Precision and accuracy in a metabolic monitor for indirect calorimetry

Assessment of the Physical Invasiveness of Peroral Endoscopic Myotomy during the Perioperative Period Based on Changes in Energy Metabolism

A novel treatment method for achalasia of the esophagus and related disorders is known as peroral endoscopic myotomy (POEM). This study aimed to calculate the resting energy expenditure (REE) and evaluated the degree of physical invasiveness based on metabolic changes during the perioperative period of POEM. Fifty-eight patients who underwent POEM were prospectively enrolled; REE, body weight (BW), and basal energy expenditure were measured on the day of POEM, postoperative day 1 (POD 1), and three days after POEM (POD 3). The median REE/BW increased from 19.6 kcal/kg on the day of POEM to 24.5 kcal/kg on POD 1. On POD 3, it remained elevated at 20.9 kcal/kg. The stress factor on POD 1 was 1.20. Among the factors, including the Eckardt score, operation time, and the length of myotomy, the length of myotomy was associated with changes in REE/BW. During the perioperative period of POEM, the level of variation in energy expenditure was lower than that of esophageal cancer surgeries performed under general anesthesia. However, because the length of myotomy is a factor affecting changes in energy expenditure, careful perioperative management is desirable for patients with longer myotomy lengths.

Influence of Esophageal Endoscopic Submucosal Dissection on the Changes of Energy Metabolism during the Perioperative Period

Esophageal endoscopic submucosal dissection (ESD) is considered to be more complex than gastric ESD. This study aimed to assess the physical invasiveness of esophageal ESD during perioperative periods by measuring resting energy expenditure (REE). The factors affecting REE that could be used to identify patients requiring perioperative management were also investigated. Overall, 75 patients who had undergone esophageal ESD were prospectively enrolled. REE, body weight, and basal energy expenditure were measured on the day of and the day following ESD. The mean REE/body weight was 20.2 kcal/kg/day on the day of ESD and significantly increased to 23.0 kcal/kg/day one day after ESD. The stress factor on the day after ESD was 1.11. White blood cell, neutrophil, and C-reactive protein levels increased on the day after ESD and correlated with the changes in REE. Among the factors including age, body mass index, total resection area, operation time, and sarcopenia, only the total resection area was associated with changes in REE. In conclusion, energy metabolism increases during the perioperative period for esophageal ESD. The increase in the stress factor for esophageal ESD was higher than that in gastric and colorectal ESD. Furthermore, patients with large resection areas require greater attention in perioperative management. 

Erythrocyte Long-Chain ω-3 Fatty Acids Are Positively Associated with Lean Mass and Grip Strength in Women with Recent Diagnoses of Breast Cancer

BACKGROUND

Sarcopenia may hasten the risk of mortality in women with breast cancer. Long-chain omega-3 (n-3) polyunsaturated fatty acids (LCn-3PUFAs) may favor muscle mass which, in turn, could enhance resilience of cancer patients toward cancer treatment.

OBJECTIVES

The objective of this study was to measure the relation of erythrocyte LCn-3PUFA concentrations with lean mass, grip strength, and postprandial energy metabolism in women with newly diagnosed breast cancer.

METHODS

This cross-sectional analysis evaluated women (n = 150) ages 65 y and younger who were recently diagnosed with breast cancer (stages I-III). Erythrocyte LCn-3PUFA composition was measured using GC. Body composition was measured by DXA. Grip strength was assessed at the same visit. Postprandial energy metabolism was measured for 7.5 h after the consumption of a high-calorie, high-saturated-fat test meal using indirect calorimetry. Associations of fatty acids with outcomes were analyzed using multiple linear regression models and linear mixed-effects models.

RESULTS

The ω-3 index, a measurement of LCn-3PUFA status, was positively associated with appendicular lean mass (ALM)/BMI (β = 0.015, P = 0.01) and grip strength (β = 0.757, P = 0.04) after adjusting data for age and cancer stage. However, when cardiorespiratory fitness was also included in the analyses, these relations were no longer significant (P > 0.08). After a test meal, a higher ω-3 index was associated with a less steep rise in fat oxidation (P = 0.02) and a steeper decline in glucose (P = 0.01) when adjusting for age, BMI, cancer stage, and cardiorespiratory fitness.

CONCLUSIONS

The ω-3 index was positively associated with ALM/BMI and grip strength in women newly diagnosed with breast cancer and was associated with altered postprandial substrate metabolism. These findings warrant further studies to determine whether enriching the diet with LCn-3PUFAs during and after cancer treatments is causally linked with better muscle health and metabolic outcomes in breast cancer survivors.

Shortcomings of human-in-the-loop optimization of an ankle-foot prosthesis emulator: a case series

Human-in-the-loop optimization allows for individualized device control based on measured human performance. This technique has been used to produce large reductions in energy expenditure during walking with exoskeletons but has not yet been applied to prosthetic devices. In this series of case studies, we applied human-in-the-loop optimization to the control of an active ankle-foot prosthesis used by participants with unilateral transtibial amputation. We optimized the parameters of five control architectures that captured aspects of successful exoskeletons and commercial prostheses, but none resulted in significantly lower metabolic rate than generic control. In one control architecture, we increased the exposure time per condition by a factor of five, but the optimized controller still resulted in higher metabolic rate. Finally, we optimized for self-reported comfort instead of metabolic rate, but the resulting controller was not preferred. There are several reasons why human-in-the-loop optimization may have failed for people with amputation. Control architecture is an unlikely cause given the variety of controllers tested. The lack of effect likely relates to changes in motor adaptation, learning, or objectives in people with amputation. Future work should investigate these potential causes to determine whether human-in-the-loop optimization for prostheses could be successful.

