A method for treating circulatory fluid constituents with an apparatus which includes a first switching device which connects the upstream side of a first circulatory fluid treatment device with a flow of circulatory fluid from a source, and a second switching device which connects the downstream side of the first circulatory fluid treatment device with a destination of the circulatory fluid. Next, the second switching device maintains the flow of circulatory fluid to the destination from the downstream side of the first circulatory fluid treatment device, the upstream side of the first circulatory fluid treatment device is disconnected with the flow of circulatory fluid from the source, and further a third switching device connects the upstream side of a second circulatory fluid treatment device to the flow of a circulatory fluid from the source, and a fourth switching device connects the downstream side of the second circulatory fluid treatment device to communicate with the upstream side of the first circulatory fluid treatment device. Finally, the third switching device maintains the flow of circulatory fluid from the source into the upstream side of the second circulatory fluid treatment device, the downstream side of the first circulatory fluid treatment device is disconnected from sending the flow of circulatory fluid to the destination, and a fifth switching device connects the downstream side of the second circulatory fluid treatment device with the destination for the flow of circulatory fluid thereto.