If patients have dyspnea on the left side of the chest, the specific causes are as follows: 1. To consider cardiogenic factors, such as coronary heart disease, unstable angina, acute left heart failure, acute myocarditis, pericarditis, infective endocarditis, hypertrophic obstructive cardiomyopathy, rheumatic cardiomyopathy, hypertensive cardiomyopathy, all will have dyspnea on the left side of the chest. 2. For chronic respiratory diseases, such as Acute attacks occur, there will also be such symptoms, such as acute attacks of chronic bronchitis, acute attacks of asthma, bronchiectasis, chronic obstructive pulmonary emphysema, acute pulmonary heart disease, pulmonary hypertension, patients will also have acute dyspnea in the left chest. 3, pneumothorax, such as tension pneumothorax, traffic pneumothorax, open pneumothorax, patients will also have pain in the left chest with breathing, accompanied by dyspnea. 4. If the left side of the chest is traumatized, there will also be dyspnea. 5. Large pneumonia, pleural effusion, and infectious factors in the left side will also lead to dyspnea.