Identification of pulse frequency spectrum of chronic kidney disease patients measured at TCM points using FFT processing

Mortality due to chronic kidney disease (CKD) increases significantly in a recent year. The disease often is diagnosed in an advanced stage. On the other hand, there has been traditional Chinese method or technique to diagnose the presence of the CKD. The diagnosis is carried out by examining pulse palpation at three points namely cun, guan and chi located at the radial artery of the left hand. Records of the pulse pattern of the CKD patients showed irregular characteristics compared with regular pattern obtained from healthy subjects. The aim of this study was to determine the relationship between the frequency spectrum of the irregular pulses related to the stages of the CKD especially from the chi area. Data of the irregular pulse were categorized into 6 stages i.e. 1, 2, 3a, 3b, 4, and 5 of the CKD patients. The data were collected by measuring pressure during systolic periods or when blood vessels were in a relaxed state. In this period, the instrumentation records reflections of the pulse including information about the amplitudes, frequencies, and pulse wave patterns. Observations were focused on the part of the signal between low and high amplitude on pulse patterns (systolic period). The irregular patterns were processed by a Fast Fourier Transform (FFT) technique to find out their special characteristics quantitatively. Results showed that the pattern irregularity was related to the severity of the kidney dysfunction. The FFT processing results showed a number of different special characters in the spectrum. The data were clustered related to the CKD stages. The clustered data of the CKD patients indicates a correlation between the stages and the shifting of the spectrum to lower frequencies which are 0.26 Hz compared to health subject's data 1.11 Hz.