Heart rate variability in 1-day-old infants born at 4330 m altitude

Abstract

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.

Heart and breathing rate variability in the avian perinatal period: The chicken embryo as a model

“…The quantification of variability from a time series of IBI was based on five criteria commonly adopted in the time-domain analysis of IBI; 44,45 then, the results of these five criteria were lumped together into a 'variability index' (VI; Table 2). The first criterion was the coefficient of variation of all the IBI, computed as the percent ratio of standard deviation (the square root of the variance) and mean.…”

“…25,26 In hypoxia, the short- and long-term prognostic values of HRV and BRV are unknown because of the ethical and practical difficulties encountered by studies on human infants. Data on infants born at high altitude could be informative 45 but need to consider the responses of the pregnant mother to hypobaric hypoxia. The current study has shown that the avian embryo can be an excellent model for the investigations of HRV and BRV in the transition from prenatal to postnatal life and their responses to hypoxia, and could offer a valuable experimental approach to assess the role of BRV and HRV as predictors of outcome.…”