| A threshold lung volume for optimal mechanical effects on upper airway airflow dynamics: studies in an anesthetized rabbit model. | |
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MedLine Citation:
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PMID: 22241061 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Increasing lung volume improves upper airway airflow dynamics via passive mechanisms such as reducing upper airway extraluminal tissue pressures (ETP) and increasing longitudinal tension via tracheal displacement. We hypothesized a threshold lung volume for optimal mechanical effects on upper airway airflow dynamics. Methods: Seven supine, anaesthetised, spontaneously breathing NZ white rabbits were studied. Extrathoracic pressure was altered and, lung volume change, airflow pharyngeal pressure, ETP laterally (ETPlat) and anteriorly (ETPant), tracheal displacement, and sternohyoid muscle activity (EMG%max) monitored. Airflow dynamics were quantified via peak inspiratory airflow, flow limitation upper airway resistance and conductance. Results: Every 10ml lung volume increase resulted in: caudal tracheal displacement of 2.1±0.4 mm (mean±SEM), decreased ETPlat by 0.7±0.3 cmH2O, increased peak inspiratory airflow of 22.8±2.6%baseline (all p<0.02), and no significant change in ETPant or EMG%max. Flow limitation was present in most rabbits at baseline, and abolished 15.7±10.5ml above baseline. Every 10ml lung volume decrease resulted in: cranial tracheal displacement of 2.6±0.4mm, increased ETPant by 0.9±0.2cmH2O, ETPlat was unchanged, increased EMG%max of 11.1±0.3%, and a reduction in peak inspiratory airflow of 10.8±1.0%baseline (all p<0.01). Lung volume, resistance, and conductance relationships were described by exponential functions. Conclusions. Increasing lung volume displaced the trachea caudally, reduced ETP, abolished flow limitation but had little effect on resistance or conductance, whereas decreasing lung volume resulted in cranial tracheal displacement, increased ETP and increased resistance, reduced conductance, and flow limitation persisted despite increased muscle activity. We conclude that there is a threshold for lung volume influences on upper airway airflow dynamics. |
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Authors:
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Kristina Kairaitis; Manisha Verma; Jason Amatoury; John R Wheatley; David P White; Terence Charles Amis |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-1-12 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: - ISSN: 1522-1601 ISO Abbreviation: - Publication Date: 2012 Jan |
Date Detail:
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Created Date: 2012-1-13 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1Ludwig Engel Centre for Respiratory Research,Westmead Millennium Institute and the University of Sydney. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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