Methods Six ewes underwent laparotomy . The fetal lambs were exposed by uterotomy and underwent median sternotomy . A 10 F arterial perfusion cannula was inserted into pulmonary artery and a 12 ~ 14 F venous cannula was put into right atrium .

方法 选用6 头 怀孕 山羊，切开 子宫，暴露胎羊，正中开胸，经肺总动脉插10F动脉管，右心房插12～ 14F静脉管。