OK, I get systolic blood pressure: The cuff increases in pressure, and if you blood pressure is high and banging hard on the blood vessels, it will be more resistant to having the sound cut off. When the pulse can’t be heard any more, that’s the top number.
But then diastolic seems wrong: If that pulse is really banging, then it would seem to be able to be heard longer not shorter. But if the pulse can’t be heard sooner on the way down, then that number is high. Seems counterintuitive. It would seem lower blood pressure would result in the pulse sound cutting out sooner as cuff pressure goes down.
I thought the diastolic was measured at the point where there was no more sound. That’s the point where the cuff no longer restricts the blood flow, which would be lower for lower pressure. I’m not sure how longer or shorter comes into play, that’s just the rate that the cuff is being deflated.
OP has the procedure reversed. You don’t listen while increasing pressure, you listen while decreasing pressure.
First you fully inflate the cuff. Listen through the stethoscope and you hear nothing, because there’s no blood flow. Now slowly release the pressure. At the point where blood just barely begins to flow, you’ll start hearing the pulse: boom, boom, boom. This is the systolic pressure. Now keep releasing pressure. You’ll continue to hear the pulse: boom, boom, boom. Then the blood starts to flow freely and you’ll no longer hear the boom, boom, boom. This is the diastolic pressure.
OK, makes sense. But still: It would seem a higher blood pressure would keep the “booms” going for longer, whereas a lower blood pressure keeps them going for longer.
An example. Say diastolic is a high, around 100. That sound then cuts out around 100, whereas if it were 60 you’d be listening longer. But it would seem the higher pressure would cause it to boom for longer, not shorter.
I’m not a doctor, but looking up hypertension it shows both diastolic and systolic increasing, with systolic increasing more than diastolic. So both higher tides and higher waves, to use usedtobe’s analogy.
ETA: What I mean is, what are you actually asking about?
What you’re listening to is the clamped off side of the hose refilling. So high blood pressure is going to refill faster (therefore higher systolic and diastolic readings). Normal to low pressure will take longer to refill and you get lower numbers. Think in terms of a hose filling a bucket, where you can’t hear the bucket side until the water reaches the top and starts to pour out the spout.
Sorry I didn’t quite put that right - think of it as hearing the bucket while it’s refilling. So the first (systolic) sound you’re hearing is the blood hitting the bottom of the bucket. You continue to hear the pulse as the bucket fills, and the sound drops off as the bucket is full (diastolic) and flows again.