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At least 55 records · Page 3Linked to original sources
PubMed1992

Continuous breathing circuit flow and tracheal tube cuff leak: sources of error during pediatric indirect calorimetry.

OBJECTIVE: To determine whether continuous gas flow in the breathing circuit or an airleak around the tracheal tube cuff will introduce errors into the measurement of oxygen consumption (VO2) with indirect calorimetry. DESIGN: Nonrandomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Ten healthy, anesthetized mongrel dogs, weighing 8 to 12 kg. INTERVENTIONS: Data were recorded at seven levels of flow, from 0 to 12 L/min in excess of minute ventilation, through a continuous breathing circuit. Data were recorded at five levels of tracheal tube cuff leak from 0% to 40% of inspiratory minute volume. MEASUREMENTS AND MAIN RESULTS: VO2 was measured using an indirect calorimeter with constant internal gas flow and calculated from results of blood gas analysis, cooximetry, and thermodilution cardiac output determinations at all levels of continuous breathing circuit flow and cuff leak. BP, heart rate, respiratory rate, arterial and mixed venous blood gases, and body temperature were measured to assess stability of cardiopulmonary function. Continuous breathing circuit flow did not affect the accuracy of indirect calorimetry until the total flow reached a critical value (11.5 L/min) that was slightly below the internal flow constant of the metabolic monitor (12.4 L/min). At higher circuit flows, measured VO2 decreased in a linear fashion, while calculated VO2 remained unchanged. Above the critical flow, the error of indirect calorimetry correlated significantly only with the total circuit flow (r2 = .64), not with the exhaled concentration of CO2 (r2 = .005) or the inspiratory-expiratory oxygen difference (r2 = .004). The continuous flow rate at the critical circuit flow was 66 +/- 15% of the subjects' peak inspiratory flow. Increasing tracheal tube cuff leak produced a progressive decrease in measured VO2 but not in calculated VO2. The difference between measured and calculated VO2 was linearly related to the magnitude of the leak (r2 = .56), and was statistically significantly larger at all levels of cuff leak, when compared with measurements during complete cuff seal. CONCLUSIONS: An indirect calorimeter in which measurement of VO2 is based on internal constant flow rather than spirometry can be used to accurately measure VO2 from a continuous-flow breathing circuit, if the total circuit flow is less than the internal flow. This limitation may restrict the use of continuous flow to a level below the subject's peak inspiratory flow. The accuracy of indirect calorimetry cannot be guaranteed for any amount of tracheal tube cuff leak.

Analysis of Variance↗
PubMed1995

Indirect calorimetry in mechanically ventilated children: a new technique that overcomes the problem of endotracheal tube leak.

OBJECTIVES: To develop indirect calorimetry to enable measurement of energy expenditure in mechanically ventilated children and to assess the effect of endotracheal tube leak on the accuracy of indirect calorimetry measurements. DESIGN: Prospective, observational study, using a convenience sample. SETTING: Tertiary pediatric intensive care unit in a university-associated children's hospital. PATIENTS: Eighteen patients, 3 months to 10 yrs of age, with various diagnoses, and requiring mechanical ventilation. INTERVENTIONS: Patients were intubated and received routine intensive care treatment. MEASUREMENTS AND MAIN RESULTS: Energy expenditure and respiratory quotient were measured using a new modification to the technique of indirect calorimetry, which includes an assessment of any expired gas lost around the endotracheal tube. Mean energy expenditure was 97% of predicted energy expenditure, but there was great variability between patients, and energy expenditure could not be estimated reliably from predictive equations. The amount of expired gas lost because of gas leak around the endotracheal tube was often a clinically important proportion of total expired gas, and this lost gas could not be predicted by audible endotracheal tube leak. CONCLUSIONS: Measurement of energy expenditure by indirect calorimetry may be useful in the nutritional management of critically ill children. Results may be inaccurate if the gas lost because of leak around uncuffed endotracheal tubes is not taken into account.

Calorimetry, Indirect↗
PubMed2000

Comparison of methods of measurements of oxygen consumption in mechanically ventilated patients with multiple trauma: the Fick method versus indirect calorimetry.

