Consequences of non steady-state CO2 production for accuracy of the doubly labelled water technique: The importance of recapture interval

1988 ◽  
Vol 90 (2) ◽  
pp. 337-340 ◽  
Author(s):  
J.R. Speakman ◽  
P.A. Racey
Keyword(s):  
Steady State ◽  
Co2 Production ◽  
Doubly Labelled Water

Continuous Estimation of CO2 Production during Exercise

1997 ◽  
Vol 36 (04/05) ◽  
pp. 368-371
Author(s):  
R. Soma ◽  
Y. Yamamoto
Keyword(s):  
Fuzzy Logic ◽  
Steady State ◽  
Infusion Rate ◽  
Feedback System ◽  
Whole Body ◽  
Co2 Production ◽  
Cycle Exercise ◽  
Continuous Estimation ◽  
Breath Measurement ◽  
13Co2 Enrichment

Abstract.A new method was developed for continuous isotopic estimation of human whole body CO2 rate of appearance (Ra) during non-steady state exercise. The technique consisted of a breath-by-breath measurement of 13CO2 enrichment (E) and a real-time fuzzy logic feedback system which controlled NaH13CO3 infusion rate to achieve an isotopic steady state. Ra was estimated from the isotope infusion rate and body 13CO2 enrichment which was equal to E at the isotopic steady state. During a non-steady state incremental cycle exercise (5 w/min or 10 w/min), NaH13CO3 infusion rate was successfully increased by the action of feedback controller so as to keep E constant.

Measurement of leucine metabolism in man from a primed, continuous infusion of L-[1-3C]leucine

1980 ◽  
Vol 238 (5) ◽  
pp. E473-E479 ◽  
Author(s):  
D. E. Matthews ◽  
K. J. Motil ◽  
D. K. Rohrbaugh ◽  
J. F. Burke ◽  
V. R. Young ◽  
...  
Keyword(s):  
Steady State ◽  
Continuous Infusion ◽  
Co2 Production ◽  
Human Beings ◽  
Priming Dose ◽  
Leucine Metabolism ◽  
Kinetics Of ◽  
13Co2 Enrichment

Leucine metabolism in vivo can be determined from a primed, continuous infusion of L-[1-13C]leucine by measuring, at isotopic steady state, plasm [-13C]leucine enrichment, expired 13CO2 enrichment, and CO2 production rate. With an appropriate priming dose of L-[1-13C]leucine and NaH13CO3, isotopic steady state is reached in less than 2 h, and the infusion is completed in 4 h. The method can determine rates of leucine turnover, oxidation, and incorporation into protein with typical relative uncertainties of 2, 10, and 4%, respectively. The method requires no more than 1 ml of blood and uses stable isotope rather than radioisotope techniques. Thus, the method is applicable to studies of human beings of all ages. L-[1-13C]leucine may be infused with a second amino acid labeled with 15N for simultaneous determination of the kinetics of two amino acids.

scholarly journals Energy expenditure of free-living reindeer estimated by the doubly labelled water method

Rangifer ◽  
2000 ◽  
Vol 20 (2-3) ◽  
pp. 211 ◽  
Author(s):  
Geir Gotaas ◽  
Eric Milne ◽  
Paul Haggarty ◽  
Nicholas J.C. Tyler
Keyword(s):  
Energy Expenditure ◽  
Rangifer Tarandus ◽  
Water Flux ◽  
Co2 Production ◽  
Wild Ungulates ◽  
Free Living ◽  
Doubly Labelled Water ◽  
Svalbard Reindeer ◽  
Mountain Pasture ◽  
The Mean

The doubly labelled water (DLW) method was used to measure total energy expenditure (TEE) in three male reindeer (Rangifer tarandus tarandus) aged 22 months in winter (February) while the animals were living unrestricted at natural mountain pasture in northern Norway (69°20'N). The concentrations of 2H and l8O were measured in water extracted from samples of faeces collecred from the animals 0.4 and 11.2 days after injection of the isotopes. Calculated rates of water flux and CO2-production were adjusted to compensate for estimated losses of 2H in faecal solids and in methane produced by microbial fermentation of forage in the rumen. The mean specific TEE in the three animals was 3.057 W.kg-1 (range 2.436 - 3.728 W.kg1). This value is 64% higher than TEE measured by the DLW method in four captive, non-pregnant adult female reindeer in winter and probably mainly reflects higher levels of locomotor activity in the free-living animals. Previous estimates of TEE in free-living Rangifer in winter based on factorial models range from 3.038 W.kg-1 in female woodland caribou (R. t. caribou) to 1.813 W.kg-1 in female Svalbard reindeer (R. t. platyrhynchus). Thus, it seems that existing factorial models are unlikely to overestimate TEE in reindeer/caribou: they may, instead, be unduly conservative. While the present study serves as a general validation of the factorial approach, we suggest that the route to progress in the understanding of field energetics in wild ungulates is via application of the DLW method.

