Abstract: There is described a non-invasive device designed to assist expectoration pulmonary secretions in humans, particularly in those whose natural exhalation and natural coughing ability are impaired. The device has a valve that opens fully in not more than 10 milliseconds, a pressure sensing means generating a signal indicative of a pressure in the upper part of the subject's respiratory tract, detecting means indicating the imminent collapse of the subject's respiratory tract or a part thereof, and control means opening or closing the valve respectively in response to the signals from the sensing means and the detecting means so as to create supramaximal flows in the respiratory tract in order to stimulate the movement of secretions towards the mouth of the subject.