This decrease in the resistance and the pressure in the lungs. And as a result, the blood rushes from the right side of the heart and into the lungs. Now, as the blood moves along this side of the heart more easily the pressure inside the right atrium and the right ventricle decreases. And that decreases the pressure on the right side of the heart. Now, as we have more blood being pumped into the lungs, more blood is coming out of the lungs and moving into the left side of the heart. And so eventually what happens is the pressure on the left side of the heart increases.