Ventilatory and blood acid-base adjustments to a decrease in body temperature from 30 to 10YC in black racer snakes Coluber constrictor

1996 ◽  
Vol 199 (4) ◽  
pp. 815-823
Author(s):  
J Stinner ◽  
M Grguric ◽  
S Beaty
Keyword(s):  
Steady State ◽  
Body Temperature ◽  
Minute Ventilation ◽  
Co2 Production ◽  
Bicarbonate Concentration ◽  
Acid Base ◽  
Slow Increase ◽  
Coluber Constrictor ◽  
Steady State Levels ◽  
Time Required

There is increasing evidence that many amphibian and reptilian species use relatively slow ion-exchange mechanisms in addition to ventilation to adjust pH as body temperature changes. Large changes in blood bicarbonate concentration with changes in temperature have previously been reported for the snake Coluber constrictor. The purpose of the present study was to determine the ventilatory and pH adjustments associated with the increase in CO2 stores when the snakes are cooled. Body temperature was lowered from 30 to 10 °C within 4 h, at which time measurements of inspired minute ventilation (V.air), O2 consumption (VO2) and CO2 production (V.CO2) were started and continued for 56 h. The decrease in temperature produced a transient fall in the respiratory exchange ratio (V.CO2/VO2) to 0.2-0.3 and a steady-state value of 0.65±0.14 (mean ± s.d., N=7) was not achieved until about 35 h. There were concomitant transient reductions in V.air and V.air/V.O2. However, V.air/V.CO2 initially increased, with a corresponding reduction in arterial PCO2 (PaCO2) and increase in arterial pH. By 35 h, V.air/V.CO2 had decreased and PaCO2 had increased to steady-state levels, but pH decreased very little because of a gradual increase in bicarbonate concentration. We conclude that the drop in temperature imposed a metabolic acidosis for approximately 35 h because of the time required to increase bicarbonate concentration, and that the acidosis was compensated for by an elevated V.air/V.CO2. Steady-state breathing and acid-base status were not achieved until the relatively slow increase in CO2 stores had been completed.

Doubly labelled water measurements of field metabolic rate in White-tailed Ptarmigan: variation in background isotope abundances and effect on CO2 production estimates

1994 ◽  
Vol 72 (11) ◽  
pp. 1967-1972 ◽  
Author(s):  
Donald W. Thomas ◽  
Kathy Martin ◽  
Hélène Lapierre
Keyword(s):  
Metabolic Rate ◽  
Ambient Temperature ◽  
Body Mass ◽  
Empirical Model ◽  
Rocky Mountains ◽  
Co2 Production ◽  
Doubly Labelled Water ◽  
Field Metabolic Rate ◽  
Lagopus Leucurus ◽  
Colorado Rocky Mountains

We measured background 2H and 18O abundances and field metabolic rate (FMR) for White-tailed Ptarmigan (Lagopus leucurus) above 3600 m elevation in the Colorado Rocky Mountains between May and July. 18O abundances ranged from 1982.4 to 2018.6 ppm [Formula: see text], while 2H abundance ranged from 142.8 to 154.0 ppm [Formula: see text]. Mean 2H abundance followed closely (−0.3 ppm deviation) the level predicted by Tatner's empirical model relating 2H and ambient temperature. However, 18O was more enriched than predicted (+3.4 ppm), which may reflect 18O fractionation in the plant diet. FMR, measured by means of the doubly labelled water method, ranged from 206.4 to 442.7 kJ/d and was not related to body mass. However, for males, FMR was significantly and positively related to age. Because of high variation in background isotope levels, the use of mean 2H and 18O background abundances instead of individual backgrounds would introduce a mean error of 7.1% (range −8.9 to +11.4%) in calculations of CO2 production and FMR.

Computer simulation of ventilatory control by both neural and humoral CO2 signals

1980 ◽  
Vol 238 (1) ◽  
pp. R28-R35 ◽  
Author(s):  
W. S. Yamamoto
Keyword(s):  
Computer Simulation ◽  
Steady State ◽  
Reciprocal Inhibition ◽  
Carbon Dioxide Tension ◽  
Central Mechanism ◽  
Co2 Production ◽  
State Behavior ◽  
Afferent Pathways ◽  
Neural Signal ◽  
Isocapnic Hyperpnea

A mathematical model portraying a humoral signal derived from time-dependent variations in arterial carbon dioxide tension (PaCO2) and a neural signal proportional to the metabolic CO2 production was tested by computer simulation. The signals were assumed to enter the central mechanism through afferent pathways connected in reciprocal inhibition. The central mechanism, previously described, contained proportional, gradient, and positive feedback components. The model simulates steady-state isocapnic hyperpnea under endogenous CO2 load and hyperpnea proportional to PaCO2 under exogenous CO2 load. This behavior is consistent whether the neural signal is present alone, the humoral signal is present alone, or both are present and synergistic. When the neural and humoral signals are opposed hypocapnia and hyperventilation ensue; the values being consistent with the isometabolic hyperbola. The model also portrays steady-state behavior when CO2 is inhaled during exercise. During hypometabolic states of rest the mechanism appears to become insensitive to PaCO2 levels.

Application of the Fick principle to the continuous measurement of energy expenditure in pigs

1993 ◽  
Vol 44 (7) ◽  
pp. 1423
Author(s):  
LR Giles ◽  
JM Gooden
Keyword(s):  
Heat Exchange ◽  
Energy Expenditure ◽  
Continuous Measurement ◽  
Open Circuit ◽  
Growing Pigs ◽  
Whole Body ◽  
Co2 Production ◽  
Entry Rate ◽  
Doubly Labelled Water ◽  
Fick Principle

The paper reviews the current methods available for the measurement of heat exchange in pigs. The cost of construction of automated open-circuit respiration chambers, in association with climate-controlled facilites, has restricted continuous measurement of energy expenditure in pigs to a small number of laboratories around the world. Ventilated hoods and face mask techniques are not viable alternatives because of difficulties in maintaining a uniform environment around the animal and restriction of food intake. Indirect techniques, including carbon dioxide (CO2) entry rate and doubly-labelled water are only applicable when other technique are not available because of the errors involved when energy expenditure is based on CO2 production alone. An alternative procedure is described for the measurement of energy expenditure in the growing pig. Whole-body oxygen (O2) consumption is calculated from the product of cardiac output and the arteriovenous difference in blood O2 concentration across the lungs (Fick principle). Oxygen consumption recorded with the new procedure was compared with the ventilated hood and CO2 entry-rate techniques, and used to examine the heat exchange of growing pigs maintained at high ambient temperatures

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