Original article
A Comparison of Hydrostatic Weighing and Air Displacement Plethysmography in Adults With Spinal Cord Injury

Preliminary results presented to the American College of Sports Medicine, June 2000, Indianapolis, IN, and the 6th International Symposium In Vivo Body Composition Studies, October 2002, Rome, Italy.
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Abstract

Clasey JL, Gater DR Jr. A comparison of hydrostatic weighing and air displacement plethysmography in adults with spinal cord injury.

Objectives

To compare (1) total body volume (Vb) and density (Db) measurements obtained by hydrostatic weighing (HW) and air displacement plethysmography (ADP) in adults with spinal cord injury (SCI); (2) measured and predicted thoracic gas volume (VTG); and (3) differences in percentage of fat measurements using ADP-obtained Db and HW-obtained Db measures that were interchanged in a 4-compartment body composition model (4-comp %fat).

Design

Twenty adults with SCI underwent ADP and VTG, and HW testing. In a subgroup (n=13) of subjects, 4-comp %fat procedures were computed.

Setting

Research laboratories in a university setting.

Participants

Twenty adults with SCI below the T3 vertebrae and motor complete paraplegia.

Interventions

Not applicable.

Main Outcome Measures

Statistical analyses, including determination of group mean differences, shared variance, total error, and 95% confidence intervals.

Results

The 2 methods yielded small yet significantly different Vb and Db. The groups’ mean VTG did not differ significantly, but the large relative differences indicated an unacceptable amount of individual error. When the 4-comp %fat measurements were compared, there was a trend toward significant differences (P=.08).

Conclusions

ADP is a valid alternative method of determining the Vb and Db in adults with SCI; however, the predicted VTG should be used with caution.

Section snippets

Participants

Twenty adults with SCI (14 men, 6 women; age range, 18.5–56.4y) participated in this study. Subjects were recruited from the SCI and medicine clinics of the University of Kentucky, the Cardinal Hill Rehabilitation Hospital, and the Lexington Veterans Affairs Medical Center for participation in a variety of ongoing clinical collaborative research efforts of the University of Kentucky Body Composition Core Laboratory, the Spinal Cord Injury Exercise Laboratory, and the General Clinical Research

Comparison of Vb and Db Measurements

The relation between the HWV and ADPV measurements, and between the HWDb and ADPDb measurements are presented in table 2. Significant shared variances (P<.01) were found between the Vb (r2=.99) and the Db (r2=.77) measurements. Group mean comparisons showed that HWV measurements were significantly lower than ADPV measurements (mean difference ± standard error [SE], −.55±.13; P<.01) and HWDb measurements were significantly greater than ADPDb measurements (mean difference ± SE, .0085±.0022; P

Discussion

Until recently, the only practical method of obtaining Db measurements for use in body composition models was to perform an HW technique. Using standardized validated procedures, combined with appropriate residual lung volume measures, this method provides an accurate measure of Vb and thus Db. Although HW has been successfully used to determine Vb in a variety of populations, this method is difficult and at times impossible to use in certain people. The HW method can be used for adults with

Conclusions

Unfortunately, there have been no other reported studies comparing ADP with HW in adults with SCI and other disabilities. The reduction in time, effort, and risk provided by the ADP measurement make it an attractive alternative measurement for HW, and the findings of this study support the use of ADP as a valid method for Vb and Db in adults with SCI below T3. We further conclude that the use of predicted VTG should be avoided if possible until further SCI population specific refinement of this

Acknowledgments

We thank Jantzen Inc (Portland, OR) for generously donating the swimming suits used during body composition assessment. We also thank Linda Rice, Tammy Ellis, Phoebe Brown, and Susan Berryman of the University of Kentucky General Clinical Research Center for expert clinical care. We thank Flo Witte for editorial assistance, and Craig Winsor, Adrienne Janowiak, and Carol Beth Mize for their technical support.

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  • Cited by (0)

    Supported in part by the National Center for Research Resources (grant no. NCRR NIH M01 RR02602), the University of Kentucky Body Composition Core Laboratory, the National Institute on Drug Abuse (grant no. K12 DA14040-03), the Veterans Affairs Rehabilitation Research and Development (grant no. B2247V), and National Institutes of Health (grant no. K23 RR16182-01).

    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s)or upon any organization with which the author(s) is/are associated.

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