Variations in the resting oxygen consumption of small babies.

Abstract

al., 1969). It is therefore current policy in many neonatal units to try to nurse small babies at a temperature at which heat production is at a minimum and at which sweating does not take place. The range of ambient temperature over which this occurs is termed thermoneutral, and estimates of this thermoneutral range have been made for babies of different birthweights and postnatal ages, and for both naked and clothed babies (Hey and Katz, 1970;Hey and O'Connell, 1970). These estimates are based on measurements of heat production and evaporative water loss from babies nursed in an experimental metabolism chamber at different ambient temperatures.In practice however, it has proved difficult to nurse babies according to Hey's recommendations which are based on average values of resting heat production and require that babies of the same birthweight and postnatal age are nursed under the same temperatures. It is our experience that nursing staff prefer to alter the incubator air temperature according to small changes in the baby's rectal temperature, whether his skin feels warm or cold, and whether he appears to be comfortable or restless. In effect, Received 8 December 1977 they feel that babies vary in their temperature requirements.The object of this inquiry was to examine the individuality of a group of small babies in a newborn nursery by measuring their rates of heat production serially. MethodHeat production was measured indirectly by determining 02 consumption using an open-circuit method, as described by Smales (1978). Warm, humid air was passed at a rate of 1 0 1/min through a soft rubber face mask secured over the baby's nose and mouth, and the 02 content of the outflow measured with a paramagnetic oxygen analyser (Servomex OA250). The rate Of 02 consumption is the product of the rate of flow and the difference in 02 concentration in the inflow and outflow gas. Measurements were made more than an hour after the end of a feed so as to minimise changes in 02 consumption due to the specific dynamic action of food. The baby usually settled and went to sleep after the face mask was applied, and a measurement was then made 10 to 15 minutes later. Measurements were made over a period of 3 to 15 minutes when the record was stable. The resting 02 consumption was calculated in ml/min, corrected to standard temperature and pressure, and expressed per kg body weight.Oxygen consumption was measured serially in 15 babies. The first measurement was made within 24 hours of delivery and subsequent measurements were made daily for the first few days and then less 850 on 11 May 2018 by guest. Protected by copyright.

Metabolic Cost of Growth in Very Low-Birth-Weight Infants

“…The stable pattern of oxygen consumption throughout the day confirms earlier observations in very low-birth-weight infants (28).…”

Longitudinal Studies on Metabolic Rate, Heat Loss, and Energy Cost of Growth in Low Birth Weight Infants

“…It is not known if the oxygen consumption at rest increases after the age of 1 wk. Some studies (7,12,12,28) show an increase, but in other studies it is found to remain constant (9,16,23,25).…”

“…The metabolic rate of LBW infants at rest has been calculated in many studies of oxygen consumption. Many authors (3,7,9,12,16,17,23,25,28) have shown that it increases slowly during the first week. It is not known if the oxygen consumption at rest increases after the age of 1 wk.…”

Energy Balance, Physical Activity, and Thermogenic Effect of Feeding in Premature Infants

“…However, measurements of energy expenditure in premature babies have been generally of short duration (5,(7)(8)(9), i.e. approximately 1-3 h. Therefore the extent to which these limited periods of measurement can be extrapolated to 24 h is still uncertain.…”