OBJECTIVE: The purpose of this study was to compare the measurements of whole body oxygen consumption determined by the Fick method and by indirect calorimetry in mechanically ventilated patients with multiple trauma. DESIGN: A prospective, correlational, within-subjects design. SETTING: Surgical intensive care unit of a Level I trauma center. PATIENTS: Thirty-eight mechanically ventilated adults with multiple injuries who received a pulmonary artery catheter within 24 hrs of admission to the surgical intensive care unit. MEASUREMENTS AND MAIN RESULTS: After the initial resuscitation, simultaneous measurements of oxygen consumption (V(O2) by the reverse Fick equation and by indirect calorimetry were performed every 6 hrs for 24 hrs in normothermic patients who were at rest for at least 30 mins. At each measurement period, the mean V(O2) values determined by indirect calorimetry were significantly greater than the mean V(O2) values determined by the Fick method (time 1: 172+/-38 vs. 125+/-47 mL/min/m2, p < .0001; time 2: 170+/-31 vs. 130+/-48 mL/min/m2, p < .0001; time 3: 170+/-32 vs. 132+/-53 mL/min/m2, p < .0001; time 4: 169+/-29 vs. 130+/-60 mL/min/m2, p < .0002). By using the Bland and Altman technique, the mean bias was 41+/-3.95 mL/min/m2. Correlation coefficients of VO2 values between methods of measurements were statistically significant (r2 = .32, p = .0001; r2 = .32, p = .0001; r2 = .33, p = .0001; r2 = .18, p = .0001). CONCLUSIONS: Indirect calorimetry should be the preferred standard for measurement of oxygen consumption in severely injured patients.

Adult↗
PubMed1997

Automated VO2max calibrator for open-circuit indirect calorimetry systems.

The complete calibration of indirect calorimetry systems involves simultaneous checks of gas analyzers, volume device, and software, and this requires a machine that can mimic accurately and precisely the ventilation and expired gases of an athlete. While previous calibrators have been built successfully, none have matched the ventilatory flows produced by athletes during high intensity exercise. A calibrator able to simulate high aerobic power (VO2max calibrator) was fabricated and tested against conventional indirect calorimetry systems that use chain-compensated gasometers to measure expired volume (VE systems) and calibrated electronic gas analyzers. The calibrator was also checked against a system that measures inspired volume (VI system) with a turbine ventilometer. The pooled data from both VE and VI systems for predicted VO2 ranging from 2.9 to 7.9 L.min-1 and ventilation ranging from 89 to 246 L.min-1 how that the absolute accuracy (bias) of values measured by conventional indirect calorimetry systems compared with those predicted by the calibrator was excellent. The bias was < 35 mL.min-1 for VO2 and carbon dioxide production, < 0.50 L.min-1 for ventilator (VE BTPS), -0.02% absolute for the percentage of expired O2 and +0.02% absolute for the percentage of expired CO2. Overall, the precision of the measured VO2, VCO2, and VE BTPS was approximately 1%. This VO2max calibrator is a versatile device that can be used for routine calibration of most indirect calorimetry systems that assess the ventilation and aerobic power of athletes.

Blood Gas Analysis↗
PubMed2006

Indirect calorimetry: methodology, instruments and clinical application.

PURPOSE OF REVIEW: This review aims to identify the basic methods for accurately measuring a patient's energy expenditure in clinical nutrition practice by indirect calorimetry, and the impact upon a disease state of applying the results obtained. RECENT FINDINGS: The open-circuit method is the most widely used in the majority of classical instruments for measuring energy consumption. Advances in gas exchange measurement have made this technique readily and precisely available at the bedside. Nevertheless, it is important to understand its intricate primary methodology for safe and correct application. The stress and activity factors should be carefully and specifically applied, and the respiratory quotient abandoned, for tailoring a patient's daily nutrition regimens. Caloric expenditure measured by indirect calorimetry coupled with the doubly labeled water technique introduced the concept of physical activity energy expenditure, which added to resting energy expenditure results in total daily energy expenditure. Compact modular and handheld devices have been introduced into the market, together with similar technology for evaluating exercise energy expenditure, making utilization easier, safer and precise. In the critically ill population, which is exposed to medical and surgical interventions, indirect calorimetry has greatly changed the practice of caloric administration, significantly reducing the total daily amount. SUMMARY: In conclusion, one has to be careful when choosing devices, and understanding and clinically applying the results obtained by indirect calorimetry, bearing in mind that measured resting energy expenditure should be the daily caloric goal in order to diminish clinical morbidity.

Calorimetry, Indirect↗
PubMed2005

Measured pulmonary oxygen consumption: difference between systemic oxygen uptake measured by the reverse Fick method and indirect calorimetry in cardiac surgery.

