A system is provided including a respiratory detection module, a circulatory detection module, and an analysis module. The respiratory detection module is configured to detect respiratory information representative of respiration of a patient. The circulatory detection module configured to detect circulatory information representative of circulation of the patient. The analysis module is configured to obtain a respiratory waveform based at least in part on the respiratory information, obtain a circulatory waveform based at least in part on the circulatory information, combine the respiratory waveform and the circulatory waveform to provide a mixed waveform, and isolate a portion of the mixed waveform to identify a respiratory responsiveness waveform representative of an effect of the respiration of the patient on the mixed waveform
