The pressure cuff + stethoscope combo is called a sphygmomanometer. It's a pretty fascinating piece of technology: A heartbeat is only audible in the earpiece when the cuff is compressing between someone's systolic and diastolic pressure.

To use it, you get the cuff pressure high enough that you stop hearing a heartbeat in the earpiece. Start releasing pressure slowly. As it comes down, take note of where on the dial you start hearing the heartbeat. That's systolic pressure. Keep listening, and take note of where you stop hearing the heartbeat. That's diastolic pressure.

Using one feels kind of magic.

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devilbunny 3 hours ago | parent | next [-]

And if you use a mercury sphygmomanometer, you can actually see those pulses appear and then disappear. (It's harder to see them with a gauge-based one.)

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M95D 2 hours ago | parent [-]

The pulses you see are no substitute for a stethoscope. You see them later and they dissappear sooner than what you hear with a stethoscope.

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devilbunny 30 minutes ago | parent | next [-]

You need a closer eye on it ;)

Or go slower.

I'm an anesthesiologist; we will sometimes use a pulse oximeter below the cuff as a quick estimate. With practice you can estimate SBP to within 5 mm Hg or so, which is more than enough for our needs.

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dzhiurgis 33 minutes ago | parent | prev [-]

How about feeling in your arm? I think I can gauge it reasonably accurately.

	▲	devilbunny 27 minutes ago \| parent [-]
		Palpation BP's are good enough for +/- 10 mm Hg, but not much more, and won't give you diastolic.

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lukko 2 hours ago | parent | prev [-]

It does feel magical, especially when the first sound comes in. More details here [0].

[0] https://en.wikipedia.org/wiki/Korotkoff_sounds