Document Detail

Ventilation and carbon dioxide exchange in exercising horses: effect of inspired oxygen fraction.
MedLine Citation:
PMID:  7759436     Owner:  NLM     Status:  MEDLINE    
Thoroughbred horses (TB) have no ventilatory response to added CO2 during near-maximal exercise. To see whether that reflects mechanical limits to ventilation or the control of breathing, we examined the effects of varying inspired O2 fraction (0.16, 0.21, or 0.30) in five normal TB standing quietly and galloping at 10 and 14 m/s on a level treadmill. We measured gas exchange (O2 consumption and CO2 production) and ventilation with a flow-through mask system. We also measured PO2, PCO2, and O2 contents in arterial and mixed venous blood and calculated cardiac output by using the Fick equation. Low inspired O2 fraction (0.16 vs. 0.21) had significant effects in TB galloping at 14 m/s. Arterial PO2 then was 38 Torr compared with 56 Torr for horses on air. Tidal volume and minute ventilation were 20% greater than their corresponding values on air, which were 12 liters and 1,475 l/min, respectively, whereas respiratory frequency did not change. O2 consumption and CO2 production were unchanged, but alveolar ventilation was 6% greater, despite increased alveolar and physiological dead spaces, so arterial PCO2 was lower (45 vs. 50 Torr on air). Thus, hypoxia was an effective stimulus to breathing, and minute ventilation was not mechanically limited in TB breathing air at the speeds studied.
N Pelletier; D E Leith
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  78     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1995 Feb 
Date Detail:
Created Date:  1995-06-29     Completed Date:  1995-06-29     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:  654-62     Citation Subset:  IM; S    
Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan 66506, USA.
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MeSH Terms
Carbon Dioxide / blood,  metabolism*
Cardiac Output / physiology
Hyperoxia / metabolism,  physiopathology*
Oxygen / blood
Oxygen Consumption / physiology
Physical Exertion / physiology*
Pulmonary Gas Exchange / physiology
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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