A manually-operable resuscitator operable also to inject medication into air being supplied to a patient. The resuscitator has a resiliently compressible air bag having an inlet and an outlet. The inlet has a one-way valve through which air passes into the bag from the atmosphere and a patient valve through which air flows in passing from the bag to the patient. The patient valve has a one-way valve member through which air flows in passing from the bag to the patient. The patient valve also has a passage extending from the atmosphere to the interior thereof adjacent to the one-way valve member and upstream thereof through which medication can be injected into the air as it passes from the bag to the one-way valve member.