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Why aren't my other blood pressures high? Are there two sets of blood pressures?

You do have two sets of blood pressures -- "pulmonary" and "systemic". Usually when people talk about blood pressure, they are referring to the pressure that gets measured on your arm with a blood pressure cuff or machine when you go to the doctor's office. This is more accurately called systemic blood pressure (the systemic blood circulation serves the entire body except for the lungs).

The 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 pressure in all of these arteries is similar, and when people typically say they have hypertension or high blood pressure, they are talking about this type of blood vessel and the type of measurement taken with an inflatable cuff. Systemic blood pressure is often termed one of your 'vital' signs (along with your heart rate, your respiratory rate, and your temperature) because it is a very important overall measure of how your heart is functioning.

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The other blood pressure is the pulmonary arterial pressure. As discussed in other sections, the pulmonary arteries are the blood vessels that carry blood from the right side of the heart to the lungs. Since they are not easily accessible (i.e. close to the skin) like the arteries in your arm, this pressure cannot be measured so readily. Instead, an estimation of the pulmonary artery pressure can be obtained non-invasively (without putting anything inside the body) by an ultrasound test (called a transthoracic echocardiogram or "cardiac echo"). The only way to get an absolutely accurate measurement of the pulmonary artery pressure is to measure it directly by a right heart catheterization. This is a more invasive procedure that involves carefully placing a pressure monitor into the pulmonary arteries themselves.

Your pulmonary arteries and systemic arteries are different in several ways. Normally, the pulmonary arterial pressure is much lower than the systemic blood pressure. Pulmonary arteries carry blood that is not loaded with oxygen in contrast to all other arteries in the body that carry blood from the heart and that has been completely loaded up with oxygen. Pulmonary arteries are also generally not as affected by the types of problems (such as diabetes, smoking, high cholesterol, and obesity) that cause systemic arteries to develop hypertension. Pulmonary arterial hypertension can be caused by several other problems that only affect the pulmonary, and not systemic, arteries. As a result, it is possible for you to have systemic hypertension and not have pulmonary arterial hypertension, and vice versa; there are many people with pulmonary arterial hypertension who don't have systemic hypertension.