Measurement of oxygen uptake by indirect calorimetry was compared with the reverse Fick method in a series of patients undergoing cardiac surgery. Oxygen uptake measurements for indirect calorimetry were made using a calibrated measurement system utilizing the Haldane transformation in a simple semiclosed breathing system based upon a modified Bain circuit. Pulmonary blood flow for the reverse Fick method was measured using bolus thermodilution. The results were (mean [standard deviation]): indirect calorimetry 167[26] ml.min(-1), and reverse Fick 148[27] ml.min(-1). Indirect calorimetry overestimated the reverse Fick value by 11.3% (p < 0.001). These results are consistent with the findings of previous studies in similar patient groups and are explained by lung tissue oxygen consumption.

Aged↗
PubMed1984

Corticosteroids as effectors of lipid polymorphism of dielaidoylglycerophosphoethanolamine. A study using 31P NMR and differential scanning calorimetry.

The influence of corticosteroids on the lipid polymorphism of dielaidoylglycerophosphoethanolamine was studied by 31P NMR spectroscopy and differential scanning calorimetry. Both techniques evidenced two transitions in the pure lipid samples. The first one corresponded to the gel----liquid crystalline phase transition. It occurred at a temperature of 38.9 degrees C, as measured by differential scanning calorimetry and at 35-40 degrees C as detected by 31P NMR. The second transition corresponded to the bilayer----hexagonal HII phase transition. It occurred at 64.2 degrees C as measured by differential scanning calorimetry and at 60 degrees C as detected by NMR. Addition of corticosteroids led to different specific effects on the bilayer----hexagonal HII phase transition, according to their chemical structure. These effects appear to be the result of low amounts of incorporated steroids, according to binding studies (partition coefficient values range between 5 and 54). The presence of a conjugated 3-keto group in the steroid molecule (progesterone) promoted a downward shift in the bilayer----hexagonal HII phase transition temperature by about 6 -7 degrees C as compared to the 3 beta-OH-bearing compound (pregnenolone), which did not exhibit any appreciable effect. No change in the delta H of transition could be measured. The presence of the 21-OH group (like in deoxycorticosterone) induced the formation of a structure, characterized by an isotropic lineshape of the 31P NMR spectrum at temperatures where the 'hexagonal' type of lineshape is present, without steroid. The transition from the bilayer to this other structure occurred at a slightly higher temperature than the bilayer----hexagonal HII phase transition. It corresponded to a peak in differential scanning calorimetry scans with a delta H of 2.1 kJ X mol-1. The presence of the 17 beta-OH group as present in 17 beta-OH-progesterone and 11-deoxycortisol suppressed the two former effects. These compounds had no influence on the bilayer----hexagonal HII phase HII phase transition. The additional presence of the 11 beta-OH group like in corticosterone and cortisol, evoked a stabilization of the bilayer organization as the bilayer----hexagonal HII phase transition temperature is shifted upward by about 10 degrees C. This was accompanied by a decrease of the delta H to 0.8 kJ X mol-1. Besides this, the corticosteroids did not affect to a large extent the gel----liquid crystalline phase transition: a general slight downward shift of the transition temperature and a small broadening of the transition were observed without significant change in the delta H.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Cortex Hormones↗
PubMed1997

Comparison of indirect calorimetry and thermodilution cardiac output measurement in children.

We validated experimentally the ability of hood indirect calorimetry to measure accurately VO2. For this purpose we compared cardiac output calculated from the Fick equation Q = VO2/(Ca(O2) - CV(O2)), in which VO2 was obtained by hood indirect calorimetry, to thermodilution cardiac output (Qth) measured simultaneously during cardiac catheterization in children (n = 16). Because FI(CO2) is a critical factor in hood indirect calorimetry calculations, we also assessed the consequence of taking into account measured FI(CO2) rather than using the usual standard value of 0.0004. We found a good agreement between Q and Qth whether we used experimentally measured FI(CO2) in ambient air (Qth = 0.89 Q + 0.39, r = 0.941) or standard FI(CO2) (Qth = 0.84 Q + 0.55, r = 0.930). However, VCO2 and R computed from standard FI(CO2) differed significantly (p < 0.001) from values derived from measured FI(CO2). This demonstrates that indirect calorimetry allows reasonable estimates of Q, VO2, VCO2, and R provided that the actual values of FI(CO2) are used.