Effects of core temperature, skin temperature, and inter-beat interval on resting metabolic rate measurements in thermoneutral conditions

It is important to identify potential underlying factors that can affect the variability of resting metabolic rate (RMR) measurements. The RMRs of 20 college-aged men were tested twice in stable environmental conditions, with each measurement separated by 40 min. Skin temperature, core temperature, and inter-beat interval were monitored throughout the study as identified factors that could affect RMR measurements. Since environmental conditions in a clinic or laboratory can vary, skin temperature and core temperature can be affected which may affect RMR. Similarly, prior physical activity, stress, sleep, and caffeine intake can affect inter-beat interval and may be a co-variable affecting RMR. Higher RMR measurements were compared to lower RMR measurements. RMR for the higher trial was 2068 ± 66 kcal/day, the lower trial was 1975 ± 65 kcal/day (t = 4.23; p < 0.01). Core temperature for higher trial was 37.1 ± 0.1 °C, the lower trial was 36.8 ± 0.1 °C (s = 105.00; p < 0.01). Skin temperature measurements were significantly different for the anterior bicep site (t = -2.52; p = 0.02), but not for any other site. Inter-beat interval for the higher measurement was 1038 ± 33 ms, the lower measurement was 998 ± 32 ms (t = 3.82; p < 0.01). However, regression analysis found that none of the variables were significant predictors for the higher RMR, lower RMR, or change in RMR. While the factors affecting RMR measurement variability remain unclear, the results suggest that typical fluctuations in core temperature, skin temperature, and inter-beat interval do not effectively predict changes in RMR in a thermoneutral environment.

Evaluation of the accuracy and precision of a new generation indirect calorimeter in canopy dilution mode

BACKGROUND & AIMS

Indirect calorimetry (IC) is the only way to measure in real time energy expenditure (EE) and to optimize nutrition support in acutely and chronically ill patients. Unfortunately, most of the commercially available indirect calorimeters are rather complex to use, expensive and poorly accurate and precise. Therefore, an innovative device (Q-NRG®, COSMED, Rome, Italy) that matches clinicians' needs has been developed as part of the multicenter ICALIC study supported by the two academic societies ESPEN and ESICM. The aim of this study was to evaluate the accuracy and intra- and inter-unit precision of this new device in canopy dilution mode in vitro and in spontaneously breathing adults.

METHODS

Accuracy and precision of oxygen consumption (VO₂) and carbon dioxide production (VCO₂) measurements were evaluated in vitro and in 15 spontaneously breathing healthy adults by interchanging three Q-NRG® units in a random order. In vitro validation was performed by gas exchange simulation using high-precision gas mixture and mass flow controller. Accuracy was calculated as error of measured values against expected ones based on volume of gas infused. Respiratory coefficient (RQ) accuracy was furthermore assessed using the ethanol-burning test. To evaluate the intra- and inter-unit precisions, the coefficient of variation (CV% = SD/Mean*100) was calculated, respectively, from the mean ± SD or the mean ± SD of the three mean values of VO₂, VCO₂, RQ and EE measured by each Q-NRG® units. In vivo accuracy measurement of the Q-NRG® was assessed by simultaneous comparison with mass spectrometry (MS) gas analysis, using Bland-Altman plot, Pearson correlation and paired t-test (significance level of p = 0.05).

RESULTS

In vitro evaluation of the Q-NRG® accuracy showed measurement errors <1% for VO₂, VCO₂ and EE and <1.5% for RQ. Evaluation of the intra- and inter-unit precision showed CV% ≤1% for VO₂ and EE and CV% ≤1.5% for VCO₂ and RQ measurements, except for one Q-NRG® unit where CV% was 2.3% for VO₂ and 3% for RQ. Very good inter-unit precision was confirmed in vivo with CV% equal to 2.4%, 3%, 2.8% and 2.3% for VO₂, VCCO₂, RQ and EE, respectively. Comparison with MS showed correlation of 0.997, 0.987, 0.913 and 0.997 for VO₂, VCO₂, RQ and EE respectively (p ≤ 0.05). Mean deviation of paired differences was 1.6 ± 1.4% for VO₂, -1.5 ± 2.5% for VCO₂, -3.1 ± 2.6% for RQ and 0.9 ± 1.4% for EE.

CONCLUSION

Both in vitro and in vivo measurements of VO₂, VCO₂, RQ and EE on three Q-NRG® units showed minimal differences compared to expected values and MS and very low intra- and inter-unit variability. These results confirm the very good accuracy and precision of the Q-NRG® indirect calorimeter in canopy dilution mode in spontaneously breathing adults.

