Respiratory therapy is an allied health field involved in the treatment of breathing disorders which include chronic lung problems (i.e., asthma, bronchitis, and emphysema) as well as more acute health problems related to other injury. Cystic fibrosis patients require respiratory therapy for their entire lives.

The treatment a Respiratory Therapist provides depends on the patient's individual needs for support of their respiratory tract. These include the upper airways from the nose and mouth to the larynx, and the lower airways including the bronchi, bronchioles, and alveloi. Responsibilities of an RT include therapies designed to improve the operations of all these things. Respiratory therapy might be needed to clear excess mucus and fluid from the bronchial tree, or to control swelling and inflammation of the bronchial passages. Supplemental oxygen may be provided by an RT to help all manner of patients undergoing stresses affecting their pulmonary status. Patients with no control over their breathing may need the assistance of a mechanical ventilator.

The operating principle of a Respiratory Therapist is to assisting patients to generally improve breathing capacity and the quality of life.

Because the cardiopulmonary system is so intertwined, respiratory therapists are also skilled with the cardiac system, and help in advanced life support situations or "codes".