DENJIRO: I have here a digital blood pressure monitor. It’s showing a reading of 115 over 58. So how does this device measure blood pressure? This is a simplified model of a human heart. When I push the pump, it shows that the heart contracts and sends out blood. When I let go, the heart expands, and blood returns to the heart. When the heart contracts, you can tell that the blood vessel expands a bit.
Now I’m going to attach a pressure gauge to the blood vessel. When I push down on the pump… the water level on the pressure gauge rises. When I let go, the water level goes down. We see that the blood pressure goes up and down as the heart contracts and expands.
So, how does a blood pressure monitor measure the top and bottom numbers? You can actually tell if you listen to the sound. I’m going to place a stethoscope on her arm where pressure is applied. We’re going to attach the stethoscope to a speaker and listen to the sound.
BOY: I can hear a sound!
DENJIRO: These are called Korotkoff sounds. The noise has stopped. Pressure is applied to the arm to stop blood flow. Pressure is then slowly relieved, and after a certain point, blood starts to flow again, and we hear Korotkoff sounds. This is the moment when blood pressure is at its highest. As pressure gets relieved even more, the blood vessel starts to expand, and the Korotkoff sounds become quieter. Blood pressure is at its lowest when blood is flowing freely like this. Back in the day, the top and bottom numbers were measured by listening to the Korotkoff sounds with a stethoscope. A digital blood pressure monitor detects the change in blood flow with a pressure sensor.
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16 окт 2024
