Indirect Calorimetry Method Research Articles

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

To evaluate energy expenditure (EE) in dogs by estimating rate of CO2 production (rCO2). 15 Beagles. 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. 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. Energy expenditure calculated by indirect calorimetry in unfed dogs can be considered representative of basal metabolic rate.

Energy Expenditure of Heavy to Severe Exercise and Recovery

A method of indirect calorimetry is proposed that attempts to better quantify the energy expenditure associated with heavy/severe exercise and the recovery from that exertion. To accomplish this objective, the energy expenditure associated with rapid anaerobic glycolysis is separated from that of mitochondrial respiration both during and after heavy/severe exercise. This model contrasts with those hypotheses that employ oxygen uptake as the sole measure of energy expenditure (e.g. the oxygen debt) or that utilizing a measure of anaerobic energy expenditure while ignoring the recovery energy expenditure. Anaerobic metabolism and its energy promoting effect on oxidative recovery must be independently acknowledged regardless of the eventual fate of lactate.

The application of mass and energy conservation laws in physiologically structured population models of heterotrophic organisms

Rules for energy uptake, and subsequent utilization, form the basis of population dynamics and, therefore, explain the dynamics of the ecosystem structure in terms of changes in standing crops and size distributions of individuals. Mass fluxes are concomitant with energy flows and delineate functional aspects of ecosystems by defining the roles of individuals and populations. The assumption of homeostasis of body components, and an assumption about the general structure of energy budgets, imply that mass fluxes can be written as weighted sums of three organizing energy fluxes with the weight coefficients determined by the conservation law of mass. These energy fluxes are assimilation, maintenance and growth, and provide a theoretical underpinning of the widely applied empirical method of indirect calorimetry, which relates dissipating heat linearly to three mass fluxes: carbon dioxide production, oxygen consumption and N-waste production. A generic approach to the stoichiometry of population energetics from the perspective of the individual organism is proposed and illustrated for heterotrophic organisms. This approach indicates that mass transformations can be identified by accounting for maintenance requirements and overhead costs for the various metabolic processes at the population level. The theoretical background for coupling the dynamics of the structure of communities to nutrient cycles, including the water balance, as well as explicit expressions for the dissipating heat at the population level are obtained based on the conservation law of energy. Specifications of the general theory employ the Dynamic Energy Budget model for individuals. Copyright 1999 Academic Press.

Fat oxidation in nonobese and obese adolescents: Effect of body composition and pubertal development

Objectives: To measure postabsorptive fat oxidation (F ox) and to assess its association with body composition (lean body mass [LBM] and body fat mass [BFM]) and pubertal development. Design: We studied 235 control (male/female ratio = 116/119; age [mean ± SD]: 13.1 ± 1.7 years; weight: 45.3 ± 10.5 kg; LBM: 34.3 ± 7.1 kg; BFM: 11.0 ± 4.5 kg) and 159 obese (male/female ratio = 93/66; age: 12.9 ± 2.1 years; weight: 76.2 ± 19.1 kg; LBM: 47.4 ± 10.9 kg; BFM: 28.8 ± 9.2 kg) adolescents. Postabsorptive F ox was calculated from oxygen consumption, carbon dioxide production, and urinary nitrogen as measured by indirect calorimetry and Kjeldahl's method, respectively. Body composition was determined by anthropometry. Results: Postabsorptive F ox (absolute value and percentage of resting metabolic rate) was significantly ( p < 0.001) higher in the obese adolescents (76.7 ± 26.3 gm/24 hours, 42.3% ± 18.7%) than in the control subjects (40.0 ± 26.3 gm/24 hours, 28.7% ± 17.0%), even if adjusted for LBM. F ox corrected for BFM was similar in control and in obese children, but was significantly lower in girls compared with boys (control male subjects: 62.1 ± 29.1 gm/24 hours, control female subjects: 51.6 ± 28.4 gm/24 hours, obese male subjects: 57.3 ± 29 gm/24 hour, obese female subjects: 45.0 ± 28.4 gm/24 hours). BFM and LBM showed a significant positive correlation with F ox. By stepwise regression analysis the most important determinant of F ox was BFM in obese and LBM in control children. There was a significant rise in F ox during puberty; however, it was mainly explained by changes in body composition. Conclusions: Obese adolescents have higher F ox rates than their normal-weight counterparts. Both LBM and fat mass are important determinants of F ox. (J Pediatr 1998;132:98-104)

Long- and medium-chain triglycerides during parenteral nutrition in critically ill patients.

