It has long been known that arterial stiffness increases with aging. This observation was deduced from the increase in pulse pressure in the elderly. What is less obvious is that there is also arterial dilatation: at similar blood pressures the cerebral blood flow velocity is lower in elderly than in the young. Since blood flow velocity is also a function of arterial diameter it was concluded that it true cerebral blood flow changes little with aging, it must be an increase in arterial diameter that explains for blood flow velocity reduction.
In other words, in the young arteries are more elastic and their lumen is narrower than in elderly. The biomechanics of the arterial system changes. These changes have been added to the cardiovascular simulation app by fine-tuning the Z-scores: at different ages the Z-scores were adjusted to the expected means causing the modeled flow velocity to initially divert from this mean. By trial and error the model's systemic arterial capacitance, systemic arterial resistance, middle cerebral artery diameter and acceleration strength were altered linearly with age until the model output matched with the expect Z-score graph for that age.
Without reflexes active, this results in the following waveform profiles
20 years of age 50 years of age and 80 years of age
And then the model produces the following Z-score graphs:
20 years of age 50 years of age and 80 years of age
