Apparatus for heart rate fluctuation power spectrum analysis obtains an electrocardiogram signal from an electrocardiograph machine and a respiratory rate signal from an electroplethysmograph machine. These signals are processed by a data acquisition system to provide output suitable for heart rate fluctuation...http://www.google.com.au/patents/US4832038?utm_source=gb-gplus-sharePatent US4832038 - Apparatus for monitoring cardiovascular regulation using heart rate power spectral analysis