Determining the Accuracy and Reliability of Indirect Calorimeters Utilizing the Methanol Combustion Technique

BACKGROUND

Several indirect calorimetry (IC) instruments are commercially available, but comparative validity and reliability data are lacking. Existing data are limited by inconsistencies in protocols, subject characteristics, or single-instrument validation comparisons. The aim of this study was to compare accuracy and reliability of metabolic carts using methanol combustion as the cross-laboratory criterion.

METHODS

Eight 20-minute methanol burn trials were completed on 12 metabolic carts. Respiratory exchange ratio (RER) and percent O₂ and CO₂ recovery were calculated.

RESULTS

For accuracy, 1 Omnical, Cosmed Quark CPET (Cosmed), and both Parvos (Parvo Medics trueOne 2400) measured all 3 variables within 2% of the true value; both DeltaTracs and the Vmax Encore System (Vmax) showed similar accuracy in measuring 1 or 2, but not all, variables. For reliability, 8 instruments were shown to be reliable, with the 2 Omnicals ranking best (coefficient of variation [CV] < 1.26%). Both Cosmeds, Parvos, DeltaTracs, 1 Jaeger Oxycon Pro (Oxycon), Max-II Metabolic Systems (Max-II), and Vmax were reliable for at least 1 variable (CV ≤ 3%). For multiple regression, humidity and amount of combusted methanol were significant predictors of RER (R² = 0.33, P < .001). Temperature and amount of burned methanol were significant predictors of O₂ recovery (R² = 0.18, P < .001); only humidity was a predictor for CO₂ recovery (R² = 0.15, P < .001).

CONCLUSIONS

Omnical, Parvo, Cosmed, and DeltaTrac had greater accuracy and reliability. The small number of instruments tested and expected differences in gas calibration variability limits the generalizability of conclusions. Finally, humidity and temperature could be modified in the laboratory to optimize IC conditions.

The Measurement of Energy Expenditure

Proper nutrition support depends upon the clinician's ability to estimate the patient's energy expenditure. The accuracy of estimation is inversely proportional to the severity of the patient's illness. This fact has spurred academic and industry groups to pursue the measurement of energy expenditure. Harris and Benedict used indirect calorimetry to develop their now-famous equation nearly 100 years ago. The concept of indirect calorimetry is simple; if you know the concentration of inspired gases and expired gases, along with the flow, you can determine the amount of a gas consumed or produced. The complexity and expense of indirect calorimeters suggest that this simple concept is technically challenging. Because we desire to know the energy expenditure of the most critically ill patients, indirect calorimetry is further confounded by the presence of oxygen and mechanical ventilation. This paper will discuss the myriad of variables and obstacles that complicate the measurement of energy expenditure and will suggest methods to avoid or overcome them.

Assessing resting energy expenditure in overweight and obese adolescents in a clinical setting: validity of a handheld indirect calorimeter

BACKGROUND

Accurately determining energy requirements is key for nutritional management of pediatric obesity. Recently, a portable handheld indirect calorimeter, MedGem (MG) has become available to measure resting energy expenditure (REE). Our work aims to determine the clinical validity and usefulness of MG to measure REE in overweight and obese adolescents.

METHODS

Thirty-nine overweight and obese adolescents (16 male (M): 23 female (F), 15.2 ± 1.9 y, BMI percentile: 98.6 ± 2.2%) and 15 normal weight adolescents (7M: 8F, age 15.2 ± 2.0 y, BMI percentile: 39.2 ± 20.9%) participated. REE was measured with both MG and standard indirect calorimeter (VMax) in random order.

RESULTS

MG REE (1,600 ± 372 kcal/d) was lower than VMax REE (1,727 ± 327 kcal/) in the overweight and obese adolescents. Bland Altman analysis (MG -VMax) showed a mean bias of -127 kcal/d (95% CI = -72 to -182 kcal/d, P < 0.001), and a proportional bias existed such that lower measured REE by VMax was underestimated by MG, and higher measured REE by VMax were overestimated by MG.

CONCLUSION

MG systematically underestimates REE in the overweight and adolescent population, thus the MG portable indirect calorimeter is not recommended for routine use. Considering that it is a systematic underestimation of REE, MG may be clinically acceptable, only if used with caution.

Maternal investment, life-history strategy of the offspring and adult chronic disease risk in South Asian women in the UK

BACKGROUND AND OBJECTIVES

Patterns of development predict cardiovascular disease (CVD) risk, and ethnic differences therein, but it remains unclear why apparently 'adaptive plasticity' in early life should generate health costs in later life. We hypothesized that offspring receiving low maternal investment during fetal life, the primary period of organogenesis, should predict a shorter reproductive career and develop a fast life-history strategy, prioritizing reproduction over growth and homeostatic maintenance.

METHODOLOGY

We studied 58 young adult South Asian women living in the UK, a group with high susceptibility to CVD. We obtained gestational age, birth weight (BW) and menarcheal age by recall and measured anthropometry, body composition, resting metabolic rate (RMR) and blood pressure (BP).

RESULTS

BW and gestational age were inversely associated with menarcheal age, indicating that lower maternal investment is associated with faster maturation. Menarcheal age was positively associated with height but inversely with adiposity, indicating that rapid maturation prioritizes lipid stores over somatic growth. BW was inversely associated with BP, whereas adiposity was positively associated, indicating that lower maternal investment reduces BP homeostasis. BW was positively associated with RMR, whereas menarche was inversely associated, indicating that maternal investment influences adult metabolism.

