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Effect of chronic hypoxia on breathing and EMGs of respiratory muscles in awake ponies. J Appl Physiol (1985) 1992 Feb;72(2):739-47



Pubmed ID




Scopus ID

2-s2.0-0026548846   4 Citations


Breathing, diaphragmatic and transversus abdominis electromyograms (EMGdi and EMGta, respectively), and arterial blood gases were studied during normoxia (arterial PO2 = 95 Torr) and 48 h of hypoxia (arterial PO2 = 40-50 Torr) in intact (n = 11) and carotid body-denervated (CBD, n = 9) awake ponies. In intact ponies, arterial PCO2 was 7, 5, 9, and 11 Torr below control (P less than 0.01) at 1 and 10 min and 5 and 24-48 h of hypoxia, respectively. In CBD ponies, arterial PCO2 was 3-4 Torr below control (P less than 0.01) at 4, 5, 6, and 24 h of hypoxia. In intact ponies, pulmonary ventilation, mean inspiratory flow rate, and rate of rise of EMGdi and EMGta changed in a multi-phasic fashion during hypoxia; each reached a maximum during the 1st h (P less than 0.05), declined between 1 and 5 h (P less than 0.05), and increased between 5 and 24-48 h of hypoxia. As a result of the increased drive to the diaphragm, the mean EMGdi was above control throughout hypoxia (P less than 0.05). In contrast, as a result of a sustained reduction in duration of the EMGta, the mean EMGta was below control for most of the hypoxic period. In CBD ponies, pulmonary ventilation and mean inspiratory flow rate did not change during chronic hypoxia (P greater than 0.10). In these ponies, the rate of rise of the EMGdi was less than control (P less than 0.05) for most of the hypoxic period, which resulted in the mean EMGdi to also be less than control (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Author List

Brown DR, Forster HV, Lowry TF, Forster MA, Forster AL, Gutting SM, Erickson BK, Pan LG


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

Carotid Body
Central Nervous System
Chemoreceptor Cells
Chronic Disease
Muscle Contraction
Respiratory Mechanics
Respiratory Muscles
jenkins-FCD Prod-466 5b81815b8b3d1f46bfec16512ed5f574613f59c5