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.

Food For Thought

A guy came around last week. We met in a technical environment (IBM) so it was good to talk vaguely technical to somebody, and of course I told him about the application that I am currently up to.

I only worked with him for a few months, the role at IBM was my first contract so the priority was simply to prove that I was good enough to do the job, rather than worrying exactly how interesting the project was. As it happened the IBM role was not-at-all challenging, I got out as soon as the contract finished, and I went on to do many more interesting roles both locally and in London. His job was to support, rather than develop, one of IBM’s flagship products, MQ Series. I make the point about “support” because IBM had a definite structure where developers developed, they were the glory boys, and supporters supported – there was limited crossover between the two. Rightly or wrongly – as a consultant on a specific project, I worked separately to both, although geographically closely. . But this guy obviously got very intimate with that one product, and eventually he himself became a consultant. I know myself that there is a small but well-paid market for MQ consultants (i.e. people who can configure systems to use it), whereas my skills included only a small amount of MQ – I’ve used it a few times since – but lots of other things too. By the sounds of things, the chap spent a lot of time not working, but when he did, he would have been well paid. It’s a very niche market.

Anyway I talked to this guy about my application. He had a few thoughts. Some were off the planet (the environment in which I’m writing is very different to the environment in which he wrote), some were things I’d already thought of, but some did force me to think. I mean, most of my application is developed now but there are a few bits and bobs to complete. In software development, you start off with a vague notion about how you’ll go about something, then put flesh on the bones as you make progress. For that reason it is difficult to cost projects up-front, but experience, where you’ve seen such-and-such a problem before, is invaluable.

One such area was the multi-user aspect of my application. I had a vague notion that the application would be written for one user, the currently-logged-on user. But would be usable by other people just by virtue of different users having different Windows logons, different file areas etc. Certainly my app is all files, so I’d always thought that it would be possible to have many different DIEM data files, in many different locations. But I got to thinking over the weekend, how exactly would I make it happen?

I didn’t do anything until this morning, when I decided to check that the application would work for mutiple users. In the end it was easy, just because the application is pretty modular already so I only had to change a couple of tiny things.

But of course the big win is knowing not just that I want to do it, and knowing vaguely how I would do it, but having actually implemented it, I know exactly what steps I had to take to accomplish it.

At one extreme, I could have had my own database of users, passwords, data etc. but I decided that was too much overhead, and that the data here is not critical enough, plus I want the application to be as open as possible At the other extreme, I could have had no security whatsoever, just to keep the database in a single place, but the knock-on implication of that would be that I could only support a single user. So I’m in a halfway house, using Windows’ inbuilt security features to separate users. I  wouldn’t claim that it is 100% foolproof – I am an administrator on the machine and I can see everyone’s area (I happen to be the only person who uses it) – but the application is as secure as you make Windows itself, and that seems fair enough to me.

Getting Started

Tekkie post – I’ll make it brief.

When I used to work commercially, the last phase of any project was creating an installer for whatever we happened to be writing, and I always used to underestimate just how long it would take. You’d be clapping each other on the back because you’d finished the application, but there was still one significant hurdle left to jump. In the early days I mainly worked on web stuff – it’d not only be installing the files to the required folder, but stuff like creating web sites, virtual directories etc. plus capturing and sorting the account credentials to make sure it had the necessary permissions. All of which I did by setup program, just because it was 100% repeatable if there was a problem – I wasn’t reliant on some operations guy typing the wrong thing in.

In later years it was mainly desktop applications. I designed a lot of stuff (tek alert!) late bound if I could so there were always config files which needed updating. Late bound is: an application would need to use such-and-such a technology, but rather than just lump the technology in with the application, you’d keep the two parts separate. This allowed you to move from Technology A to Technology B, say, without impacting the application itself. At run-time, the application just used to look inside a configuration file to find out which approach it had to use. There were also things like database usernames and passwords – I never knew these for the “live” systems, so the Operations guy would type them in during install. And I wrote simple credentials-checking things to check that the operator himself hadn’t mistyped things. Over the years I learned to leave as liyyle as possible to chance But again, it took time and effort.

But I have just had a wonderful experience with Microsoft’s Setup program creator tool. I’d budgeted a month to do the setup program for my app, but it has only taken me a day! In fact, most of it was already done for me, I mainly just entered product-specific stuff. ‘Course, it helps that this installer doesn’t do anything complicated (one of my goals here was to avoid complication), but still, I’m pleasantly surprised. So, task number next!