Comparison of Short Term Indirect Calorimetry and Doubly Labeled Water Method for the Assessment of Energy Expenditure in Preterm Infants

Abstract

The accuracy of 8-hour indirect calorimetry (IDC) as an estimate of energy expenditure was investigated in 8 healthy preterm infants (birth weight 1,270 ± 193 g, gestational age 32 ± 3 weeks, mean ± SD) in comparison with an analysis over 5 days using the doubly-labeled water (²H₂¹⁸O) method (DLW). The infants that were fed continuously by nasogastric drip with 120 kcal/kg/day of special infant formula were measured twice under thermoneutral conditions in a closed system indirect calorimeter during 8 h with a 4-day interval; simultaneously isotope decay was measured by isotope ratio mass spectrometry in urine samples collected daily during 5 days from 6 h after an oral dose of 2H2180 on the first day of IDC, all during the 4th postnatal week. The mean differences between carbon dioxide production rate (rCO₂) measured either by single 8-hour IDC or by duplicate 8-hour IDC and the 5-day DLW method, using the two-point analysis or the multipoint analysis were not significantly different from zero. The rCO₂ calculated from the DLW method using the two-point analysis differed ––1.4 ± 1.7% from that measured by the multipoint analysis. The mean differences between the metabolic rate estimated from 8 h of IDC and from the 5-day DLW method based on a measured RQ of 0.90 was ––6.7 ± 6.2% and based on the RQ of the feeding ––4.5 ± 6.0%. These differences were not significantly different from zero. We conclude that IDC over 8 h and two-point DLW measurement over 5 days, both methods that can be applied with relative ease in practice, offer an adequate average estimate of energy expenditure in continuously fed preterm infants under thermoneutral conditions.

Total energy expenditure in infants with bronchopulmonary dysplasia is associated with respiratory status

“…From days 1 to 6 total daily Ee was measured with the doubly labeled water technique as previously described [20]. Briefly, isotopes (0.25 g H 2 18 O and 0.13 g 2 H 2 O per kg) were administered through a nasogastric tube, urine samples were collected daily, and isotope enrichment was measured by isotope ratio mass spectrometry.…”

“…Briefly, isotopes (0.25 g H 2 18 O and 0.13 g 2 H 2 O per kg) were administered through a nasogastric tube, urine samples were collected daily, and isotope enrichment was measured by isotope ratio mass spectrometry. Water turnover and Ee were calculated from isotope disappearance [20], assuming a respiratory quotient of 0.89 in both groups of infants [8].…”

Measurement of Fat-Free Mass in Infants

“…Until now very few authors reported data on infant TBW using 1 8 0 dilution, especially for older infants. More TBW and FFM data from isotope dilution will certainly become available in the near future, as the doubly labeled water method used for estimation of energy expenditure has recently been validated for use in infants and TBW and FFM are among the outcome parameters (27)(28)(29).…”

Nutrition for Preterm Infants: 75 Years of History

“…Pivotal in that development were the studies by Kashyap and Heird [11,12] who studied the effects of varying protein and energy intakes. These studies followed the observation that premature infants have high rates of energy expenditure, using different techniques [13,14]. Acknowledging that sufficient energy must be provided for maintaining high rates of protein synthesis, many studies were undertaken to determine the optimal protein energy ratio in various groups [15].…”