Dyspnea is a subjective feeling of difficult, labored, or uncomfortable breathing. This common emergency department complaint is often described as "shortness of breath," "breathlessness," "not getting enough air," and a variety of other phrases. Dyspnea does not result from a single pathophysiologic mechanism and may result from many disorders. Approximately two-thirds of patients presenting to the emergency department with dyspnea have either a cardiac or a pulmonary disorder. An emergency physician can usually distinguish these on the basis of history, physical examination, and, occasionally, ancillary tests.
Dyspnea must be distinguished from a number of other signs and symptoms. Tachypnea is rapid breathing; it may or may not be associated with dyspnea, and dyspnea is not always accompanied by tachypnea. Orthopnea is dyspnea in the recumbent position. It is most often the result of left ventricular failure and may be associated with diaphragmatic paralysis or chronic obstructive pulmonary disease (COPD). Paroxysmal nocturnal dyspnea is orthopnea that awakens the patient from sleep. Trepopnea is dyspnea associated with only one of several recumbent positions. Trepopnea can occur with unilateral diaphragmatic paralysis, with ball-valve airway obstruction, or after surgical pneumonectomy. Platypnea is the opposite of orthopnea: dyspnea in the upright position. Platypnea results from the loss of abdominal wall muscular tone and, in rare cases, from right-to-left intracardiac shunting, as occurs from a patent foramen ovale. Hyperpnea is essentially hyperventilation and is defined as minute ventilation in excess of metabolic demand. Hyperpnea may not be associated with dyspnea, and dyspnea is not always associated with increased minute ventilation.
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