Comprehensive assessment of the components of energy expenditure in infants using a new infant respiratory chamber.
BACKGROUND
Current methods for energy expenditure (EE) measurements in term infants do not include simultaneous measurements of basal and sleeping metabolic rates (BMR and SMR) or a measure of physical activity (PA). Furthermore, prediction equations for calculating EE are not appropriate for use in infants with metabolic disorders.


OBJECTIVE
To develop and utilize a new infant respiratory chamber for simultaneous measurements of EE (kJ/d), preprandial BMR (kJ/d), SMR (kJ/d) and an index of PA (oscillations/min/kg body weight) in infants with a variety of metabolic disorders, for up to four hours in a hospital setting, while allowing parental interaction in a comfortable environment.


METHODS
We obtained simultaneous measurements of EE, BMR, SMR and PA in 21 infants (66+/-73 days of age, 4.5+/-1.7 kg body weight, 55+/-8 cm in length and 16+/-7% body fat) using our new infant respiratory chamber. Six of these infants were healthy, seven had thyroid dysfunction, five were HIV-exposed, one had AIDS, one had intrauterine and postnatal growth retardation and one was a hypothermic preterm infant. Energy expenditure, BMR and SMR were extrapolated for 24 hours. Body composition was estimated by skin-fold thickness, using age-appropriate formulae. Basal metabolic rate obtained with the infant respiratory chamber was compared to BMR that was calculated using the appropriate World Health Organization (WHO) equations.


RESULTS
In all infants both extrapolated 24-hour EE and BMR correlated with fat-free mass (r = 0.89, p<0.01 and r = 0.88, p<0.01 respectively). Twenty-four hour EE also correlated with PA (r = 0.52, p<0.05). The HIV-exposed infants had higher BMR (p<0.05) than that calculated by the appropriate WHO equation. We found that the caloric requirements for the infant with growth retardation were underestimated based on the infant's weight and age.


CONCLUSIONS
The infant respiratory chamber can measure all of the main components of EE. Some of the results obtained differed significantly from those obtained by the WHO equations; therefore, the new infant respiratory chamber is necessary for estimating EE in infants with metabolic and growth disorders.
Cole
C R
CR
Maimonides Medical Center, Department of Pediatrics, Brooklyn, New York, USA.
Rising
R
R
Hakim
A
A
Danon
M
M
Mehta
R
R
Choudhury
S
S
Sundaresh
M
M
Lifshitz
F
F
D000163:Acquired Immunodeficiency Syndrome / Q000378:metabolism; D001481:Basal Metabolism; D002153:Calorimetry, Indirect / Q000295:instrumentation*; D004734:Energy Metabolism; D004867:Equipment Design; D005260:Female; D005317:Fetal Growth Retardation / Q000378:metabolism; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008659:Metabolic Diseases / Q000378:metabolism*; D005082:Physical Exertion; D013959:Thyroid Diseases / Q000378:metabolism