Measurement of CO2 production by the doubly labeled water technique

1986 ◽  
Vol 61 (3) ◽  
pp. 1200-1202 ◽  
Author(s):  
J. R. Speakman ◽  
P. A. Racey
Keyword(s):  
Isotopic Analysis ◽  
Accurate Estimate ◽  
The Body ◽  
Co2 Production ◽  
Doubly Labeled Water ◽  
Human Metabolism ◽  
Multiple Sampling ◽  
Final Sample ◽  
Nonsteady State ◽  
Sample Method

Recent applications of the doubly labeled water technique to the study of human metabolism have employed multiple sampling of body water over protracted periods, rather than the more traditional method of taking only an initial and final sample for isotopic analysis. In addition fractional turnovers of the body pools have been estimated by fitting curves to the sequential log-converted isotope enrichment against time. By manipulation of data collected in the field in a study of metabolism of vespertilionid bats, it is shown the curve-fitting technique results in an accurate estimate of CO2 production only when the rate of CO2 production is constant. Biologically realistic nonsteady-state conditions result in errors in estimates of CO2 production of up to 30%. In conditions where CO2 production is known to be temporally variable, the more traditional two-sample method may provide a more accurate estimate of 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).

The doubly labeled water method: errors due to deuterium exchange and sequestration in ruminants

1993 ◽  
Vol 264 (3) ◽  
pp. R561-R567 ◽  
Author(s):  
A. J. Midwood ◽  
P. Haggarty ◽  
B. A. McGaw
Keyword(s):  
Maximum Error ◽  
The Body ◽  
Co2 Production ◽  
Average Error ◽  
Doubly Labeled Water ◽  
Correction Factors ◽  
Evaporative Water ◽  
Matter Production ◽  
Ruminant Animals ◽  
The Difference

The doubly labeled water (DLW) technique allows the CO2 production (rCO2) of free living animals to be estimated from the difference between the turnover of 2H2O and H218O in the body water. A fundamental assumption of this technique is that neither of the isotopes used are lost in products other than CO2 and H2O. We found, however, that 2H was lost in both exchangeable and nonexchangeable positions in the feces of sheep. Negligible amounts of 18O were lost in exchangeable positions. 2H losses led to a 0.75% (SE 0.06, n = 4) overestimation of the measured 2H2O flux, leading to an average error in rCO2 estimates of 20.3 l/day. For a typical rCO2 rate of 370 l/day, this would amount to an error of approximately 5% (range -7.0 to -4.3%, n = 4). Correction factors to account for this loss were presented. The error in rCO2 due to 2H sequestration into fat was calculated to be at most 2.1 l/day or about -0.66% in lambs with a rCO2 of 320 l/day. In a triply labeled water (TLW) study the maximum error in the estimation of fractionated evaporative water loss (X) would lead to a 0.81% underestimation of rCO2. We recommend that during a DLW study involving ruminant animals the correction factors presented here be used to compensate for 2H loss in feces. This may be particularly important where the diet has a high roughage content leading to a significant fecal dry matter production.

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)

Experimental validation of measurements of glucose turnover in nonsteady state.

1978 ◽  
Vol 234 (1) ◽  
pp. E84 ◽  
Author(s):  
J Radziuk ◽  
K H Norwich ◽  
M Vranic
Keyword(s):  
Dispersion Model ◽  
Glucose Production ◽  
Compartment Model ◽  
Sole Source ◽  
Volume Of Distribution ◽  
Endogenous Glucose Production ◽  
The Body ◽  
Glucose Turnover ◽  
Turnover Rates ◽  
Nonsteady State

The aim of the present experiments is to validate, in conscious dogs, the tracer infusion methods of measuring nonsteady turnover rates. This was done in nine experiments performed in four normal dogs by infusing isotopically labeled glucose (2-3H, 6-3H, 1-14C) and monitoring the concentrations of both the labeled and unlabeled substances. The validation is based on the observation that a high exogenous infusion of glucose will suppress endogenous glucose production and become the sole source of glucose in the body. By infusing glucose at a high, time-varying rate, calculating its rate of appearance, (Ra) and comparing it to the infused rate, the method can be verified. The calculations were based on: a) a single-compartment model with a modified volume of distribution; b) a two-compartment model; and c) a generalized dispersion model. The absolute values of the areas of the deviations of the calculated from the infused curves were found to be, respectively, 9.5, 8.4, and 7.8 percent of the total area under the infused curve. It was concluded that the tracer infusion method can reliably measure Ra of glucose when it is changing rapidly, and the system is out of steady state.

scholarly journals Estado nutricional y preferencia del sabor dulce en adultos chilenos

