AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 6 1099-R1107, Copyright © 1986 by American Physiological Society
Uteroplacental O2 uptake: continuous measurements during uterine quiescence and contractions
L. D. Longo, P. S. Dale and R. D. Gilbert
To determine the constancy of uteroplacental O2 uptake (VO2) during uterine
quiescence and both spontaneous and oxytocin-induced uterine contractions,
we have developed a method to measure VO2 continuously and reproducibly. In
seven ewes during uterine quiescence, total uterine blood flow (Qut)
averaged 200 ml X min-1 X kg uterine contents-1, with intra-animal SD of 18
min X min-1 X kg-1 and interanimal SD of 86 ml X min-1 X kg-1. Uterine
arteriovenous O2 content difference averaged 4.2 +/- 0.5 ml X dl-1. VO2
averaged 8.2 +/- 1.2 ml X min-1 X kg-1, with interanimal SD of 3.6 ml X
min-1 X kg-1. During 21 spontaneous prelabor contractions, VO2 decreased
3.8% to 8.7 +/- 0.3 ml X min-1 X kg-1 (NS) during the contraction and
subsequently increased 12.3% to 10.1 +/- 0.3 ml X min-1 X kg-1 (P less than
0.05) near the end of the contraction. With oxytocin-induced contractions,
VO2 fell 10% to 6.4 +/- 0.2 ml X min-1 X kg-1 at the contraction onset (P
less than 0.05) but by the end of the contraction had increased 6.1% to 7.6
+/- 0.2 ml X min-1 X kg-1 (NS). In conclusion, uteroplacental VO2 was
measured continuously and reproducibly using relatively straightforward
methodology; uteroplacental blood flow, arteriovenous O2 content
difference, and uteroplacental O2 uptake were normally distributed with
coefficients of variation less than 15%; and during both spontaneous and
oxytocin-induced uterine contractions Qut decreased significantly, while
VO2 initially decreased moderately and then showed an overshoot, during the
contraction.
