Oct 5, 2010

Blood pressure anxiety

Posted in Science at 1:00 pm by David Bradley

Is it a sign of hypochondria to get white coat syndrome when measuring your own blood pressure? I asked this question on my personal Facebook page as a little joke with a hint of seriousness. My doctor and I are currently re-evaluating my blood pressure medicine, and I have been instructed to keep tabs on my bp and pulse for a couple of weeks.

Now, I am well aware that a visit to the doctor causes anxiety in a lot of people, especially when they have to have their blood pressure taken. Just the site of a sphygmomanometer’s pumping cuff can cause a hypertensive spike. It’s known in the trade as white-coat syndrome, although I don’t think I’ve ever had a doctor in a white coat measure my blood pressure. Anyway, hypertensive or pensive, I am curious as to whether WCS is a common issue for people taking their own blood pressure as I certainly get tense when I wrap the cuff around my bicep and get pumping (it’s an automated device, as it happens, so the machine does the pumping and recording for me).

Maria Sosa suggested that my anxiety is simply a transference of the fear of the white coat to the inflatable cuff, although Diane Richards suggested that it would only be a sign of hypochondria if I were wearing a white coat. So, maybe I need to get a stethoscope to hang around my neck too, although my handwriting is probably too legible for me to have ever been a practicing GP. Richards added that in the US filling in the health insurance forms is enough to raise anyone’s blood pressure.

The conversation went on…but then it occurred to me that perhaps the only way around the problem, whether it’s hypochondria or not, would be to have a device that could monitor blood pressure continuously. I believe some research has been done in that area, but could not find a portable device for home use that is available anywhere. The problem is that a conventional blood pressure monitor, the “sphyg” with the inflatable cuff, works on the principle of squeezing an artery, usually in your arm to the point where it stops (temporarily) the flow of blood like a tourniquet. The pressure on the cuff is then slowly released and the pressure at which the pulse first returns is recorded. That’s the systolic, pumping pressure of your cardiovascular system. The doctor or machine continues to slowly release the pressure on the cuff until again the pulse cannot be heard/felt (the cuff isn’t pressing hard enough at that point to feel the pulse of blood in the artery), and the pressure is recorded at this point. That’s the diastolic, “resting”, pressure of the system.

A nice healthy blood pressure would be 120 mmHg (millimetres of mercury) systolic over 70 diastolic, but anything up to 140/85 is fine, according to the British Heart Foundation. “If you have heart or circulatory disease, including being told you have coronary heart disease, angina, heart attack or stroke, have diabetes or kidney disease, then your blood pressure should be below 130/80mmHg,” the BHF says.

Even higher is perfectly normal, but epidemiology suggests that the higher the blood pressure the greater the risk of cardiovascular disease (heart problems and stroke, in particular) if the raised blood pressure is left untreated. Meanwhile, I’ve been keeping a record of my home bp readings on BP-Chart.com, an aptly named site. It’s a simple matter to register and then add your readings together with any notes you think pertinent. Not sure whether my GP will want me to turn up with my iPod Touch to show her the readings, so I may have to print them off in advance.

In searching for a continuous blood pressure monitor I also spotted FitBit, which looks quite interesting. It’s basically a clip on device with an accelerometer inside (like the ones found in Wii controllers and iPhones) that simply keeps tabs on your activity and sleeping it then converts your movements into an estimate of “calories” burned, steps taken, distance travelled and your sleep quality. You then hook it up to your PC to see how you’re doing in your fitness program or whether you are sleeping well. The FitBit was also mentioned in a recent TED Talk (by Gary Wolf on the quantified self) about how we are heading towards greater awareness of our biometrics as part of improvements in taking care of our own health.

When I mentioned the FitBit on the Facebook page, Richards chipped in with the idea that it would be “cool if a lot of people were wired up and we could begin to correlate blood pressure with national news cycles.” Many a true word said in jest. Continual monitoring of health indicators for a random sample of the population would be very useful for all kinds of epidemiology. Although Robert Slinn thinks he would be panicked if he were being monitored continuously. Continuous monitoring of blood pressure, blood glucose etc might also be coupled to automated drug dispensing, perhaps from an implanted (MEMS type) device to give fine control over one’s vital signs throughout the day and night. Prescribing on auto pilot, you might call it.