1. A method for use in a system comprising a sensor for acquiring photo-plethysmographic data of a patient and a signal processing system for removing a plurality of motion artifacts from said photo-plethysmographic data and for obtaining a measure of at least one physiological parameter from said data, the method comprising: (a) acquiring said photo-plethysmographic data; (b) transforming said data; (c) analyzing said transformed data to locate candidate spectral peaks; (d) reconstructing a photo-plethysmographic signal; (e) computing the second order derivative of said reconstructed photo-plethysmographic signal; (f) analyzing said second order derivative photo-plethysmographic signal to determine a plurality of parameters; (g) identifying signal representations of a plurality of motion artifacts; and (h) selecting a candidate spectral peak from a plurality of potential cardiac spectral peaks.