Remote Ischemic Preconditioning on Pulmonary Injury in Cardic Surgery

Inclusion Criteria: 1. Patients undergoing heart surgery on cardiopulmonary bypass 2. Patients aged 18 years to 80 years Exclusion Criteria: 1. Inability to give informed consent 2. Preoperative severe impairment of respiratory function (arterial oxygen tension (PaO2) \<60 mmHg or FEV1\<50% predicted) 3. Prior receipt of chemotherapy or radiation therapy or immunotherapy 4. left ventricular ejection fraction less than 30% 5. preoperative use of inotropics or mechanical assist device 6. Patients with significant hepatic dysfunction (Prothrombin\>2.0 ratio) 7. Patients with known renal failure with a GFR\<30 mL/min/1.73 m2 8. recent myocardial infarction (within 7 days) 9. Systemic or local active infections (either clinically defined or suggested by evidence such as elevated C-reactive protein levels, leukocytosis, or a body temperature\>38℃) 10. Significant peripheral arterial disease affecting the upper limbs 11. surgeries: cardiac transplantation, concomitant carotid endarterectomy , previous heart surgery,, off-pump surgery, emergency surgery