CONCLUSIONS AND IMPLICATIONS

Supporting our hypothesis, low maternal investment promoted faster life histories, demonstrated by earlier menarche, reduced growth and elevated adiposity. These traits were associated with poorer BP regulation. This is the first study demonstrating strategic adjustment of the balance between reproduction and metabolic health in response to the level of maternal investment during fetal life.

Clinical Guide for the Use of Metabolic Carts: Indirect Calorimetry--No Longer the Orphan of Energy Estimation

Critically ill patients often require nutrition support, but accurately determining energy needs in these patients is difficult. Energy expenditure is affected by patient characteristics such as weight, height, age, and sex but is also influenced by factors such as body temperature, nutrition support, sepsis, sedation, and therapies. Using predictive equations to estimate energy needs is known to be inaccurate. Therefore, indirect calorimetry measurement is considered the gold standard to evaluate energy needs in clinical practice. This review defines the indications, limitations, and pitfalls of this technique and gives practice suggestions in various clinical situations.

Comparison of the GEM and the ECAL indirect calorimeters against the Deltatrac for measures of RMR and diet-induced thermogenesis

The Deltatrac™ II Metabolic Monitor (Datex-Ohmeda Inc.) is considered the standard reference machine in indirect calorimetry; however, it is no longer commercially available thus there is a need for new machines. The gas exchange measurement (GEM; GEM Nutrition Ltd) and the ECAL (Health Professional Solutions) are alternative measuring systems. The aim of this study was to compare the ECAL and GEM with Deltatrac for measures of RMR and the GEM to the Deltatrac for measures of diet-induced thermogenesis (DIT). Twenty healthy participants were tested on test day 1 (T1) and test day 2 (T2). RMR was measured in a randomised order for 30 min on the Deltatrac, the GEM and the ECAL. Following this, a 1553 kJ meal was consumed and DIT was measured on the Deltatrac and the GEM in alternating 15 min intervals for 4 h. The GEM reported consistently higher values than the Deltatrac for VO2, VCO2, RMR and fat oxidation (P < 0·005). The ECAL was significantly higher than the Deltatrac for measures of VO2, RMR, carbohydrate oxidation (T2) and respiratory quotient and fat oxidation (T1, T2) (P < 0·05). There were no significant differences within repeated RMR measures on the ECAL, the GEM or the Deltatrac. DIT measures were consistently higher on the GEM (T1) (P < 0·005); however, there were no significant differences between repeated measures. The findings suggest that while the GEM and the ECAL were not accurate alternatives to the Deltatrac, they may be reliable for repeated measures.

Nutritional care of the obese adult burn patient: a U.K. Survey and literature review

Obesity is an emerging healthcare problem and affects an increasing number of burn patients worldwide. An email survey questionnaire was constructed and distributed among the 16 U.K. burn services providing adult inpatient facilities to investigate nutritional practices in obese thermally injured patients. Responses received from all dieticians invited to participate in the study were analyzed, and a relevant literature review of key aspects of nutritional care is presented. The majority of services believe that obese patients warrant a different nutritional approach with specific emphasis to avoid overfeeding. The most common algebraic formulae used to calculate calorific requirements include the Schofield, Henry, and modified Penn State equations. Indirect calorimetry despite being considered the "criterion standard" tool to calculate energy requirements is not currently used by any of the U.K. burn services. Gastric/enteral nutrition is initiated within 24 hours of admission in the services surveyed, and a variety of different practices were noted in terms of fasting protocols before procedures requiring general anesthesia/sedation. Hypocaloric regimens for obese patients are not supported by the majority of U.K. facilities, given the limited evidence base supporting their use. The results of this survey outline the wide diversity of dietetic practices adopted in the care of obese burn patients and reveal the need for further study to determine optimal nutritional strategies.

Comparison of three indirect calorimetry devices and three methods of gas collection: a prospective observational study

BACKGROUND & AIMS

Indirect calorimetry was performed for a long time with the DeltatracII(®) device (Datex, Finland), considered as a reference but no longer produced. This study aims at comparing the energy expenditure (EE), the volume of oxygen (VO2) and carbon dioxide (VCO2) measured by two new available indirect calorimeters, the QuarkRMR(®) (Cosmed, Italy) and the CCMexpress(®) (MedGraphic,USA), using three different methods of gas collection, with the DeltatracII(®) in healthy subjects.

METHODS

Twenty-four healthy subjects (15 women and 9 men, age 53 ± 15 yrs, mean BMI 25.5 ± 7.1 kg/m(2)) underwent measurements of EE with DeltatracII(®) using canopy, QuarkRMR(®) using canopy and CCMexpress(®) using canopy, face tent and facemask. All measurements were performed for 10 min in random order. Results are presented as mean ± SD and compared by linear regression, repeated measure one-way ANOVA with Bonferroni's post hoc test and Bland & Altman test.

RESULTS

EE was 1630 ± 340 kcal for DeltatracII(®) and 1607 ± 307 kcal, 1741 ± 360 kcal, 1666 ± 315 and 1626 ± 336 kcal for QuarkRMR(®) and CCMexpress(®) with canopy, face tent and facemask, respectively (p = 0.001). Compared to DeltatracII(®), Bland & Altman test showed a mean EE difference (2SD) of 24(220)kcal for QuarkRMR(®), and -111(260) kcal, -36(304) kcal, 5(402) kcal for CCMexpress(®) with canopy, face tent and facemask, respectively. There was no systematic over- or underestimation with any device or gas collection method.

