A medical monitoring system includes an oximetry sensor having a light emitter positioned to emit light into a patient and a photodetector positioned to generate a plethysmography signal. The system includes a monitor having a processor configured to receive the plethysmography signal from the oximetry sensor and to identify a non-cardiac pulse based on a first pulse shape metric, the non-cardiac pulse being generated by the administration of cardiopulmonary resuscitation (CPR) to the patient. The processor is also configured to measure an oxygen saturation of the patient from the identified non-cardiac pulse and to output the measured oxygen saturation to a visual display.