The Double-Labeled Water Method is a measurement method developed 50 years ago to measure the energy consumption of animals' free living. Using this technique, both the hydrogen and oxygen atoms in the water molecule are replaced by their stable isotopes for partial or complete tracing purposes. When the body ingests a quantitative double-labeled water (2H218O), the two isotopes balance with the total body water and are then consumed by the body in different forms. Radon (2H) is excreted in the form of water, while 18O is discharged as H2O and CO2. Therefore, CO2 can be calculated by subtracting the consumption of 2H from the consumption of 18O.
Principle of double standard water (DLW) method (From: Doubly Labeled Water for Energy Expenditure, James P. DeLany, Emerging Technologies for Nutrition Research: Potential for Assessing Military Performance Capability. Institute of Medicine (US) Committee on Military Nutrition Research; Carlson- Newberry SJ, Costello RB, editors. Washington (DC): National Academies Press (US); 1997.)
The barrier to this approach applied to the human body has always been costly – a large amount of 18O labeled water (H218O) is needed to obtain sufficient isotopic enrichment to calculate an effective elimination rate. This obstacle was first conquered after the improvement of the gas isotope mass spectrometer (IRMS) and the cost reduction of H218O. This method was also verified by the reference method "in-house indirect calorimetry (IC)".
Recently, the ABB LGR three-parameter water isotope analyzer (912-0032) evaluated the application of laser spectroscopy and DLW in measuring total daily heat energy consumption (TDEE) and published in the American Journal of Physiology-Endocrinology and Metabolism ( Journal of Physiology-Endocrinology and Metabolism (October 2017) "Validation of the doubly labeled water method using off-axis" (Validation of the doubly labeled water method using off-axis) Integrated cavity output spectroscopy and isotope ratio mass spectrometry)
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ABB LGR three-parameter water isotope analyzer (δ2H, δ17O, δ18O) (912-0032)
In previous studies, OA-ICOS technology has been shown to provide results consistent with IRMS measurements (water and human urine standards), and new studies have shown that in 17 subjects, OA-ICOS technology The accuracy and accuracy of the measurements are consistent with the average daily CO2 exhalation (VCO2) confirmed by IRMS and IC.
17 subjects VCO2 measurement comparison (IC, OA-ICOS, IRMS)
In addition to verifying the analytical performance of ABB LGR devices, this study also highlights the price advantage of OA-ICOS technology over IRMS technology. In fact, OA-ICOS technology does not require trained technicians compared to IRMS technology. Multiple isotopic samples can also be measured simultaneously, and the cumbersome sample preparation process can be reduced. The authors also point out that the amount of sample (~ 1000 NL) and measurement time (~ 100 seconds) required for OA-ICOS technology is significantly reduced compared to other forms of laser absorption techniques (such as CRDS). Therefore, using the method of multiple injections per sample can better avoid the memory effect between samples without mathematical correction.
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