Validation in sheep of the doubly labeled water method for estimating CO2 production

1994 ◽  
Vol 266 (1) ◽  
pp. R169-R179 ◽  
Author(s):  
A. J. Midwood ◽  
P. Haggarty ◽  
B. A. McGaw ◽  
G. S. Mollison ◽  
E. Milne ◽  
...  
Keyword(s):  
Poisson Model ◽  
Carbon Dioxide Production ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Evaporative Water ◽  
Respiration Chamber ◽  
Direct Measurements ◽  
Doubly Labeled Water Method ◽  
The Mean ◽  
Selection Of

Carbon dioxide production (rCO2) was estimated in four sheep over a period of 10 days using doubly labeled water (2H and 18O) and was compared with simultaneous respiration chamber measurements of CO2. The excess 2H and 18O measurements were corrected for the empirically determined effects of isotope rebreathing within the confines of the chambers. A weighted monoexponential curve was then fitted to the data from which isotope flux rates and ultimately rCO2 and water turnover (rH2O) estimates were made. The curve fits were weighted assuming a Poisson model. Selection of this weighting policy did not bias the results, and curvature in the data also appeared to have little effect on the rCO2 estimates. Fractionated evaporative water loss expressed as a fraction of rH2O (X) was estimated from water balance and breath water production estimates; the mean X was 0.145 and ranged from 0.108 to 0.183. Corrections for 2H loss in fecal solids reduced the mean rH2O (4,746 g/day) by 35.5 g/day and increased the mean rCO2 (332.3 l/day) by 21.2 l/day. Further corrections to account for 2H loss in methane (mean production rate 27.2 l/day) reduced rH2O by 33.8 g/day and increased rCO2 by 20.3 l/day. The final isotopic estimates of rH2O were 14.6 +/- 6.59% (n = 4) lower than direct measurements and the mean rCO2 was 3.5 +/- 14.48% (n = 4) lower than the chamber measured rCO2. However, in one of the animals studied the rCO2 deviated markedly from the chamber-derived value, and this discrepancy has yet to be explained. When this animal was excluded from the comparisons, the standard deviation was greatly reduced (+/- 3.6, n = 3) and the mean overall error on rCO2 was +3.6%.

Effect of fasting and feeding on measurement of carbon dioxide production using doubly labeled water

1993 ◽  
Vol 74 (4) ◽  
pp. 1824-1829 ◽  
Author(s):  
C. M. Calazel ◽  
V. R. Young ◽  
W. J. Evans ◽  
S. B. Roberts
Keyword(s):  
Human Subjects ◽  
Carbon Dioxide Production ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Prolonged Fasting ◽  
Free Living ◽  
Noninvasive Technique ◽  
Significant Difference ◽  
Before And After ◽  
Doubly Labeled Water Method

The doubly labeled water method is a noninvasive technique for measurement of rates of CO2 production and total energy expenditure in free-living human subjects. The experimental protocol used in validation studies usually involves prolonged fasting before and after the isotope dose is given to start the study, although it is not clear whether this intrusive aspect of the method is necessary. We investigated this issue in four healthy adults [3 women and 1 man: age 29 +/- 2 (SD) yr, body mass index 22 +/- 2.7 kg.m2] with monitored constant physical activity who underwent two doubly labeled water studies that differed only in the duration of fasting before and after isotope dosing (either 6 h of fasting before and 5 h after dosing or 0.5 h before and 3 h afterward). No significant difference between the two measurements was found in the rate constants for isotope disappearance, the ratio of the dilution spaces of the isotopes, or CO2 production rate. These results indicate that prolonged fasting before and after isotope administration should not be necessary in doubly labeled water studies.

Doubly labeled water method: in vivo oxygen and hydrogen isotope fractionation

1986 ◽  
Vol 251 (6) ◽  
pp. R1137-R1143 ◽  
Author(s):  
D. A. Schoeller ◽  
C. A. Leitch ◽  
C. Brown
Keyword(s):  
Water Loss ◽  
Isotope Fractionation ◽  
Isotopic Fractionation ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Water Turnover ◽  
Evaporative Water ◽  
Equilibrium Control ◽  
Doubly Labeled Water Method

The accuracy and precision of the doubly labeled water method for measuring energy expenditure are influenced by isotope fractionation during evaporative water loss and CO2 excretion. To characterize in vivo isotope fractionation, we collected and isotopically analyzed physiological fluids and gases. Breath and transcutaneous water vapor were isotopically fractionated. The degree of fractionation indicated that the former was fractionated under equilibrium control at 37 degrees C, and the latter was kinetically fractionated. Sweat and urine were unfractionated. By use of isotopic balance models, the fraction of water lost via fractionating routes was estimated from the isotopic abundances of body water, local drinking water, and dietary solids. Fractionated water loss averaged 23% (SD = 10%) of water turnover, which agreed with our previous estimates based on metabolic rate, but there was a systematic difference between the results based on O2 and hydrogen. Corrections for isotopic fractionation of water lost in breath and (nonsweat) transcutaneous loss should be made when using labeled water to measure water turnover or CO2 production.