2020 ◽  
Vol 70 (4) ◽  
pp. 247-254
Author(s):  
Paula Ledesma Gutiérrez ◽  
Rocío Martínez Garrido ◽  
Fanny Flores Sandoval ◽  
Ana Acuña Dericke ◽  
Favián Treulen Seguel ◽  
...  
Keyword(s):  
Nutritional Status ◽  
Negative Impact ◽  
Sweet Taste ◽  
Nutritional Composition ◽  
Lifestyle Changes ◽  
The Body ◽  
Final Sample ◽  
Sweet Solution ◽  
Degree Of Satisfaction ◽  
Para Determinar

El dramático aumento de la prevalencia e incidencia de la obesidad sugiere que factores ambientales y cambios en el estilo de vida contribuyen de forma importante a su tendencia epidémica. En humanos, se han reportado diferencias interindividuales en los umbrales de detección y preferencia del sabor dulce, lo que podría afectar la ingesta habitual de azúcares, y por ende al estado nutricional. Objetivo: El presente estudio busca determinar la relación entre el estado nutricional y la preferencia al sabor dulce en la comunidad de un establecimiento de educación superior. Método: Muestra fue constituida por estudiantes, funcionarios y docentes, entre 18 y 60 años, pertenecientes a la Universidad Mayor, Sede Temuco. Para determinar preferencia al sabor dulce se empleó prueba organoléptica que mide grado de satisfacción frente a solución dulce, junto a ello se realizaron mediciones de peso y talla para determinar el Índice de Masa Corporal. Resultados: Muestra final comprendió de 319 personas, de las cuales un 30,1% fueron hombres y 69,9% mujeres. No se observaron diferencias significativas en la preferencia hacia las soluciones con mayor concentración de sacarosa según el estado nutricional. Sin embargo, el modelo predictivo desarrollado arrojó que hombres prefieren las soluciones con mayor concentración de azúcar independiente de la edad y estado nutricional. Conclusiones: Es necesario desarrollar nuevos estudios que permitan aclarar si la preferencia al sabor dulce favorece el desarrollo de obesidad y sobrepeso, o si es la composición nutricional de los alimentos procesados o ultraprocesados, lo que está teniendo un mayor impacto negativo en el estado nutricional de la población. The dramatic increase in the prevalence and incidence of obesity seems to suggest that environmental factors and lifestyle changes are contributing significantly to the epidemic trend of this pathology. In humans, inter-individual differences in the thresholds of preference of sweet taste have been reported, which could affect habitual sugar intake, and therefore the nutritional status. Objective: The present study seeks to determine the relationship between nutritional status and the preference of sweet taste in the population of a higher education establishment. Method: Sample was constituted by students, officials and teachers between 18 and 60 years, belonging to the Universidad Mayor, Temuco. To determine the perception of the sweet taste, an organoleptic test was used that measures the degree of satisfaction with the sweet solution, along with this, weight and height measurements were made to determine the Body Mass Index. Results: Final sample comprised 319 people, of which 30.1% were men and 69.9% women. No significant differences were observed in the preference for solutions with a higher concentration of sucrose according to nutritional status. However, a predictive model developed showed that men prefer the solutions with the highest concentration of sugar regardless of age and nutritional status. Conclusions: It is necessary to develop new studies to clarify whether the preference for sweet taste favors the development of obesity and overweight, or if it is the nutritional composition of processed or ultraprocessed foods, which is having a greater negative impact on the nutritional status of the population.

Effect of gender, body composition, and equilibration time on the 2H-to-18O dilution space ratio

2006 ◽  
Vol 263 (6) ◽  
pp. E1119-E1124 ◽  
Author(s):  
M. I. Goran ◽  
E. T. Poehlman ◽  
K. S. Nair ◽  
E. Danforth
Keyword(s):  
Body Composition ◽  
Bioelectrical Impedance ◽  
Gender Effect ◽  
The Body ◽  
Equilibration Time ◽  
Doubly Labeled Water ◽  
Sources Of Variation ◽  
Chemical Availability ◽  
The Mean ◽  
Space Ratio

