Abstract: The apparatus comprises a first tubular part (2) comprising an air inlet (4) wherein the patient may breathe out and a second part (3) comprising a conical channel (5) of which the axis (15) is inclined upwardly by an angle of 60.degree. with respect to the axis (16) of the first tubular part. A steel ball (8) is arranged in the conical channel (5) so as to occlude said channel before expiration. During expiration, the ball is displaced along the lowest portion (17') of the channel and induces oscillating effects of resistance to expiration and allows a percusion ventilation of high efficiency. The apparatus further comprises a cover (9) presenting openings (10) and intended to prevent the ball from escaping.