Due to their special metabolic pathway, medium-chain triglycerides (MCT) have been claimed to be oxidized more extensively, compared with long-chain triglycerides (LCT), when administered as a parenteral nutritional support. This enhanced lipid oxidation rate of MCT emulsions could be particularly disclosed in hyperglycemic and hyperinsulinemic conditions. In an attempt to further elucidate this question, we measured substrate oxidation rates in critically ill patients liable to experience such metabolic conditions, that is to say postoperative patients after esophageal resection receiving 1.5 times their measured energy expenditure (n = 12) or after liver transplantation (n = 8). These patients received either LCT or MCT-LCT emulsions. The metabolic measurements were performed simultaneously by two methods, namely indirect calorimetry and isotopic methods based on natural abundance of nutrients. Although both groups of patients were hyperglycemic and hyperinsulinemic, the measured carbohydrate and lipid oxidation rates were not different with whatever type of lipid was administered. The MCT-LCT emulsions did not offer clear-cut advantages over LCT emulsions in critically ill patients when lipid energetic fate was considered.

Coût en oxygène de la ventilation au cours du sevrage de la ventilation artificielle

The oxygen cost of breathing (OCB) can be directly estimated during the weaning process from mechanical ventilation: it is a difference between whole-body oxygen uptake (VO 2 ) during spontaneous breathing and VO 2 during controlled ventilation, when respiratory muscles are supposed to be at rest. The recent development of new methods of indirect calorimetry allows an accurate and continuous measurement of VO 2 in intubated and mechanically ventilated patients. The value of the OCB is mainly dependent on the underlying pulmonary disease. Finally, this measurement provides an objective evaluation of the efficay of new modalities of partial ventilatory support, such as pressure support ventilation.

Comparison of two methods, the thermodilution method of Fick and the Douglas bag method, in estimating the resting energy expenditure (REE)

Critically ill patients need appropriate nutritional support strictly correlated to their REE to avoid complications either from hypo or hyper alimentation. Resting Energy Expenditure (REE) in the I.C.U setting can be measured or calculated by several methods. The aim of our study was to compare two methods of indirect calorimetry. The REE calculated by the Fick equation (REET) and the traditional method of Douglas bag (REEi). Twelve ICU patients on mechanical ventilation were studied and the following results were obtained REET = 2295±552 Kcal/day and REEi = 2339±512 Kcal/day (mean±sd). A good correlation between the two methods showed by regression analysis. We conclude that the evaluation of REE using the thermodilution method of Fick is reliable in estimating the energy expenditure of critical ill patients.

Failure in Measuring Gas Exchange in the ICU

This study was performed on patients after coronary artery bypass surgery, and in healthy volunteers to assess discrepant oxygen consumption (VO2) measurement between indirect calorimetry and Fick methods. Further evaluations were performed to point out the technical failure. In this prospective study, the VO2 was assessed in the patients using a commercial indirect calorimeter and the reverse Fick method. This calorimeter does not directly measure gas flow, but it assumes a constant preset flow. Bench testing of the calorimeter was performed in spontaneous and respirator mode using a reference calorimeter in healthy volunteers. An important overestimation of VO2 and carbon dioxide production (VCO2) of approximately 30% was found in both groups. The actual flow was lower than the preprogrammed value. This lead to spuriously high fractions of carbon dioxide and low fraction of oxygen. VCO2 and VO2, calculated with the overestimated gas flow value were overestimated, while respiratory quotient remained unchanged. Technical check-up revealed leaks in the mixing chamber and in the sampling lines. Indirect calorimetry is a useful clinical tool, but the investigator has to be very attentive to all potentially interfering factors and hazards.

