Blood pressure can be a little hard to understand, and often my patients have little idea what the numbers mean.
I think of it like this: your heart is a pump, and your blood vessels are the tank that stores your blood and the pipes it runs through. As your heart beats, it squeezes blood into those pipes, and the pressure pops up in the pipes with each squeeze. In between beats, the pressure drops back to the base pressure.
When a blood pressure cuff is put on you, it is inflated enough that it halts the blood flow in your arteries. As the pressure in the cuff is lowered, the blood starts squirting through. We can hear this with a stethoscope; this is the systolic or top pressure of a blood pressure reading – the 120 of 120 over 80. As we continue to lower the pressure in the cuff and listen, we eventually cannot hear the blood squirting past the cuff. The pressure when we cannot hear that anymore is your resting pressure; the diastolic or lower pressure of a blood pressure reading – the 80 of 120 over 80. As Dr. Alisa Hideg discussed in this column in April 2014, when your blood pressure is too high, it can damage your blood vessels and other organs over time, so controlling your blood pressure is an important part of good health.
Exercise is really good for lowering your blood pressure. It makes the vessels springier so they can absorb more of the heart’s pressure energy. In my 30s, I found my blood pressure creeping up. At age 37, when I moved to Spokane, I took up running to run Bloomsday, and I have kept up with that habit. Running on a regular basis got my blood pressure down to where it was when I was much younger.
You can lower blood pressure by relaxing the pump, lowering the amount of blood in the system or making the system bigger. Eating less salt lowers the blood volume a little and for some people it lowers blood pressure. Different medicines act on these different aspects of the system to lower the pressures. In some people one medication is enough, and in others it takes a number of medications to get blood pressure to a safe level.
The most common medicines we use at this time are ACE inhibitors. They work by relaxing blood vessels and making the “tank” bigger. They have the additional benefit of reducing the work that the heart has to do and protecting the heart from too much long-term strain. Beta-blockers reduce the effect of adrenaline on the heart, slow it a bit and make it pump less hard. Diuretics (water pills) lower the volume in the tank, which convinces your kidneys to allow your blood pressure to be lower. Calcium channel blockers can dilate blood vessels and make the heart not pump quite as hard.
Some medicines that lower blood pressure have a better chance of leading to a longer life than others, so we initially choose the ones that typically produce the best outcomes. A patient may feel like a guinea pig as we try to find the right medication for him or her, but we are not all the same, so it is often necessary to try more than one medication to find the medication that works best, is safe, has good outcomes and is cost effective.
Next time I will discuss an exciting new study on blood pressure targets and how it may relate to you.
Dr. Bob Riggs is a family medicine physician practicing at Group Health’s Riverfront Medical Center.
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