A system and method for obtaining the intravascular plasma volume, red blood cell volume, oxygen saturation SpO2 and Hgb hemoglobin concentration from a sample of in vivo tissue. A sample is irradiated with pulses of single incident wavelength light on a sample of tissue. The prompt emission (PE) and the delayed (DE) light emitted from the tissue are measured simultaneously. A relative volume of light emitted from two phases contained within the tissue is then determined, wherein the two phases comprise a first Rayleigh and Mie scattering and fluorescent phase associated with red blood cells, and a second, non-scattering phase associated with plasma. The plasma volume, Hct, Hgb and SpO2 is calculated from the relative volume of light emitted by the first phase and the relative volume of light emitted from the second phase differentiated by state of oxygenation.
