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Hydration

HYD: Assessing Hydration Status (2007)

Citation:

Koulmann N, Jimenez C, Regal D, Bolliet P, Launay JC, Savourey G, Melin B.  Use of bioelectrical inpedance analysis to estimate body fluid compartments after acute variations of the body hydration level.  Med Sci Sports & Exercise 2000; 32(4): 857-864.

 
Study Design:
Experimental
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
Using bioelectrical impedance analysis (BIA) to estimate changes in body fluid compartments after different acute stages in body hydration level (i.e. heat-induced dehydration, exercise-induced dehydration, glycerol hyperhydration).
Inclusion Criteria:
informed consent; none others mentioned
Exclusion Criteria:
none mentioned
Description of Study Protocol:

Recruitment not mentioned

 

Design

 between Feb and May, each subject performed 4 trials, each separated by at least 15d.  Randomized, cross-over design.  3d before each trial, subjects asked to refrain from strenuous exercise and to drink at least 2L water/d to be normohydrated.

Protocol, 3 Phases:

Phase 1) Semi-recumbant position for 90 min, thermoneutral environment, 25-25C, 40-60% RH; Plasma vol, TBW, Extra-Cellular Water (ECW) determined by BIA.

Phase 2) Variation of body hydration level, according to 4 trials:

        1)(Control, C): euhydrated, sitting for 2 h

        2)(Heat-induced dehydration, D): passive heating session in climatic chamber until lost 2.8% BM; 45-50C, 70-30%RH.

       3)(Exercise-induced dehydration, E): treadmill at 60% VO2max in controlled thermal environment, 25-26C, 35-50%RH; maintain core temp at 39C.  Exercise stopped q. 30 min to verify BM loss, which had to reach 2.8% at end of 2h phase.

      4)Hyperhydration experiment, H: subjects sitting for 2h; induced by ingestion of glycerol and water at beginning of phase 2, and q 30 min during phase 2 so total water intake corresponded to 21.4ml/kg BM.

Phase 3) Same as phase 1, 90 min semi-recumbant, thermoneutral environment; second measure Pvol; TBW and ECW  by bia.

Blinding used (if applicable)

 not mentioned

Intervention (if applicable)

 Protocol and trials mentioned above

Statistical Analysis

 Repeated measures ANOVA; Tukey's post hoc test to comparedifferences in individual stages; Linear regression analysis to compare TBW (2H) and TBW (bia) in normohydrated state; and to compare variation in TBW and change in BM.  Sig level p<0.05.

Data Collection Summary:

Timing of Measurements

 TBW (2H) measured 1x at beginning of the study.  Urine collected before and day after dose.

Subjects asked to empty bladder at end of each phase, weight was then taken.

HR, and temps recorded q. 1 min

VO2max measured during 10 min at beginning of phase 2; Total body sweat loss calculated before and after Phase 2 (weight difference, adjusting for metabolic and water respiratory losses.

BIA at beginning and end of each trial

Plasma vol meas before and after variation of hydration level.

other blood measured sampled at 90 min (t90) of Phase 1, before and phase 2 (t 120 min; t150, 180, 240 min); and phase 3 (t300, 360 min)

Dependent Variables

  • TBW (bia)
  • TBW (2H dilution - NMR spectroscopy, repeatability 2-3%)
  •  Wt
  • HR (Polar monitor)
  • Temp (rectal and skin)
  • VO2max
  • Pvol (Evans blue dye method)
  • Posm (freezing pint depression)
  • Pna (flame photometry)
  • Urinary vol

Independent Variables

 3 phases of each trial, mentioned above

Control Variables

 Room temp

Description of Actual Data Sample:

 

Initial N: 8 M

Attrition (final N):

Age: 27±1 y

Ethnicity: Caucasian

Other relevant demographics: endurance-trained athletes, unaccustomed to heat; VO2max: 56.6±1.5 ml/min/kg

Anthropometrics BM: 73±2 kg; ht: 1.77±0.001m

Location: winter and spring; Lab, France

 

Summary of Results:

 

 

Variables

Control (C)

 Heat-induced dehydration (D)

Exercise-induced dehydration (E)

Hyperhydration (H)

Statistical Significance of Group Difference

Change TBW (bia TBW2-TBW1) (L)

-0.560±0.187

-1.921±0.096

-0.958±0.102

+0.738±0.145

p<0.05:

C compared to D, E, H;

