Validation of an indirect calorimeter using n-of-1 methodology

Indirect Calorimetry in Spontaneously Breathing, Mechanically Ventilated and Extracorporeally Oxygenated Patients: An Engineering Review

Indirect calorimetry (IC) is considered the gold standard for measuring resting energy expenditure (REE). This review presents an overview of the different techniques to assess REE with special regard to the use of IC in critically ill patients on extracorporeal membrane oxygenation (ECMO), as well as to the sensors used in commercially available indirect calorimeters. The theoretical and technical aspects of IC in spontaneously breathing subjects and critically ill patients on mechanical ventilation and/or ECMO are covered and a critical review and comparison of the different techniques and sensors is provided. This review also aims to accurately present the physical quantities and mathematical concepts regarding IC to reduce errors and promote consistency in further research. By studying IC on ECMO from an engineering point of view rather than a medical point of view, new problem definitions come into play to further advance these techniques.

The estimation of the resting metabolic rate is affected by the method of gas exchange data selection in high-level athletes

BACKGROUND & AIMS

there is no consensus in the literature about the best method to estimate the RMR in a high-level athlete's cohort. Additionally, a shortening protocol may allow researchers, nutritionists, and clinicians to follow the RMR across the season and to propose better nutritional interventions, but this kind of protocol was not proposed in this cohort yet. Thus, this study aims to analyze the effect of the method of gas exchange data selection upon the RMR estimate and, possibly propose a shortening protocol with a valid and accurate RMR value.

METHODS

Eighty-three healthy high-level athletes underwent a 30-minute RMR measurement with no rest period before the test. Different methods of gas exchange data selection were used: short and long time intervals (TI) [6-10, 11-15, 16-20, 21-25, 26-30, 6-25, or 6-30], Steady State (SS) with 3, 4, 5, or 10 min period length, and Filtering (low, medium, and high). Single and multiple linear regressions were used to examine the variance in the RMR provided by each method of gas exchange data selection.

RESULTS

The High Filter method provided the lowest RMR estimate (1854 kcal.day^-1), and most methods presented a mean absolute difference of ~43 kcal.day^-1 from the High Filter method. There were no differences in RER among methods (F = 2.01, p = 0.10). Besides, twenty minutes of gas exchange measurement was necessary to obtain a valid and accurate RMR with no rest period before the test. The linear regression model that included sex, lean body mass, and fat mass better explained the variance in the RMR using the high filter method (~88%).

CONCLUSIONS

The High Filter provided the lowest RMR value. Furthermore, a 20-minute protocol estimated a valid and accurate RMR value with no acclimation period before the measurement in high-level athletes.

Resting energy expenditure in HIV/AIDS patients: Development and validation of a predictive equation

BACKGROUND

Accurate measurements of resting energy expenditure (REE) are important for determining nutritional needs in HIV patients. Indirect calorimetry (IC) is a noninvasive method that reflects REE but can be costly and is frequently calculated with predictive equations. Research suggests that REE obtained by predictive equations in people living with HIV/AIDS (PLWH) is inaccurate. The aim of the study is to develop and validate a new predictive equation of REE based on a population of PLWH.

METHODS

Cross-sectional study including 164 PLWH (82 to develop and 82 to validate the equation). Multiple linear regression was used to determine the relationship between variables and to develop the new predictive equation. Intraclass correlation coefficient (ICC) and Bland-Altman methods were used to evaluate agreement between the new predictive equation and indirect calorimetry.

RESULTS

A new predictive equation with an accuracy of 67% when compared with IC was developed. This equation included as covariates: fat free mass, antiretroviral therapy status and age.

CONCLUSION

A new equation to predict energy expenditure in PLWH was developed and validated. This formula can be used to estimate REE if IC is not available.

New equation to estimate resting energy expenditure in non-critically ill patients

BACKGROUND

Correct measurement of resting energy expenditure (REE) is essential to offer a proper nutritional management during hospital stay. Dietitians are not able to perform an effective dietary treatment if predicted REE values are obtained from invalid equations.

OBJECTIVE

The aim of this study was to develop a more valid method to estimate REE in non-critically ill Portuguese patients.

