A medical device includes a control interface for operating the medical device in a hands-free mode. To control the medical device in a hands-free mode, the control interface includes multiple proximity sensors, each sensor associated with a level of adjustment. For example, a sensor located on a top portion of the medical device is used to increase the level of adjustment. And similarly, a sensor located on a bottom portion of the medical device is used to decrease the level of adjustment. The magnitude of the level of adjustment applied to a parameter of the medical device is controlled based at least in part on the length of time an object remains in proximity to a respective sensor. In one embodiment, the longer the object is held over a respective sensor the more adjustment the control interface will make to the parameter.