Energy and nitrogen metabolism of pregnant and lactating sows and suckling piglets. 5. Energy and nitrogen metabolism of pregnant sows

The energy and nitrogen metabolism of pregnant sows was measured with the method of indirect calorimetry in dependence on the number of gestation (1,2 and 4), on the energy supply (120, 100 and 80% of the requirement recommendation) and on the gestation stage. Values of maintenance requirement and of energy and nitrogen utilization for body deposition were calculated on the basis of results of energy and nitrogen metabolism. The energy maintenance requirement increased from 389 to 435 and 473 kJ metabolizable energy per kg LW0.75.d with rising number of gestation. The heat production increased from 85th to 115th day of gestation by 6%. The efficiency of the partial energy utilization for the energy deposition amounted to 66% on the average. The efficiency of the partial utilization of digestible nitrogen for the nitrogen deposition was calculated to 75%. The nitrogen maintenance requirement values amounted to 0.5 and 0.4 g digestible nitrogen per kg LW0.75.d in the 1st and 2nd half of gestation.

96 ENERGY EXPENDITURE IN VERY LOW BIRTHWEIGHT INFANTS (VLBW): INDIRECT CALORIMETRY VERSUS 2H18O METHOD

Information on individual energy expenditure should help to meet the special and increased nutritional needs of VLBW. We evaluated the accuracy, precision and overall performance of a newly designed portable indirect calorimeter (DELTATRAC II, Datex, Helsinki, Finland) in 20 spontaneously breathing VLBW. Initial infant weight, age, and postconoeptional age were (means ± SD) 1,351 ± 250 g, 3.6 ± 2.8 wk, and 33.9±2.2 wk. Mean values for O2 consumption (VO2), CO2 production rate (VCO2), RQ, and energy expenditure by indirect calorimetry were (means ± SD) 7.5 ± 0.9 ml/kg/min, 7.4 ± = 0.8 ml/kg/min, 0.99 ± 0.06, and 59.6 ± 6.8 kcal/kg/d. Although the thermogenic effect of muscular activity on VO2 and VCO2 was clearly demonstrable, mean 24-hour VO2 and VCO2 did not differ from quiet periods. Measurements over 6 hours explained > 95% of the variance of 24 h. In 8 infants the 2H18O method was simultaneously applied. Isotope turnover rates of 18O, isotope dilution space of 18O as percentage of total body weight, ant VCO2 were (means ± SD) 0.246±0.021/d, 79.6±4.5%, and 7.6±1.1 ml/kg/min, VCO2 as estimated by indirect calorimetry and 2H18O method differed no more than 12% in any baby. In conclusion, individual energy expenditure can be reliably determined in VLBW by indirect calorimetry as well as by 2H18O method. Physical activity scores do not need to be recorded.

Resting metabolic rate and daily energy expenditure among two indigenous Siberian populations.

AbstractResting metabolic rate (RMR) and total daily energy expenditure (TDEE) were measured on a sample of 47 adults (35 males, 12 females) from two indigenous Siberian populations, the Evenki and Keto. The Douglas bag method of indirect calorimetry was used to measure the energy cost of lying, sitting, standing, and three exercise levels of the Canadian aerobic test of fitness (step test). The flex‐heart rate method of heart rate monitoring (flex‐HR; Spurr et al. [1988], Am. J. Clin. Nutr. 48:552–559) was utilized to predict TDEE from the measured energy costs. Measured RMR was 6.66 kJ/min (1.59 kcal/min) for males and 5.19 kJ/min (1.24 kcal/min) for the females. Subjects living in the bush in brigade work parties had significantly higher RMRs than those residing in the villages. Comparison of RMR to selected populations suggests that the elevated metabolism of the subjects living in the brigades is due to short‐term environmental acclimatization to the ambient conditions of the taiga rather than long‐term adaptation to living in a northern climate. TDEE was estimated at 11.8 ± 3.0 MJ (2,815 kcal) for men and 8.6 ± 1.9 MJ (2,056 kcal) for women, and there were no brigade‐town differences in DEE. Based on their physical activity level (PAL = TDEE: basal metabolic rate [TDEE:BMR]), which was 1.77 for males and 1.59 for females, the Evenki and Keto have “moderately” active lifestyles during the summer according to FAO/WHO/UNU guidelines (FAO/WHO/UNU [1985] WHO Technical Support Series No. 724). © 1994 Wiley‐Liss, Inc.