Physiological sources of variation in the 2H-to-18O dilution space ratio (DSR) were examined in 34 males and 20 females (4-78 yr; 14.7-143.2 kg; 1.8-61.0% body fat). Dilution spaces were obtained by time 0 extrapolation of isotope washout over 10-14 days, and body composition was obtained by underwater weight (adults) or bioelectrical impedance (children). The mean DSR was 1.050 +/- 0.015 (range 1.029-1.111), significantly higher (P < 0.001) than the traditionally assumed value of 1.029 based on exchange over 4 h. Use of the value 1.029 causes a systematic 8% overestimate of energy expenditure from doubly labeled water, relative to use of the value 1.05. The DSR was not related to body composition or age but was significantly higher (P < 0.05) in males (1.052 +/- 0.016) than in females (1.044 +/- 0.012). This gender effect was not explained by differences in the number of exchangeable hydrogens in the body. We conclude 1) variation in the 2H-to-18O DSR is not explained by body composition but is influenced by the chemical availability of exchangeable hydrogens to undergo exchange; 2) because the DSR is not easily predicted, use of the observed dilution spaces are recommended; 3) if a fixed DSR is used, values of 1.044 and 1.052 are recommended in females and males, respectively.

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)

D2 18O (deuterium oxide) method for CO2 output in small mammals and economic feasibility in man

1975 ◽  
Vol 39 (4) ◽  
pp. 657-664 ◽  
Author(s):  
N. Lifson ◽  
W. S. Little ◽  
D. G. Levitt ◽  
R. M. Henderson
Keyword(s):  
Small Mammals ◽  
Deuterium Oxide ◽  
Body Water ◽  
Economic Feasibility ◽  
The Body ◽  
Doubly Labeled Water ◽  
Co2 Output ◽  
Isotopic Analyses ◽  
Human Energy ◽  
Intake Water

A test of the validity of the isotopic steady state relationships of the doubly labeled water (H2O) method has been carried out with D2 18O in small mammals (three chipmunks and one mouse). CO2 outputs calculated just from 1) the rate of water intake and 2) the ratios of the isotopic concentrations in the body water to the intake water agreed satisfactorily with observed values. Moreover, reconstructed energy and material balances agreed reasonably with similar balances reconstructed for an immediately succeeding period on the same animals studied by the previously validated decay procedure. We conclude from an error analysis that by expressing the isotopic specific activities as abundances in excess of the body water of a subject on a given regimen, the decay procedure is economically feasible in the human with available accuracy of isotopic analyses and the present cost of H2 18O. The method therefore appears to be a useful tool ready for application to the field of human energy metabolism.

Recovery of 13C in breath from NaH13CO3 infused by gut and vein: effect of feeding

1989 ◽  
Vol 257 (3) ◽  
pp. E426-E438 ◽  
Author(s):  
R. A. Hoerr ◽  
Y. M. Yu ◽  
D. A. Wagner ◽  
J. F. Burke ◽  
V. R. Young
Keyword(s):  
Statistical Significance ◽  
The Body ◽  
Co2 Production ◽  
Base Line ◽  
Experimental Diet ◽  
Factors Affecting ◽  
Routes Of Administration ◽  
Line P ◽  
Male Subjects ◽  
Atom Percent Excess

Estimates of substrate oxidation obtained from appearance of 13C or 14C from tracers in breath must be corrected for retention of labeled carbon in the body. We aimed to determine the effect of a defined experimental diet and metabolic status on recovery of infused Na [13C]bicarbonate in breath. Six healthy male subjects consumed an experimental diet for 7 days before receiving a continuous infusion of formula without tracer on day 8 and received either an intragastric (ig) or intravenous (iv) infusion of Na [13C]bicarbonate on day 9 or 11 during a 4-h postabsorptive (PA), 4-h continuously fed period. A trend toward increasing PA breath enrichment during the first 7 diet days approached statistical significance (P = 0.051), whereas breath enrichments measured 3 h postbreakfast were consistently higher than PA values throughout and did not change over the 7-day period. Breath enrichments during a 4-h continuous ig infusion of formula without tracer on day 8 rose 2.0 +/- 0.5 atom percent excess (APE).10(-3) above base line (P less than 0.001, ANOVA). In the tracer studies, breath enrichments were similar for the ig and iv routes of tracer infusion. For the ig infusion the fraction of infused Na [13C]bicarbonate recovered in breath as 13CO2 was 0.74 +/- 0.02 for the PA period and 0.79 +/- 0.02 for the fed period. For the iv infusion the fraction recovered was 0.70 +/- 0.04 for the PA period and 0.82 +/- 0.03 for the fed period. Fractional recoveries were not significantly different for ig and iv routes of administration but were different for PA and fed periods (P less than 0.0001, 2-way ANOVA). The fractional recoveries for the fed period obtained here were similar to the value 0.81 reported in a number of other studies. Recovery of tracer in breath increased linearly with O2 uptake and CO2 production, suggesting that factors affecting respiratory gas exchange may alter recovery. We conclude that the primary factor determining label recovery is the immediate and recent nutritional status of the host.

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