The above picture shows a paramedic practicing cardiopulmonary resuscitation and CPR on a dummy.
They are using what is known as an Ambu bag. Ambu bags are common medical devices which are used to deliver oxygen and ventilations to patients who are having trouble breathing. They should ideally be used by trained medical professionals but in an emergency can be used by anyone brave enough to attempt to save a life.
The term Ambu bag is actually branded, but is commonly used to refer to any Bag Valve Mask (BVM).
Bag Valve Masks/Ambu bags work by squeezing oxygen into a patient’s lungs and is used instead of doing mouth-to-mouth resuscitation. The advantage of an Ambu bag is that it’s more precise and consistent in delivering oxygen than mouth-to-mouth. Additionally, it allows for the rescuer to maintain more space between themselves and the victim, which is occasionally important depending on the environment and the victim’s positioning.
The amount of oxygen Ambu bags deliver during CPR ventilations varies depending on its size, whether its attached to an oxygen tank, and what the settings of the tank are set to. Although an oxygen tank is not necessary to use an Ambu bag, they usually come equipped with a connection port for a tube which will deliver pure oxygen from a cylinder. The amount of oxygen being supplied can be adjusted using this cylinder.
Ambu bags and BVMs in general can be used on people who have been drowning, are undergoing cardiac arrest, or are suffering the effects of a drug overdose (legal or illegal).
The reason training is usually necessary for Ambu bags is that if used improperly, they can cause damage to a victim’s airway or lungs. Ambu bags and BVMs look pretty simple to use, but if someone is too aggressive with oxygen delivery or uses improper timing, the treatment will be ineffective at best, and cause additional injury at worst.
Recognizing when and how to give artificial ventilations in CPR using an Ambu bag is actually a highly technical skill.
You can read more about Ambu bags and their usage here.