Document Detail

Time course of air hunger mirrors the biphasic ventilatory response to hypoxia.
MedLine Citation:
PMID:  15286044     Owner:  NLM     Status:  MEDLINE    
Determining response dynamics of hypoxic air hunger may provide information of use in clinical practice and will improve understanding of basic dyspnea mechanisms. It is hypothesized that air hunger arises from projection of reflex brain stem ventilatory drive ("corollary discharge") to forebrain centers. If perceptual response dynamics are unmodified by events between brain stem and cortical awareness, this hypothesis predicts that air hunger will exactly track ventilatory response. Thus, during sustained hypoxia, initial increase in air hunger would be followed by a progressive decline reflecting biphasic reflex ventilatory drive. To test this prediction, we applied a sharp-onset 20-min step of normocapnic hypoxia and compared dynamic response characteristics of air hunger with that of ventilation in 10 healthy subjects. Air hunger was measured during mechanical ventilation (minute ventilation = 9 +/- 1.4 l/min; end-tidal Pco(2) = 37 +/- 2 Torr; end-tidal Po(2) = 45 +/- 7 Torr); ventilatory response was measured during separate free-breathing trials in the same subjects. Discomfort caused by "urge to breathe" was rated every 30 s on a visual analog scale. Both ventilatory and air hunger responses were modeled as delayed double exponentials corresponding to a simple linear first-order response but with a separate first-order adaptation. These models provided adequate fits to both ventilatory and air hunger data (r(2) = 0.88 and 0.66). Mean time constant and time-to-peak response for the average perceptual response (0.36 min(-1) and 3.3 min, respectively) closely matched corresponding values for the average ventilatory response (0.39 min(-1) and 3.1 min). Air hunger response to sustained hypoxia tracked ventilatory drive with a delay of approximately 30 s. Our data provide further support for the corollary discharge hypothesis for air hunger.
S H Moosavi; R B Banzett; J P Butler
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.     Date:  2004-07-30
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  97     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2004 Dec 
Date Detail:
Created Date:  2004-11-08     Completed Date:  2005-04-06     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:  2098-103     Citation Subset:  IM    
Physiology Program, Harvard School of Public Health, Harvard Medical School, Boston, MA 02115, USA.
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MeSH Terms
Anoxia / physiopathology*
Carbon Dioxide / blood
Dyspnea / physiopathology*
Middle Aged
Pain Measurement
Perception / physiology*
Reaction Time / physiology
Respiratory Center / physiology
Respiratory Mechanics / physiology*
Grant Support
Reg. No./Substance:
124-38-9/Carbon Dioxide

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

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