What a blood pressure measurement is in reality

Seems a bit daft to post on this subject, but I struggled to find anything out on the web about what the numbers actually represent. There’s plenty of stuff telling you what values are high, normal etc. but nothing about what is actually happening during the course of a measurement. But I found some documentation eventually, looks like it is aimed at clinicians, which I’ll try to explain.

You wrap the cuff around your upper arm. At that point, you’re over your brachial artery, so a direct route to the heart. The documentation I looked at made a big deal of this, so this is important.

The cuff inflates sufficiently high that it stops blood flowing. If you were listening with a stethoscope, you’d hear nothing.

You gradually let the pressure out of the cuff. Your heart pumps with sufficient pressure that, sooner or later, it overcomes the pressure in the cuff, and the blood starts flowing again. Again, if you had a stethoscope, you’d hear the heart beating. When blood first starts flowing, this is the systolic blood pressure – the pressure when the heart beats.(

You keep releasing pressure from the cuff. You can still hear the heart beating. Again, sooner or later, you stop hearing anything. At that point, this is the diastolic blood pressure. Basically the pressure in the cuff is sufficiently low that your heartbeat can’t be heard. It’s the pressure when your heart is resting. In my simple world, I think of the heart as a machine which is either on (pumping) or off (resting). In this scenario, at any rate.

I mean, a stethoscope is just one way of detecting these signals. I would imagine an electronic machine would detect these points by “feeling” when the pulse starts and stops (a momentary slight increase in pressure, say, as the heart pulses). I think my next task is to find this out.

I’ve tried to explain this briefly and in layman’s terms. If you feel i could do better, please leave a comment, or there’s a link at the bottom of the page which you can use to contact me.

People’s knowledge of diabetes

We went over to see my mother-in-law at the weekend. We also met up with my sister-in-law while we were over there. It was funny that, for both of them, a lot of their knowledge of diabetes was just plain wrong.

I mean, nothing against them. Neither of them has diabetes, certainly not to the extent where they’re shoving meds into their body to control their sugar, so why should they be expected to know about something they don’t have?

But it was interesting that they have picked up their (mis)knowledge from the media, and a lot of that is just wrong. There is an implicit assumption that diabetes is about sugary food, whereas it is carbs in general. Sure, sugar is carb, but a portion of bread might have every bit as much effect on my sugar. I know, because I measure it. And there’s a hereditary link, it’s not just down to lifestyle. I know this because much of my father’s family have it, too. In fact, I can tolerate a bit of chocolate every now and again, a 50g bar every week or so, and it doesn’t raise my  sugar noticeably. Certainly not as much as if I have hot dogs/rolls for lunch.

But it really gets my goat that the media continually spreads this misinformation. I’ve even argued online with somebody who’ve said to me, “change your diet and you’ll reverse your diabetes”. And I can stop taking insulin, just like that. Actually it made me have a stroke, smartass.

Information Exchange

Developing sortware, you’d often come up with a problem and think “how do I solve that?” There is documentation available online, of course, but often it doesn’t hit the mark, People have written blog posts, too, but often they are very simplistic, I suppose to help convey their main point.

There was another type of site, one which used the community’s collective knowledge to help solve a problem. Once one person has accomplished something, they can teach somebody else to solve that problem, and pretty soon the “thing” isn’t a problem any more.

One such site was Experts Exchange. They would tantalise you with the same question you had but, oops, before you were allowed to see it, they just wanted you to subscribe to their site. The idea of knowledge being so directly associated with money really used to put me off, although when you think about it, it is everywhere these days. But, in my book, why would you not share knowledge, especially in a niche subject with a willing pupil?

So I never went near Experts’ Exchange.

One other site was Stack Exchange. This site, at least, was free to both request and contribute. In fact, for several years I was actively involved in the Bicycles version of the board, until shortly before the stroke. They also have a board on the subject of software development, in which I’ve dabbled but was never a serious participant. Of course, all these boards are the same thing – it is just the subject matter of each which is different. In theory, you join the site for free and post your question for everyone to see, and people can try to help, normally with a partial answer. You end up with several of these answers, and hopefully by aggregating them together you get a decent idea. The site has nuances, such as the duplication of information. If you ask the same question as somebody else, people will close your question and point you to the other question/answers instead. If people like your question, you earn some points, known as your reputation. If people like your answer, you get more points. In that way, the helpful people, and those who ask the most meaningful questions, float to the top.

This sounds like a great site, but it has its own drawbacks.

Because of these points, people who are naturally competitive will follow the site in minute detail, and will put forward anything that they can possibly think of, in the hope that somebody gives them points. Sometimes it is useful, but often not. So it degenerates into a pissing contest, and in fact you do see rivalries played out there, and the primary aim of helping people soon becomes no more than a by-product – the casual visitor won’t notice this, but I found it surprising how personal things could get. And very often, this translates into voting patterns, too, and I’m afraid I sometimes fell into this trap. So-and-so thinks a contribution is good/bad, you trust their judgement so you vote that way too, possibly not paying as much attention to the actual contribution as you might. In the bicycles forum, a group of us would also go to a bolted-on chatroom quite frequently, so we became friends with each other, as well as participants in the forum. And it is certainly easier to be kind to someone when you know and like them.

Similarly, in a zealous attempt to avoid duplication of data, somebody will spend two seconds looking at a question, pick out a few keywords, see that those keywords appear in another question, and close the question because it is a duplicate. Of course it very often isn’t a duplicate, but a totally different question which is unfortunate enough to be in the same area. If people read the question, they’d know that, but they don’t. And that there is somebody out there asking for help, who might have spent an hour or more just writing their question, counts for nothing.And again, people tend to vote with them, although in some cases they have the power to act unilaterally.

I mean, this was primarily the reason why I disengaged from the Bicycle site. The whole ethos of the site is that someone is out there asking for help. But some people decide not to give that help fro the most arbitrary of reasons.

I suppose it is a fine line. On the bicycles site, we often used to get questions like “I found this bike in a dumpster, how much is it worth?”. And you’d straight away think, “its previous owner put it out in the trash, so how much do you think it’s worth?” So a question like that, I suppose it is reasonable to conclude that it is time wasting. One man’s meat is another man’s poison I guess.