When measuring your own blood pressure, first get yourself comfortable with your measurement arm supported by a table. Make sure that the sphygmomanometer is placed so that you can see the scale easily and put your stethoscope around your neck. The most convenient kind of stethoscope to use has a diaphragm at the end, not a “bell”.
Wrap the inflatable cuff around your upper arm. If it has a Velcro fastening, make sure that this isn’t full or fluff or it won’t anchor properly (you can clean it with an old brush). If it’s the older cloth type of cuff without Velcro, tuck in the end. Fit the earpiece of the stethoscope into both your ears and jiggle them around a bit to have a good fit. Find your brachial artery pulse, the main artery in your arm with the stethoscope and place the diaphragm of the stethoscope over it, particularly in the crook of your arm. If you tuck half the diaphragm under the cuff, it will leave your right hand free to operate the bulb that inflates the cuff. Your left hand will need to be free if you are left-handed – as usual, left-handed people are asked to imagine mirror images of instructions.
Turn your left hand palm upwards. With the fingers of your right hand, find the wrist pulse on your left hand. This is just so you know how to find it later.
Now take the inflating bulb in your right hand. With your left hand, tighten up the knurled screw clockwise until the valve is closed. After a bit of practice you’ll find you can do this easily with you right hand while you hold the bulb in your palm. By repeatedly squeezing the bulb with the valve closed, pump up the pressure to about 90 mmHg on the glass column and then feel again for the pulse in your left wrist. It will still be there. Now resume pumping up the pressure, now and then checking your pulse in your left wrist. You may be slow and clumsy at first and if your left arm is beginning to feel as through it might burst or drop off, release the valve by turning the knurled nut counter clockwise, stop for a while and start again when your arm feels comfortable.
The reason you have to keep checking the pulse in your left wrist is that when it disappears, it’s a signal that you’ve pushed the pressure in the cuff above your systolic pressure. As blood varies so much, different people need to start measuring if from different levels. Of course, it could be suggested that everyone start from 350 mmHg or more, higher than any systolic pressure even in people with severe high blood pressure, but this would inflict a lot of unnecessary pain on the enormous majority of people whose systolic pressures lies at 150 mmHg or lower than this – so tailor the procedure to 20 mmHg or so above your own systolic blood pressure. After a while, you’ll be able to do this without checking your wrist pulse, because you’ll have a rough idea of what to expect.
For example, if your wrist pulse disappears at around 150 mmHg, keep on squeezing the bulb another 20 mmHg or so and then stop. Now very slowly and cautiously, start turning the knurled nut counter clockwise (this is easily done using the thumb and forefinger of your right hand, while the bulb remains the in the palm) until you see the top of the column of mercury falling. With a normal heartbeat of around 75 beats per minute, that means roughly 2 mmHg (one division on the glass column) for each pulse beat, which you can see easily because the top of the mercury bobs up and down in time with the pulse. This part of the process is very slow, usually very uncomfortable and occasionally painful, but there is no alternative if you want to make accurate measurements of your own blood pressure. If you zip down the pressure to make a quick, comfortable reading, you will record a false low systolic pressure and a false high diastolic pressure. This is the commonest mistake made in measuring blood pressure.
Listen through your stethoscope as you continue to deflate the cuff very slowly. You may hear occasional clicks but after 10 mmHg or so, you’ll start to hear a regular tapping sound. This is your systolic pressure. Look at the level of the mercury column, measure it against the scale on the glass tube and read off the measurement to the nearest 2 mmHg. Write it down before you forget it.
Keep on dropping the pressure. While you’re learning, keep dropping the pressure at the same very slow rate. Eventually, as you get used to the procedure, you’ll be able to drop the pressure faster until you’re about 20 mmHg above your expected diastolic pressure and you’ll find this much less uncomfortable. Probably somewhere around 50 mmHg to 60 mmHg below your systolic pressure, the regular tapping sounds will first become much softer and then disappear. When it disappears, this is your diastolic pressure. Look again at the column of mercury and again measure its height against the scale on the glass tube. Write it down, under the first figure.
After you’ve recorded both systolic and diastolic pressure, turn the knurled knob fully counter clockwise to open the valve completely and release all the pressure on your left arm. It may ache for as long as half an hour afterwards, but the discomfort will get less as you get used to the procedure and do it more quickly.
Michael RussellYour Independent guide to Blood Pressure