DESIGN

In this cross-sectional study, REE was measured by indirect calorimetry (IC) in 180 non-critically patients during hospital stay (50 participants were allocated to the validation group by simple randomization and the remaining 130 were allocated to the derivation group). The best accurate equations were derived by multiple linear regression analysis (stepwise) based on anthropometric variables. The equations were tested on the validation group and compared with published predictive equations.

RESULTS

Data was collected from 130 patients, 68 women (52.3%) and 62 men (47.7%), mean age was 58.9 ± 16.8 years and REE-IC was 1918 ± 721 kcal/day. The new best-fit equation REE (kcal/day) = 14.4 (Height) + 52.7 (MUAC) + 453.4 (1 if male, 0 if female) - 371.2 (if Obese) - 2138.3 showed strength of evidence decisive (BF₁₀ = 8008), when compared by Bayesian model, and r² = 0.315. Only estimated REE values obtained using new equations did not present significant difference when compared with measured REE values (kcal/kg).

CONCLUSIONS

In this study, new equations derived from a non-critically ill population showed higher validity in estimating REE than currently used equations. A better estimation of REE may lead to a better nutritional intervention and a decreased risk of undernutrition in hospitalized patients.

Validation of predictive equations for resting energy expenditure in treatment-seeking adults with overweight and obesity: Measured versus estimated

The quantification of resting energy expenditure (REE) in patients with obesity is an important measure. We aimed to evaluate the validity of predictive equations in estimating REE compared with indirect calorimetry (IC) in treatment-seeking Arab adults with overweight or obesity. Twenty-three predictive equations were compared with REE values measured by IC (Vmax Encore 229) in 89 adult participants with overweight or obesity (mean age = 40.62 ± 15.96 years and mean body mass index [BMI] = 35.02 ± 4.60 kg/m²) referred to the Department of Nutrition and Dietetics of Beirut Arab University (Lebanon). The accuracy of the predictive equations was evaluated on the basis of whether the percentage prediction was within 10% of the measured REE, and the mean difference between predicted and measured values (bias). The Bland-Altman method was used to assess the agreement between the predicted and measured values. The equations that demonstrated the closest agreement with IC were the De La Cruz equation in males (accurate predictions: 68.2%; bias: -19.52 kcal/day) and the Mifflin equation in females (accurate prediction: 61.2%; bias: -36.43 kcal/day). In conclusion, we suggest that these two equations produce the least biased estimations for REE in this population.

Reduction of Resting Energy Expenditure and Sarcopenic Obesity in Adults with Overweight and Obesity: A Brief Report

BACKGROUND AND AIM

The last decade has seen the emergence of a new condition, describing the coexistence of obesity and sarcopenia, termed Sarcopenic Obesity (SO). The aim of this study was to assess the potential association between SO and reduced Resting Energy Expenditure (REE).

METHODS

Body composition and REE were measured using a bioimpedance analyser (Tanita BC-418) and Indirect Calorimeter (Vmax Encore 229), respectively in 89 adults with overweight or obesity of both genders, referred to the Outpatient Clinic of the Department of Nutrition and Dietetics at Beirut Arab University (Lebanon). Participants were then categorized on the basis of having SO or not.

RESULTS

Thirty-nine of the 89 participants met the criteria for SO (43.8%), and these participants displayed a significantly lower REE per unit body weight than those in the group without SO (19.02 ± 2.26 vs. 20.87 ± 2.77; p = 0.001). Linear regression analysis showed that the presence of SO decreases REE by 1.557 kcal/day for each kg of body weight (β = -1.557; CI = -0.261 - (-0.503); p = 0.004), after adjusting for age and gender.

CONCLUSION

SO appears to be present in a high proportion of treatment-seeking adults with overweight or obesity of both genders, and it seems to be associated with a reduced REE, compared with those without SO. Future studies are needed to clarify whether this may influence clinical outcomes.

Predictive Equations Based on Body Composition for Resting Energy Expenditure Estimation in Adults with Obesity

BACKGROUND AND AIM

An accurate estimation of Resting Energy Expenditure (REE) in patients with obesity is crucial. Therefore, our aim was to assess the validity of REE predictive equations based on body composition variables in treatment-seeking Arab adults with obesity.

