Baroreflex model

In another approach in which heart rate variability, variations in cardiac cycle and arterial blood pressure are modeled, also flow elements are used, in addition, a baroreflex model is introduced, affecting the heart rate and the stroke volume of the heart. By introducing a time delay between the baroreflex input and output, an unstable system is created that continues to oscillate and explains the heart rate variability and variations in the cardiac cycle. Both modeling approaches will be briefly discussed in this chapter. 

Modeling Heart Rate Variabilily using a Baroreflex Model... 

Fig. 18.13. Block diagram of simulation model including baroreflex model.

Fig. 18.14. Heart rate variability versus time using baroreflex model.

F181 l. mdl more detailed model for cardiovascular dynamics F1812.m generation cardiac period - blood pressure relationship F1813. mdl cardiovascular simulation using baroreflex model F1814plot.m plot file for Fig. 18.14... 

The responses to mental workload in this model depend, except firr the reduction of baroreflex-sensitivity, on the interference of respiration and blood pressure control on feedback gains, sympathic and vagal tone, and so on. "More than hundred combinations of their values were tested and the results showed various patterns of changes in HR, MBP and their RF and MF s [mid frequency component of HRV] that explained the divergence of experimental observations" (Ohsuga et ab, 1995, p. 774). 

We believe that an answer to these questions is of fundamental importance in interpreting the findings in both laboratory and applied studies. A model of the processes involved should be available in order to determine the nature of activation in autonomic space (e.g., Bemtson, Cacioppo, Quigley, Fabro, 1994). Such a model requires an adequate representation of the baroreflex blood pressure control subsystem. Increased activation of the baroreceptors in the vessel wall of the aortic arch and the carotid sinus is accompanied by an increase in vagal and a decrease in sympathetic activity, whereas decreased activation does the reverse (baroreflex). 

TenVoorde, B. J. (1992). Modelling the baroreflex. Master s thesis, Vrije University, Amsterdam, The Netherlands CopyPrint 2000. 

Another approach to cardiovascular modeling uses the same dynamic model for the cardiovascular system. In addition, a rather simple model is used for the baroreflex (Akay, 2001 Cavalcanti and Belardinelli, 1996). This latter model is responsible for the spontaneous fluctuations that occur in heart rate and heart pressure. Non-linear relationships are assumed between cardiac period (s) and blood pressure (mmHg). In addition, a non-linear relationship between stoke volume (ml) and blood pressure can be assumed (mmHg). The relationship between cardiac period T and blood pressure P can be given by (Cavalcanti and Belardinelli, 1996) ... 

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