Mortola J P, León-Velarde F, Aguero L, Frappell P B
Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada.
Clin Sci (Lond). 1999 Feb;96(2):147-53.
In fetuses and newborn infants heart rate variability changes in conditions of acute and chronic hypoxia; we therefore asked whether heart rate variability of infants born at high altitude differed from that of low-altitude infants. Short-term recordings (4-5 min) of inter-beat intervals were obtained in 19 infants in Lima (50 m altitude) and in 15 infants in Cerro de Pasco (4330 m, barometric pressure approximately 450 mmHg, inspired oxygen pressure approximately 94 mmHg) during quiet rest in warm conditions (ambient temperature, Ta, approximately 35 degrees C). In 12 infants from each group recordings were also obtained during cooling (Ta approximately 26 degrees C). Heart rate variability was evaluated from 512 consecutive inter-beat intervals, with analysis based on time-domain and frequency-domain methods. At warm Ta, heart rate variability did not differ between the two groups. During cooling, heart rate increased only in the low-altitude group. As in the warm, during cooling most parameters of heart rate variability did not differ between the two groups. The only exception was the inter-beat interval power of the high-frequency range of the spectrum (0.15-0.4 Hz), which, at least in adults, is believed to be a reflection of vagal activity, and was greater in the high-altitude group. It is concluded that gestation at high altitude, despite its blunting effects on fetal growth, does not have a major impact on heart rate variability of the newborn. Nevertheless, the possibility that differences in response to cooling may reflect some limitation in heart rate control needs to be examined further.
在胎儿和新生儿中，急性和慢性缺氧情况下心率变异性会发生变化；因此，我们探讨了高海拔地区出生婴儿的心率变异性是否与低海拔地区婴儿不同。在温暖环境（环境温度Ta约为35摄氏度）安静休息时，对利马的19名婴儿（海拔50米）和塞罗德帕斯科的15名婴儿（海拔4330米，气压约450 mmHg，吸入氧压约94 mmHg）进行了4 - 5分钟的心跳间期短期记录。每组12名婴儿还在降温时（Ta约为26摄氏度）进行了记录。基于512个连续心跳间期，采用时域和频域方法评估心率变异性。在温暖的Ta环境下，两组心率变异性无差异。降温过程中，仅低海拔组心率增加。与温暖环境时一样，降温时两组心率变异性的大多数参数无差异。唯一的例外是频谱高频范围（0.15 - 0.4 Hz）的心跳间期功率，至少在成年人中，该功率被认为反映迷走神经活动，且在高海拔组中更大。研究得出结论，尽管高海拔妊娠对胎儿生长有抑制作用，但对新生儿心率变异性没有重大影响。然而，对降温反应的差异可能反映心率控制存在某些局限性，这一可能性仍需进一步研究。