Diet-induced thermogenesis in chronic obstructive pulmonary disease.

Increased resting energy expenditure and malnutrition are frequently observed in patients with COPD. The aim of this study was to examine the possible contribution of an increased diet-induced thermogenesis (DIT) to weight loss. Eleven patients with COPD in stable clinical state and 11 healthy control subjects were studied. Resting energy expenditure (REE) was measured by standard methods of indirect calorimetry, using a ventilated canopy. Premeal REE was measured after an overnight fast. All subjects then received a balanced liquid test meal with a caloric content that was 0.3 times their REE extrapolated to 24 h. Diet-induced thermogenesis was measured over 130 min. Premeal REE was 109.9 +/- 11.7% of predicted values in the COPD group and 97.5 +/- 9.6% of predicted in the control group (p < 0.01). Seventy minutes after the test meal, REE had increased by 18.8 +/- 8.5% in the COPD group and by 15.1 +/- 5.8% in the control group (NS). After 130 min, REE had increased by 16.4 +/- 7.1% in the COPD group and by 12.4 +/- 5.3% in the control group (NS). The DIT expressed as a percentage of the caloric content of the meal was 4.3 +/- 1.6% in the COPD group and 3.3 +/- 1.4% in the control group (NS). We conclude that patients with stable COPD, although hypermetabolic at rest, do not show an increased DIT.

Modification of the thermogenic effect of acutely inhaled salbutamol by chronic inhalation in normal subjects.

Acute inhalation of clinical doses of salbutamol in normal volunteers increases resting metabolic rate by up to 20% above control values. This study was designed to see if chronic treatment with salbutamol causes a sustained increase in metabolic rate and whether it modifies the acute thermogenic response to the drug. The effects of chronic inhaled salbutamol on resting oxygen consumption (VO2) and carbon dioxide output (VCO2) were studied in seven normal subjects (age 20-47 years, weight 52-105 kg, five men). An open canopy method of indirect calorimetry was used to measure VO2, VCO2, and respiratory quotient (RQ). Subjects inhaled two puffs of salbutamol or placebo four times a day in a double blind manner. Measurements of resting VO2 and VCO2 after 10 days of salbutamol were compared with the values after 10 days of placebo and with those taken at the start of the study. At the end of each treatment period subjects inhaled eight puffs (800 micrograms) of salbutamol and the acute effects on VO2, VCO2 and RQ were monitored for one hour. Resting VO2, VCO2, and RQ were not significantly different at the end of the salbutamol and placebo periods but the acute response to eight puffs of salbutamol was abolished by regular inhalation. The mean VO2 integrated over one hour after 800 micrograms salbutamol given acutely was different (241.3 and 210.7 ml/kg/h in the placebo and salbutamol groups respectively). Differences were not significant between placebo and salbutamol groups for changes in VCO2, heart rate, blood pressure, and RQ after acute inhalation. Regular treatment with inhaled salbutamol (800 micrograms/day) does not cause a sustained increase in resting metabolic rate but prevents the increase in VO2 that occurs after acute inhalations in normal subjects.

Acute effects of inhaled salbutamol on the metabolic rate of normal subjects.

This study was designed to investigate the contribution of inhaled salbutamol to the increase in resting metabolic rate found in patients with chronic airflow limitation who were receiving bronchodilator therapy. The resting metabolic rate of 10 normal subjects (age 20-47 years, weight 42-105 kg, seven men) was studied after inhalations of salbutamol or placebo. An open canopy method of indirect calorimetry was used to measure resting oxygen consumption (VO2) and resting carbon dioxide production (VCO2). Subjects inhaled two, four, eight, or 12 puffs (100 micrograms/puff) of salbutamol or placebo in a double blind manner. Recordings of VO2 and VCO2 were made after inhalation of the four doses of salbutamol or placebo, integrated over one hour, and compared. VO2 and VCO2 increased in a dose dependent manner after inhaled salbutamol with a maximum effect at five minutes after inhalation. After four puffs, VO2 was 203 and 188 ml/kg/h for salbutamol and placebo respectively. After eight puffs, VO2 was 207 and 185 and VCO2 was 167 and 155 ml/kg/h. After 12 puffs, VO2 was 220 and 190 with a VCO2 of 181 and 168 ml/kg/h. Twelve puffs of salbutamol increased the mean (SE) respiratory quotient from 0.85 (0.01) to 0.93 (0.04) at five minutes indicating an increase in ventilation in excess of metabolic demand. Mean heart rate increased in parallel with VO2. Inhaled salbutamol significantly increases resting metabolic rate in a dose dependent manner.

