The new American College of Cardiology (ACC)/American Heart Association guidelines (AHA) for high blood pressure were published late last year and were in favor of using home blood pressure (BP) measurement to aid in the management of hypertension.
I was happy to hear this as I am constantly advising my hypertensive patients to buy a home BP cuff, measure their BP once when they get up and again 12 hours later, and report the values to me after 2 weeks.
I have not spent a lot of time instructing patients on exactly how to make the measurement, but the new guidelines do specify in detail how this should be done:
- Remain still
- Avoid smoking, caffeinated beverages, or exercise within 30 minutes before BP measurements
- Ensure ≥5 minutes of quiet rest before BP measurements
- Sit with the back straight and supported (on a straight-backed dining chair, for example, rather than a sofa)
- Sit with the feet flat on the floor and legs uncrossed
- Keep the arm supported on a flat surface (such as a table), with the upper arm at heart level
- The bottom of the cuff should be placed directly above the antecubital fossa (bend of the elbow)
- Take at least two readings 1 minute apart in the morning before taking medications and in the evening before supper. Optimally, measure and record BP daily. Ideally, obtain weekly BP readings beginning 2 weeks after a change in the treatment regimen and during the week before a clinic visit
- Record all readings accurately
- Monitors with built-in memory should be brought to all clinic appointments
I monitor my own BP at home and often wonder whether there is scientific evidence to support such a rigid protocol. Being a contrarian and a skeptic, I typically violate three-quarters of the recommendations that are listed.
It seems like all of the instructions are guaranteed to give you the lowest BP you are likely to experience during the day. The vast majority of the time I am not sitting quietly with my legs uncrossed, my bladder empty, and my back straight, so following these directions will underestimate my average daily BP.
I’ve spent some time looking into all the instructions, and they generally have some scientific studies to support them. For example, the position of the upper arm in relation to the heart does heavily influence BP readings (more on that in subsequent posts).
The Mandate to Uncross the Legs
The instruction that most intrigued me was the one to sit with feet flat on the floor and legs uncrossed.