METHODS

Body composition and REE were measured by Tanita BC-418 bioimpedance and Vmax Encore 229 IC, respectively, and predictive equations based on fat mass and fat-free mass were used in REE estimations among 87 adults of both genders, in the Outpatient Clinic in the Department of Nutrition and Dietetics at Beirut Arab University (Lebanon). The mean differences between the measured and estimated REE values were calculated to assess the accuracy, and the Bland-Altman method was used to assess the level of agreement.

RESULTS

Ten predictive equations were included. In males, all the predictive equations gave significantly different estimates of REE when compared to that measured by IC. On the other hand, in females, the mean difference between the REE value estimated by Huang and Horie-Waitzberg equations and that measured using IC was not significant, and the agreement was confirmed using Bland-Altman plots.

CONCLUSION

Huang and Horie-Waitzberg equations are suggested for accurate REE estimation in females; however, new validated REE estimation equations for males in this population are still needed.

Indirect Calorimetry Performance Using a Handheld Device Compared to the Metabolic Cart in Outpatients with Cirrhosis

Addressing malnutrition is important to improve health outcomes in outpatients with cirrhosis, yet assessing energy requirements in this population is challenging. Predictive equations of resting energy expenditure (REE) are thought to be unreliable, and traditional indirect calorimetry is expensive and infrequently available for clinical use. The accuracy of REE predictions using a MedGem^® handheld indirect calorimeter, the Harris Benedict Equation (HBE), the Mifflin St. Jeor equation (MSJ), and the gold standard Vmax Encore^® (Vmax) metabolic cart was compared. The REE of cirrhotic pre-liver transplant outpatients was analyzed using each of the four methods. Agreement between methods was calculated using Bland-Altman analysis. Fourteen patients with cirrhosis participated, and were primarily male (71%) and malnourished (subjective global assessment (SGA) B or C 64%). Lin's concordance coefficient (ρC) for MedGem^® vs. Vmax demonstrated poor levels of precision and accuracy (ρC = 0.80, 95% confidence interval 0.55-0.92) between measures, as did the HBE compared to Vmax (ρC = 0.56, 95% confidence interval 0.19-0.79). Mean REE by MedGem^® was similar to that measured by Vmax (-1.5%); however, only 21% of REE measures by MedGem^® were within ±5% of Vmax measures. Wide variability limits the use of MedGem^® at an individual level; a more accurate and feasible method for determination of REE in patients with cirrhosis and malnutrition is needed.

Effect of a respiratory muscle training program on lung function, respiratory muscle strength and resting oxygen consumption in sedentary young people

Introduction: Physical inactivity is a risk factor for developing noncommnunicable diseases, as well as respiratory and cardiovascular disorders. To counter this, different types of interventions have been proposed, including respiratory muscle training (RMT).Objective: To determine the effect of a respiratory muscle training program on respiratory muscle strength, lung function and resting oxygen consumption in sedentary subjects.Materials and methods: Pretest-posttest experimental study conducted in sedentary students. Lifestyle and the level of physical activity was determined using the International Physical Activity Questionnaire (IPAQ) and the FANTASTIC questionnaire, while respiratory muscle strength was established by means of expiratory and inspiratory pressure using a Dwyer Series 477 meter, and lung function and oxygen consumption was determined by spirometry and indirect calorimetry whit Vmax Encore 29C® calorimeter. Respiratory muscle training was performed for eight weeks with Threshold IMT system. R software, version 3.1.2, was used for statistical analysis.Results: Clinically and statistically significant improvements were found in maximal inspiratory pressure (MIP) (pre: 81.23±22.00/post: 96.44±24.54 cmH2O; p<0.001); maximal expiratory pressure (MEP) (pre: 94.84±21.63/post: 107.39±29.15 cmH2O; p<0.05); pulmonary function FEV1 [(pre: 3.33±0.88/post: 3.54±0.90L) (p<0.05)]; and FEV1/FVC ratio [(pre: 87.78±7.67/post: 93.20±6.02% (p<0.01)].Conclusion: The respiratory muscle training protocol implemented for eight weeks using the Threshold IMT system improved strength and FEV1. There were no significant changes in oxygen consumption.

