Capillary refill time diagnostic apparatus and methods

A method for measuring capillary refill time comprising:

• activating, by a controller, at least one source;
• emitting, by the at least one source, a first radiation having a first wavelength onto a measurement region of a subject, wherein the first wavelength has approximately equal absorption by same amounts of oxyhemoglobin and deoxyhemoglobin for detecting a rate of change in an amount of blood in the measurement region;
• emitting, by the at least one source, a second radiation having a second wavelength onto the measurement region, wherein the second radiation comprises a reference wavelength;
• detecting, by at least one detector, the first radiation and the second radiation received from the measurement region;
• receiving, with a controller, first signals from the at least one detector that are indicative of the first radiation received from the measurement region and second signals received from the at least one detector that are indicative of the second radiation signals received from the measurement region.