I keep track of my pulmonary artery pressures. What do these mean and what are normal pressures?
Pulmonary arterial hypertension (PAH) means that the pressures inside the blood vessels of the lungs are too high. Therefore, regular measurement of these pressures becomes important both in terms of making a diagnosis of PAH and in monitoring response to treatment. In some ways, pulmonary artery pressures are comparable, in terms of what they measure, to your regular blood pressure, which you've probably had measured many times when you visit your doctor. As we discussed in the introductory questions [link], your regular, or systemic, blood pressure is the pressure in the main arteries of your body that run from the left side of your heart to the rest of your body (arms, legs, intestines, kidneys, brain, etc). The pulmonary artery pressures represent the blood pressure in your pulmonary arteries (these are the blood vessels that carry blood from the right side of the heart to the lungs).
A normal systemic blood pressure is about 120/80, while a normal pulmonary artery pressure (PAP) is about 25/10. The numbers are in the units of mm Hg (millimeters of mercury). These values are usually measured when at rest (they are higher during exercise even in a healthy individual). As you can see from these numbers, the blood pressure in the pulmonary arteries is much lower than in the rest of the arteries of your body. The pulmonary circulation is a low pressure system with lower resistance to blood flow. This lower resistance is one of the key features of this system, and it is one of the factors that allows your body to respond with increased flow during times of increased demand (for instance when you are exercising and trying to circulate more blood through the lungs to receive more oxygen).