Weight-Loss Cognitive-Behavioural Treatment and Essential Amino Acid Supplementation in a Patient with Spinal Muscular Atrophy and Obesity

Spinal muscular atrophy is a genetic neuromuscular disease characterised by muscle atrophy, hypotonia, weakness, and progressive paralysis. Usually, these patients display increased fat mass deposition and reductions in fat-free mass and resting energy expenditure—an unfavourable condition that facilitates the development of obesity. However, weight management of these patients remains poorly described. Hence, the aim of this case report was to describe the clinical presentation and weight management of a 31-year-old male patient with spinal muscular atrophy type III, class I obesity, and metabolic syndrome treated for 1 year by means of a personalised multistep cognitive-behavioural treatment for obesity. The treatment produced a weight loss of 7.2 kg (7.1%), which was associated with a marked improvement in both the patient's self-reported general conditions and obesity-related cardiometabolic profile, and no adverse effects in terms of spinal muscular atrophy (i.e., reductions in fat-free mass or resting energy expenditure).

Modeling a Predictive Energy Equation Specific for Maintenance Hemodialysis

BACKGROUND

Hypermetabolism is theorized in patients diagnosed with chronic kidney disease who are receiving maintenance hemodialysis (MHD). We aimed to distinguish key disease-specific determinants of resting energy expenditure to create a predictive energy equation that more precisely establishes energy needs with the intent of preventing protein-energy wasting.

MATERIALS AND METHODS

For this 3-year multisite cross-sectional study (N = 116), eligible participants were diagnosed with chronic kidney disease and were receiving MHD for at least 3 months. Predictors for the model included weight, sex, age, C-reactive protein (CRP), glycosylated hemoglobin, and serum creatinine. The outcome variable was measured resting energy expenditure (mREE). Regression modeling was used to generate predictive formulas and Bland-Altman analyses to evaluate accuracy.

RESULTS

The majority were male (60.3%), black (81.0%), and non-Hispanic (76.7%), and 23% were ≥65 years old. After screening for multicollinearity, the best predictive model of mREE (R2 = 0.67) included weight, age, sex, and CRP. Two alternative models with acceptable predictability (R2 = 0.66) were derived with glycosylated hemoglobin or serum creatinine. Based on Bland-Altman analyses, the maintenance hemodialysis equation that included CRP had the best precision, with the highest proportion of participants' predicted energy expenditure classified as accurate (61.2%) and with the lowest number of individuals with underestimation or overestimation.

CONCLUSIONS

This study confirms disease-specific factors as key determinants of mREE in patients on MHD and provides a preliminary predictive energy equation. Further prospective research is necessary to test the reliability and validity of this equation across diverse populations of patients who are receiving MHD.

Evaluation of a short protocol for indirect calorimetry in females with eating disorders and healthy controls

BACKGROUND AND AIMS

To enable clinicians to identify the clinical picture and treatment progress and to adjust eating plans according to personal energy needs, it is important to know the patient's correct resting metabolic rate (RMR). Indirect calorimetry (IC) is the preferred method for assessment of RMR, but long duration of measurement increases the load on the patients, and reduces the effectiveness in clinical and scientific settings. Further; not all patients reach a valid RMR according to the suggested best practice protocol, with 5 min of steady state (SS) where respiratory gas volume exchange varies less than 10%. The aim of this study was to evaluate the possibility for an abbreviated RMR protocol and SS criterion.

METHODS

Forty two women diagnosed with bulimia nervosa or binge eating disorder (eating disorder group, ED), originally recruited for an outpatient treatment study, and 26 age and gender matched healthy controls (HC) were studied during a single, prolonged IC measurement. Participants rested for 10 min in supine position wearing a two-way breathing facemask, before a continuous measurement period of 20 min. Results from a standard 5 min SS criterion was compared to an abbreviated 3 min SS criterion. Both SS-criteria were evaluated through three different SS protocols (<10% variation in respiratory gas exchange), being: 1) measurement during the first 3 or 5 min, 2) measurement after discarding the first 5 min, and 3) the lowest identified RMR during the 20 min of measurement.

