As the duration of recumbency prior to tilting and angle of the tilt are not standardized, they ary considerably.因为倾斜前的仰卧时间和倾斜角度的非标准化，试验结果变化较大。
As the duration of recumbency prior to tilting and angle of the tilt are not standardized, they vary considerably.因为倾斜前的仰卧时间和倾斜角度的非标准化，试验结果变化较大。