Some of us have 02 canisters and if nothing else we pull out the bag and pump by hand.
That's nice. Some of us have clock radios, which is just as relevant.
An O2 bottle doesn't help someone in an iron lung. All it does is increase the concentration of oxygen in the air she's not breathing. A hand ventilator is slightly less useless. An iron lung expands and contracts the chest cavity; it doesn't just push air.