Document Detail


A threshold lung volume for optimal mechanical effects on upper airway airflow dynamics: studies in an anesthetized rabbit model.
MedLine Citation:
PMID:  22241061     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
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. Seven supine, anesthetized, spontaneously breathing New Zealand 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. Every 10-ml lung volume increase resulted in caudal tracheal displacement of 2.1 ± 0.4 mm (mean ± SE), decreased ETPlat by 0.7 ± 0.3 cmH(2)O, 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 ± 10.5 ml above baseline. Every 10-ml lung volume decrease resulted in cranial tracheal displacement of 2.6 ± 0.4 mm, increased ETPant by 0.9 ± 0.2 cmH(2)O, 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. In conclusion, 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, and 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.
Authors:
Kristina Kairaitis; Manisha Verma; Jason Amatoury; John R Wheatley; David P White; Terence C Amis
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-01-12
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  112     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-04-02     Completed Date:  2012-07-26     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1197-205     Citation Subset:  IM    
Affiliation:
Ludwig Engel Centre for Respiratory Research, Westmead Millennium Institute and University of Sydney at Westmead Hospital, Westmead, New South Sales, Australia. kristina.kairaitis@sydney.edu.au
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MeSH Terms
Descriptor/Qualifier:
Air Pressure
Airway Resistance / physiology
Anesthesia
Animals
Data Interpretation, Statistical
Electromyography
Lung / physiology*
Lung Volume Measurements
Male
Pharynx / physiology
Rabbits
Respiratory Mechanics / physiology*
Respiratory Muscles / physiology
Trachea / anatomy & histology,  physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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