Validation of single-sample doubly labeled water method

1989 ◽  
Vol 256 (2) ◽  
pp. R572-R576 ◽  
Author(s):  
M. D. Webster ◽  
W. W. Weathers
Keyword(s):  
Water Flux ◽  
Passerine Bird ◽  
Single Sample ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Water Turnover ◽  
Sample Technique ◽  
Doubly Labeled Water Method ◽  
The One ◽  
Sample Method

We have experimentally validated a single-sample variant of the doubly labeled water method for measuring metabolic rate and water turnover in a very small passerine bird, the verdin (Auriparus flaviceps). We measured CO2 production using the Haldane gravimetric technique and compared these values with estimates derived from isotopic data. Doubly labeled water results based on the one-sample calculations differed from Haldane values by less than 0.5% on average (range -8.3 to 11.2%, n = 9). Water flux computed by the single-sample method differed by -1.5% on average from results for the same birds based on the standard, two-sample technique (range -13.7 to 2.0%, n = 9).

Experimental reliability of the doubly labeled water technique

1994 ◽  
Vol 266 (3) ◽  
pp. E510-E515 ◽  
Author(s):  
M. I. Goran ◽  
E. T. Poehlman ◽  
E. Danforth
Keyword(s):  
Co2 Production ◽  
Eating Patterns ◽  
Doubly Labeled Water ◽  
Turnover Rates ◽  
Analytical Uncertainty ◽  
Healthy Men ◽  
Experimental Variation ◽  
Clinical Research Center ◽  
The Mean ◽  
The Relationship

The experimental reliability of measuring CO2 production rates (rCO2) with the doubly labeled water (DLW) technique was assessed in five young healthy men (23 (DLW) technique was assessed in five young healthy men (23 +/- 4 yr; 66.1 +/- 4.6 kg). To minimize the confounding effects of fluctuations in physical activity and eating patterns on variation in energy expenditure, the subjects lived under sedentary living conditions by confinement to their own room at a Clinical Research Center and were maintained on a fixed and known level of energy intake. rCO2 was determined in duplicate over two identical 9-day study periods after separate loading doses of deuterium and oxygen-18. Turnover rates were determined from multipoint sampling to reduce error from analytical uncertainty. Dilution spaces were determined by both the intercept and plateau methods. The average experimental variation for rCO2 estimates was approximately +/- 8.5% and was not significantly different among three published calculation models that differ in their assumptions regarding the relationship between the dilution spaces of deuterium and oxygen-18. The experimental reliability of +/- 8.5% exceeds theoretical values generated from calculations based on propagation of error from analytical uncertainty. Between subjects, the experimental variation ranged from 1 to 21%, and the half-width of the 95% confidence interval for the precision of rCO2 estimates was high (+/- 12 mol/day) relative to the mean reported value of approximately 16 mol/day.(ABSTRACT TRUNCATED AT 250 WORDS)

Field Metabolism of Tree Swallows during the Breeding Season

The Auk ◽  
1988 ◽  
Vol 105 (4) ◽  
pp. 706-714 ◽  
Author(s):  
Joseph B. Williams
Keyword(s):  
Body Mass ◽  
Breeding Season ◽  
Young Male ◽  
Carbon Dioxide Production ◽  
Co2 Production ◽  
Tree Swallows ◽  
Passerculus Sandwichensis ◽  
Foraging Modes ◽  
The Mean ◽  
Savannah Sparrows

Abstract I used doubly labeled water to study the field metabolic rate (FMR) of Tree Swallows (Tachycineta bicolor) on Kent Island, New Brunswick, Canada, during the breeding season. I tested the hypothesis that aerially foraging species have higher energy requirements than other species. For incubating female swallows, carbon dioxide production averaged 201.4 ± 15.8 ml CO2/h. While feeding 5 young, male and female swallows expired CO2 at a rate of 211.6 ± 23.3 and 231.0 ± 26.4 ml CO2/h, respectively. During this period males worked at similar levels to females, but the power consumption of females that fed young was significantly higher than incubating females. For both parents together, the mean number of visits to the nest/h was correlated with CO2 production: ml CO2/h = 201.6 + 2.49 (visits/h). On Kent Island, Tree Swallows had a higher FMR than Savannah Sparrows (Passerculus sandwichensis), suggesting that aerial-foraging birds have a higher FMR than ground-foraging species. For 7 species of hirundines, energy expenditure was associated positively with body mass; log(kJ/d) = 1.34 + 0.53 log(body mass, g). This relationship differed from one for species which use alternative foraging modes (ground foraging and flycatching, n = 11), log(kJ/d) = 0.89 + 0.75 log(body mass, g). Aerial foragers expend from 16-38% more energy/day than do other birds of similar size that spend less time flying.

