a system and method obtains physiologic parameter information of an animal or human , such as respiratory rate , from a blood pressure signal from an implanted blood pressure sensor in the animal or human . specifically , the blood pressure signal is externally signal processed to develop an amplitude versus time waveform . a sequence of selected blood pressure features derived from individual cardiac cycles of the amplitude versus time waveform over a selected time interval are extracted from the developed amplitude versus time waveform . a mathematical model is fitted to the extracted sequence of selected blood pressure features to yield a fitted mathematical model . the physiologic parameter information is computed from the fitted mathematical model .