More than 2 million patients worldwide receive heart surgery every year, majority of these surgical patients will undergo cardiopulmonary bypass. However, the incidence of postoperative acute lung injury due to cardiopulmonary bypass is still as high as 20% to 35%. According to clinical experience, the earlier lung damage is detected, the more successful the treatment will be. On the basis of traditional detection, the investigators found a new indicator, serum calpains, which are easy to obtain and have certain specificity. Importantly, they can predict postoperative acute lung injury within 1 hour after cardiac surgery. It is meaningful that this indicator can provide clinicians with early decision-making advice and immediate treatment for patients who may be at risk.

Inclusion Criteria:

• Age ≥ 18 years;
• Underwent cardiac surgery using CPB technology.

Exclusion criteria :

• Patient's lack of consent to participate;
• Presence of abnormal liver, kidney or other organ function;
• Pulmonary inflammation, chronic obstructive pulmonary disease or tumors;
• Underwent cardiac surgery without CPB technology;
• Postoperative need for extracorporeal membrane oxygenation support.