Design, calibration and calculation for flow-through respirometry systems

2001 ◽  
Vol 49 (4) ◽  
pp. 445 ◽  
Author(s):  
P. C. Withers
Keyword(s):  
Air Flow ◽  
Carbon Dioxide Production ◽  
Gas Composition ◽  
Evaporative Water ◽  
Standard Values ◽  
Flow Through ◽  
Gas Flame ◽  
Measure Oxygen Consumption ◽  
Composition I ◽  
Selection Of

Flow-through respirometry systems that measure oxygen consumption (VO2), carbon dioxide production (VCO2) and evaporative water loss (EWL) require the accurate calibration of the flow meter and three separate analysers (O2, CO2 and H2O vapour). Correct measurement of VO2, VCO2 and EWL depends on the incurrent air flow (VI) and its condition (e.g. dry, CO2-free), and the excurrent air flow (VE) and its condition (e.g. dry, CO2-free), which can differ in different parts of the excurrent circuit. Usually either VI or VE is measured and the other is calculated from the gas composition. I describe here a procedure for precise calibration of CO2 and H2O analysers in a flow-through respirometry system by reference to a calibrated O2 analyser, using a small gas flame. Generic equations are derived for calculation of VO2, VO2 and EWL with a variety of configurations for a flow-through respirometry system. Procedures for selection of data from continuous records of VO2, VCO2 and EWL for calculation of minimal (basal or standard) values are briefly described. Finally, the importance of the correct order of data treatment prior to calculation is described.

Validation of the doubly labeled water method in growing pigs

1994 ◽  
Vol 267 (6) ◽  
pp. R1574-R1588 ◽  
Author(s):  
P. Haggarty ◽  
M. F. Franklin ◽  
M. F. Fuller ◽  
B. A. McGaw ◽  
E. Milne ◽  
...  
Keyword(s):  
Weight Gain ◽  
Growing Pigs ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Rapid Weight Gain ◽  
Sources Of Error ◽  
True Value ◽  
Significant Bias ◽  
Before And After ◽  
Doubly Labeled Water Method

The CO2 production (rCO2) of eight growing pigs was determined by continuous collection of CO2 over 21 days and simultaneously estimated using the doubly labeled water (DLW) method. The aim was to assess the accuracy of the method before and after correction for known sources of error and to test for any residual discrepancy arising from as yet unidentified sources of error. Mass spectrometer accuracy was verified by analyzing serial dilutions of the dose material in the form of an artificial decay curve; no significant bias was detected. The physiological errors were linearly dependent on weight gain. DLW-derived rCO2 (corrected only for fractionated water loss) underestimated the true value by 0.270 l CO2/g wt gain or -8% in the restricted (group R) and -16% in the ad libitum-fed (group AL) groups. Known sources of error accounted for -0.006 (methane), -0.032 (fecal 2H losses), -0.108 (fat synthesis), and -0.146 (changing pool size) l CO2/g wt gain. After correction for these sources of error the DLW-derived rCO2 differed from the true value by -2 +/- 3% in group R and 0 +/- 3% in group AL. Thus there was no significant bias in the DLW method after correction for known sources of error, even during rapid weight gain or at weight stability with or without correction. The precision estimates include both dose and background errors and uncertainty in the correction factors used. Strategies for optimizing precision are presented.

Use of the doubly labeled water method for measurement of energy expenditure, total body water, water intake, and metabolizable energy intake in humans and small animals

1989 ◽  
Vol 67 (10) ◽  
pp. 1190-1198 ◽  
Author(s):  
S. B. Roberts
Keyword(s):  
Energy Expenditure ◽  
Water Intake ◽  
Carbon Dioxide Production ◽  
Body Water ◽  
Metabolizable Energy ◽  
Small Animals ◽  
Doubly Labeled Water ◽  
Doubly Labeled Water Method ◽  
Metabolizable Energy Intake ◽  
Total Body

The basis of the doubly labeled water method is measurement of the differential rates of disappearance of two isotopes of water (H218O and either 2H2O or 3H2O, administered at the start of the study) from body water. Published studies indicate that, in its current forms, this technique can be used to provide accurate and reasonably precise information on carbon dioxide production, total body water, and water intake in free-living humans and many small animals. Total energy expenditure can be calculated from carbon dioxide production with little loss of precision. Metabolizable energy intake can also be predicted, as the sum of total energy expenditure plus an estimate for the change in body energy stores during the measurement, but this prediction is unlikely to be accurate and precise unless the subject is in approximate energy balance.Key words: doubly labeled water, energy metabolism, energy expenditure, water intake, body composition.

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