Air tightness usually refers to shortness of breath, laborious, squatting when breathing air tight, usually a normal physiological phenomenon, but also may be cardiac insufficiency, coronary heart disease or lung diseases such as emphysema, chronic obstructive pulmonary disease and so on. 1. Physiological phenomenon: when the normal human body squats, it will compress the heart and lungs, there will be a slight tightness of breath for a long time. Overweight or obese people, the burden on the heart and lungs would have been heavier, this phenomenon is more obvious. 2. cardiac insufficiency: if the patient has a cardiac insufficiency, lungs bruising, squatting will appear tight. 3. Coronary heart disease: due to coronary artery stenosis or occlusion, myocardial oxygen consumption will increase when squatting, which will lead to the blood and oxygen can not be supplied in a timely manner, there will also be tightness of breath when squatting. 4. Lung diseases: such as emphysema, chronic obstructive pulmonary disease, etc., the patient if the lung function is reduced, squatting lungs are compressed, there will also be tight breathing. Squatting breathing tightness symptoms are serious, it is recommended that timely medical treatment, can improve the lung CT, electrocardiogram and other tests to determine the cause of the disease, follow the doctor’s instructions to standardize the treatment.