EAL

HF: Energy Needs (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine biological determininants of daily energy expenditure in heart failure patients
To develop a model to predict daily energy requirements in heart failure patients from biological markers of daily energy expenditure
To compare daily energy expenditure requirements with those of the healthy elderly.

Inclusion Criteria:

Healthy Subjects

No symptoms or signs of heart disease or diabetes
Normal resting electrocardiogram
Normal electrocardiogram in response to an exercise stress test
Absence of medicinal or non-medicinal drugs that could affect cardiovascular or metabolic function
Weight stability within six months prior to testing.

Heart Failure Patients

Hemodynamically stable
Free of edema.

Exclusion Criteria:

Description of Study Protocol:

Recruitment: Heart failure patients were recruited from the Heart Failure Service of the Baltimore Veterans Affairs Medical Center and the University of Maryland Medical Center. Recruitment of the healthy volunteers was not described.
Design: Cross-sectional.

Statistical Analysis

The mean ±SD was calculated for each variable
Differences in physical characteristics and energy expenditure between heart failure patients and healthy controls were determined using an unpaired Student's T-test
Relationships (Pearson product-moment correlations) between variables were determined by linear regression analysis
Measures of physical activity, resting energy expenditure, body composition, age and disease severity were examined as possible correlates of daily energy expenditure
Plasma markers of nutritional status were examined as possible indicators of disease severity or nutritional status, to explain the variation in daily energy expenditure
Stepwise regression analysis was used to determine the set of variables that best predicted daily energy expenditure. Variables that had a significant bivariate relationship with daily energy expenditure were included as independent variables in the stepwise regression model: Ejection fraction, fat-free mass, leisure time physical activity and resting energy expenditure
Daily energy requirements were estimated for heart failure patients from three prediction equations previously developed in healthy elderly subjects and were compared with measured daily energy expenditure values, using a paried T-test.

Data Collection Summary:

Timing of Measurements

All measurements were performed during a 10-day period:

On Day One, each subject received an oral dose of doubly-labeled water after a baseline urine sample was obtained
On Day Two, resting energy expenditure and body composition were measured, blood was drawn and two urine samples were collected to mark the beginning of the doubly-labeled water measurement period. All subjects left the research center and resumed their daily free-living activiites.
10 days after the beginning of the doubly-labeled water measurement period, volunteers returned to provide two urine samples and to undergo an assessment of peak oxygen consumption.

Dependent Variables

Variable One
- Daily energy expenditure was determined over a 10-day period
- After providing a baseline urine sample between noon and 4:00 p.m., each subject consumed a mixed oral dose of ²H₂0 and H₂¹⁸0 (0.075g and 0.15g per kg body mass, respectively)
- A weighed 1:400 dilution (dose:tap water) was prepared from each subject's dose and a sample of the tap water used for the dilution was also saved and analyzed along with subject's urine sample set
- Two urine samples were obtained the morning after dosing to mark the beginning of the measurement period and 10 days later to mark the end (all between 8:00 a.m. and noon)
- All subjects were weight-stable and consuming a self-selected diet during the meaurement period
- Urine samples were stored in sealed vacutainers at -20ºC until analysis in triplicate by isotope ratio mass spectrometry
- All samples were analyzed within six months of collections.
Variable Two
- Resting energy expenditure was measured on an outpatient basis after a 12-hour overnight fast (8:00 a.m.) in heart failure patients and on an inpatient basis in healthy controls
- Resting energy expenditure was measured by indirect calorimetry, using the ventilated-hood technique for 45 minutes
- Energy expenditure was calculated using the Weir equation
- Upon arrival at the hospital, heart failure patients were tranported to the testing areas by wheelchair and rested quietly in a dark room for 20 minutes prior to measurement.
Physical activity energy expenditure was calulated based on the three-component model of daily energy expenditure: [(0.9x daily energy expenditure) - resting energy expenditure], assuming the thermic effect of meals constitutes 10% of daily energy expenditure in older individuals
Fat mass and fat-free mass were measured by dual-energy X-ray absorptionmetry using a DPX-L densitometer. All scans were analyzed using the Lunar Version 1.3z DPX-L extended analysis program for body composition.
Peak VO₂ was assessed by a treadmill test to volitional fatigue, using an open-circuit indirect calorimetry system. Peak VO₂ was meaured in 16 heart failure patients and all healthy controls.
Leisure time physical activity: The Minnesota Leisure Time Physical Activity Questionnaire was completed for each subject. The cumulative energy cost for leisure time physical activity of the past year was averaged and expressed as kilocalories per day.
Nutritional status was determined by measuring serum albumin, plama cholesterol and glucose.

