A comparison of hydrostatic weighing and air displacement plethysmography in adults with spinal cord injury.

Abstract

To compare (1) total body volume (V(b)) and density (D(b)) 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 (V(TG)); and (3) differences in percentage of fat measurements using ADP-obtained D(b) and HW-obtained D(b) measures that were interchanged in a 4-compartment body composition model (4-comp %fat). Twenty adults with SCI underwent ADP and V(TG), and HW testing. In a subgroup (n=13) of subjects, 4-comp %fat procedures were computed. Research laboratories in a university setting. Twenty adults with SCI below the T3 vertebrae and motor complete paraplegia. Not applicable. Statistical analyses, including determination of group mean differences, shared variance, total error, and 95% confidence intervals. The 2 methods yielded small yet significantly different V(b) and D(b). The groups' mean V(TG) 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). ADP is a valid alternative method of determining the V(b) and D(b) in adults with SCI; however, the predicted V(TG) should be used with caution.