Electrocortical activity, electroocular activity, and breathing movements in fetal sheep with prolonged and graded hypoxemia.
OBJECTIVE
Our objective was to determine the effect of a prolonged and graded reduction in fetal arterial oxygen saturation on electrocortical activity and associated biophysical variables.


METHODS
Fourteen unanesthetized fetal sheep were studied between 126 and 135 days' gestation with continuous monitoring of electrocortical and electroocular activity and breathing movements, during a 24-hour control period, and subsequently during 4 days of prolonged and graded hypoxemia induced by progressively lowering the maternal inspired oxygen concentration.


RESULTS
Graded reduction in fetal arterial oxygen saturation resulted in little change in arterial pH until close to 30% when metabolic acidemia was apparent. The incidence of low-voltage electrocortical activity, electroocular activity, and breathing movements were marginally decreased with hypoxemia alone; however, a significant decrease was not apparent until associated with the onset of fetal acidemia.


CONCLUSIONS
Hypoxemia of a chronic nature must approach the level at which acidemia becomes apparent before a marked change in fetal behavioral activity is noted.
Richardson
B S
BS
Department of Obstetrics and Gynaecology and Physiology, St. Joseph's Health Centre, Lawson Research Institute, University of Western Ontario, London, Canada.
Carmichael
L
L
Homan
J
J
Patrick
J E
JE
D000818:Animals; D016122:Brachiocephalic Trunk; D002245:Carbon Dioxide / Q000097:blood; D002540:Cerebral Cortex / Q000502:physiology*; D002908:Chronic Disease; D004562:Electrocardiography; D004585:Electrooculography; D005260:Female; D005324:Fetal Movement; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D012119:Respiration; D012756:Sheep / Q000196:embryology
D002245:Carbon Dioxide; D010100:Oxygen