Mobil-O-Graph 24-hour ambulatory blood pressure monitor review

Originally published in GP magazine .

Written for GP magazine around 2003. This is the version I submitted - the published article may have been edited.

My practice has recently had the opportunity to trial the Mobil-O-Graph 24-hour ambulatory blood pressure machine supplied by Numed, and I am happy to report that we were very impressed with it.

The machine is very small, measuring 128mm x 78mm x 27mm, and is claimed to be the lightest on the market at 250g with batteries. It has two connectors: one for attaching to the computer whilst programming it and one for the blood pressure cuff.

The machine uses the oscillometric technique to measure blood pressure. Basically this technique uses vibrations that are naturally caused while deflating the cuff (which can be seen in the mercury in mercury sphygmomanometers) and are maximal at mean arterial pressure, to determine systolic and diastolic blood pressure. It is a validated technique and indeed the machine has a BHS grade A validation.

The great advantage to the patient and the staff is that there aren’t any special transducers in the cuff and no microphones that have to be positioned over the brachial artery and constantly repositioned as the day goes on. For anyone who has had experience of the older style machine this is a great advance, and it dramatically increases the number of successful readings. The other advantage is that as you don’t need a special cuff and can use any cuff that you may have lying around, if any of the three cuffs of various sizes that are included wear out they can be replaced cheaply, keeping ongoing costs down.

The machine is supplied with rechargeable batteries and a charger, though it will also take two standard AA size batteries. It also comes with a belt or holster for holding the device. The machine itself is made of hard plastic and is fairly tough. The connectors are also tough and would take quite a lot to damage.

The machine, before fitting, needs to be programmed with the patient’s details, and this can be done at any time before the patient attends; in my practice we have decided this should be done by administrative staff to reduce the nurses’ workload. There are a lot of possible settings about the number of inflations that can be done, though most people apparently leave it in the default of one reading every 30 minutes during the day and one every hour at night.

The patient then needs to be seen and have the machine explained to them. The right size cuff needs to be chosen and should be worn next to bare skin for best results. A couple of initial readings should be taken in the surgery to give the patient an idea of what it will feel like. For patients who insist on being able to shower or bath, they can be instructed on how to take the cuff on and off, and it is probably a good idea to do this anyway so that they feel confident about repositioning it should it slip. The machine beeps just before a reading to warn the patient about the inflation and it uses a special algorithm to try to reduce the time spent inflating. There is a button on the machine that they can press if they want to take extra readings, for example when experiencing symptoms. These user-initiated readings will be highlighted in the subsequent report.

Once returned to the surgery, the data doesn’t have to be uploaded straight away, though it does need to be done before someone else uses it. Again the uploading can be done by an administrator and utilises the ViewMed virtual printer driver software, also supplied by Numed, to produce an electronic report that is easily attached to the patient’s notes on our computer system. What you want on the report can be customised, and we found the graphs of blood pressures the most useful.

We have had very interesting and useful results from the machine, with a very low number of blank readings. Our patients have commented favourably on the machine and agree it is very quiet, though no matter how quiet it is some will be disturbed by it.

Installation of the software is included and doesn’t take long or require any special access to your computer system, other than a computer to be designated as the upload and download machine. Again we felt this would be best as an administrative machine rather than one in the treatment room. Excellent on-site training is given and there is good access to telephone support. The machine is guaranteed for one year and if you pay for an annual maintenance contract the machine is calibrated for you at the yearly service.