Adolescent↗
PubMed2005

Direct calorimetry reveals large errors in respirometric estimates of energy expenditure.

Knowledge of animal energetics is based largely upon indirect calorimetry, which is estimation of metabolic heat production by an organism from measurement of indices such as oxygen consumption or carbon dioxide production. Remarkably, indirect calorimetry has been validated by comparison to direct measurements of metabolic heat production (direct calorimetry) only for highly restricted conditions, primarily with a few species of medium-to-large mammals. Taxa with differing physiologies are little studied. For birds, for example, validations are limited to chickens and waterfowl exposed to mild environmental conditions and typically fasted for prolonged periods. Workers rely upon these restricted validations when studying animals ranging greatly in activity, phylogeny, body size and nutritional status. We tested the accuracy of respirometric estimates of energy expenditure by simultaneous indirect and direct calorimetry in a small mammal (the kangaroo rat Dipodomys merriami Mearns), a small bird (the dove Columbina inca Lesson) and a medium-sized bird (the quail Coturnix communis Linnaeus). We find that conventional respirometric estimates of energy expenditure may incorporate large errors (up to 38%) that are sufficient to call into question generalizations regarding patterns of animal energy use in many studies.

Analysis of Variance↗
PubMed2002

Rate of carbon dioxide production and energy expenditure in fed and food-deprived adult dogs determined by indirect calorimetry and isotopic methods.

OBJECTIVE: To evaluate energy expenditure (EE) in dogs by estimating rate of CO2 production (rCO2). ANIMALS: 15 Beagles. PROCEDURE: Food was withheld for 24 hours, and all dogs received an IV infusion of 13C sodium bicarbonate for 8 hours. Breath samples were collected before infusion and at 30-minute intervals from 4 to 8 hours, and 13C enrichment in breath CO2 was measured, using gas chromatography-isotopic ratio mass spectrometry. Food was withheld from 6 dogs, and rCO2 and O2 consumption were measured, using a conventional indirect calorimeter. The CO2 production and O2 consumption were measured by use of indirect calorimetry in 6 other fed dogs that were injected with 2H2O and H2(18)O. Blood samples were collected before tracer injection, 4 hours later, and on days 4, 7, and 11. Deuterium and 18O enrichments in plasma water were determined. RESULTS: Mean rCO2 measured by indirect calorimetry was 516 +/- 34 and 410 +/- 16 micromol/kg(0.75)/min in 6 fed and 6 food-deprived dogs, respectively. The rCO2 calculated from 13C-bicarbonate dilution was 482 +/- 30 micromol/kg(0.75)/min. Mean rCO2 determined by use of the double-labeled water method was 1,036 +/- 46 mmol/kg(0.75)/d. Mean energy expenditure calculated from rCO2 determined by infusion of 13C bicarbonate, indirect calorimetry in fed and food-deprived dogs, and infusion of double-labeled water was 386 +/- 39, 379 +/- 25, 338 +/- 14, and 552 +/- 25 kJ/kg(0.75)/d, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Energy expenditure calculated by indirect calorimetry in unfed dogs can be considered representative of basal metabolic rate.

Animals↗
PubMedDate not supplied

[Non-metabolic application of indirect calorimetry].

INTRODUCTION: The metabolic monitoring of the critical patient by means of indirect calorimetry is a technique that is used more and more often in ICU's. OBJECTIVES: To establish the methodological basis for the application of indirect calorimetry in the ventilatory monitoring of the critical patient. METHODS: 20 critical patients with complete support ventilation, who because of their clinical condition required an increased or decreased ventilatory minute volume, are monitored with indirect calorimetry (Deltatrac). The dead space was calculated (Vd/Vt ratio) using the formula; Vd/Vt = 1 - (0.863 x VeCO2/PaCO2 x Vm). The changes in carbon dioxide exhalation (VeCO2) were measured, and so was the dead space after changing the ventilation parameters, and the stabilization time of both parameters was measured also. RESULTS: The average oxygen use (VO2) was 265 +/- 45 ml/min, the average baseline VeCO2 was 219 +/- 38 ml/min, and the mean baseline PaCO2 was 37.8 +/- 8 mm Hg. The mean initial minute volume (Vm) was 10.8 +/- 3.2 l/min; in 10 patients this increased in 74 +/- 20%, and in the rest it decreased by 42 +/- 7%. The time required to reach the new equilibrium was less when the minute volume increased than if this decreased: 45.6 +/- 10 vs. 74.2 +/- 7 min (p < 0.01) for the VeCO2, and 45.4 +/- 7 vs. 76 +/- 6.8 min (p < 0.01) for the PaCO2. Both the PaCO2 and the VeCO2 reached the new equilibrium in similar times. The Vd/Vt prior to the ventilatory change was 0.5 +/- 0.12 and after the change the ratio was 0.49 +/- 0.1; in patients in whom the Vm decreased, the Vd/Vt also decreased (p < 0.01), but in contrast, when the Vm increased, the dead space did too (p < 0.01). CONCLUSIONS: On one hand indirect calorimetry permits monitoring of the metabolic equilibrium, and on the other hand in can monitor the patient's hemodynamics (Fick method) and finally, as has been show by this study, it allows a monitoring of the ventilatory situation of the critical patient with complete supported ventilation.

