A system determines cardiac output and stroke volume by using non-invasive oximetric signals, such as SPO2 data and waveform, to determine blood flow quantitatively. A non-invasive system determines cardiac output or stroke volume. The system includes an input processor for receiving signal data representing oxygen content of blood of a patient at a particular anatomical location. A computation processor uses the received signal data in calculating a heart stroke volume of the patient comprising volume of blood transferred through the blood vessel in a heart cycle, in response to, a blood volume derived in response to oxygen content of patient blood and at least one factor representing reduction in blood flow volume from a patient heart to the particular anatomical location. An output processor provides data representing the calculated heart stroke volume to a destination device.
