What Exactly is Blood Pressure?
Nikolai Korotkoff MD (1874-1920)
The heart pumps and then it relaxes to fill up again about 100,000 times a day. Normal – right? But the heart depends on other structures to deliver the blood to our organs – the blood vessels we call arteries.
In the 17th century, scientists studied animals and realized that the heart and the blood vessels worked together to generate pressure to propel blood. In the 1870’s an Englishman named Frederick Mohammed used a device placed over the artery in the wrist to record human “blood pressure” – a high number when the heart contracts, and a lower number when it relaxes.
Then a Russian named Korotkoff used a new device – a stethoscope – to listen to the sounds of the artery in the arm. The “Korotkoff sounds” are used by all doctors to determine our blood pressure. But what was “normal” blood pressure, and if it was high, could cause disease?
Age had something to do with the blood pressure. The upper number of blood pressure, the systolic number, was rarely over 140 mm of mercury until people were over 65. By 1906, the life insurance companies got interested, as doctors suspected that high blood pressure was strongly associated with damage to the brain (stroke), the kidneys, the eyes, and the heart. They priced their insurance policies largely based on blood pressure measurements.
The exact cause of high blood pressure in most people, now defined as frequent readings of greater than 130/80, is unknown. It is due to a complex relationship between the brain, the kidneys, and the heart. It’s possible than high blood pressure has always been in the human genome but that didn’t really matter when the average life span was 45 years – now it does!
We know how to control blood pressure, by reducing salt, weight control, exercise, and a large number of effective medications. There has been a decrease in the incidence of all of the dreaded complications of high blood pressure for decades, a dramatic success for modern medicine.
But there is much more to do. Millions don’t know they have high blood pressure, and not enough people taking medication have low enough blood pressures. More good news is that checking your blood pressure yourself with automated machines you can buy for about $60 has become easy and accurate. Give yourself a present for the holidays – buy your own blood pressure machine and keep an eye on it!