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

Clasey JL, Gater DR Jr. A comparison of hydrostatic weighing and air displacement plethysmography in adults with spinal cord injury.ObjectivesTo 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).DesignTwenty adults with SCI underwent ADP and VTG, and HW testing. In a subgroup (n=13) of subjects, 4-comp %fat procedures were computed.SettingResearch laboratories in a university setting.ParticipantsTwenty adults with SCI below the T3 vertebrae and motor complete paraplegia.InterventionsNot applicable.Main Outcome MeasuresStatistical analyses, including determination of group mean differences, shared variance, total error, and 95% confidence intervals.ResultsThe 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).ConclusionsADP is a valid alternative method of determining the Vb and Db in adults with SCI; however, the predicted VTG should be used with caution.