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Diameter compliance of a vascular graft quantifies how the measured diameter of a vascular graft changes with distending pressure. A fractional differential convention isThis logarithmic diameter compliance has inverse-pressure units. State whether $D$ is an internal or external diameter and use the same convention throughout a comparison. The distending pressure is lumen pressure minus surrounding pressure.

An interval estimate often uses the lower-pressure diameter as reference:For constructed external diameters $D(80\mathrm{mmHg})=4.00\mathrm{mm}$ and $D(120\mathrm{mmHg})=4.16\mathrm{mm}$, this gives $0.0010\mathrm{mmH}{\mathrm{g}}^{-1}$. Expressed as percent diameter change per 100 millimeters of mercury, its numerical value is $10^4{\overline{C}}_D=10$. The factor $10^4$ combines percent conversion and the 100-millimeter pressure interval; it is not a change in the measured deformation.

A logarithmic interval average instead givesIt differs slightly because its normalization follows the changing diameter. Neither interval value is automatically the local derivative at every pressure.

A primary apparatus measured external vessel-edge motion with video and paired it with transducer measurements of static or pulsatile pressure. The published compliance equation uses systolic and diastolic diameters and pressures, expressed as percent per 100 millimeters of mercury.^[ref] Thus loading frequency, pressure interval and the chosen diameter observable belong to the reported result.

This fractional diameter response differs from volume-based vascular compliance $dV/dp$. For a cylindrical segment with fixed length, $V=\pi D^{2}L/4$ implies $(1/V)dV/dp=2C_D$. Comparisons of vascular graft compliance mismatch should therefore identify both the observable and normalization before comparing numbers.