RESULTS

About 50% of the participants reached an early SS in both the defined SS minute criteria. Participants reaching a valid SS throughout the 20 min of measurement increased from ∼90% to 100% with an abbreviated 3 min SS. With a 5 min SS criterion, the median (range) RMR for the 3 protocols were 1639.9 (1239.2), 1508.8 (1457.6) and 1500.6 (1328.8) respectively for the ED group, and 1702.2 (1239.4), 1608.4 (1076.4) and 1594.8 (1029.2) respectively for the HC group, (p > 0.05 for all between-group analysis). With a 3 min SS criterion, the median (range) RMR were 1533.6 (1298.2), 1461.2 (1406.1), and 1395.8 (1447.3) respectively for the ED group and 1681.7 (1332.4), 1613.7 (1266.0) and 1523.1 (1050.3), respectively for the HC group, (p > 0.05 for all between-group analysis). Lowest measured RMR was different compared to the other two SS protocols in both the ED- and the HC group, and for both the 5 min- and the 3 min SS criteria, respectively (p < 0.04). Furthermore, a SS of 3 min resulted in lower RMR compared to 5 min SS (p < 0.00) and an increased number of participants classified as hypo-metabolic (RMRmeasured/RMRcalculated < 0.9).

CONCLUSIONS

An abbreviated measurement protocol to identify the lowest RMR using IC was not successful. Abbreviating the SS criteria from 5 to 3 min, resulted in a lower RMR, hence encouraging further examination of the validity of shorter SS criterion than practiced today. Registered in Clinical Trials by id-number NCT02079935, and approved by the Norwegian Regional Committee for Medical and Health Research Ethics with id-number 2013/1871. The trial in which control persons were recruited, is approved by the Norwegian Regional Committees for Medical and Health Research Ethics with the id-number 2016/1718, and prospectively registered in Clinical Trials with the id-number NCT03007459.

Objective and subjective measures of exercise intensity during thermo-neutral and hot yoga

While hot yoga has gained enormous popularity in recent years, owing in part to increased environmental challenge associated with exercise in the heat, it is not clear whether hot yoga is more vigorous than thermo-neutral yoga. Therefore, the aim of this study was to determine objective and subjective measures of exercise intensity during constant intensity yoga in a hot and thermo-neutral environment. Using a randomized, crossover design, 14 participants completed 2 identical ∼20-min yoga sessions in a hot (35.3 ± 0.8 °C; humidity: 20.5% ± 1.4%) and thermo-neutral (22.1 ± 0.2 °C; humidity: 27.8% ± 1.6%) environment. Oxygen consumption and heart rate (HR) were recorded as objective measures (percentage of maximal oxygen consumption and percentage of maximal HR (%HRmax)) and rating of perceived exertion (RPE) was recorded as a subjective measure of exercise intensity. There was no difference in exercise intensity based on percentage of maximal oxygen consumption during hot versus thermo-neutral yoga (30.9% ± 2.3% vs. 30.5% ± 1.8%, p = 0.68). However, exercise intensity was significantly higher during hot versus thermo-neutral yoga based on %HRmax (67.0% ± 2.3% vs. 60.8% ± 1.9%, p = 0.01) and RPE (12 ± 1 vs. 11 ± 1, p = 0.04). According to established exercise intensities, hot yoga was classified as light-intensity exercise based on percentage of maximal oxygen consumption but moderate-intensity exercise based on %HRmax and RPE while thermo-neutral yoga was classified as light-intensity exercise based on percentage of maximal oxygen uptake, %HRmax, and RPE. Despite the added hemodynamic stress and perception that yoga is more strenuous in a hot environment, we observed similar oxygen consumption during hot versus thermo-neutral yoga, classifying both exercise modalities as light-intensity exercise.

Weight cycling in adults with severe obesity: A longitudinal study

AIM

Although weight cycling is a common phenomenon in treatment-seeking patients with obesity, its consequences on health outcomes have not yet been completely clarified. We therefore aimed to investigate the effect of one cycle of intentional weight loss and regain on energy expenditure, body composition, cardiovascular risk factors and psychosocial variables in patients with severe obesity.

METHODS

Clinical and psychosocial variables were measured in 38 adult patients with severe obesity (body mass index (BMI): 43.5 ± 7.2 kg/m² ) consecutively readmitted to rehabilitative residential treatment (T1) for severe obesity after a cycle of weight loss (16.7 ±7.7 kg) and regain (15.1 ±11.3 kg), and compared with those recorded at a prior admission (T0).

RESULTS

No significant differences were found between T0 and T1 values for weight, BMI, waist circumference, total body fat percentage, fat-free mass percentage, respiratory quotient, measured or predicted resting energy expenditure, metabolic adaptation, cardiovascular risk factors or psychosocial variables. However, younger patients (r = -0.38, P = 0.023) and those with higher historical weight (r = 0.43, P = 0.010) tended to regain more weight.

