The Accuracy and Precision of an Open-Circuit System To Measure Oxygen Consumption and Carbon Dioxide Production in Neonates

Marks, Keith H; Coen, Patricia; Kerrigan, James R.; Francalancia, Nick A; Nardis, Elizabeth E; Snider, Michael T.

doi:10.1203/00006450-198701000-00014

Cited by 27 publications

(13 citation statements)

References 10 publications

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“…The relative accuracy of this apparatus has been determined in vitro to be ± 3.0% for V0:, VCo;. and respiratory quotient by previously established techniques [20].…”

Section: Discussionmentioning

confidence: 99%

Radiant Heat Loss versus Radiant Heat Gain in Premature Neonates under Radiant Warmers

Baumgart¹

1990

Neonatology

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Premature infants nursed on open radiant warmer beds are exposed to short-wavelength infrared power density distributed evenly over the bed surface. Additionally, infants’ sides are exposed to relatively cooler nursery walls, and to the radiant warmer bed platform which may heat and reradiate to the baby. Therefore, infants may not only gain heat from the warmer (Q_{radiant warmer}) but lose or gain radiant heat to the sides as well ( ± Q_{radiant loss}). In order to quantitate these parameters, ten premature newborn infants nursed under radiant warmers servocontrolled to 36.5 °C skin temperature (weight 1.27 ± 0.24 SD kg, gestation 31 ± 3 weeks) were investigated, and partitional calorimetry previously reported. In the present study, calculation of net rate of radiant heat transfer (Q_{net radiant}) was made from these data (––2.63 ± ––1.52 kcal/kg/h), and compared to direct measurements of Q_{radiant warmer} (––2.49 ± ––0.90 kcal/kg/h). The present report further partitions net radiant heat transfer to evaluate Q_{radiant loss}: ––0.13 ± 1.82 kcal/kg/h (range-3.16 to 1.93). From these calculations mean radiant temperature of this environment was estimated (45.3 ± 4.3 °C) and compared to the radiant warmer temperature received (45.0 ± 2.9 °C). This information suggests other strategies to reduce radiant heat loss as well as convective and evaporative losses in premature neonates nursed on open radiant warmer beds.

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“…The relative accuracy of this apparatus has been determined in vitro to be ± 3.0% for V0:, VCo;. and respiratory quotient by previously established techniques [20].…”

Section: Discussionmentioning

confidence: 99%

Radiant Heat Loss versus Radiant Heat Gain in Premature Neonates under Radiant Warmers

Baumgart¹

1990

Neonatology

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“…The measurement of oxygen uptake (~ro2) and carbon dioxide elimination (VCO2) has been focused mainly on the tailoring of enteral or parenteral nutrition, control of therapeutic efforts to balance the oxygen supply -demand relationship and, recently, automated measurement of cardiac output by the 'continuous' Fick method in combination with catheter oximetry [1]. Most of the present methods for paediatric measurements are based on canopy techniques [4][5][6] and confined to room air spontaneous breathing conditions. Only a few methods for measurement in ventilated neonates are described [2,3].…”

mentioning

confidence: 99%

A new paediatric metabolic monitor

Weyland

Fritz

et al. 1994

Intensive Care Med

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“…There was a previous history of undernutrition (mean % ideal body weight = 61 %, range 33-85%) in all patients coincident with their extreme prematurity or serious illness in the first weeks of life. All infants gained weight during the study although the rate of daily weight gain was very variable from one and its 95% confidence bands was estimated from measured values related to true values using laboratory standards (15,16). V represents the mean value of ( n ) measurements per infant.…”

Section: Resultsmentioning

confidence: 99%

“…It should be kept in mind that the dynamic responsiveness of any combination of flow meter and gas analyzer should be determined and the compensation for lag and delay time must be considered for the accurate analysis of respiratory gas exchange. Although the methods of respiratory gas exchange measurements are highly system specific, they all require meticulous calibration aimed to validate 0: uptake and C 0 2 production rates of similar magnitude to those encountered in normal calorimetric use (15).…”

Section: Marks Et Almentioning

confidence: 99%

Day-to-Day Energy Expenditure Variability in Low Birth Weight Neonates

1987

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ABSTRACT. We estimated the metabolic rate of 13 low birth weight infants over a 9-day period, using indirect calorimetry in conjunction with serial measurements of oxygen consumption, carbon dioxide production, and total urinary nitrogen excretion. The mean percent error for oxygen consumption and carbon dioxide production measurements (determined by alcohol combustion experiments) assignable to the open-circuit system was 0.4 and 3.8%, respectively. Error in the total urinary nitrogen excretion measurement was 4 % by the Kjeldahl technique. In the clinical setting, however, the range of deviation of measured oxygen consumption, carbon dioxide production and total urinary nitrogen excretion was f 12, 12, and 15% of the mean value respectively for an individual patient under standardized controlled conditions. The variability of metabolic rate between infants may be as much as 76%. Factors that had a small effect on metabolic rate were difficult to detect because of the variability inherent in the short-term measurement of metabolic rate. It was virtually impossible to control the sources of variation in the resting metabolism of low birth weight neonates over extended experimental periods. Day-to-day variations in resting energy expenditure may explain, in part, the widely different growth rates of premature infants receiving similar caloric intakes. (Pediatr Res 21: 66-71, 1987) Abbreviations MR, metabolic rate VOz, oxygen consumption VC02, carbon dioxide production TUN, total urinary nitrogen excretion NPRQ, nonprotein respiratory quotient EOG, electrooculogram There has been an increased interest in the sources of variation in energy expenditure that occur among very low birth weight infants in the modern clinical setting (1-6). Recently, Schulze et a/. (7-9) made an assessment of minute ventilation, heart rate, and gaseous metabolism in relation to the state of activity and feeding cycle of growing low birthweight infants. They showed that the infants were prone to significant (4.7 to 24.6%) swings in energy expenditure even under (apparently) strict basal con- ditions, and concluded that steady state conditions do not occur in growing low birth weight infants.Abdu1razzaq and Brooke (10) measured respiratory metabolism of premature infants and discussed body weight, activity, and energy intake in relation to 24-h measurements of energy expenditure. These authors found that V02 measured over a 3-h period might lie anywhere between 13.8% above to 12.6% below the value obtained from the 24-h mean VOz. In contrast, Rutter et al. Interest in the mechanisms responsible for these conflicting results led us to make longitudinal replicate measurements of VOz, VCO?, and total urinary nitrogen to determine with indirect calorimetry the average day-to-day variability of metabolic rate within and between low birth weight infants under controlled conditions. PATIENTS AND METHODSThe 13 very low birth weight infants were without major medical problems, were tolerating feeds and gaining weight. Informed parental consent w...

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The Accuracy and Precision of an Open-Circuit System To Measure Oxygen Consumption and Carbon Dioxide Production in Neonates

Cited by 27 publications

References 10 publications

Radiant Heat Loss versus Radiant Heat Gain in Premature Neonates under Radiant Warmers

Radiant Heat Loss versus Radiant Heat Gain in Premature Neonates under Radiant Warmers

A new paediatric metabolic monitor

Day-to-Day Energy Expenditure Variability in Low Birth Weight Neonates

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