Predicting body weight by measuring weight underneath the buttock in supine position: A quantitative observation study.

BACKGROUND: Measuring body weight (BW) for bedridden patients often presents difficulty and challenge.

OBJECTIVES: The present study aimed at providing a self-designed indirect method to predict BW by measuring weight underneath the buttock (WUB) of an individual in supine position, thereby providing an easy, safe and effective way of BW measurement for bedridden patients.

METHODS: A total of 180 subjects participated in the present study and agreed to have their BW and WUB to be measured. BW was measured normally at the standing position through an electronic weighing machine without any special requirement. By placing the electronic weighing machine under the subject's buttock along with an additional hard board set under the electronic weighing machine, WUB was measured in subjects who were asked to assume a supine position in beds to simulate conditions of bedridden individuals. Measurement was repeated thrice to minimise the test error.

RESULTS: Average BW (62.7 ± 11.7 kg) was 2.0 ± 0.1 (≈ 2) folds of WUB (31.4 ± 6.0 kg). Significant linear correlation was identified between BW and WUB in all subjects with a linear equation yielded (y= 1.8 x + 6.0). Further multiple regression analysis resulted in an equation of BW (kg) =-36.8 + 1.66*WUB (kg) + 29.0*height (m). Predicted BW (PBW) was calculated out based on the results described above: the multiple relationship (2 folds), the linear equation, and the multiple regression equation, and differed from the measured BW by 3.6 ± 2.8, 3.5 ± 2.7 and 4.2 ± 3.1 kg respectively.

CONCLUSIONS: Predicting BW through WUB in supine position is effective and reliable because the latter can be easily measured and features a strong linear relationship with BW. This method provides clinical staff with remarkable benefits in BW determination for bedridden patients.