Energy expenditure and fuel selection in biological systems: the theory and practice of calculations based on indirect calorimetry and tracer methods.

Energy expenditure and fuel selection in biological systems: the theory and practice of calculations based on indirect calorimetry and tracer methods.

Digestibility, intestinal passage time and energy value of wheat bran in model studies in sows

An energy metabolism trial was conducted with four sows allocated to each of four levels of wheat bran (7, 14, 21 or 28 g/kg body weight 0.75.day). During 2-week experimental periods half the number of animals received increasing levels of the wheat bran supplementation, the other sows were fed in decreasing order. The basal diet was given constantly at a level of 36 g/kg Bw 0.75. Total digestibility of energy was determined by the collection method. For partioning the digestible energy into a prececal and postileal component the diet was supplemented with 0.3% Cr2O3, and samples of digesta taken by means of a cecum cannula were analyzed for this marker. The rate of passage of food was evaluated by using plastic pellets fed orally as well as inserted into the cecum. During each experimental period a complete energy balance was performed according to the methods of indirect calorimetry. The digestibility and metabolizability of wheat bran energy over the total alimentary tract was 60% and 57%, respectively. As a percentage of the total digestible energy, 70% were found in the prececal site of the digestive tract, and 30% in the hindgut fermentation. The efficiency of utilization of metabolizable energy (ME) for energy retention was 66.2%. Utilization of hindgut energy was lower by about a quarter than utilization of energy digested in the small intestine. The mean contents of ME of wheat bran amounted to 10.1 kJ/g dry matter. The ME of the wheat bran fiber (non-starch poly-saccharides) was calculated to be 5 kJ/g. The excretion of short-chain fatty acids in the feces was only 1-2% of fecal energy. The rate of passage of food decreased from 78 h (basal diet alone) to 52 h with the highest wheat bran supplementation. The prececal retention time was only 20% of the total rate of passage through the alimentary tract.

Description of a direct-indirect room-sized calorimeter

A calorimeter suitable for measuring human energy expenditure has been assembled by the US Department of Agriculture in Beltsville, Maryland. The room-sized calorimeter is 3.05 X 2.74 X 2.44 m (20.39 m3). Direct and indirect calorimetry methods are used to simultaneously measure heat emission and energy expenditure. A water-cooled gradient layer chamber is used to measure human heat production directly. Indirect calorimetry is ascertained by measuring the changes in gas composition of the air entering and existing the chamber. The inlet and outlet air are each sampled three times every 100 s with a multiple gas analyzer to determine carbon dioxide and methane production and oxygen consumption within the chamber. A total of 30 measurements, which include temperature, pressure, gas fractions, flow rates, direct heat transfer, electrical power, and motion within the chamber, are converted from electrical to digital signals and recorded on magnetic disk nine times each minute. Real-time calculations for directly and indirectly measured energy expenditure are continuously updated and displayed. The performance of the calorimeter is assessed by the combustion of alcohol within the chamber. Results of these tests indicate that the direct heat recovery is 99.7 +/- 2.6 (SD) % and the indirect heat recovery is 100.3 +/- 1.3 (SD) %.