CONCLUSION

Mean EE was similar between QuarkRMR(®) and DeltatracII(®) but not between CCMexpress(®), in any mode of gas collection, and DeltatracII(®). Bland & Altman test shows a large variability in EE differences with both devices compared to DeltatracII(®), highlighting the need for refining their accuracy.

A standardized approach to study human variability in isometric thermogenesis during low-intensity physical activity

Limitations of current methods: The assessment of human variability in various compartments of daily energy expenditure (EE) under standardized conditions is well defined at rest [as basal metabolic rate (BMR) and thermic effect of feeding (TEF)], and currently under validation for assessing the energy cost of low-intensity dynamic work. However, because physical activities of daily life consist of a combination of both dynamic and isometric work, there is also a need to develop standardized tests for assessing human variability in the energy cost of low-intensity isometric work.

EXPERIMENTAL OBJECTIVES

Development of an approach to study human variability in isometric thermogenesis by incorporating a protocol of intermittent leg press exercise of varying low-intensity isometric loads with measurements of EE by indirect calorimetry.

RESULTS

EE was measured in the seated position with the subject at rest or while intermittently pressing both legs against a press-platform at 5 low-intensity isometric loads (+5, +10, +15, +20, and +25 kg force), each consisting of a succession of 8 cycles of press (30 s) and rest (30 s). EE, integrated over each 8-min period of the intermittent leg press exercise, was found to increase linearly across the 5 isometric loads with a correlation coefficient (r) > 0.9 for each individual. The slope of this EE-Load relationship, which provides the energy cost of this standardized isometric exercise expressed per kg force applied intermittently (30 s in every min), was found to show good repeatability when assessed in subjects who repeated the same experimental protocol on 3 separate days: its low intra-individual coefficient of variation (CV) of ~ 10% contrasted with its much higher inter-individual CV of 35%; the latter being mass-independent but partly explained by height.

CONCLUSION

This standardized approach to study isometric thermogenesis opens up a new avenue for research in EE phenotyping and metabolic predisposition to obesity.

Resting energy expenditure in young adults born preterm--the Helsinki study of very low birth weight adults

Background

Adults born preterm with very low birth weight (VLBW; <1500g) have higher levels of cardiovascular and metabolic risk factors than their counterparts born at term. Resting energy expenditure (REE) could be one factor contributing to, or protecting from, these risks. We studied the effects of premature birth with VLBW on REE.

Methodology/Principal Findings

We used indirect calorimetry to measure REE and dual x-ray absorptiometry (DXA) to measure lean body mass (LBM) in 116 VLBW and in 118 term-born control individuals (mean age: 22.5 years, SD 2.2) participating in a cohort study. Compared with controls VLBW adults had 6.3% lower REE (95% CI 3.2, 9.3) adjusted for age and sex, but 6.1% higher REE/LBM ratio (95% CI 3.4, 8.6). These differences remained similar when further adjusted for parental education, daily smoking, body fat percentage and self-reported leisure time exercise intensity, duration and frequency.

Conclusions/Significance

Adults born prematurely with very low birth weight have higher resting energy expenditure per unit lean body mass than their peers born at term. This is not explained by differences in childhood socio-economic status, current fat percentage, smoking or leisure time physical activity. Presence of metabolically more active tissue could protect people with very low birth weight from obesity and subsequent risk of chronic disease.

Increased resting energy expenditure in children with attention-deficit-hyperactivity disorder

BACKGROUND

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most frequently reported neuropsychiatric disorders in childhood. However, there is limited data on the biological basis for this disorder. Disturbances in neurotransmitters have been suggested to play a pathophysiologic role. Phenotypically an increased prevalence of obesity has been reported.

OBJECTIVE

To investigate resting energy expenditure (REE) and diet-induced thermogenesis in stimulant medication-naïve children with ADHD.

DESIGN

Case control study of 12 pre-pubertal boys with ADHD of the hyperactive-impulsive type and 12 control boys without ADHD. Anthropometric testing and indirect calorimetry were performed before and after a standardized meal. REE and thermogenesis were measured in each subject at 2 time points. In an independent group of 60 boys with ADHD, BMI standard deviation scores (BMI-SDS) were compared to age-adapted reference values.

RESULTS

REE was on average 6.5 kcal/kg fat free mass/day higher in the ADHD compared to the control group (p<0.01). In contrast, the thermogenic effect of food was not different between the two groups (average increase by 16%, p=n.s.). The repeat measurements, an average of 5±1 months apart, were highly reproducible in all subjects. Age and restlessness did not explain the differences in REE. Boys with ADHD had similar BMI-SDS values (mean BMI-SDS -0.10±0.98) as reference groups.

CONCLUSIONS

REE, in contrast to diet-induced thermogenesis, is higher in medication-naïve boys with ADHD. The normal BMI levels suggest increased energy intake in these children.

