After Downing is regaining his bearings after being punched at the train station, he's trying to focus his vision on Elinor Fairchild, who is looking right at him. However, the camera view that starts blurry, before focusing on Miss Fairchild, has her in profile, which is not what Downing would be seeing if he were looking right at her and trying to focus.
The iron lung was not turned on. If on, the membrane around the man's head would be pulsating in and out.
Obvious stunt double when Lucky is escaping his room.