A NONLINEAR MODEL FOR MYOGENIC REGULATION OF BLOOD-FLOW TO BONE - EQUILIBRIUM STATES AND STABILITY CHARACTERISTICS

A simple compartmental model for myogenic regulation of interstitial p ressure in bone is developed, and the interaction between changes in i nterstitial pressure and changes in arterial and venous resistances is studied. The arterial resistance is modeled by a myogenic model that depends on transmural pressure, and the venous resistance is modeled b y using a vascular waterfall. Two series capacitances model blood stor age in the vascular system and interstitial fluid storage in the extra vascular space. The static results mimic the observed effect that vaso dilators work less well in bone than do vasoconstrictors. The static r esults also show that the model gives constant flow rates over a limit ed range of arterial pressure. The dynamic model shows unstable behavi or at small values of bony capacitance and at high enough myogenic gai n. At low myogenic gain, only a single equilibrium state is present, b ut at high enough myogenic gain, two new equilibrium states appear. At additional increases in gain, one of the two new states merges with a nd then separates from the original state, and the original state beco mes a saddle point. The appearance of the new states and the transitio n of the original state to a saddle point do not depend on the bony ca pacitance, and these results are relevant to general fluid compartment s. Numerical integration of the rate equations confirms the stability calculations and shows limit cycling behavior in several situations. T he relevance of this model to circulation in bone and to other compart ments is discussed.