Changes in resting metabolic rate in an elderly German population: cross-sectional and longitudinal data

BACKGROUND/OBJECTIVES

This study investigates age-dependent changes in resting metabolic rate (RMR) considering changes in body composition and fat distribution within the longitudinal study on nutrition and health status in an aging population in Giessen (GISELA), Germany, using three different approaches.

SUBJECTS/METHODS

In approach 1 cross-sectional data from 358 female and 155 male participants of the GISELA study were evaluated (mean age of 67.4 +/- 5.9 and 66.9 +/- 5.2 y, respectively). In approach 2 longitudinal data of 107 female and 55 male subjects who participated over a follow up period of 10 years were analysed. In approach 3 all data obtained at a total of 3033 visits from 363 women and 153 men between 1994 and 2006 were evaluated. The mean duration of follow-up was eight years. RMR was assessed by indirect calorimetry.

RESULTS

Approach 1: RMR correlates significantly negatively with age in women and men. Considering fat free mass, fat mass, and WHR, age proved to be a significant predictor of RMR in both sexes in multiple regression analysis; RMR falls by 11.2 kJ/d and 34.1 kJ/d per year in females and males, respectively. Approach 2: In males but not in females RMR decreases significantly in the course of the follow up. After ten years measured RMR is significantly lower than expected RMR predicted on the basis of body composition and fat distribution in females and males. Deviations correspond to a decline in RMR by 11.4 and 27.5 kJ/d per year independently of changes in body composition and fat distribution. Approach 3: Results of the mixed linear model show that RMR decreases in the course of aging in both women and men; after considering changes in body composition and fat distribution respective decreases were 8.7 and 30.7 kJ/d per year.

CONCLUSIONS

These results indicate that the decline in RMR with advancing age cannot be totally due to changes in body composition.

Metabolic support of the obese intensive care unit patient: a current perspective

PURPOSE OF REVIEW

Obesity is a widespread condition associated with a variety of mechanical, metabolic, and physiologic changes that affect both health outcomes and delivery of care. Nutrition support is a key element of management during critical illness known to improve outcomes favorably, but is likewise complicated in the presence of obesity. This review serves to discuss the challenges unique to management of critically ill obese patients and an evidence-based approach to nutrition support in this patient population.

RECENT FINDINGS

High-protein, hypocaloric feeding has emerged as a nutrition support strategy capable of reducing hyperglycemia and protein catabolism, while promoting favorable changes in body composition and fluid mobilization. Recent data have shown a protective effect of mild-moderate obesity (BMI 30-39.9 kg/m2), with improved morbidity and mortality outcomes in this subgroup. Therefore, it is unclear whether hypocaloric feeding represents an inferior approach in this subgroup in which weight maintenance may be preferable.

SUMMARY

There are many obstacles that limit provision of nutrition support in the obese ICU patient. Calculating energy needs accurately is extremely problematic due to a lack of reliable prediction equations and a wide variability in body composition among the obese patients. Further research is needed to determine a better approach to estimating energy needs in this population, in addition to validating hypocaloric feeding as the standard approach to nutrition support in the obese patients.

Recent advances in free-living physical activity monitoring: a review

It has become clear recently that the epidemic of type 2 diabetes sweeping the globe is associated with decreased levels of physical activity and an increase in obesity. Incorporating appropriate and sufficient physical activity into one's life is an essential component of achieving and maintaining a healthy weight and overall health, especially for those with type II diabetes mellitus. Regular physical activity can have a positive impact by lowering blood glucose, helping the body to be more efficient at using insulin. There are other substantial benefits for patients with diabetes, including prevention of cardiovascular disease, hyperlipidemia, hypertension, and obesity. Several complications of utilizing a self-care treatment methodology involving exercise include (1) patients may not know how much activity that they engage in and (2) health-care providers do not have objective measurements of how much activity their patients perform. However, several technological advances have brought a variety of activity monitoring devices to the market that can address these concerns. Ranging from simple pedometers to multisensor devices, the different technologies offer varying levels of accuracy, comfort, and reliability. The key notion is that by providing feedback to the patient, motivation can be increased and targets can be set and aimed toward. Although these devices are not specific to the treatment of diabetes, the importance of physical activity in treating the disease makes an understanding of these devices important. This article reviews these physical activity monitors and describes the advantages and disadvantages of each.

Intra-individual variation in RMR in older people

In the factorial estimation of total energy expenditure it is assumed that the intra-individual variation in RMR is small. Little is known about the intra-individual variation in RMR in older subjects. The present study investigated the intra-individual variation in RMR in older people. Measurements of RMR were made in twenty-seven older subjects, mean age 71·6 (sd 6·1) years, on two separate occasions (T1 and T2) and on a third occasion (T3) in nineteen of the subjects. Measurements of height and weight were taken in all subjects. RMR measurements were made in the laboratory using a Deltatrac™ (ventilated-hood indirect calorimeter; Datex, Helsinki, Finland). All subjects had fasted overnight for 12h and refrained from strenuous exercise before measurements. The intra-individual CV in RMR (kJ/d) after T1 and T2 was 2·5% in women and 3·6% in men and was 2·6% in women and 3·4% in men after all three sets of measurements. Although mean RMR did not vary across T1, T2 and T3, there was significant ‘crossing tracks’ across the three measurement occasions in some individuals, reflecting a high degree of within-subject variability. The methods used had a significant measurement error associated with them (high R value; significant F ratio in three-way ANOVA). In conclusion, the results from the present study indicate that intra-individual variation in RMR was low in older people. The intra-individual variation in the elderly is similar to that seen in younger age groups.

