Document Detail

Reflex modulation of airflow dynamics through the upper airway.
MedLine Citation:
PMID:  7928902     Owner:  NLM     Status:  MEDLINE    
We studied the effect of respiratory reflexes on maximal inspiratory flow (VImax) and its mechanical determinants, pharyngeal critical pressure (Pcrit) and nasal resistance, in an isolated feline upper airway preparation. Chemoreceptor reflexes were evaluated by varying inspired oxygen and end-tidal CO2 concentrations. At each gas concentration, we found that changes in VImax were related to changes in Pcrit. As CO2 increased, Pcrit became increasingly subatmospheric (P < 0.02), indicating reductions in pharyngeal collapsibility. In contrast, progressive hypoxia had no effect on Pcrit. We then examined the effects of vagal afferents and upper airway mucosal receptors on airflow dynamics at three levels of CO2. We confirmed that CO2 increased VImax (P < 0.01) and decreased Pcrit to more subatmospheric levels (P < 0.05) in both the presence and absence of vagal and airway mucosal afferent activity. Moreover, airway mucosal afferents led to smaller reductions in Pcrit (a less collapsible airway) (P < 0.05), whereas vagal afferents led to a larger increase in Pcrit (a more collapsible pharynx) under hypercapnic conditions (P < 0.01). We conclude that CO2 had a major effect on pharyngeal collapsability and that its effect was modulated by vagal and mucosal afferents. We speculate that the sensitivity and threshold to reflex CO2 responses play a major role in the maintenance of airway patency.
M M Seelagy; A R Schwartz; D B Russ; E D King; R A Wise; P L Smith
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  76     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1994 Jun 
Date Detail:
Created Date:  1994-11-01     Completed Date:  1994-11-01     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:  2692-700     Citation Subset:  IM    
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224.
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MeSH Terms
Airway Resistance / physiology
Carbon Dioxide / pharmacology
Chemoreceptor Cells / physiology
Mucous Membrane / innervation,  physiology
Neurons, Afferent / physiology
Nose / physiology
Oxygen / pharmacology
Pharynx / physiology
Reflex / physiology*
Respiratory Mechanics / physiology
Respiratory Physiological Phenomena*
Stimulation, Chemical
Vagus Nerve / physiology
Grant Support
Reg. No./Substance:
124-38-9/Carbon Dioxide; 7782-44-7/Oxygen

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

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