Am. J. Respir. Crit. Care Med.,
Volume 158, Number 6, December 1998, 1751-1756
Response to Cooling Temperature in Infants
Born at an Altitude of 4,330 Meters
PETER B.
FRAPPELL,
FABIOLA
LEÓN-VELARDE,
LOURDES
AGUERO,
and
JACOPO P.
MORTOLA
School of Zoology, La Trobe University, Melbourne, Australia; Departmento de Ciencias Fisioløgicas, Universitad Peruana Cayetano
Heredia and Instituto de Investigaciones de la Altura; Hospital San Bartolome, Lima, Peru; and Department of Physiology, McGill
University, Montreal, Canada
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 ~ 450 mm
Hg, n = 20), Peru. Oxygen consumption (
O2) and carbon dioxide production ( CO2) were measured
with an open-flow system as each infant rested quietly in a cylindrical humicrib, at wall temperatures
of 35° C (warm) and 26° C (cool). The infants were exposed for 20 min to both temperatures, with
the higher temperature followed by the lower, and oxygen consumption ( O2) and carbon dioxide
production ( 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 O2 and heart rate (HR). Neither body nor skin temperature changed in either group during cooling. At low altitude, cooling increased O2 (~ 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.
