Electrocorticographic activity during repeated vs continuous hypoxia in piglets.
To assess the effects on brain activity of repeated vs continuous hypoxia, 16, 10- to 22-day-old piglets were instrumented chronically for electrocortical and arterial pH and gas tension measurements. They inhaled 10% or 6% O2 in N2 for 21 min, either continuously, or during seven, 3 min exposures interrupted by 3 min recovery periods in air, all while behaving naturally within a sealed, temperature controlled, plexiglass box. An isoelectric electrocorticogram (ECoG) and/or seizures, related to the onset of hypoxia, occurred repeatedly in 6 of the 10 exposures to 6% repetitive hypoxia, only twice in 8 exposures to 6% continuous hypoxia, and never in 10% hypoxia. A frequency analysis of the ECoG, excluding all sections exhibiting isoelectric and seizure activity, revealed no changes with 10% hypoxia, but a shift towards the lower bands during both repetitive and continuous 6% hypoxia. The extent of these shifts was greater in records that also displayed isoelectric ECoG and/or seizures. The ECoG spectrum recovered at the end of the hypoxic exposure, but not when isoelectric ECoG and/or seizures coexisted. We conclude that repeated, frequent episodes of hypoxia are more detrimental than a prolonged single event, and may contribute to the occurrence of Sudden Infant Death.
Waters
K A
KA
Department of Pediatrics, McGill University, Montreal, Quebec, Canada.
Beardsmore
C S
CS
Paquette
J
J
Turner
G A
GA
Moss
I R
IR
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D002540:Cerebral Cortex / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008564:Membrane Potentials / Q000502:physiology*; D013552:Swine