Predicted Versus Measured Thoracic Gas Volume for the Bod Pod® Air Displacement Plethysmography System

The purpose of this study was to determine whether there is a significant difference between measured values of thoracic gas volume (MTGV) and predicted values of thoracic gas volume (PTGV) using the Bod Pod®. One hundred and thirteen college freshmen, both males and females, were tested using the Bod Pod® by first measuring thoracic gas volume with the Bod Pod® technique, then by using pre-determined values based on height, weight, and age that predict thoracic gas volume. Results of a paired t test showed that measured thoracic gas volume and predicted thoracic gas volume were significantly different. A Pearson’s product-moment correlation coefficient was calculated to be r = .60 which is significant at the p ≤ .05 level. A Bland and Altman plot was used to reveal any variability about the mean for individual participants MTGV and PTGV and the averages of each. A Pearson’s product-moment correlation coefficient was calculated for the data in the Bland and Altman plot. The correlation was calculated as .56, which is significant at the p ≤ .001 level. It was concluded that within the limitations of this study, there is a significant difference between MTGV and PTGV when using the Bod Pod® air displacement plethysmography system