If patients appear to be frequently short of breath and out of breath: First, cardiogenic diseases should be considered. For coronary artery disease unstable angina, acute myocarditis, acute pericarditis, or when patients have malignant arrhythmia, or even heart failure there will be a decrease in arterial oxygen saturation and insufficient myocardial blood supply and oxygenation, at which time there will be clinical symptoms of shortness of breath and out of breath. Second, for respiratory system diseases, such as chronic bronchitis, chronic bronchiectasis, chronic obstructive pulmonary emphysema, pulmonary heart disease, pulmonary arterial hypertension. All of them have low partial pressure of oxygen and high partial pressure of carbon dioxide, at which time there will also be shortness of breath and breathlessness. For acute infections of the respiratory system, such as massive pneumonia, pleural effusion or pleurisy, there will also be the above symptoms. Thirdly, patients with certain plant nerve disorders, especially in cardiac neurosis, will also have the above symptoms.