care Med"},{"key":"2026081907202367000_13.1.e004135.2","doi-asserted-by":"publisher","DOI":"10.1378\/chest.108.3.772"},{"key":"2026081907202367000_13.1.e004135.3","doi-asserted-by":"crossref","DOI":"10.1186\/1471-2466-14-19","article-title":"Timing of noninvasive ventilation failure: causes, risk factors and potential remedies","volume":"14","author":"Ozyilmaz","year":"2014","journal-title":"BMC Pulm 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