Validation of the VO2000 calorimeter for measuring resting metabolic rate

BACKGROUND & AIMS

Metabolic carts used in laboratory settings for the measurement of resting metabolism are cumbersome limiting their use in the field. The validity of a newly developed portable calorimeter (Medical Graphics VO2000) under resting conditions was assessed in comparison to a well-established reference system, the DELTATRAC.

METHODS

Gas exchange and energy expenditure were measured for 25 min consecutively using the two devices. Values of the last 20 min were averaged and used in the analysis. The order of device for the first subject was randomly chosen and the calorimeters were alternated thereafter.

RESULTS

Among 33 subjects, acceptable measures of resting metabolism were obtained in 25 (11 men) aged 20-78 years because eight subjects (three men) either hyperventilated or did not adapt well enough to the facemask. VO(2), VCO(2), and RQ were not significantly different between devices. Small (2.8%) non-clinically relevant mean differences (-0.145+/-0.341 MJ day(-1)) were found. Results of the two devices were highly correlated (r=0.95) yielding a more accurate estimate than predictive equations.

CONCLUSIONS

The VO2000 calorimeter is a valid system to measure resting metabolism but the facemask may not be suitable for some people.

Variability in energy expenditure and its components

PURPOSE OF REVIEW

To review factors contributing to variation in total daily energy expenditure and its primary components: (1) resting metabolic rate; (2) diet-induced thermogenesis; and (3) activity thermogenesis, including exercise energy expenditure and nonexercise activity. For each component, the expected magnitude of intra-individual variability is also considered. We also reviewed studies that quantified the variability in 24 h energy expenditure.

RECENT FINDINGS

In humans, the coefficient of variation in the components of total daily energy expenditure is around 5-8% for resting metabolic rate, 1-2% for exercise energy expenditure, and around 20% for diet-induced thermogenesis. The coefficient of variance for 24 h energy expenditure measured using a room calorimeter for resting metabolic rate is around 5-10%. Thus, these measures are all rather reproducible. Total daily energy expenditure varies several-fold in humans, not due to variation in resting metabolic rate, diet-induced thermogenesis, or exercise thermogenesis, but rather, due to variations in nonexercise activity. A variety of factors impact nonexercise activity, including occupation, environment, education, genetics, age, gender, and body composition, but little is known about the magnitude of effect.

SUMMARY

Resting metabolic rate, diet-induced thermogenesis, exercise energy expenditure, and 24 h energy expenditure are highly reproducible. Coefficient of variation is smallest for exercise energy expenditure, followed by resting metabolic rate, 24 h energy expenditure, and diet-induced thermogenesis. There is considerable variability in total daily energy expenditure, largely due to variations in nonexercise activity. Although the factors that impact upon nonexercise activity are understood, their contribution to variation in total daily energy expenditure is unclear.

Variability of measured resting metabolic rate

BACKGROUND

The necessity of a 12-h fast before resting metabolic rate (RMR) is measured is often a barrier to measuring RMR.

OBJECTIVE

We compared RMR measurements obtained in the morning and afternoon and across repeated days to elucidate the magnitude and sources of variability.

DESIGN

Healthy men (n = 12) and women (n = 25) aged 21-67 y, with body mass indexes (in kg/m(2)) ranging from 17 to 34 and body fat ranging from 6% to 54%, completed 4 RMR measurements. RMR measurements were made in the morning (after a 12-h fast and 12 h postexercise) and in the afternoon (after a 4-h fast and 12 h postexercise) on 2 separate days with the ventilated-hood technique. Body composition was assessed by dual-energy X-ray absorptiometry.

RESULTS

Mean (+/- SE) afternoon RMR was significantly higher than morning RMR on both visit 1 (1593.5 +/- 35.6 compared with 1508.0 +/- 31.5 kcal/d; P = 0.001) and visit 2 (1602 +/- 29.3 compared with 1511.4 +/- 35.9 kcal/d; P = 0.001). The 2 morning measurements (r = 0.93) and the 2 afternoon measurements (r = 0.93) were highly correlated, and no significant differences between measurements were observed. The mean difference between the morning and afternoon measurements was 99.0 +/- 35.8 kcal/d (6%).

CONCLUSIONS

Repeated morning and evening measurements of RMR were stable and highly correlated. Day-to-day measurements of RMR were not significantly different. RMR measured in the afternoon after a 4-h fast and exercise was approximately 100 kcal/d higher than RMR measured in the morning.

Indirect calorimetry: a trend toward continuous metabolic assessment

Physiologic monitoring of the patient's metabolic response to illness and nutritional needs has been available for many decades. Traditional methods for estimating and intermittently assessing the patient's metabolic status provide incomplete and often misleading information. The measurement oxygen consumption (VO2) and carbon dioxide production (VCO2) for assessment of the critically ill patient's metabolic status has been underutilized partly because of the limitations of available technologies. Recent advances in gas exchange technologies have made VO2 and VCO2 assessment readily available at the bedside on a continuous basis. This article provides a clinical review of specific current literature related to indirect calorimetry. A synthesis of the data supports the use of gas exchange measurements of VO2 and VCO2 for serial assessment of metabolic changes and for monitoring of the patient's nutritional status. Furthermore, a multidisciplinary approach to metabolic monitoring and nutritional assessment provides a cost-efficient means of patient care, which, when properly implemented, improves patient outcomes.

