Figure 32-11 Clinical measurement of natural frequency and damping coefficient. A, Two square-wave fast-flush artifacts interrupt an arterial pressure waveform recorded on standard 1-mm grid paper at a speed of 25 mm/sec. Natural frequency is determined by measuring the period of one cycle of adjacent oscillation peaks (1.7 mm). The damping coefficient is determined by measuring the heights of adjacent oscillation peaks (17 and 24 mm). From these measurements, a natural frequency of 14.7 Hz and an amplitude ratio of 0.71 may be calculated. See the text for greater detail. B, Relationship between the amplitude ratio and the damping coefficient. The amplitude ratio determined in the fast-flush test in A corresponds to a damping coefficient of 0.11. (Redrawn from Mark JB: Atlas of Cardiovascular Monitoring. New York, Churchill Livingstone, 1998, Figs. 9-9 and 9-10.)