Hanania R, Dubin S, Zietz S, Naim A, Schrope B
Biomedical Engineering and Science Institute, Drexel University, Philadelphia, PA 19104, USA.
Biomed Sci Instrum. 1995;31:219-24.
The Differential Buoyancy method uses Archimedes' principle to non-invasively determine body fat percentage by measuring the subject's weight in breathable high and low densities atmospheres. We currently use both air and helium/oxygen mixtures in our experiments[1]. When the method was tested on rats, an anomaly was observed. As helium/oxygen mixture was admitted to the weighing chamber, while the atmospheric density monotonically decreased, the rat's weight first increased but then after several minutes decreased. Water loss from the rat's body was found to be the main cause of this anomaly. Therefore it was necessary to compensate for this water loss. Consistent with experimental findings the water loss was modeled as a constant rate process, and determined experimentally from weight measurements at the beginning and at the end of the experiment. Making these corrections allowed for accurate predictions of the rat's volume and body fat percentage.
差分浮力法利用阿基米德原理，通过测量受试者在高、低密度可呼吸大气中的体重，以非侵入性方式测定体脂百分比。我们目前在实验中同时使用空气和氦氧混合气体[1]。当该方法在大鼠身上进行测试时，观察到了一个异常现象。当向称重室通入氦氧混合气体时，虽然大气密度单调下降，但大鼠的体重先增加，几分钟后又下降。发现大鼠身体失水是造成这种异常的主要原因。因此，有必要对这种失水进行补偿。与实验结果一致，失水被建模为一个恒定速率过程，并根据实验开始和结束时的体重测量值通过实验确定。进行这些校正后，可以准确预测大鼠的体积和体脂百分比。
