Document Detail

Unventilated airway is time-dependently constricted in paralyzed dogs.
MedLine Citation:
PMID:  11748409     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Apnea has been reported to produce bronchoconstriction and to cause hypoxia, hypercapnia, and modulation of vagal afferent nerves, which also change airway tone. In this study, the authors determined the mechanism of apnea-induced bronchoconstriction. METHODS: Twenty-eight dogs anesthetized and paralyzed were assigned to four groups (n = 7 each): apnea after artificial ventilation with 50% and 100% O2 groups (apnea-50% O2 and apnea-100% O2 groups, respectively), an apnea plus vagotomy group (fraction of inspired oxygen [FiO2] = 1.0), and a one-lung ventilation group (FiO2 = 1.0). The trachea was intubated with a single- or double-lumen tube in the three apnea groups or the one-lung ventilation group, respectively. The bronchial cross-sectional area (BCA) was assessed by the authors' bronchoscopic method. In the apnea-100% O2 and apnea plus vagotomy groups, a respirator was turned off for 5 min to produce apnea. In the apnea-50% O2 group, apnea was produced for 3 min. In the one-lung ventilation group, the right lumen was blocked for 5 min, and 15 min later, the left lumen was blocked for 5 min. BCA, arterial oxygen tension (PaO2), and arterial carbon dioxide tension (PaCO2) were assessed every minute. RESULTS: The BCA in intact dogs time-dependently decreased by approximately 20% and 40% at 3 and 5 min after apnea started, respectively, whereas they did not in vagotomized dogs. In the apnea-50% O2 and apnea-100% O2 groups, bronchoconstriction could occur without hypoxemia, although hypercapnia was observed in all dogs. In the one-lung ventilation group, despite the fact that PaCO2 increased by only 2 mmHg without hypoxemia, unventilated BCA time-dependently decreased by 33.6 +/- 10.3%, whereas ventilated BCA did not. CONCLUSION: The current study suggests that the unventilated airway may constrict spontaneously. In addition, the airway constriction could be vagally mediated but not due to hypoxia and hypercapnia.
K Hirota; E Hashiba; S Kabara; H Yoshioka; H Ishihara; A Matsuki
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Anesthesiology     Volume:  95     ISSN:  0003-3022     ISO Abbreviation:  Anesthesiology     Publication Date:  2001 Dec 
Date Detail:
Created Date:  2001-12-18     Completed Date:  2002-01-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  1300217     Medline TA:  Anesthesiology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1480-4     Citation Subset:  AIM; IM    
Department of Anesthesiology, University of Hirosaki School of Medicine, Japan.
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MeSH Terms
Apnea / physiopathology
Blood Gas Analysis
Bronchi / pathology,  physiopathology
Carbon Dioxide / blood
Constriction, Pathologic / pathology,  physiopathology*
Hydrogen-Ion Concentration
Oxygen / blood
Paralysis / pathology,  physiopathology*
Respiratory Mechanics / physiology
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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