{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,29]],"date-time":"2025-12-29T04:41:49Z","timestamp":1766983309205,"version":"3.41.2"},"reference-count":44,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2023,1,9]],"date-time":"2023-01-09T00:00:00Z","timestamp":1673222400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["81500782 81873696 82171126"],"award-info":[{"award-number":["81500782 81873696 82171126"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Bioeng. Biotechnol."],"abstract":"<jats:p><jats:bold>Objective:<\/jats:bold> During inspiration, mechanical energy generated from respiratory muscle produces a negative pressure gradient to fulfill enough pulmonary ventilation. The pressure loss, a surrogate for energy loss, is considered as the portion of negative pressure without converting into the kinetic energy of airflow. Mouth opening (MO) during sleep is a common symptom in patients with obstructive sleep apnoea-hypopnea syndrome (OSAHS). This study aimed to evaluate the effects of mouth opening on pharyngeal pressure loss using computational fluid dynamics (CFD) simulation.<\/jats:p><jats:p><jats:bold>Methods:<\/jats:bold> A total of four subjects who were morphologically distinct in the pharyngeal characteristics based on Friedman tongue position (FTP) grades were selected. Upper airway computed tomography (CT) scan was performed under two conditions: Mouth closing (MC) and mouth opening, in order to reconstruct the upper airway models. computational fluid dynamics was used to simulate the flow on the two different occasions: Mouth closing and mouth opening.<\/jats:p><jats:p><jats:bold>Results:<\/jats:bold> The pharyngeal jet was the typical aerodynamic feature and its formation and development were different from mouth closing to mouth opening in subjects with different Friedman tongue position grades. For FTP I with mouth closing, a pharyngeal jet gradually formed with proximity to the velopharyngeal minimum area plane (plane<jats:sub>Amin<\/jats:sub>). Downstream the plane<jats:sub>Amin<\/jats:sub>, the jet impingement on the pharyngeal wall resulted in the frictional loss associated with wall shear stress (WSS). A rapid luminal expansion led to flow separation and large recirculation region, corresponding to the interior flow loss. They all contributed to the pharyngeal total pressure loss. While for FTP I with mouth opening, the improved velopharyngeal constriction led to smoother flow and a lower total pressure loss. For FTP IV, the narrower the plane<jats:sub>Amin<\/jats:sub> after mouth opening, the stronger the jet formation and its impingement on the pharyngeal wall, predicting a higher frictional loss resulted from higher WSS. Besides, a longer length of the mouth opening-associated constant constrictive segment was another important morphological factor promoting frictional loss.<\/jats:p><jats:p><jats:bold>Conclusion:<\/jats:bold> For certain OSAHS patients with higher Friedman tongue position grade, mouth opening-related stronger jet formation, more jet breakdown and stronger jet flow separation might contribute to the increased pharyngeal pressure loss. It might require compensation from more inspiratory negative static pressure that would potentially increase the severity of OSAHS.<\/jats:p>","DOI":"10.3389\/fbioe.2022.1081465","type":"journal-article","created":{"date-parts":[[2023,1,9]],"date-time":"2023-01-09T07:55:28Z","timestamp":1673250928000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":3,"title":["The influence of mouth opening on pharyngeal pressure loss and its underlying mechanism: A computational fluid dynamic analysis"],"prefix":"10.3389","volume":"10","author":[{"given":"Bin","family":"Hu","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guoping","family":"Yin","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Song","family":"Fu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Baoshou","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yan","family":"Shang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuhuan","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jingying","family":"Ye","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2023,1,9]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"604","DOI":"10.1115\/1.1800554","article-title":"Computational simulations of airflow in an in vitro model of the pediatric upper airways","volume":"126","author":"Allen","year":"2004","journal-title":"J. Biomech. Eng."