Kim H. Parker edited textbf_C1_This_is_the__.tex  almost 9 years ago

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\textbf{[C1].} This is the basic error about Pr pointed out above. Pr is not based on the assumption that there are no waves during diastole. In our first paper we suggested that the arterial pressure $P(x,t)$ could be separated into a Windkessel pressure $P_{Wk}(t)$ and an excess pressure   $P_{ex}(x,t)$, where $P = P_{Wk} + P_{ex}$. We did not use the term 'reservoir pressure' in that paper. After publishing that paper, we realised that this definition was not viable, mainly because we observed in our experiments that what we had defined as the Windkessel pressure was propagating down the aorta which is incompatible with the Windkessel pressure as defined by Frank. In our subsequent papers we coined the term 'reservoir pressure' so that it would not be confused with the Windkessel pressure. Obviously our efforts to distinguish the two failed because WSW have confused reservoir pressure with Frank's Windkessel pressure.  \textbf{[C2].} The sequence of definitions is wrong. No \textit{a priori} assumptions are made about $P_{exc}$; it is simply defined as the difference between $P$ and $P_{res}$. $P_{res}$ is defined in the following way: During diastole we assume that $P_{res} $P_{res}$  falls exponentially $P_{res}(t - T_N) - P_{inf} = (P(T_N) - P_{inf}) e^{-(t - T_N)/\tau}$, where $T_N$ is the time of the start of diastole. $P_{inf}$ is, as WSW state, the asymptotic pressure that would be reached after a long asystole. $P_{inf}$ is included in the definition because we found that this 2-parameter model achieved a significantly better fit to measured diastolic pressures than the more common 1-parameter equation that fits the time constant $\tau$ to a curve that decays to zero pressure. We note that the existence of $P_{inf}$ (i.e. a positive pressure at zero flow) is supported by considerable experimental evidence from several groups. [refs] The form of Pr during systole is then determined in one of two ways. If local flow measurements   $Q(x,t)$ are available, as they are in our experiments on dogs, then $P_{res}$ is obtained by solving the differential equation describing overall mass conservation (assuming that net arterial compliance $C$ is constant so that $dV/dt = C dP/dt$)   \[