Browsing by Author "Shrive, N. G."

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    P3.02 Describing Waves in the Pulmonary Veins: Application of a Reservoir-Wave Model
    (2012-11-17) Bouwmeester, J. C.; Shrive, N. G.; Tyberg, J. V.
    Abstract Background The pulmonary venous pressure waveform is typically described by the downstream events in the left atrium and ventricle. These downstream events create waves that contribute to the overall waveform. Methods In anesthetised open-chest dogs, measurements of pressure and flow were made in the pulmonary artery and vein. Experiments involved increases to blood volume and the application of 10 cm H2O positive end-expiratory pressure (PEEP). The reservoir-wave model describes the reservoir pressure, which is subtracted from measured pressure, to result in the excess pressure (Pexcess). Excess velocity (Uexcess) is similarly formulated. Pexcess and Uexcess are used in wave intensity analysis to calculate wave speed and separate the contributions of waves originating upstream (forward waves) and downstream (backward waves). Results Separated waves are shown in the bottom panel of Figure 1. The effect of PEEP resulted in larger decreases to Pbackward (p < 0.001) after the mitral valve opened. As a result, y was lower than x by ~2.0 mmHg. With PEEP, the delay between arterial and venous forward waves increased from 155 ± 4 ms to 183 ± 4 ms (mean ± SE, p < 0.001). Conclusion The majority of pulmonary venous pressure landmarks can be attributed to the actions of the left atrium and ventricle but the v wave has substantial contributions from waves originating in the pulmonary artery. Diastolic suction has a larger effect with PEEP, presumably from some external constraint applied to the heart and consequently lowered end-systolic left ventricular volume. Figure 1 Common venous markers related to measured pressures (top panel) and the separation of Pexcess into forward and backward components (bottom panel) at control conditions.