Ascites increases the resting energy expenditure in liver cirrhosis

The purpose of this study was to investigate the effect of ascites on the energy metabolism of patients with liver cirrhosis. The resting energy expenditure was determined in 10 patients with liver cirrhosis and ascites of moderate or large volume. The resting energy expenditure measurement was performed using indirect calorimetry and the resting energy expenditure predictive value was calculated with the Harris-Benedict equation, both before and after removal of ascitic fluid by paracentesis. Metabolic stress factors were absent in all cases. After an interval of 11.2 +/- 7.7 days between measurements, a weight loss of 16.6 +/- 10.3 kg was observed with paracentesis. The resting energy expenditure measured by indirect calorimetry showed a statistically significant decrease from 1682 +/- 291 to 1523 +/- 240 kcal/day (P less than 0.005) after removal of ascites. The repeatability of our indirect calorimetry method only allowed for the analysis of the results in 4 of 10 patients in whom ascites removal produced a consistent decrease in resting energy expenditure. There were no statistically significant differences between the measurements obtained by indirect calorimetry and those provided by the Harris-Benedict equation, but the latter had a moderate reliability in predicting the real resting energy expenditure of every patient. Our results suggest that, far from being an inert volume, ascites may be associated, at least in some patients, with an increased resting energy expenditure and therefore accelerate the appearance of protein energy malnutrition with corresponding complications.

Energieumsatz Wachsender Ratten in Abhängigkeit von der Umgebungstemperatur

8 experiments were carried out with 9 albino rats each (Wistar line, bred at the institute) in the live weight range between 70 and 200 g and at environmental temperatures (ET) of 34, 32, 30, 28, 26, 24, 22 and 20 degrees C. In the course of each individual experiment the rats were alternatively fed for maintenance and weight gain (semi ad libitum) with feed mixtures containing 10, 25 and 40% crude protein (3 animals/variant). Energy metabolism was measured according to the method of indirect calorimetry over a total of 780 metabolism periods. In the temperature range studied there was no compensation between thermoregulatory heat and heat from other processes of the metabolism. The partial utilization of metabolizable energy for energy retention in the body was independent of ET and ranged between 73 and 80% for the 7 experiments with ET between 32 and 20 degrees C. Energy utilization depended on the protein content of the feed and decreased from 81 to 79 or 73 resp. when the protein content increased from 10 to 25% or to 40% resp. Energy requirement for protein retention varied between 1.61 and 2.09 kJ metabolizable energy/kJ and was independent of ET. Energy maintenance requirement (measured at 28, 30 and 32 degrees C) increased with the growing protein content from 415 to 439 and 447 kJ/kg LW0.75.d resp. (regression analysis) and from 411 to 420 and 432 kJ/kg LW0.75.d (measuring at maintenance level). The relative weight gain with the increased protein content of the feed largely corresponds to the expected values according to the efficiency of ATP synthesis in the oxidative degradation of nutrients. The relationship between heat production and ET is parabolic. In the live weight range studied the average thermoneutral temperature (TNT) was 32 degrees C. It decreased during the course of development from 34 to 30 degrees C. TNT decreased with the growing protein content of the feed. Thermoregulatory heat production depended on both environmental temperature and the stage of development. Its average value in the development range studied decreased with an increase of the environmental temperature by 2 K each, starting from 20 degrees C and rising to 32 degrees C, in the following linear sequence: 23.3, 21.0, 16.8, 12.5, 8.3, 4.0 and 0.3 kJ/kg LW0.75.d.K.

Resting Energy Expenditure in Interstitial Lung Disease

Because interstitial lung disease increases the work of breathing, the aim of this study was to determine if this condition is associated with increased energy requirements. A group of 12 clinically stable patients with interstitial lung disease was studied. Patients with a history of weight loss had significantly more severe lung volume restriction. Regression analysis showed that 42% of body weight variation was explained by vital capacity (p less than 0.025). Resting energy expenditure was measured by standard methods of indirect calorimetry. The measurements were performed with a ventilated hood during prolonged steady-state periods after an overnight fast. We found that resting energy expenditure was increased to 117.3 and 118.7% of the predicted basal metabolic rate, according to Fleisch and to Harris and Benedict reference values, respectively (p less than 0.001). Furthermore, resting energy expenditure was increased to 120.8% of the predicted value according to body fat-free mass (p less than 0.001). This extra energy expenditure in patients with interstitial lung disease is similar to that recently reported in patients with chronic obstructive pulmonary disease.