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.

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.

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).

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%.

Revision of calculations in the doubly labeled water method for measurement of energy expenditure in humans

1994 ◽  
Vol 267 (6) ◽  
pp. E805-E807 ◽  
Author(s):  
W. A. Coward ◽  
P. Ritz ◽  
T. J. Cole
Keyword(s):  
Experimental Study ◽  
Energy Expenditure ◽  
Recent Work ◽  
Isotope Dilution ◽  
Rate Constants ◽  
Isotope Fractionation ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Doubly Labeled Water Method ◽  
The Difference

In the doubly labeled water (DLW) method for the measurement of energy expenditure in humans, the basis of the calculation for CO2 production is the difference between the products of the rate constants for the disappearance of 18O and 2H from body water (KO, and KD, respectively) and the matching isotope dilution spaces (NO and ND, respectively). Thus, omitting corrections for isotope fractionation, CO2 production = 0.5 (KONO-KDND). In this calculation, it is also customary to normalize observed NO and ND values to a fixed value for ND/NO. The increasing use of the method has resulted in the generation of substantially more information on the normal value for ND/NO than existed at the time the method was first developed, and recent work has suggested that revisions of the originally used value of 1.03 may now be deemed appropriate. Values of 1.034 or 1.0427 have recently been suggested, but when applied in energy expenditure studies these estimates would lead to significantly different expenditure measurements. It can, however, be shown from published work and direct experimental study that ND/NO values are method dependent, and for these reasons the lower revised value of 1.034 appears to be more acceptable. The possibility that particular populations may ultimately be shown to be different from 1.034 should not, however, be dismissed entirely, and for this reason we suggest that information derived in individual experiments could be used in a Bayesian fashion to generate new ND/NO estimates. The appropriate techniques are described.

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.

Energy expenditure by doubly labeled water: validation in humans and proposed calculation

1986 ◽  
Vol 250 (5) ◽  
pp. R823-R830 ◽  
Author(s):  
D. A. Schoeller ◽  
E. Ravussin ◽  
Y. Schutz ◽  
K. J. Acheson ◽  
P. Baertschi ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Isotope Dilution ◽  
Isotope Ratio Mass Spectrometry ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Adult Males ◽  
Doubly Labeled Water Method ◽  
The Difference ◽  
Total Body ◽  
Atom Percent Excess

To further validate the doubly labeled water method for measurement of CO2 production and energy expenditure in humans, we compared it with near-continuous respiratory gas exchange in nine healthy young adult males. Subjects were housed in a respiratory chamber for 4 days. Each received 2H2(18)O at either a low (n = 6) or a moderate (n = 3) isotope dose. Low and moderate doses produced initial 2H enrichments of 5 and 10 X 10(-3) atom percent excess, respectively, and initial 18O enrichments of 2 and 2.5 X 10(-2) atom percent excess, respectively. Total body water was calculated from isotope dilution in saliva collected at 4 and 5 h after the dose. CO2 production was calculated by the two-point method using the isotopic enrichments of urines collected just before each subject entered and left the chamber. Isotope enrichments relative to predose samples were measured by isotope ratio mass spectrometry. At low isotope dose, doubly labeled water overestimated average daily energy expenditure by 8 +/- 9% (SD) (range -7 to 22%). At moderate dose the difference was reduced to +4 +/- 5% (range 0-9%). The isotope elimination curves for 2H and 18O from serial urines collected from one of the subjects showed expected diurnal variations but were otherwise quite smooth. The overestimate may be due to approximations in the corrections for isotope fractionation and isotope dilution. An alternative approach to the corrections is presented that reduces the overestimate to 1%.

Methane production in ruminants: its effect on the doubly labeled water method

1989 ◽  
Vol 257 (6) ◽  
pp. R1488-R1495 ◽  
Author(s):  
A. J. Midwood ◽  
P. Haggarty ◽  
B. A. McGaw ◽  
J. J. Robinson
Keyword(s):  
Methane Production ◽  
Limited Range ◽  
The Body ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Flux Rate ◽  
Free Living ◽  
Use Of Data ◽  
Ruminant Animals ◽  
Doubly Labeled Water Method

The doubly labeled water (DLW) technique for measuring CO2 production (rCO2) in free-living animals requires an assessment of the elimination of both 2H and 18O from the body over a long period of time. To calculate rCO2, it is necessary to calculate water turnover (rH2O) from the 2H flux rate. In ruminant animals, the accuracy of this calculation is affected by the loss of 2H in methane. We have quantified the effect of methane production (rCH4) on the 2H flux rate, determined in four sheep given 2H2O. The methane produced was depleted in 2H relative to the urine. A relationship between the enrichment of the methane and urine was established. The ratio of urine to methane enrichment was found on average to be 0.6536, and this value was unaffected by the level of rCH4 but showed some dependence on the absolute concentration of 2H in urine. For this reason, the ratio value obtained from four sheep not given 2H2O was different, a mean of 0.6886 was measured, this ratio was unaffected by changes in the diet supplied to the animals. Computer modeling was used to illustrate the dependence of the isotopically derived value for rCO2 on not only rCH4 but also the magnitude of rCO2 itself. The effect of rCH4 on the DLW method can be predicted from the observed ratio of rCO2 to rCH4 and the value of 0.6536 obtained for the ratio of methane to urine enrichment. With the use of data from several studies at this Institute, a limited range of 10 to 20 was found for rCO2/rCH4 in animals fed at or above maintenance.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of doubly labeled water method using a ruminant

1986 ◽  
Vol 251 (1) ◽  
pp. R143-R149 ◽  
Author(s):  
S. G. Fancy ◽  
J. M. Blanchard ◽  
D. F. Holleman ◽  
K. J. Kokjer ◽  
R. G. White
Keyword(s):  
Growth Rates ◽  
Total Body Water ◽  
Rangifer Tarandus ◽  
Accurate Method ◽  
Open Circuit ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Doubly Labeled Water Method ◽  
Water Volumes ◽  
Total Body

CO2 production (CDP, ml CO2 . g-1 . h-1) by captive caribou and reindeer (Rangifer tarandus) was measured using the doubly labeled water method (3H2O and H2(18)O) and compared with CO2 expiration rates (VCO2), adjusted for CO2 losses in CH4 and urine, as determined by open-circuit respirometry. CDP calculated from samples of blood or urine from a reindeer in winter was 1-3% higher than the adjusted VCO2. Differences between values derived by the two methods of 5-20% were found in summer trials with caribou. None of these differences were statistically significant (P greater than 0.05). Differences in summer could in part be explained by the net deposition of 3H, 18O, and unlabeled CO2 in antlers and other growing tissues. Total body water volumes calculated from 3H2O dilution were up to 15% higher than those calculated from H2(18)O dilution. The doubly labeled water method appears to be a reasonably accurate method for measuring CDP by caribou and reindeer in winter when growth rates are low, but the method may overestimate CDP by rapidly growing and/or fattening animals.

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