B-type natriuretic peptide, or BNP for short, is used to evaluate cardiac function, reflecting the presence of heart failure as well as cardiac insufficiency. Thirty to 40% of patients with acute dyspnea are difficult for doctors to determine, so BNP is checked to determine whether the patient’s dyspnea is caused by heart failure or pulmonary disease. The normal value of BNP should be less than 100pg/mL, less than this value can exclude heart failure; if it is more than 100pg/mL and less than 400pg/mL, it suggests that there may be heart failure but it is not certain, or it can be caused by other reasons such as lung disease or pulmonary embolism; if it is more than 400pg/mL, heart failure is highly suspected.