Document Detail

Effects of hypocapnic hyperventilation on the response to hypoxia in normal subjects receiving intermittent positive-pressure ventilation.
MedLine Citation:
PMID:  11948044     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To confirm the hypothesis that the ventilatory response to hypoxia (VRH) may be abolished by hypocapnia. METHODS: We studied four healthy subjects during intermittent positive-pressure ventilation delivered through a nasal mask (nIPPV). Delivered minute ventilation (Ed) was progressively increased to lower end-tidal carbon dioxide pressure (PETCO(2)) below the apneic threshold. Then, at different hypocapnic levels, nitrogen was added to induce falls in oxygen saturation, a hypoxic run (N(2) run). For each N(2) run, the reappearance of a diaphragmatic muscle activity and/or an increase in effective minute ventilation (E) and/or deformations in mask-pressure tracings were considered as a VRH, whereas unchanged tracings signified absence of a VRH. For the N(2) runs eliciting a VRH, the threshold response to hypoxia (TRh) was defined as the transcutaneous oxygen saturation level that corresponds to the beginning of the ventilatory changes. RESULTS: Thirty-seven N(2) runs were performed (7 N(2) runs during wakefulness and 30 N(2) runs during sleep). For severe hypocapnia (PETCO(2) of 27.1 +/- 5.2 mm Hg), no VRH was noted, whereas a VRH was observed for N(2) runs performed at significantly higher PETCO(2) levels (PETCO(2) of 34.0 +/- 2.1 mm Hg, p < 0.001). Deep oxygen desaturation (up to 64%) never elicited a VRH when the PETCO(2) level was < 29.3 mm Hg, which was considered the carbon dioxide inhibition threshold. For the 16 N(2) runs inducing a VRH, no correlations were found between PETCO(2) and TRh and between TRh and both Ed and E. CONCLUSION: During nIPPV, VRH is highly dependent on the carbon dioxide level and can be definitely abolished for severe hypocapnia.
Vincent Jounieaux; Veronica F Parreira; Genevieve Aubert; Myriam Dury; Pierre Delguste; Daniel O Rodenstein
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Chest     Volume:  121     ISSN:  0012-3692     ISO Abbreviation:  Chest     Publication Date:  2002 Apr 
Date Detail:
Created Date:  2002-04-11     Completed Date:  2002-05-09     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1141-8     Citation Subset:  AIM; IM    
Pneumology Unit, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium.
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MeSH Terms
Anoxia / physiopathology*
Brain Stem / physiopathology
Carotid Body / physiopathology
Chemoreceptor Cells / physiopathology
Diaphragm / physiopathology
Hyperventilation / physiopathology*
Hypocapnia / physiopathology*
Positive-Pressure Respiration*
Reference Values
Sleep Stages / physiology

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

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