Abstract
Summary: Continuous measurements of minute ventilation (vI), oxygen consumption (vO2), heart rate (HR), activity, and temperature were made in eleven low birth weight infants during the interval between feedings. Significant increases in vI, vO2, and HR were noted between quiet and active sleep. (vI Active − vI Quiet/vI Quiet) × 100 = 18.4% vO2 Active − vO2 Quiet/vO2 Quiet) × 100 = 10.1% and HRActive − HRQuiet/HRQuiet) × 100 = 6.4%. Significant differences were also noted within epochs of the same state of sleep: mean slope vI versus time in epoch (t) = −156 ml/kg·min/hr, vO2 versus t. = 1.49 ml/kg·min/hr and HR versus t = −15.0 beats/min/hr. Differences between successive epochs of the same state of sleep were also observed: vI, +5.9 to 46.6%; vO2, 4.7 to 24.6%; HR, 1.0 to 9.7%. These differences were related to the length of time after feeding. These data indicate that steady state conditions do not occur in growing low birth weight infants and that the design of studies of respiration and metabolism in these infants should include continuous assessment of the state of sleep or activity and time after feeding to ensure that experimental and control periods are truly comparable.
Speculation: The significant variability in minute ventilation, oxygen consumption, and heart rate which occurs spontaneously in low birth weight infants secondary to changes in activity and postprandial interval must be acknowledged in the design of clinical research. It is probable that these factors influence not only mean levels of metabolic and respiratory activity but also the sensitivity to experimental stimuli such as hypoxia, hypercarbia, and drugs.
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Schulze, K., Kairam, R., Stefanski, M. et al. Spontaneous Variability in Minute Ventilation Oxygen Consumption and Heart Rate of Low Birth Weight Infants. Pediatr Res 15, 1111–1116 (1981). https://doi.org/10.1203/00006450-198108000-00008
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DOI: https://doi.org/10.1203/00006450-198108000-00008