Faculty Collaboration Database

Comparison of ventilatory responses to sustained reduction in arterial oxygen tension vs. content in awake ponies. J Appl Physiol (1985) 1994 May;76(5):2147-53

Date

05/01/1994

Pubmed ID

8063679

DOI

10.1152/jappl.1994.76.5.2147

Scopus ID

2-s2.0-0028247021 (requires institutional sign-in at Scopus site)   11 Citations

Abstract

To gain insight into central and peripheral contributions to changes in breathing during hypoxia, we compared effects on breathing of reducing inspired PO2 (hypoxic hypoxia) with reducing arterial O2 content (CaO2) through elevation of carboxy-hemoglobin (COHb) (CO hypoxia). Twelve awake ponies were studied during 1 h of breathing room air followed by 6 h when COHb was increased to 25% and CaO2 was decreased by 17%. When COHb was increased, arterial PCO2 (PaCO2) increased gradually to 1.3 Torr above (P < 0.05) control level between 30 and 45 min of CO exposure. Pulmonary ventilation (VE) decreased (P = 0.09) approximately 1 liter the first 30 min of CO exposure. After approximately 45 min, PaCO2 began to decrease, steadily reaching 1.5 Torr below (P < 0.05) control level by 4.5 h of CO hypoxia. VE did not change significantly after 30 min of elevated COHb. Eight ponies were also studied during 5 h of hypoxic hypoxia (arterial PO2 approximately 40 Torr). PaCO2 decreased 5 Torr (P < 0.05) within 5 min of hypoxia and decreased another 4 Torr (P < 0.05) between 30 min and 5 h of hypoxia consistent with hypoxic ventilatory acclimatization. VE increased (P < 0.05) within 3 min of hypoxic hypoxia but then decreased (P < 0.05; VE roll off) toward control and did not increase significantly with acclimatization. Because CO and hypoxic hypoxia both decrease brain oxygenation but only hypoxic hypoxia increases carotid chemoreceptor activity, we conclude that initial hypoventilation with CO hypoxia and VE roll off with hypoxic hypoxia are consistent with hypoxic ventilatory depression within the brain. In addition, hyperventilation with prolonged CO hypoxia is consistent with a central nervous system mechanism contributing to this phase of hypoxic ventilatory acclimatization in ponies.

Author List

Lowry TF, Forster HV, Korducki MJ, Forster AL, Forster MA

Author

Hubert V. Forster PhD Professor in the Physiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Blood Gas Analysis
Carbon Monoxide
Carboxyhemoglobin
Carotid Body
Electromyography
Horses
Hypoxia
Hypoxia, Brain
Oxygen
Respiration
Respiratory Muscles
Spirometry