CONCLUSIONS

The absence of negative physical and psychological effects of weight cycling indicates that the risk of weight regain should not be a barrier to encouraging weight loss efforts in patients with severe obesity.

Abbreviated Steady State Intervals for Measuring Resting Energy Expenditure in Patients on Maintenance Hemodialysis

BACKGROUND

Indirect calorimetry requires a steady state (SS) protocol to determine measured resting energy expenditure (mREE). Achieving stringent criteria for an SS interval may be difficult for patients on maintenance hemodialysis (MHD), as they may become uncomfortable because of the test itself or their health status. The study aim was to explore if a shortened SS interval was within acceptable limits for bias and precision.

MATERIALS AND METHODS

For this cross-sectional secondary analysis, adults (N = 125) who received MHD thrice weekly were enrolled. The indirect calorimetry test was performed for a length of total time ≤30 consecutive minutes. SS was evaluated in accordance with intervals of 10, 5, 4, 3, and 2 minutes. The mREE at the 10-minute SS was compared with the mREE at 5, 4, 3, and 2 minutes, via t tests and Bland-Altman analysis, to determine degree of bias and level of agreement. The a priori alpha level was set at ≤0.5.

RESULTS

The sample was primarily male, African American, and non-Hispanic, with a mean ± SD age of 55.4 ± 12.2 years, who reported being on MHD for an average of 62.4 ± 74.3 months. None of the mREE measures were significantly different from that of the 10-minute SS interval. Seventy-two percent of the participants were able to achieve SS at the 10-minute interval, 83.2% at 5 minutes, 87.2% at 4 minutes, and 89.6% for both 3 and 2 minutes.

CONCLUSION

For patients on MHD, an abbreviated SS interval of <10 minutes (eg, 5 minutes) yielded valid mREE measurements.

"Cool" Topic: Feeding During Moderate Hypothermia After Intracranial Hemorrhage

BACKGROUND

Therapeutic moderate hypothermia (MH; T _core 33°C-34°C) is being studied for treatment of spontaneous intracerebral hemorrhage (ICH). Nutrition assessment begins with accurate basal metabolic rate (BMR) determination. Although early enteral nutrition (EN) is associated with improved outcomes, it is often deferred until rewarming. We sought to determine the accuracy of predictive BMR equations and the safety and tolerance of EN during MH after ICH.

MATERIALS AND METHODS

Patients were randomized to 72 hours of MH or normothermia (NT; T _core 36°C-37°C). Harris-Benedict (BMR-HB) and Penn-State equation (BMR-PS) calculations were compared with indirect calorimetry (IC) at day (D) 0 and D1-3. Patients with MH received trophic semi-elemental gastric EN. Occurrences of feeding intolerance, gastrointestinal (GI)-related adverse events, and ventilator-associated pneumonia (VAP) were analyzed with a double-sided matched pairs t test.

RESULTS

Thirteen patients with ICH participated (6 MH, 7 NT). Mean time to initiate EN: 29.9 (MH) vs 18.4 (NT) hours ( P = .046). Average daily EN calories received D0-3: 398 (MH) vs 1006 (NT) ( P < .01). Three patients with MH experienced high gastric residuals prior to prokinetic agents, 1 had mild ileus, and 1 patient with NT vomited. No GI-related adverse events were reported. One patient with MH and 1 patient with NT had VAP. Two patients with MH received IC, and from D0 to D1-3, BMR-HB remained stable (1331 kcal), BMR-PS decreased (1511 vs 1145 kcal, P = .5), and IC decreased (1413 vs 985 kcal, P = .2).

CONCLUSIONS

In patients with ICH undergoing MH, resting energy expenditure is decreased and predictive equations overestimate BMR. EN is feasible, although delayed EN initiation, high gastric residuals, and less EN provision are common. Future studies should focus on EN initiation within 24 hours, advanced EN rates, and postpyloric feeds during hypothermia.

New generation indirect calorimeters for measuring energy expenditure in the critically ill: a rampant or reticent revolution?

To lower the risk of incorrectly feeding critically ill patients, indirect calorimetry (IC) is proposed as the most ideal method to evaluate energy expenditure and to establish caloric goals. New IC devices are progressively introduced but validation of this new generation remains challenging and arduous.