 The exact molecular pathways behind this phenomenon have yet to be fully understood.If the blood supply to an organ or a tissue is impaired for a short time (usually less than five minutes) then restored so that blood flow is resumed, and the process repeated two or more times, the cells downstream of the tissue or organ are robustly protected from a final ischemic insult when the blood supply is cut off entirely and permanently.The protective effect which is imparted by IPC has two windows of protection.