},{"key":"B2","doi-asserted-by":"publisher","first-page":"718","DOI":"10.1177\/154405910408300912","article-title":"Mouth-opening increases upper-airway collapsibility without changing resistance during midazolam sedation","volume":"83","author":"Ayuse","year":"2004","journal-title":"J. Dent. Res."},{"key":"B3","doi-asserted-by":"publisher","first-page":"69","DOI":"10.1016\/j.resp.2016.09.002","article-title":"The effects of curvature and constriction on airflow and energy loss in pathological tracheas","volume":"234","author":"Bates","year":"","journal-title":"Respir. Physiol. Neurobiol."},{"key":"B4","doi-asserted-by":"publisher","first-page":"2187","DOI":"10.1016\/j.jbiomech.2015.11.033","article-title":"Power loss mechanisms in pathological tracheas","volume":"49","author":"Bates","year":"","journal-title":"J. Biomech."},{"key":"B5","doi-asserted-by":"publisher","first-page":"20140880","DOI":"10.1098\/rsif.2014.0880","article-title":"Dynamics of airflow in a short inhalation","volume":"12","author":"Bates","year":"2015","journal-title":"J. R. Soc. Interface"},{"key":"B6","doi-asserted-by":"publisher","first-page":"1559.e1","DOI":"10.1016\/j.joms.2018.02.017","article-title":"The effects of noncontinuous positive airway pressure therapies on the aerodynamic characteristics of the upper airway of obstructive sleep apnea patients: A systematic review","volume":"76","author":"Chen","year":"2018","journal-title":"J. Oral Maxillofac. Surg."},{"key":"B7","doi-asserted-by":"publisher","first-page":"17722","DOI":"10.1038\/s41598-019-53515-5","article-title":"Parapharyngeal fat pad area at the subglosso-supraglottic level is associated with corresponding lateral wall collapse and apnea-hypopnea index in patients with obstructive sleep apnea: A pilot study","volume":"9","author":"Chen","year":"2019","journal-title":"Sci. Rep."},{"key":"B8","doi-asserted-by":"publisher","first-page":"960","DOI":"10.1152\/japplphysiol.00440.2018","article-title":"Sex differences in large conducting airway anatomy","volume":"125","author":"Dominelli","year":"2018","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B9","doi-asserted-by":"publisher","first-page":"105627","DOI":"10.1016\/j.cmpb.2020.105627","article-title":"Computational fluid dynamics modelling of human upper airway: A review","volume":"196","author":"Faizal","year":"2020","journal-title":"Comput. Methods Programs Biomed."},{"key":"B10","doi-asserted-by":"publisher","first-page":"123","DOI":"10.1186\/s12903-021-01488-1","article-title":"The effect of rapid maxillary expansion on the upper airway's aerodynamic characteristics","volume":"21","author":"Feng","year":"2021","journal-title":"BMC Oral Health"},{"key":"B11","doi-asserted-by":"publisher","first-page":"827","DOI":"10.1183\/09031936.03.00047903","article-title":"Effect of nasal or oral breathing route on upper airway resistance during sleep","volume":"22","author":"Fitzpatrick","year":"2003","journal-title":"Eur. Respir. J."},{"key":"B12","doi-asserted-by":"publisher","first-page":"1000","DOI":"10.1177\/0194599811400977","article-title":"Impact of nasal obstruction on obstructive sleep apnea","volume":"144","author":"Friedman","year":"2011","journal-title":"Otolaryngol. Head. Neck Surg."},{"key":"B13","doi-asserted-by":"publisher","first-page":"1901","DOI":"10.1097\/00005537-199912000-00002","article-title":"Clinical predictors of obstructive sleep apnea","volume":"109","author":"Friedman","year":"1999","journal-title":"Laryngoscope"},{"key":"B14","doi-asserted-by":"publisher","first-page":"1673","DOI":"10.5665\/sleep.4078","article-title":"Upper airway collapsibility is associated with obesity and hyoid position","volume":"37","author":"Genta","year":"2014","journal-title":"Sleep"},{"key":"B15","doi-asserted-by":"publisher","first-page":"21","DOI":"10.1186\/s13023-020-01627-x","article-title":"Chest MRI to diagnose early diaphragmatic weakness in Pompe disease","volume":"16","author":"Harlaar","year":"2021","journal-title":"Orphanet J. Rare Dis."