Background: Pulmonary Artery Pressure (PAP) is influenced by a range of pathological conditions, including heart failure, COPD, and pulmonary embolism. Gold standard assessment of PAP is invasive right heart catheterization. Noninvasive methods such as echocardiography, impedance cardiography and analyses of the second heart sound have been suggested for estimation of PAP. The aim of the current study is to develop an animal model for validation of a heart sound based method for noninvasive estimation of PAP.
Methods: Anaesthetized and mechanically ventilated Danish Landrace pigs underwent arterial catheterization with a 6 Fr catheter in the femoral artery ( Avanti, Cordis Corporation, Tipperary, Ireland) and right ventricle catheterization with a Swan-Ganz catheter /Edwards Lifesciences) through a 10 Fr venous catheter (Avanti, Cordis Corporation, Tipperary, Ireland) inserted in a jugular vein. To avoid any effect of the catheter on the second heart sound, the pressure tip was placed in the right ventricle and right ventricular systolic pressure was used as a surrogate of PAP. Two approaches were used to increase PAP through pulmonary vasoconstriction. In one method hypoxic pulmonary vasoconstriction was caused by replacing inhalation oxygen with nitrogen and in the second approach, hypercapnic pulmonary vasoconstriction was caused by adding carbon dioxide to the inhalation air.
Results: Nitrogen and carbon dioxide administration were repeated 2-3 times in three pigs. Right ventricular systolic pressure increased from a baseline pressure at 28.7±3.4 mmHg to 48.1±7.5 mmHg after nitrogen inhalation and to 60.0±23.0 mmHg after carbon dioxide administration. Between administrations, the right ventricular systolic pressure returned to 31.2±4.3 mmHg.
Conclusion: This porcine model alters the pulmonary arteries pressure reversibly, which makes it a valuable model for validation of noninvasive PAP estimation methods.