Rawles J M, Schneider K T, Huch R, Huch A
Br J Obstet Gynaecol. 1987 Jun;94(6):507-11. doi: 10.1111/j.1471-0528.1987.tb03141.x.
Stroke and minute distance were measured in 12 women in late pregnancy using Doppler ultrasound. In each patient two sets of measurements were made every 2 min for 20 min in the supine and left lateral positions, the sequence of positions being reversed on the second occasion. Within each of the four 20 min measurement periods there were no significant changes with time in stroke distance, heart rate, or minute distance, or in their coefficients of variation. From this evidence there is no justification for delaying the measurement of cardiac output until a 'steady state' is reached. The measurements were influenced both by the sequence and the position in which they were taken, the effects being additive. Overall, stroke distance was 5.1% greater in the left lateral than in the supine position, heart rate was 3.7% less and minute distance not significantly different. Independent of posture, stroke distance was 6.5% greater in the second period of measurement than in the first, heart rate was 3% less and minute distance 2.8% more. In late pregnancy the relative magnitude of cardiac output in the left lateral and supine positions has to be interpreted in the light of a stepwise increase of aortic blood flow with change of posture.
采用多普勒超声对12名妊娠晚期妇女进行了每搏输出量和每分输出量的测量。在每位患者中，于仰卧位和左侧卧位每隔2分钟进行两组测量，共测量20分钟，两次测量时体位顺序相反。在四个20分钟测量时段中的每一个时段内，每搏输出量、心率、每分输出量及其变异系数均未随时间出现显著变化。基于此证据，没有理由将心输出量的测量推迟到达到“稳定状态”。测量结果受测量顺序和测量时体位的影响，这些影响是累加的。总体而言，左侧卧位时的每搏输出量比仰卧位时大5.1%，心率低3.7%，每分输出量无显著差异。与体位无关，第二次测量时段的每搏输出量比第一次大6.5%，心率低3%，每分输出量多2.8%。在妊娠晚期，必须根据随着体位改变主动脉血流的逐步增加来解释左侧卧位和仰卧位时心输出量的相对大小。
