Comparison of Physiological Variables During Blood Donation

The investigators have developed a system based on a pulse oximeter, a tablet, and an algorithm running on the tablet that analyzes the pulse oximeter waveform. The algorithm that runs on this system should be able to accurately keep track of blood loss during blood donation. The investigators will compare the algorithm with the blood loss tracked by a device called a flow meter. The algorithm that runs on this system should be able to accurately keep track of stroke volume changes. The investigators will compare the algorithm with the stroke volume changes tracked by a device called a CCNexfin. The algorithm that runs on this system should work whether it's in place for the whole blood donation, or if it's placed after the blood donation has started. The investigators will use two pulse oximeters for the system on each hand and compare one that is used for the whole blood donation versus one that is not used for the whole blood donation.