},{"key":"B16","doi-asserted-by":"publisher","first-page":"2902","DOI":"10.1002\/lary.27212","article-title":"The influential factors on the morphological changes of upper airway associated with mouth opening","volume":"128","author":"Hu","year":"2018","journal-title":"Laryngoscope"},{"key":"B17","doi-asserted-by":"publisher","first-page":"32","DOI":"10.1111\/j.1440-1843.2011.02093.x","article-title":"Obesity and obstructive sleep apnoea: Mechanisms for increased collapsibility of the passive pharyngeal airway","volume":"17","author":"Isono","year":"2012","journal-title":"Respirology"},{"key":"B18","doi-asserted-by":"publisher","first-page":"1295","DOI":"10.1007\/s00784-012-0810-5","article-title":"Effects of open mouth and rubber dam on upper airway patency and breathing","volume":"17","author":"Iwatani","year":"2013","journal-title":"Clin. Oral Investig."},{"key":"B19","doi-asserted-by":"publisher","first-page":"637","DOI":"10.1016\/j.medengphy.2006.08.017","article-title":"Numerical investigation on the flow characteristics and aerodynamic force of the upper airway of patient with obstructive sleep apnea using computational fluid dynamics","volume":"29","author":"Jeong","year":"2007","journal-title":"Med. Eng. Phys."},{"key":"B20","doi-asserted-by":"publisher","first-page":"85","DOI":"10.4187\/respcare.01411","article-title":"What does airway resistance tell us about lung function?","volume":"57","author":"Kaminsky","year":"2012","journal-title":"Respir. Care"},{"key":"B21","doi-asserted-by":"publisher","first-page":"221","DOI":"10.1186\/s12931-019-1200-1","article-title":"Influence of \u03b22 adrenergic receptor genotype on risk of nocturnal ventilation in patients with Duchenne muscular dystrophy","volume":"20","author":"Kelley","year":"2019","journal-title":"Respir. Res."},{"key":"B22","doi-asserted-by":"publisher","first-page":"1222","DOI":"10.1183\/09031936.00058406","article-title":"Obstructive sleep apnoea and oral breathing in patients free of nasal obstruction","volume":"28","author":"Koutsourelakis","year":"2006","journal-title":"Eur. Respir. J."},{"key":"B23","first-page":"37","article-title":"Craniofacial phenotyping in obstructive sleep apnea-a novel quantitative photographic approach","volume":"32","author":"Lee","year":"2009","journal-title":"Sleep"},{"key":"B24","doi-asserted-by":"crossref","first-page":"225","DOI":"10.1016\/B978-0-08-101123-2.00013-3","article-title":"Chapter 13 - fluid flow: General Principles","volume-title":"Air conditioning system design","author":"Legg","year":"2017"},{"key":"B25","doi-asserted-by":"publisher","first-page":"295","DOI":"10.1016\/j.resp.2007.02.006","article-title":"Characteristics of the turbulent laryngeal jet and its effect on airflow in the human intra-thoracic airways","volume":"157","author":"Lin","year":"2007","journal-title":"Respir. Physiol. Neurobiol."},{"key":"B26","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1155\/2016\/3181654","article-title":"Numerical investigation of flow characteristics in the obstructed realistic human upper airway","volume":"2016","author":"Liu","year":"2016","journal-title":"Comput. Math. Methods Med."},{"key":"B27","doi-asserted-by":"publisher","first-page":"2498","DOI":"10.1016\/j.jbiomech.2014.03.023","article-title":"Computational fluid dynamics endpoints for assessment of adenotonsillectomy outcome in obese children with obstructive sleep apnea syndrome","volume":"47","author":"Luo","year":"2014","journal-title":"J. Biomech."},{"key":"B28","doi-asserted-by":"publisher","first-page":"e52572","DOI":"10.7554\/eLife.52572","article-title":"C1 neurons are part of the circuitry that recruits active expiration in response to the activation of peripheral chemoreceptors","volume":"9","author":"Malheiros-Lima","year":"2020","journal-title":"Elife"},{"key":"B29","doi-asserted-by":"publisher","first-page":"2221","DOI":"10.1016\/j.jbiomech.2011.06.006","article-title":"Large eddy simulation of the pharyngeal airflow associated with obstructive sleep apnea syndrome at pre and post-surgical treatment","volume":"44","author":"Mihaescu","year":"2011","journal-title":"J. Biomech."},{"key":"B30","doi-asserted-by":"publisher","first-page":"1979","DOI":"10.1016\/j.jbiomech.2013.06.016","article-title":"Planning human upper airway surgery using computational fluid dynamics","volume":"46","author":"Mylavarapu","year":"2013","journal-title":"J. Biomech."