par Pagnamenta, Alberto ;Vanderpool, Rebecca R;Brimioulle, Serge ;Naeije, Robert
Référence Journal of applied physiology (Bethesda, Md. : 1985), 114, 11, page (1586-1592)
Publication Publié, 2013-03
Article révisé par les pairs
Résumé : The time constant of the pulmonary circulation, or product of pulmonary vascular resistance (PVR) and compliance (Ca), called the RC-time, has been reported to remain constant over a wide range of pressures, etiologies of pulmonary hypertension, and treatments. We wondered whether increased wave reflection on proximal pulmonary vascular obstruction, like in operable chronic thromboembolic pulmonary hypertension (CTEPH), might also decrease the RC-time and thereby increase pulse pressure and right ventricular afterload. Pulmonary hypertension of variable severity was induced either by proximal obstruction (pulmonary arterial ensnarement) or distal obstruction (micro-embolism) in 8 anesthetized dogs. Pulmonary artery pressures (Ppa) were measured with high-fidelity micromanometer-tipped catheters, and pulmonary flow with transonic technology. Pulmonary ensnarement increased mean Ppa, PVR and characteristic impedance (ZC), decreased Ca and the RC-time (from 0.46 ± 0.07 to 0.30 ± 0.03 s) and increased the oscillatory component of hydraulic load (Wosc/Wtot) from 25 ± 2 to 29 ± 2 %. Pulmonary micro-embolism increased mean Ppa and PVR, with no significant change in Ca and ZC, increased RC-time from 0.53 ± 0.09 to 0.74 ± 0.05 s and decreased Wosc/Wtot from 26 ± 2 to 13 ± 2 %. Pulse pressure increased more after ensnarement than after microembolism. Concomitant measurements with fluid-filled catheters showed the same functional differences between the two types of pulmonary hypertension, with however an underestimation of Wosc. We conclude that pulmonary hypertension caused by proximal versus distal obstruction is associated with a decreased RC-time and an increased pulsatile component of right ventricular hydraulic load.

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