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Validation of doubly labeled water for assessing energy expenditure in infants
Insights
The doubly labeled water (DLW) method accurately measures infant energy expenditure and carbon dioxide production. This validation in infants post-surgery confirms DLW
Area of Science:
- Pediatric Metabolism
- Human Physiology
- Nutritional Science
Background:
- The doubly labeled water (DLW) method is established for accurate energy expenditure measurement in adults.
- Validation of DLW in infants is crucial for pediatric metabolic research and clinical applications.
- Infants undergoing abdominal surgery present a unique population for method validation due to altered physiological states.
Purpose of the Study:
- To validate the doubly labeled water (DLW) method for measuring energy expenditure in infants.
- To compare DLW-derived measurements of carbon dioxide production and energy expenditure with periodic open circuit respiratory gas exchange (RGE).
Main Methods:
- Ten blinded studies were conducted on nine infants following abdominal surgery.
- Energy expenditure and carbon dioxide production were measured over 5-6 days using DLW and RGE.
- Infants received consistent oral or parenteral nutrition to minimize diet-related isotopic enrichment errors.
Main Results:
- DLW-measured carbon dioxide production rates were not significantly different from RGE (10.4 vs. 10.5 l/kg/day).
- Energy expenditure calculated by DLW (using dietary intake or RGE data) showed no significant difference compared to RGE measurements (approx. 57-58 kcal/kg/day).
- Percentage differences between DLW and RGE for carbon dioxide production and energy expenditure were within acceptable margins (-0.9% to 1.6%).
Conclusions:
- The doubly labeled water method is a valid and accurate tool for determining energy expenditure in infants.
- Concurrent water balance studies are not necessary for accurate DLW measurements in this population.
- Findings support the use of DLW in pediatric research and clinical settings for metabolic assessment.
Abstract:
Previous studies show that the doubly labeled water method is accurate for measuring energy expenditure in the adult human. To validate this method in infants, carbon dioxide production rate and energy expenditure were measured for 5 to 6 days by doubly labeled water (DLW) and periodic open circuit respiratory gas exchange (RGE) in 10 blinded studies in nine infants following abdominal surgery. Infants were maintained on consistent oral or parenteral nutrition prior to and during study. This avoided diet-related changes in baseline isotopic enrichment of body water which could theoretically contribute to significant errors in calculation of carbon dioxide production rate. For DLW, insensible water loss was assumed to be proportional to respiratory volume and body surface area, where the former was predicted from carbon dioxide production rate. Insensible water loss thus calculated averaged 18% of water turnover. Rates of carbon dioxide production measured by DLW were not significantly different from that of RGE (10.4 +/- 1.1 and 10.5 +/- 0.9 l/kg/day, mean +/- SD, respectively). Energy expenditure was calculated using respiratory quotients from dietary intake (DLW:DIET) and RGE (DLW:RGE) data. There was no significant difference between energy expenditure determined by DLW (DLW:DIET and DLW:RGE) and that measured by RGE (58.5 +/- 6.1, 56.8 +/- 6.1, and 57.3 +/- 5.1 kcal/kg/day, mean +/- SD, respectively). Rate of carbon dioxide production, DLW:diet, and DLW:RGE calculated by DLW differed from corresponding RGE values by -0.9 +/- 6.2, -1.1 +/- 6.1, and 1.6 +/- 6.2%, mean +/- SD, respectively. These findings demonstrate the validity of the doubly labeled water method for determining energy expenditure in infants without concurrent water balance studies.