When does the pulmonary valve open passively?

The pulmonary valve opens passively when the pressure in the right ventricle exceeds the pressure in the pulmonary artery. This occurs during the systolic phase of the cardiac cycle when the right ventricle contracts. As the right ventricle contracts and generates pressure, it forces blood through the pulmonary valve into the pulmonary artery, facilitating the flow of deoxygenated blood to the lungs for oxygenation.

This passive opening mechanism means that it does not require any muscular effort from the valve itself; rather, it is the pressure gradient created by the contraction of the ventricle that causes the pulmonary valve to open. This process is fundamental to maintaining effective pulmonary circulation and ensuring adequate blood flow to the lungs.

Understanding this mechanism is critical for perfusionists, as it relates to the management of hemodynamics and the functioning of the heart-lung machine during cardiac surgery.