Effect of selective and nonselective beta-blockers on resting energy production rate and total body substrate utilization in chronic heart failure

BACKGROUND

In chronic heart failure (CHF) beta-blockers reduce myocardial oxygen consumption and improve myocardial efficiency by shifting myocardial substrate utilization from increased free fatty acid oxidation to increased glucose oxidation. The effect of selective and nonselective beta-blockers on total body resting energy production rate (EPR) and substrate utilization is not known.

METHODS

Twenty-six noncachectic patients with moderately severe heart failure (New York Heart Association class II or III, left ventricular ejection fraction < 0.40) were treated with carvedilol (37.5 +/- 13.5 mg/12 h) or bisoprolol (5.4 +/- 3.0 mg/d) for 6 months. Indirect calorimetry was performed before and after 6 months of treatment.

RESULTS

Resting EPR was decreased in carvedilol (5.021 +/- 0.803 to 4.552 +/- 0.615 kJ/min, P <.001) and bisoprolol group (5.230 +/- 0.828 to 4.978 +/- 0.640 kJ/min, P <.05; nonsignificant difference between groups). Lipid oxidation rate decreased in carvedilol and remained unchanged in bisoprolol group (2.4 +/- 1.4 to 1.5 +/- 0.9 mg m(2)/kg min versus 2.7 +/- 1.1 to 2.5 +/- 1.1 mg m(2)/kg min, P <.05). Glucose oxidation rate was increased only in carvedilol (2.6 +/- 1.4 to 4.4 +/- 1.6 mg m(2)/kg min, P <.05), but did not change in bisoprolol group.

CONCLUSIONS

Both selective and nonselective beta-blockers reduce total body resting EPR in noncachectic CHF patients. Carvedilol compared to bisoprolol shifts total body substrate utilization from lipid to glucose oxidation.

Estimating energy expenditure in critically ill adults and children

Designing effective nutrition support regimens for critically ill patients requires an understanding of the energy needs of each patient. Many disease processes result in elevated caloric requirements, whereas some clinical procedures and medications may diminish the metabolic response. Experienced clinicians are unable to predict the extent to which trauma or injury will affect energy requirements for an individual. Both under- and overfeeding a critically ill patient may prolong hospitalization and increase morbidity and mortality. Applying equations that were originally developed for healthy nonhospitalized individuals to predict the energy requirements of critically ill patients will often result in significant errors and may lead to provision of inappropriate nutritional support. The measurement of resting energy expenditure by indirect calorimetry is a valuable tool and can be used to predict energy requirements for most spontaneously breathing critically ill patients, but may lead to spurious results in mechanically ventilated pediatric patients. In the complex and rapidly changing context of critical illness, individualized assessment of energy requirements is crucial. Whichever technique is used initially to assess energy requirements, sequential monitoring and constant reassessment of each patient is essential to provide the appropriate nutritional care regimen. The purpose of this article is to review the equations for estimating and the techniques, practical aspects, and interpretation of measuring energy expenditure in critically ill patients.

System of automated gas-exchange analysis for the investigation of metabolic processes

Conventional gas-exchange instruments are confined to the measurement of O(2) consumption (VO(2)) and CO(2) production (VCO(2)) and are subject to a variety of errors. This handicaps the performance of these devices at inspired O(2) fraction (FI(O(2))) > 0.40 and limits their applicability to indirect calorimetry only. We describe a device based on the automation of the Douglas bag technique that is capable of making continuous gas-exchange measurements of multiple species over a broad range of experimental conditions. This system is validated by using a quantitative methanol-burning lung model modified to provide reproducible (13)CO(2) production. The average error for VO(2) and VCO(2) over the FI(O(2)) range of 0.21-0.8. is 2.4 and 0.8%, respectively. The instrument is capable of determining the differential atom% volume of known references of (13)CO(2) to within 3.4%. This device reduces the sources of error that thwart other instruments at FI(O(2)) > 0. 40 and demonstrates the capacity to explore other expressions of metabolic activity in exhaled gases related to the excretion of (13)CO(2).

Reproducibility of resting metabolic rate measurement in children

The aim of the present study was to determine the reproducibility of measurement of resting metabolic rate (RMR) using a ventilated-hood indirect calorimeter in children using a short protocol suitable for the outpatient setting or home visit. The protocol consisted of an overnight (10-12 h) fast, 5-10 min supine rest, 5-10 min 'settling in' under the ventilated hood, and 12-16 min of measurement. Three measurements of RMR were made in eighteen healthy children (nine boys, nine girls, aged 6-11 years) on alternate days. Reproducibility of RMR was assessed using a reproducibility index and by calculating the CV for intra-individual measurements. The mean CV was 2.6 (SD 1.7)% and the reproducibility index was 95.0%, indicating excellent reliability. The short protocol had higher reproducibility than more stringent protocols described in the literature. The new protocol has a number of practical advantages and should be adequate for most clinical or research purposes.