Calorimetry↗
PubMed1986

Direct calorimetry and the energetics of exercise and weight loss.

Laboratory studies using direct calorimetry, a technique which is no longer either rare or difficult, have shown no essential differences between men and women who gain weight easily and the always lean. Both groups gained weight similarly when overeating by 1,000 kcal X d-1. Thermogenic responses to eating and the energy losses in food and urine were similar in the overweight and lean. Daily sedentary energy expenditure is a function of fat-free mass, and fat-free mass increases with obesity. During exercise, calorimetry has shown that heat losses are not always exactly matched to heat production as calculated from respiratory gas exchange, but a 24-h exercise period with a cycle ergometer showed reasonable energy balance when subjects ate as much as they spent. During weight loss from restricting food intake by 1,000 kcal X d-1, calorimetry showed a 12% reduction in sedentary energy expenditure. Based on calorimetry studies and other evidence in the literature, exercise increases energy expenditure, it may eliminate the reduced energy expenditure of caloric restriction, and it can increase muscle mass and thus increase both fat-free mass and daily expenditure.

Adult↗
PubMedDate not supplied

Direct calorimetry for the measurement of heat release in preterm infants: methods and applications.

Direct calorimetry is a sensitive and accurate method for the measurement of biologic heat release in humans. At the Children's Medical Center of Brooklyn, State University of New York, we have established direct calorimetry for the measurement of heat release by low birth weight premature infants. We have tested the method and find it to be simple, safe, and accurate. We studied heat release in 10 low birth weight infants on 22 occasions. The smallest infant in the study group weighed 1.43 kg. All the infant underwent direct calorimetry between 1 week and 18 weeks of age. Heat release in the infants ranged from 1.31 kcal/kg/hr. This method of direct calorimetry offers a tool for measuring total metabolic heat release from the first weeks of life in very low birth weight infants to estimate the insensible water losses and to examine the effect of various feeding regimens and disease states on total heat release.

Body Temperature Regulation↗
PubMed1989

Assessment of oxygen-consumption by use of reverse Fick-principle and indirect calorimetry in critically ill patients.

Oxygen consumption was measured simultaneously by the reverse Fick-principle (V02FICK) and by indirect calorimetry ("Metabolic Measurement Cart Horizon") (V02MMC) in 31 critically ill patients; 24 men and 7 women. Seventeen patients were breathing spontaneously, 14 patients were on mechanical ventilation. The fractional inspiratory oxygen concentration (FI02) in ventilated patients ranged from 0.21 to 0.4 (mean 0.302). Total oxygen consumption as measured by indirect calorimetry was 286.7 +/- 59.7 ml/min (mean +/- SD), and measured by reverse Fick-principle 258.9 +/- 52.2 ml/min (mean +/- SD). The coefficient of correlation between the two methods was r = 0.873. The absolute difference of oxygen consumption between reverse Fick-method and indirect calorimetry was 11.3%. Regression analysis according to Theil revealed a similar regression between spontaneously breathing and mechanically ventilated patients for the studied FI02 values below 0.4. It is concluded that indirect calorimetry is a reliable method for measuring oxygen consumption in spontaneously breathing as well as mechanically ventilated critically ill patients.

Journal Article↗
PubMed2002

Pitfalls in predicting resting energy requirements in critically ill children: a comparison of predictive methods to indirect calorimetry.

