The relationship between environmental temperature, metabolic rate, sleep state, and evaporative water loss in infants from birth to three months
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Y Azaz1, P J Fleming, M Levine
1Institute of Child Health, University of Bristol, United Kingdom.
Insights
Infant metabolic rate and water loss are influenced by environmental temperature. Cooling increased oxygen consumption and reduced quiet sleep duration in newborns, with sweating occurring across a wide temperature range.
Area of Science:
- Neonatal physiology
- Environmental thermoregulation
- Infant sleep studies
Background:
- Infant metabolic rate and thermoregulation are critical for survival.
- Understanding how environmental temperature affects infant physiology is essential for care.
- Previous research has not fully elucidated the interplay between temperature, sleep, and water loss in early infancy.
Purpose of the Study:
- To investigate the impact of changing environmental temperatures on metabolic rate, sleep state, and water loss in infants.
- To longitudinally track these physiological responses from 2 days to 3 months of age.
- To determine the optimal temperature range for minimizing metabolic rate and evaporative water loss.
Main Methods:
- Longitudinal study of 22 lightly clothed infants from 2 days to 3 months old.
- Measurements taken in a modified barometric plethysmograph.
- Recorded sleep state, oxygen consumption, and skin/axillary temperatures.
Main Results:
- Oxygen consumption was higher during rapid eye movement (REM) sleep than quiet sleep.
- Within the first week, cooling to 19-22°C increased oxygen consumption by 19% during REM sleep and 6% during quiet sleep.
- Quiet sleep duration decreased with cooling in the first week but not later; axillary temperature decreased at 3 months during cooling.
- Evaporative water loss decreased linearly with falling environmental temperature, but sweating occurred even at minimal metabolic rates.
Conclusions:
- Infant metabolic response to cooling and sweating are in dynamic equilibrium across a range of temperatures.
- A distinct temperature range minimizing both metabolic rate and evaporative water loss could not be defined.
- These findings highlight the complex thermoregulatory adaptations in early infancy.
Abstract:
We have investigated the effect of changing environmental temperature on metabolic rate, sleep state, and water loss in a longitudinal study of 22 lightly clothed babies from 2 d to 3 mo of age. Studies were performed in a modified barometric plethysmograph while recording sleep state, oxygen consumption, and skin and axillary temperatures. Oxygen consumption was higher in rapid eye movement sleep than in quiet sleep at all ages and varied widely between infants at each temperature. Within the first week, there was a 19% rise in oxygen consumption on cooling to 19-22 degrees C during rapid eye movement sleep and a 6% rise during quiet sleep. The median duration of quiet sleep periods was reduced from 17 to 12 min on cooling within the first week. No such change was seen at 1, 2, and 3 mo. Axillary temperature was reduced at 3 mo during cooling. This may be a part of normal patterns of change in temperature during sleep, unrelated to cooling. At each age, total evaporative water loss fell linearly with falling environmental temperature both within and below the temperature range at which metabolic rate was minimal. The evaporative water losses were greater than expected and suggested that sweating was occurring, both at temperatures at which metabolic rate was minimal and at those at which it was increased. The metabolic response to cooling and the process of sweating appear to be in dynamic equilibrium across this temperature range. Thus, it was not possible to define a temperature range over which both metabolic rate and evaporative water loss were at minimum values.