Final answer:
The CPCT should release the tourniquet after the blood collection tubes are filled.
Step-by-step explanation:
The CPCT should release the tourniquet after the blood collection tubes are filled. The purpose of the tourniquet is to temporarily restrict blood flow to make it easier to collect blood. However, it should not be left on for too long as it can cause changes in blood components. Once the tubes are filled, the technician can release the tourniquet to restore normal blood flow.