Description of Actual Data Sample:

Initial N: 26 (25 males, one female) heart failure patients and 50 (48 males, two females) healthy controls
Attrition (final N): Same
Age: 69±6.5
Ethnicity: Not described.

Anthropometrics

13 of the heart failure patients reported 15±6kg weight loss during the course of the disease.
Mean left ventricular EF was 23±9% (range, 10% to 45%).

Location

Maryland and Vermont.

Summary of Results:

Variables	HF Patients (Measures and Confidence Intervals)	Control Patients (Measures and Confidence Intervals)	Statistical Significance of Group Difference
Fat mass (kg)	19±12	21±8	NS
Fat-free mass (kg)	55±8	58±9	NS
Leisure time physical activity (kcal/d)	243±371	451±352	P<0.05
Peak VO₂ (L/min) N=16	1.1±0.4	1.9±0.6	P<0.01
REE (kcal/d)	1,586±281	1,561±223	NS
Daily energy expenditure (kcal/d)	2,110±500	2,543±449	P<0.01
Physical activity expenditure (kcal/d)	333±345	728±374	P<0.01

Other Findings

Variables correlated to daily energy expenditure
- Physical activity energy expenditure: Correlation coefficient (CC), 0.79; P≤0.01
- Resting energy expenditure: CC, 0.63; P≤0.01
- Leisure time physical activity: CC, 0.63; P≤0.01
- Peak VO₂: CC, 0.58; P≤0.01
- Ejection fraction: CC, 0.44; P≤0.05
- Fat-free mass: CC, 0.41; P≤0.05.
Physical activity energy expenditure was related to the ejection fraction and the leisure time physical activity (both P<0.01)
An equation to predict daily energy expenditure was derived from stepwise regression analysis. Resting energy expenditure was the strongest predictor of daily energy expenditure, accounting for 48% (R²) of the variation (P<0.01). Leisure time physical activity explained an additional 13% (R²) of the variation in daily energy expenditure (P<0.05).
The equation derived from the stepwise regression analysis model was: Daily energy expenditure (kcal per day) = [0.919 x resting energy expenditure (kcal per day)] + [0.548 x leisure time physical activity (kcal per day)] + 481 (SE±333 kcal per day)
Equations developed for healthy eldery adults were compared to the measured needs for heart failure patients. These equations overestimated needs by 6% to 30% or underestimated by 10%.

Author Conclusion:

Daily energy needs (thus energy needs) were lower in heart failure patients, compared with healthy controls. Physical activity energy expenditure, not resting energy expenditure, was the strongest correlate of daily energy expenditure in heart failure patients, accounting for 61% (R²) of individual variation.
Authors developed a practical equation to predict daily energy needs in heart failure patients. This equation took into account resting energy expenditure and leisure time physical activity and these predicted daily energy expenditure within ±333 kcal per day.
Other equations developed to predict energy expenditure in eldery adults deviated -10% to +30% from measured daily energy expenditure in heart failure patients.

Funding Source:

Reviewer Comments:

Controls were measured after an overnight stay in the hospital, while the HF patients were done as outpatients after being transported to the testing area by wheelchair and following 20 minutes of rest.
The daily energy expenditure equation generated in this study needs to be reproduced because this study was a small sample of older men.
Poehlman ET was charged with falsifying data on some of his studies. The Office of Research Integrity listed the studies that were affected by this misconduct. This paper was not one of those, therefore it is being considered and reviewed.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	???
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes