A breathing device is a piece of equipment that helps people with breathing difficulties. There are several synonyms for this term. One of the most common is a respirator. This device is used to deliver oxygen to the lungs of people who are unable to breathe on their own. Another synonym for a breathing device is a nebulizer. This equipment is used to convert liquid medicine into a fine mist that can be inhaled through a mask or mouthpiece. An oxygen concentrator is another device used to help people with breathing difficulties. This machine takes in air, concentrates the oxygen, and then delivers it to the patient.