If you want someone to measure blood pressure with a mechanical tonometer, then you need to follow the rules. Some of them are missed and forgotten even by cardiologists. It will be about measuring systolic blood pressure with your fingers.
After you have sat your patient at the table and placed the blood pressure monitor cuff on his shoulder, you need to decide to what extent to pump the bulb. Would you pump up to what time? Up to 200 millimeters of mercury or higher? Or lower?
Auscultatory failure
The fact is that when measuring blood pressure with your own ear, there is a so-called auscultatory dip.
This means that the same knocks in the phonendoscope can begin at 180 millimeters of mercury, then disappear at 165 and appear again only at 140. If we pump up to 160 in such a situation, we will not hear anything. Then the knock will start at 140, and we will happily write it down on a piece of paper. And the systolic pressure was actually 180 millimeters of mercury.
There is a fundamental difference between 180 and 140. At 180, you can't lift weights and play sports.
That is why the cuff of the tonometer is inflated only 30 millimeters of mercury higher than the systolic pressure.
Systolic pressure can be determined with fingers on the pulse:
- find the pulse,
- pump up the cuff,
- notice when the pulse has disappeared (this is the systolic pressure),
- pump up another 30 millimeters of mercury,
- start to bleed air and listen with your ear.
Where to feel
In the official recommendations, it is often advised to feel on the brachial artery exactly in the place where the phonendoscope is applied. Less commonly, it is advised to check the pulse on the radial artery (on the wrist).
Personally, I like to check on the wrist. First, this is how you can catch pseudohypertension, which we talked about in the last article. Secondly, some mechanical blood pressure monitors are designed this way, the phonendoscope membrane is already sewn to the cuff in the right place. It is not very convenient to put your finger under it to measure the pulse.
Did you do that? Ask your doctor.
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Pressure surge from inflation of the tonometer cuff
