A patient who has difficulty lying flat on his chest may have a pulmonary lesion, but to a greater extent it may be a cardiac lesion. When a patient has cardiac insufficiency, the amount of blood returning to the heart is higher in the flat position, and the burden of the patient’s cardiac function is heavier, and then the patient is required to sit up or adopt the semirecumbent position, so that the patient’s amount of blood returning to the heart is less, and the burden of the cardiac function is reduced, and at the same time, the patient feels comfortable. In many cases it is heart valve disease, cardiomyopathy and other conditions caused by cardiac insufficiency, the patient lying down chest tightness, should be timely to the relevant departments for consultation, such as cardiovascular internal medicine, cardiac ultrasound, chest radiographs, electrocardiograms and other tests in a timely manner to rule out the presence of heart disease and other lesions. After exclusion of heart disease, we can consider whether there are lungs, mediastinum and other pathologies, we need to go to respiratory medicine and thoracic surgery, chest radiographs, chest CT, pulmonary function and other tests to clarify the diagnosis.