Blood transfusion is the process of transferring whole blood or blood-derived products into the circulatory system of a patient with the purpose of treatment. The process of apheresis involves collecting whole blood from a patient or donor, separation of this blood into components, storage or therapeutic use of these components, and obtaining the blood balance of the patient or donor. With the use of improved devices of developing technology, apheresis techniques are also improved. These techniques are used both in blood donation and in the treatment of patients.

 Basic Principles of Apheresis
The main objective of apheresis is collecting blood components for donational or therapeutic purposes. Separation of whole blood into components is performed with the help of filtration methods.

 Centrifugation
Centrifugation is the act of separation of blood into plasma and the cellular components with the help of the centrifugal force. The theoretical basis of centrifugation is the fact that each component of blood has a different specific gravity. When the anticoagulant added whole blood is centrifuged in a test tube, blood components will be separated from each other according to their specific gravity.

 Filtration
Since the ingredients of blood differ in size, separation can be achieved via filtration method, too. In this method, membrane technology is used in order to decompose the plasma from cellular components. Various sizes of pores on the membrane allow blood components to be collected. Centrifugation and filtration methods can be combined.

 Technology
Open or closed disposable kits are used in apheresis with current technological devices for blood separation processes. These kits include device-specific bags, solutions, tube systems, and containers for separation and collection.