Computer Modelling of Heart Rate and Blood Pressure

A computer model of the cardiovascular system which models beat-to-beat changes in heart period, systolic pressure, diastolic pressure and the arterial time constant has been studied. The original model, produced by de Boer et al. (1987), was developed with limited data. The authors have shown that in some situations the model may be highly inaccurate, but that it is possible to adapt the model to fit a wide range of data move accurately. From 7 normal subjects the authors recorded a single channel ECG, blood pressure non-invasively using a Finapres monitor, and depth of respiration. The mean values of RR interval, systolic and diastolic pressure, arterial time constant, and baroreflex sensitivity were calculated. The model was produced using LabView, a graphical programming environment. The first implementation of the model used the clinical values calculated the constants specified by de Boer, and the respiration signal the amplitude of which was set so that the power in the high frequency (0.15-0.4 Hz) systolic pressure peak from the model matched that of the real data. The model output was compared with the recorded data for the low frequency (0.04-0.15 Hz) and high frequency spectral peaks of RR interval and low frequency spectral peak of systolic pressure. In some subjects the model outputs were within a factor of 2 but a wide range was obtained up to a factor of 60 for a young healthy subject with high baroreflex sensitivity. It was possible to adapt the model to fit the range of all normal data to within a factor of 8 for the RR and systolic pressure spectral peaks. Overall, the model fitted the high frequency peaks best, with the adaptation having the greatest effect on the low frequency peaks