D compared to E, H;

E compared to H

Change BM (g), End phase 2

End Phase 3

 0

 

-425±74

 -2079±74*, **

 

-23370±71*,**

-1961±50*, **

 

-2225±58*,**

+1179±95

 

+563±181*

*p<0.05 compared to C;

**p<0.05 compared to H

Metabolic mass losses (g)    9±1* 82±4   *p<0.05 compared to E
Respiratory water losses (mL)    13.1±1* 136±3   *p<0.05 compared to E
Uvol (mL)    174±37* 119±25   *p<0.05 compared to E
Sweat vol (mL)    1847±71* 1582±55   *p<0.05 compared to E
Change ECW (bia ECW2-ECW1) (L) -0.143±0.06 -0.709±0.041 -0.341±0.046 +0.277±0.055

P<0.05:

C ompared to D, E, H

D compared to E, H

E compared to H

Change in Pvol (mL) (Pvol 2-Pvol1) -5±50 -450±60 -173±39 +312±45

P<0.05:

C compared to D, E, H

D compared to E, H

E compared to H

 

 

Other Findings

 Physiological Measures: 

HR did not change during phase 1; During phase 2, HR higher in exercise-induced dehydration trial  than the others(p<0.001), and higher in heat-induced dehydration trial vs control and hyperhydration trials (p<0.001).

Temperature: Rectal and skin temps had same time courses during phase 1, regardless of trial; During dehydration session, rectal temp increased sooner during exercise vs heat-induced (p<0.05); during heat-induced dehydration, rectal temp remained higher than control or hyperhydration (p<0.001).  Skin temp increased at beginning and decreased at the end of phase 2, heat-induced dehydration (p<0.001).  During exercise-induced dehydration, skin temp only slightly increased at beginning phase 2 (p<0.01), with higher calues thatn during control or hyperhydration durin 140-160min (p<0.01). 

Gain of body mass (BM) different from BM loss during C (p<0.001) in H.  BM loss similar; metabolic and respiratory mass losses higher and sweat and Uvol lower during E vs D (P<0.05). 

Variation of TBW was different during each trial - largest loss during D, 2x as important as loss in E (p<0.05), which was higher than C changes (P<0.05).  Linear regression between change in TBW and change in BM sig (r=0.92, p<0.001). 

ECW volume:  after variation of body hydration level, ECW decreased during C, D, E (P<0.05), but increased during H (P<0.05).  Loss observed during D 2x as important as that observed during E (p<0.05).  Gain durin H different than slight loss during C (P<0.05).

Posm and Pna stable throughout C; increased at beginning Phase 2 H (P<0.001), which were values higher than all other trials(p<0.001).  Pna progressively decreased during H w/lower values (P<0.001) than during C.  Time courses of Posm and Pna similar durin both dehydration sessions (E, D).

The mean coefficient of variation for trial-to-trial intraindividual impedance measurements at 100 Hz was 4.0%, which induced a mean reproducibility of TBW estimations of 3.0%.  The precision ot those estimates was 3.9% compared with TBW previously measured by deuterium dilution.

Author Conclusion:

After exercise-induced dehydration, BIA only half-predicted the TBW loss whereas the main factors usually known to affect BIA predictions appear to be uninvolved, in an unexpected result. 

Further studies including measures of TBW and ECW by dilution tracer methods are necessary to establish validity of using the BIA method to measure TBW and ECW under dehydrated or hyperhydrated conditions.

Funding Source:
Government: Centre de Recherches du Service de Sante des Armees
Reviewer Comments:

*graphs in paper denote time-course of physiological measurements;

BIA only half predicted the body water loss after exercise-induced dehydration, whereas it appears to adequately predict changes in TBW after heat-induced dehydration and glycerol-hyperhydration when compared with variations in body mass. 

The main factors usually known to affect BIA (electrode placement, side of body, limb position, posture, ambient and skin temperatures, POsm and [Na] were controlled more precisely, and therefore cannot be considered to affect these results, though these factors would be dependent on the dehydration procedures. 

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) N/A
  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) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? 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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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? ???
  2.1. 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
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? N/A
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) 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
  3.2. 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
  3.3. 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
  3.4. 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.) Yes
  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.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
  4. Was method of handling withdrawals described? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.1. 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. 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
  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. 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? 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.) Yes
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? 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? ???
  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. 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? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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
  6.3. 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? ???
  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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes