normal mean pulmonary artery pressuremean pulmonary artery pressure formulapulmonary artery pressure definitionmean pulmonary pressurepulmonary artery thrombosispulmonary artery blockagepulmonary artery aneurysmpulmonary artery embolismpulmonary artery stenosisaverage pulmonary artery pressuresevere pulmonary arterial hypertensionperipheral pulmonary artery stenosis