1. A method for performing pulse volume measurement on a patient, the method comprising: (a) taking a plethysmographic signal from the patient, the plethysmographic signal comprising a plurality of plethysmographic waveforms; (b) performing an autocorrelation on the plethysmographic signal to determine locations of the individual plethysmographic waveforms; (c) isolating one of the plethysmographic waveforms in accordance with the autocorrelation; (d) convolving the isolated plethysmographic waveform with the plethysmographic signal to align the isolated plethysmographic waveform with the plethysmographic signal; (e) performing signal averaging between the isolated plethysmographic waveform and the plethysmographic signal as aligned in step (d) to provide an averaged signal; and (f) performing the pulse volume measurement in accordance with the averaged signal.