EAL

HYD: Assessing Hydration Status (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine a new non-invasive method of measuring hydration state in vivo, based on the comparison of attenuation of radio waves (radio frquency, RF) by tissue at 2 frequencies, the lower one in the beta dispersion region, representing the solute quantitiy in the examined tissue; the higher in the gamma dispersion region, representing water quantitiy in the examined tissue. Comparing this attenuation at these 2 frequencies is indicative of the ratio of quantities of ionic solutes and the water in the examined tissue, namely, of the osmolality in this tissue.

Inclusion Criteria:

Informed consent, healthy, no meds or alcohol (no more mentioned).

Exclusion Criteria:

Not mentioned

Description of Study Protocol:

Recruitment - not mentioned

Design: Subjects performed treadmill walking in hot-dry climatic conditions of 40C and 40%RH for 70 min: 2-30min bouts with 10 min rest.

Blinding used (if applicable): not mentioned

Intervention (if applicable)

1 session drinking ad libitum, 1 no drinking during exercise sessions.

Statistical Analysis

RF device readings and body weight loss analyzed by 2-way ANOVA; significance level of p<0.05

RF device readings at the 4 frequencies used as parameters in formula to yield predictor (RF index) of hydration state, which represents the least-squares best fit between RF index from the device and the loss of body weight.

Data Collection Summary:

Timing of Measurements

Rectal temp and heart rate recorded at 1 min intervals. Sweat rate and hypohydration calculated before, after 30 and after 60 min of exercise. RF absorption measurments taken concomittantly.

Dependent Variables

Rectal temp (thermistor probe)
Heart rate (Polar monitor)
Sweat/hypohydration (body weight loss)
RF Absorption (RF Device, on wrists)
Phsyiological strain index (from HR, temp)

Independent Variables

Hydration state

Control Variables

Temperature, RH, exercise time

Description of Actual Data Sample:

Initial N: 12 young healthy M

Attrition (final N):

Age: 24±1

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics: Ht: 175±2 cm; Wt: 71.54±3.13 kg; BSA: 1.71±0.15 m2

Location: Climatic chamber at Heller Inst of Medical Research, Sheba Medical Center, Tel Hashomer, Israel

Summary of Results:

Variables	Euhydrated Measures and confidence intervals	Hypohydrated Measures and confidence intervals	Statistical Significance of Group Difference
Rectal temp	-	-	ns
Heart rate	-	-	ns
Physiological strain Index	-	-	p<0.05 (during 40-70 min)
BW loss (kg)	-	0.78±0.06 at 30 min 1.59±0.8 at 60 min	-
RF: Corr with BW loss, between predicted and actual	-	R²= 0.734	p<0.01

Other Findings

Good correlation obtained between measured (BW) and predicted (RF device data, equation) weight losses. under both conditions

Author Conclusion:

An aid tool that can be used in the decision making process, especially for exercising individuals and physical workers at risk of hypohydration. Further work is needed re: different levels of hypohydration, body mass, gender, age, physical condition, and environmental conditions in order to extrapolate info to other populations.

Funding Source:

University/Hospital:

Sheba Medical Center

Reviewer Comments:

Methodological study with promising preliminary results for device that may be useful in predicting hydration status.

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)	???
	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?	???
	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)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	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?	N/A
	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")?	???
4.	Was method of handling withdrawals described?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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?	Yes
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	???
	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.)	???
	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?	???
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?	Yes
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?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	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?	No
	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)?	No
	8.6.	Was clinical significance as well as statistical significance reported?	???
	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