Cerebral and ventilatory depression during hypoxia in anaesthetized newborn guinea-pigs.
The effects of hypoxia on ventilation and cerebral activity were studied in urethane-anaesthetized newborn guinea-pigs. Ventilation was measured by a pneumotachograph, and cerebral activity by a cerebral function monitor (CFM). All animals were subjected to either 9% O2 or 6% O2 in N2 for 10 minutes or until apnoea occurred. Hypoxia produced a biphasic response in ventilation, that is, an increase followed by a decrease. The initial increase was attributed to the elevation of the respiratory rate, whereas the tidal volume showed a pure decline. The respiratory rate reached its peak at 3 minutes of hypoxia (170 +/- 12% during 9% O2 and 169 +/- 12% during 6% O2). Cerebral activity during both 9 and 6% O2 breathing showed a small increase followed by a decrease. In the group subjected to 9% O2 the maximum CFM activity increased to 114 +/- 8% of the control level and the minimum activity increased to 113 +/- 7%, while in the group subjected to 6% O2 the maximum CFM activity increased to 104 +/- 5% and the minimum CFM activity to 101 +/- 3%. The depression of CFM activity was more pronounced with 6% O2 than with 9% O2. Regression analysis showed a linear correlation between ventilation and cerebral activity during both 9 and 6% O2 breathing. The results suggest that hypoxic ventilatory depression may be the consequence of cerebral depression produced by acute severe hypoxia.
Yuan
S Z
SZ
Nobel Institute for Neurophysiology, Karolinska Institute, Stockholm, Sweden.
Runold
M
M
Lagercrantz
H
H
D000818:Animals; D000831:Animals, Newborn; D001238:Asphyxia Neonatorum / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography / Q000295:instrumentation*; D005260:Female; D006168:Guinea Pigs; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D002534:Hypoxia, Brain / Q000503:physiopathology*; D007231:Infant, Newborn; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D010100:Oxygen / Q000097:blood; D012119:Respiration / Q000502:physiology*
D010100:Oxygen