A gas flow reversing element (1) using a gas source (14) under overpressure, in particular suction gas, for selectively generating a gas flow (8) from or to a pipe connection (6), in particular Can be connected to the patient's airway, the air flow reversing element (1) is designed as a main part (2) and an additional branch part (3), the main part (2) at least includes an inflow area (9), a nozzle area ( 15) and a mixing zone (16), the inflow zone (9) connects the pressure connection (4) for connection to the gas source (14) to at least one closable outlet hole ( 5), and the branch piece (3) connects the nozzle area (15) of the main part (2) to the pipe joint (6), wherein the nozzle (7), especially the injection nozzle, is configured and arranged in the nozzle area (15) , so that when the outlet hole (5) is opened, the air flow (8) flowing to the outlet hole (5) along the first flow path (20) through the main part (2) can be generated in the branch part (3) The gas flow (8) flowing to the outlet hole (5) along the second flow path (21), wherein the first flow path starts from the pressure joint (4), sequentially passes through the inflow zone (9), the flow zone (28) , the nozzle area (15), and enter the mixing area (16) through the nozzle (7), and the second flow path starts from the pipe joint (6), and passes through the branch piece (3), through the nozzle area (15) , and through the mixing zone (16), wherein the air flow reversing element (1) also includes a bypass pipe (18), which connects the pressure joint (4) and the pipe joint (6), so that the air flow (8) can Flow along a third flow path (22) via the inflow zone (9), the bypass tube (18) and the branch piece (3), wherein at least the bypass tube (18) and the flow zone (28) are closed by at least one The element (19) is closable so that the gas flow (8) can bypass the nozzles (7) in the nozzle zone (15) along the third flow path (22) via the bypass line (18). The invention also relates to a method of controlling a patient's exhalation.