A gas-powered resuscitator is operable either in a manual mode or an automatic mode. The resuscitator includes an oscillatory timing valve 14 having an outlet 23 connected to a bi-stable valve 25, the operation of which is piloted by a manual valve 16. The outlet 26 of the bi-stable valve 25 connects to the outlet 2 of the resuscitator via a rotatable control 32 and a patient valve 41. The outlet 26 of the bi-stable valve 25 also connects to the control inlet 34 of the timing valve 14. The manual valve 16 has a button 62 that can be pushed down manually in the manual mode or can be held down in the automatic mode by rotating a locking ring 262. The maximum duration of cycles is limited by operation of the timing valve 14, whether the resuscitator is operated manually or automatically.
