1Department of Obstetrics and Gynecology, Tohoku University School of Medicine, 2Department of Obstetrics and Gynecology, Fukushima Medical College
Blood flow measurement, Transit-time technique, Chronic animal model
We continuously measured umbilical arterial blood flow of lamb fetus in utero and uterine arterial blood flow of pregnant ewe by commercially available ultrasonic flow meter using the wide beam transit-time technique. By this technique, direct measurement of volume rate of flow is possible in contrast with electromagnetic flow meter measuring the velocity of the flow. This unique feature makes the flow probe useful on various size of vessels or a group of vessels such as umbilical arteries. Dynamic changes of blood flow can also be measured, compared with some methods as dye-dilution technique or flow measurement using radionuclide-labeled microsphere in which only noncontinuous flow determination is possible. The lamb fetuses were removed from the uterus at the gestational ages from 109 to 120 days. After performing cannulation of the femoral vessels, applying cardioelectrodes, placing an occluder around the umbilical cord, the transit-time flow probe was attached to the umbilical arteries near the umbilicus and the fetuses were returned to the uterus. After the 5th day of the operation, the experiments of serial umbilical occlusion and release to make the fetuses acidemic were performed. The umbilical arterial blood flow before the experiments was 210 ml/min per kilogram of fetal body weight in two fetuses and 105 ml/min/kg in one fetus. During the experiments the umbilical arterial flow first increased then decreased gradually, but the flow did not decrease below the preexperimental value when arterial pH was lowered as low as 7.00 units. We found the transit-time flow meter to be useful for the measurement of the blood flow in the chronic animal models.