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Response to cooling temperature in infants born at an altitude of 4,330 meters
P B Frappell1, F León-Velarde, L Aguero
1School of Zoology, La Trobe University, Melbourne, Australia. p.frappell@zoo.latrobe.edu.au
Insights
Newborn infants at high altitudes show reduced metabolic response to cold. This suggests lower thermogenic capacity in high-altitude infants due to reduced oxygen availability during gestation.
Area of Science:
- Neonatal physiology
- High-altitude adaptation
- Environmental thermoregulation
Background:
- Infants born at high altitudes may have different metabolic responses to environmental changes.
- Reduced oxygen availability during gestation could impact infant development and thermoregulation.
Purpose of the Study:
- To investigate the metabolic response to cold ambient temperatures in newborn infants born at high vs. low altitudes.
- To compare oxygen consumption and heart rate changes during cooling between two groups of infants.
Main Methods:
- Measurement of oxygen consumption (V O2) and carbon dioxide production (V CO2) using an open-flow system.
- Exposure of healthy, full-term, 1-day-old infants to warm (35°C) and cool (26°C) conditions.
- Comparison of metabolic and physiological parameters between infants from Lima (50m) and Cerro de Pasco (4,330m).
Main Results:
- High-altitude infants had lower birth weight and slightly lower body/skin temperatures in warm conditions.
- Cooling did not significantly increase oxygen consumption or heart rate in high-altitude infants.
- Low-altitude infants showed a significant increase in oxygen consumption (approx. 34%) and heart rate upon cooling.
Conclusions:
- High-altitude infants exhibit a diminished thermogenic capacity when exposed to cold.
- Reduced oxygen availability during fetal development is a likely cause for the decreased thermogenic capacity in high-altitude newborns.
- These findings highlight potential challenges for high-altitude neonates in adapting to colder environments.
Abstract:
The metabolic response to reduction in ambient temperature was studied in healthy, full-term, 1-d-old infants in Lima (50 m altitude, n = 20) and Cerro de Pasco (4,330 m, barometric pressure approximately 450 mm Hg, n = 20), Peru. Oxygen consumption (V O2) and carbon dioxide production (V CO2) were measured with an open-flow system as each infant rested quietly in a cylindrical humicrib, at wall temperatures of 35 degrees C (warm) and 26 degrees C (cool). The infants were exposed for 20 min to both temperatures, with the higher temperature followed by the lower, and oxygen consumption (V O2) and carbon dioxide production (V CO2) were measured over the last 8 min of each exposure. Average birth weight in Cerro de Pasco (2,933 +/- 77 g [mean +/- SE]) was less than in Lima (3,457 +/- 73 g). In warm conditions, infants born at high altitude had slightly yet significantly lower body and skin temperatures than did those born at low altitude, with similar values of V O2 and heart rate (HR). Neither body nor skin temperature changed in either group during cooling. At low altitude, cooling increased V O2 ( approximately 34%), whereas no significant increase occurred in the high-altitude group. A similar response occurred for HR. Among several possibilities, the most likely interpretation of the results would be that of a decreased thermogenic capacity in the high-altitude infants because of the correspondingly lower oxygen availability during gestation.