The doctor says you should point the device so the flow of air is just in front of your face.

VOA: special.2009.07.14

He was motionless, all but for one finger that moved up and down in front of his face as if he were marking time with it.

他一动也不动，除了一根手指在他的面前上下摆动,好像在用它标记时间。

耶鲁公开课 - 1945年后的美国小说课程节选