Pulmonary Arterial Pressure

Pulmonary Arterial Pressure

Pulmonary arterial pressure and its determinants

Review of flow of blood through the heart and lungs

• Deoxygenated blood is returned to the heart via the vena cavae, passes through the right atrium, and is pumped by the right ventricle into the pulmonary trunk, which bifurcates to give rise to the right and left pulmonary arteries and their branches.
• Pulmonary blood pressure is generated by the right ventricle.
• Normal mean pulmonary arterial pressure is around 15 mmHg at rest.
• Pulmonary circulation is characterized by low pressure, low resistance, and high compliance.
  – Pulmonary arterial pressure (PAP) is determined by cardiac output, pulmonary vascular resistance, and pulmonary venous pressure.
  Recall that the pulmonary circulation receives the same cardiac output as the systemic circulation; the low pressure and resistance of the pulmonary vasculature allows it to receive this blood without damage.
  – Low pulmonary vascular resistance is the product of short, wide vessels with relatively little smooth muscle in their walls.
  In our drawing, we compare the less muscular pulmonary arterioles to the systemic arterioles.
  – Key modulators of pulmonary vascular resistance include lung volume, perfusion pressure, oxygen, carbon dioxide, and pH levels.
  For example, hypoxia causes pulmonary vasoconstriction; when chronic, this can lead to hypertension.
  – High compliance of the pulmonary circulation is facilitated by the thin vessel walls with little muscular tone.