BACKGROUND: Critical illness in children is thought to have profound effects on nutritional status. It is essential to avoid complications associated with inadequate nutrition support and delivery of excess energy. OBJECTIVE: To compare the results of several commonly used methods for predicting energy requirements in a group of critically ill children indirect calorimetry was used to measure energy expenditure in these children. DESIGN: Resting energy expenditures estimated by different prediction methods for energy were compared with measurements of actual resting energy expenditure obtained by indirect calorimetry in 52 children admitted to a pediatric intensive care unit. Agreement between each predictive method and indirect calorimetry was evaluated by Bland-Altman limits of agreement and by whether the methods met the predetermined criterion for accuracy of within 10% of the measured value. RESULTS: None of the equations predicted individual values accurately. Each of the predictive equations gave a wide and variable scatter of predicted values around the median. The recommended dietary allowance for energy was the least accurate and differed significantly even from the other predictive methods, overestimating energy expenditure in 50 of 52 patients. None of the remaining methods stood out as being more precise. CONCLUSIONS: Predictive methods commonly used to estimate energy expenditure in critically ill children are very imprecise and may lead to overprovision or underprovision of nutrition support. Resting energy expenditure should be measured by indirect calorimetry whenever possible.

Journal Article↗
PubMed1989

Evaluation of methods for indirect calorimetry with a ventilated lung model.

A combined lung and ventilator model was built, validated and used to test commercial systems for indirect calorimetry. It simulates O2 uptake and CO2 excretion under ventilator treatment conditions. In the model inspiratory gases are diluted with N2 and CO2 to give the desired expiratory concentrations. Minute volume, FIO2, ventilatory pressure, VO2, VCO2 and consequently RQ can be altered to simulate the adult clinical situation. A selected respiratory pattern is maintained by the lung model. Equipment for indirect calorimetry can then be connected to it and the results compared. Reference values are derived from measurements with a mass spectrometer and a Godart spirometer. Three commercially available instruments (Beckman MMC, Horizon MMC and Engström MC) were evaluated with this system. The limits of agreement with the reference values under different conditions (FIO2 0.4-0.7, ventilatory pressure 0-50 cmH2O) were determined. Differences as high as 15% from the true values of VO2 and V CO2 were observed. The pattern of mechanical ventilation and the intrinsic properties of the analyzers in the equipment used for indirect calorimetry influence measurements to a significant extent.

Calorimetry↗
PubMed1988

The theoretical bases of indirect calorimetry: a review.

Indirect calorimetry is the method by which the type and rate of substrate utilization, and energy metabolism are estimated in vivo starting from gas exchange measurements. This technique provides unique information, is noninvasive, and can be advantageously combined with other experimental methods to investigate numerous aspects of nutrient assimilation, thermogenesis, the energetics of physical exercise, and the pathogenesis of metabolic diseases. Since its use as a research tool in metabolism is growing, the theoretical bases of indirect calorimetry are here reviewed in a detailed and orderly fashion. Special cases, such as the occurrence of net lipid synthesis or gluconeogenesis, are formally considered with derivation of explicit stoichiometric equations. The limitations of indirect calorimetry, both theoretical and technical, are discussed in the context of circumstances of clinical interest in metabolism.

Adenosine Triphosphate↗
PubMed2000

Use of infrared thermographic calorimetry to determine energy expenditure in preterm infants.

BACKGROUND: Measurement of infant energy expenditure in the clinical setting is difficult and is rarely done. Both indirect and direct calorimetry require long measurement periods and frequent calibration. OBJECTIVE: The objective of this study was to validate in infants a newly developed method of determining energy expenditure, infrared thermographic calorimetry (ITC), against an established method, respiratory indirect calorimetry (IC). ITC measures mean infant body surface temperature. ITC was used in conjunction with heat loss theory to calculate radiant, convective, evaporative, and conductive heat losses and thereby determine total energy expenditure. DESIGN: Ten healthy preterm infants were studied by obtaining concurrent ITC and IC measurements over a 3.5-5.5-h study period. Continuous IC measurements were compared with ITC measurements taken every 10 min during study periods. IC values were summed over 10-min intervals covering the 5 min before and 5 min after each ITC measurement, to allow comparisons between the 2 methods. RESULTS: Comparison of paired ITC and IC mean measurements for all 10 infants over the entire study period showed no significant difference between the 2 methods. However, individual paired IC and ITC values were significantly different for 7 of 10 infants. The overall mean difference between the 2 methods was 1.3%. CONCLUSIONS: ITC is an accurate, noninvasive method for measurement of heat loss and energy expenditure in healthy preterm infants, and therefore it may be a useful clinical and research tool.

Body Temperature↗