September 29--Interface critique

Interface critique:

Home blood pressure testing apparatus

This is a pretty simple device that is quite easy to use. I have no idea how accurate it is: my experience is that blood pressure readings are all over the map, very different when taken with different equipment at different times of day and by different people. But accuracy aside, here’s my critique of the device itself.

Overall look and feel

It is a fairly small, (about 7 inches by 5 inches) lightweight plastic box with a Velcro-closing cuff attached with a plastic cable. The box is angled down to make the top easier to see. At the back it’s about 4 inches high sloping down to the front where it’s about an inch an a half high. The top features a screen with demarcations to the left that say “sys” (for systolic pressure), “dia” (for diastolic pressure) and “pulse.” Below the screen there is a small, round button and above that is a small clock icon. To the right of that is a larger button that says “memory.” To the right of the screen is a large blue button that says “start” on top and “stop” on the bottom. The cuff has a small label sewn on that has a graphic showing where the cuff goes on the arm. It is labeled “1/2” inch and ~ 2 cm to indicate that is how far above the elbow the cuff is to be placed. There is also an arrow at the edge of the cuff where the cord come out of it, which corresponds to an arrow in the graphic to indicate the cuff should be placed with the arrow facing the user’s elbow.

Function and feedback

To use the cuff you place it on your arm and hit the start button. You feel the cuff tighten on your arm and while it inflates the machine makes a whirring sound that tells you it is in the process of measuring your blood pressure. You also see a series of numbers that start higher and go lower. When the device reaches the point of inflation when it can take the measurement the numbers stop and the remaining air is let out of the cuff. You can see the three measurements (systolic pressure, diastolic pressure and pulse) as well as the time. The time is recorded because the device stores your readings. When you press the button marked “memory” the most recent reading appears with the date and then the date switches to the time. Press “memory” again and the next most recent reading appears with the date, and then time. The feedback is in the form of the sound that tells you the cuff is inflating and then deflating to the necessary point and in the form of the numbers on the screen.

Affordances

The three buttons and the cuff. They are all labeled to make clear what they do and how to use them. The cuff shows you where on your body to put it, and then you push “start” and machine measures your blood pressure. If you want to know how today’s blood pressure compares to yesterday’s reading or the one before that, push “memory.” Pretty simple.


Mapping

The cuff is literally mapped to its use since it has a diagram showing you exactly how to use it. You would have to read English to use the device since “start” and “stop” and “memory” are in words. The clock is an icon that doesn’t depend on language. When you hit the clock button you see numbers that flash first the day and then on the second push the time. There is no indication of how to change the date or time, though there must have been an instruction book that outlined a way to set that up the first time the device was used. The “start” and “stop” and “memory” buttons couldn’t be simpler.

Comment:

This is a simple device that pretty much explains how to use itself. However when the batteries run out I assume you would have to set the date and time again and there is no indication of how to do that. It also might be nice to have a brief explanation of what “sys” and “dia” mean, but I guess there is an assumption that you are using this device on doctor’s orders and have been given a basic explanation. Also it might be nice to have the basic instructions written on the back, i.e. ,whether you should have your arm resting on something or dangling down, whether it matters if you stand or sit – that sort of thing. That could also be conveyed via diagrams such as the one on the cuff.