Effects of maternal administration of 3% carbon dioxide on umbilical artery and fetal renal and middle cerebral artery Doppler waveforms.
OBJECTIVE
The null hypothesis is that umbilical, middle cerebral, and renal artery pulsed Doppler velocity waveforms in the normal term fetus may be affected during short-term maternal inhalation of 3% carbon dioxide gas mixture.


METHODS
Seventy-two observations were made on 14 term fetuses before and during maternal 3% carbon dioxide gas mixture inhalation. The umbilical, middle cerebral, and renal arteries of these fetuses were sampled with pulsed Doppler velocity waveforms and recorded on a strip chart at a preset speed of 50 mm/sec. Doppler waveforms were analyzed for differences in the systolic peak to end-diastolic velocity ratio for these three vascular beds. Peak flow velocity and time velocity integral were also analyzed for the cerebral and renal vascular beds. The data were analyzed with the paired t test.


RESULTS
A significant decrease in the systolic-to-diastolic-velocity ratio of the middle cerebral artery occurred with 3% carbon dioxide inhalation (p < 0.02). The other vascular beds had no demonstrable change.


CONCLUSIONS
Transient maternal breathing of 3% carbon dioxide gas mixture selectively causes a decrease in resistance in the fetal cerebral circulation.
Veille
J C
JC
Department of Obstetrics and Gynecology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, NC 27157.
Penry
M
M
D000280:Administration, Inhalation; D001783:Blood Flow Velocity / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000196:embryology*; D005260:Female; D005333:Fetus / Q000502:physiology*; D006801:Humans; D011247:Pregnancy; D012077:Renal Artery / Q000000981:diagnostic imaging / Q000196:embryology*; D016216:Ultrasonography, Prenatal; D014469:Umbilical Arteries / Q000187:drug effects* / Q000502:physiology
D002245:Carbon Dioxide