If the patient has shortness of breath accompanied by dyspnea, there are several factors as follows: 1, the most common factor is cardiac factors, such as patients with coronary atherosclerotic heart disease, unstable angina pectoris, arrhythmia, myocarditis, acute pericarditis, infective endocarditis, or dilated cardiomyopathy, the above factors will lead to insufficient blood supply of blood vessels to the heart, and when the cardiovascular ischemia, spasm, and stenosis. When the cardiovascular ischemia, spasm, narrowing, the patient will have obvious chest tightness, shortness of breath, accompanied by dyspnea symptoms. 2, if in the adverse gas poisoning, such as carbon monoxide poisoning, hydrogen sulfide poisoning, ammonia poisoning and a series of other conditions, the patient will also have obvious respiratory irritation symptoms, while feeling chest tightness, shortness of breath, breathing difficulties. 3, in the respiratory system of the disease, such as chronic obstructive pulmonary disease, chronic bronchial dilatation, chronic pulmonary heart disease and other conditions, the typical symptoms mentioned above will also occur.