},{"key":"B31","doi-asserted-by":"publisher","first-page":"330","DOI":"10.1152\/japplphysiol.00522.2018","article-title":"Computational analysis of airflow dynamics for predicting collapsible sites in the upper airways: A preliminary study","volume":"126","author":"Na","year":"2019","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B32","doi-asserted-by":"publisher","first-page":"1819","DOI":"10.1152\/japplphysiol.01230.2010","article-title":"Noninvasive estimation of pharyngeal airway resistance and compliance in children based on volume-gated dynamic MRI and computational fluid dynamics","volume":"111","author":"Persak","year":"2011","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B33","doi-asserted-by":"publisher","first-page":"966","DOI":"10.1016\/j.sleep.2011.08.004","article-title":"Patterns in pharyngeal airflow associated with sleep-disordered breathing","volume":"12","author":"Powell","year":"2011","journal-title":"Sleep. Med."},{"key":"B34","doi-asserted-by":"publisher","first-page":"85","DOI":"10.1186\/1475-925X-13-85","article-title":"Computational fluid dynamics simulation of airflow in the trachea and main bronchi for the subjects with left pulmonary artery sling","volume":"13","author":"Qi","year":"2014","journal-title":"Biomed. Eng. Online"},{"key":"B35","doi-asserted-by":"publisher","first-page":"130","DOI":"10.1016\/j.compbiomed.2014.06.008","article-title":"A computational study of the respiratory airflow characteristics in normal and obstructed human airways","volume":"52","author":"Sul","year":"2014","journal-title":"Comput. Biol. Med."},{"key":"B36","doi-asserted-by":"publisher","first-page":"1040","DOI":"10.1016\/j.chest.2017.08.1157","article-title":"Diaphragm dysfunction in critical illness","volume":"153","author":"Supinski","year":"2018","journal-title":"Chest"},{"key":"B37","doi-asserted-by":"publisher","first-page":"423","DOI":"10.1038\/s42003-019-0668-z","article-title":"Evaluation of human obstructive sleep apnea using computational fluid dynamics","volume":"2","author":"Taherian","year":"2019","journal-title":"Commun. Biol."},{"key":"B38","doi-asserted-by":"publisher","first-page":"125","DOI":"10.1016\/j.resp.2008.01.012","article-title":"Numerical simulations for detailed airflow dynamics in a human nasal cavity","volume":"161","author":"Wen","year":"2008","journal-title":"Respir. Physiol. Neurobiol."},{"key":"B39","doi-asserted-by":"publisher","first-page":"104","DOI":"10.1152\/japplphysiol.00746.2013","article-title":"Computational fluid dynamics endpoints to characterize obstructive sleep apnea syndrome in children","volume":"116","author":"Wootton","year":"2014","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B40","doi-asserted-by":"publisher","first-page":"2043","DOI":"10.1016\/j.jbiomech.2005.06.021","article-title":"Computational fluid dynamics modeling of the upper airway of children with obstructive sleep apnea syndrome in steady flow","volume":"39","author":"Xu","year":"2006","journal-title":"J. Biomech."},{"key":"B41","doi-asserted-by":"publisher","first-page":"zsz273","DOI":"10.1093\/sleep\/zsz273","article-title":"Differences in three-dimensional upper airway anatomy between Asian and European patients with obstructive sleep apnea","volume":"43","author":"Xu","year":"2020","journal-title":"Sleep"},{"key":"B42","doi-asserted-by":"publisher","first-page":"959","DOI":"10.1152\/japplphysiol.01033.2018","article-title":"Computational analysis of airflow dynamics for predicting collapsible sites in the upper airways: Machine learning approach","volume":"127","author":"Yeom","year":"2019","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B43","doi-asserted-by":"publisher","first-page":"45706","DOI":"10.1038\/srep45706","article-title":"Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients","volume":"7","author":"Zheng","year":"2017","journal-title":"Sci. Rep."},{"key":"B44","doi-asserted-by":"publisher","first-page":"197","DOI":"10.1016\/j.amjoto.2018.12.001","article-title":"Computational fluid dynamics analysis of H-uvulopalatopharyngoplasty in obstructive sleep apnea syndrome","volume":"40","author":"Zhu","year":"2019","journal-title":"Am. J. Otolaryngol."}],"container-title":["Frontiers in Bioengineering and Biotechnology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fbioe.2022.1081465\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,1,9]],"date-time":"2023-01-09T07:55:32Z","timestamp":1673250932000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fbioe.2022.1081465\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,1,9]]},"references-count":44,"alternative-id":["10.3389\/fbioe.2022.1081465"],"URL":"https:\/\/doi.org\/10.3389\/fbioe.2022.1081465","relation":{},"ISSN":["2296-4185"],"issn-type":[{"type":"electronic","value":"2296-4185"}],"subject":[],"published":{"date-parts":[[2023,1,9]]},"article-number":"1081465"}}