Remote Ischemic Preconditioning(RIPC) and remote ischemic postconditioning(RIPoC) seems to have a protective effect during ischemic period. Using cardiopulmonary bypass(CPB) during open heart surgery reduces pulmonary blood flow and may cause ischemic damage to lung tissue. The investigators anticipate that RIPC and RIPoC may reduce lung injury after CPB.

Cardiopulmonary bypass(CPB) can cause lung function deterioration through various mechanisms. Lung parenchymal tissue ischemia resulted by pulmonary atelectasis and decreased bronchial circulation during CPB is one of the reasons. There were few studies reported that RIPC and RIPoCcan benefit lung function of children or infant after CPB, but studies about adults are still lacking.

Purpose:

The purpose of this study is to evaluate effect of RIPC and RIPoC on the lung function after CPB.

Methods:

Patients will randomly allocated either in study group or control group. Study group will receive RIPC and RIPoC maneuver before and after CPB. Control group will have same automated cuff around their arm but it will not activated. Care givers will be blinded whether the automated cuff is on or not.

We will compare pulmonary parameters (PaO2/FiO2, dynamic and static compliances, Intrapulmonary shunts, etc.) between study group and control group, and check levels of plasma cytokines(IL-4, IL-8, IL-10, TNF-alpha) till 24hr after the operation.

Inclusion Criteria:

• those who aged 18-80 years old and planned to undergo elective open heart surgery using cardiopulmonary bypass

Exclusion Criteria:

• emergent operation
• preoperative use of inotropics or mechanical assist device,
• left ventricular ejection fraction less than 30%,
• severe liver, renal disease,
• recent myocardial infarction (within 7 days),
• recent systemic infection or sepsis (within 7 days)
• peripheral vascular disease affecting upper limbs
• amputation of the upper limbs
• major combined operation such as aortic surgery or carotid endarterectomy
• descending thoracic aortic surgery
• rare surgeries; cardiac transplantation, correction of complicated congenital anomalies, pulmonary thromboembolectomy, etc
• significantly decreased pulmonary function before the planned surgery (e.g. using ventilator, oxygen therapy, tachypnea, orthopnea, active lung lesion on chest X-ray, FEV1/FVC less than 50% of predicted level, PaO2 less than 80 mmHg)
• intracardiac shunt
• severe pulmonary artery hypertension
• systemic or local steroid therapy