Essential Steps to Home Blood Pressure Monitoring | Accurate and Reliable Measurements

"Here doc!" a well-meaning patient says as they drop a piece of paper into my hands. Looking closely, I realise it is a detailed log of their blood pressure for the past month which includes one or two blood pressure values on most days of the week. Some numbers appear quite high, while others appear normal.

I emphatically commend the patient's effort in maintaining this log which gives me a ballpark idea of their home blood pressure. However, let's see if there is a better way to monitor blood pressure.

When to Start Home Blood Pressure Monitoring?

On a previous post, we reviewed the issue of white coat hypertension and the importance of home blood pressure monitoring. While there is a place for formal studies using ambulatory monitors from the pathology provider, I feel self-measurement of blood pressure using one's own machine is perhaps the more preferable approach.

Apart from diagnosing new cases of hypertension, home blood pressure monitoring is also very useful for monitoring response to medication. Whenever a patient is started on a new blood pressure medication, or if there is a change in dose, home monitoring is an invaluable tool.

That said, there is no need to be obsessive or excessive with home blood pressure monitoring. Discuss with your doctor and seek their advice on the timing and frequency of home monitoring.

Eliminating Variables

There are many factors which influence blood pressure such that a single high reading performed randomly during the day doesn't give us a full picture. Even a series of random readings done on multiple days is hard to interpret.

Let's begin by taking the following steps to achieve a more valid reading (as outlined in this NPS article).

Preparation

• Avoid smoking and caffeine before measurements

• Comfortable ambient room temperature

• Not being under significant stress or pain

• Measurements to be taken before eating, medications or vigorous exercise

Note: If you are taking blood pressure medication, measurements before medication allow us to measure your blood pressure when medication effect is theoretically at its lowest.

Positioning

• Both feet on the floor with legs uncrossed

• Weight of arm and back supported

• Appropriate sized cuff placed on bare arm, with cuff at heart level

After putting the cuff on your arm, sit for five minutes in a quiet environment without any distractions such as your phone or TV. Now, we are ready to take blood pressure readings!

Image from this RACGP article outlining principles for the standard method of home blood pressure monitoring.

Taking Blood Pressure Measurements

Use your automated machine to:

• Take the first reading. I generally recommend patients to discard and not record this reading.

• Wait 1-2 minutes before taking and recording another reading.

• Likewise, wait another 1-2 minutes before taking and recording the final reading.

Therefore, two readings are recorded with every session.

To improve the reliability of our measurements, blood pressure is measured in this manner consistently over a period of at least 5 days.

We typically aim for recordings over a 7 day period, twice a day with measurements at the same time every morning and every evening on the same arm.

Note: If you are on blood pressure medication, and the blood pressure appears too high or too low, do NOT change treatment without first consulting your doctor.

Recording Home Blood Pressure Readings

All this information should be recorded either on paper or electronically. The average blood pressure of days 2-7 is then calculated; preferably in the format of a morning and evening average.

The Heart Foundation has both a print-friendly PDF and an electronic excel spreadsheet to record these measurements.

One of my friends has even extended this spreadsheet to include three rather than two trials to improve the reliability of measurements.

Home Blood Pressure Diary Extended

.xlsx

Download XLSX • 158KB

Interpreting Results and Next Steps

After completing your 7 days of measurements, it is time to bring these results to your doctor and have a discussion! Generally results in excess of 135mmHg systolic, and/or 85mmHg diastolic can be diagnostic of high blood pressure or inadequate control of hypertension. However, our target for blood pressure should be individualised, for instance in diabetes or pregnancy. Your doctor will have more to share about the nuances of interpretation and next steps in management.

Your efforts will allow your doctor to make a better-informed decision about your blood pressure management, while you have taken charge of your health and gained an invaluable tool in the management of blood pressure going forward!

Summary image below from the AHA

Extended Working Hours

More than seeing my GP role as a job, I view the privilege of caring for patients as a service which has been my absolute delight. It has indeed been a pleasure to be able to serve the local community in the Hornsby area and I am excited to announce that my hours will be increased from Monday 23rd August 2021. I will be opening bookings for all weekdays, including earlier 8am starts on Tuesday and Wednesday for those early birds. Saturdays will continue to be available at a 1 in 3 cadence.

While we continue through this challenging time in Sydney, I am so thankful for the vaccine work that Summer's Avenue has been providing. I have been working with many other GPs at the practice to roll out hundreds of Covid-19 vaccines every week and we were surprised to find Hornsby listed among the highest vaccination rates in Sydney!

If you have not been vaccinated yet, visit the eligibility checker and consider booking in with us. We will be more than happy to answer any vaccination questions you may have to help your decision.

While there is much need to participate in the vaccine effort, normal diseases don't just go away. I am hoping that the extra hours I am serving allows for both increased sessions of vaccine delivery as well as more opportunities to engage patients in their ongoing health needs. Looking forward to serving more in Hornsby!

One Easy Trick for High Blood Pressure | White Coat Hypertension

You're sitting in the GP's office and the GP suggests measuring your blood pressure. "That's fine," you think as they put the cuff on your arm. "It's always been normal in the past."

The strange sensation of the cuff tightening around your arm makes you feel uncomfortable. You don't remember it being so tight the previous times, but it will be over soon. Once the cuff deflates, you look over to the GP to see what they would say and they tell you that the blood pressure seems a bit high…

This is how it starts for most patients who eventually get diagnosed with high blood pressure, also known as hypertension. While a single high blood pressure reading is not enough to form a judgement, patients who have high blood pressure consistently are often diagnosed with the condition.

White Coat Hypertension: Do you really have high blood pressure?

Usually when GPs obtain a single high blood pressure reading, it is prudent to repeat blood pressure measurements at least a few times on that visit to ensure it is not an outlier. I've also heard it said that the ideal is for the doctor to even leave the room while the blood pressure is taken! Though I've never seen that done in actual practice.

If it remains high despite multiple trials, your GP may decide to bring you back on another day to repeat your blood pressure reading. Perhaps it was the coffee you drank that morning or the fact that you were talking excitedly or about to receive a vaccine and felt apprehensive about the needle. Even if the blood pressure remains high on multiple visits, it still doesn't necessarily mean you have high blood pressure.

You may have heard of the white coat effect and it really does affect some patients. It may even affect you, whether you are aware of it or not. You may think you're relaxed and comfortable, but even being in the different environment of a consultation room can have the effect of raising blood pressure.

If blood pressure readings are high in the clinic on more than one occasion, it is time to pursue a diagnosis. Do you truly have blood pressure, or is it just white coat?

One Easy Trick: Home Blood Pressure Monitoring

At this point, it is probably ideal for home blood pressure to be measured in some form. One method is using a 24 hour ambulatory blood pressure monitor available through most pathology services at a cost. If these are ordered by the GP, the final report displays beautiful graphs of your blood pressure over a 24 hour period amongst various other statistics (example on page 3 of this article).

As useful as this is, there are some limitations. For example, a GP makes the decision to start you on blood pressure medication after confirming hypertension using the 24 hour monitor. On following visits, the medication has been increased further but the blood pressure only improves slightly. Is this inadequate treatment or a component of white coat again?

Over the course of a few years, patients may be started on blood pressure medication, change medications, increase or decrease in weight… many factors can improve or worsen blood pressure control over a period of time. While it is possible to repeat ambulatory blood pressure every time major changes occur, my preference is to lean towards investing in a home blood pressure machine.

Taking Measurements into Your Own Hands

Usually around the same cost as a single ambulatory blood pressure test, a patient can invest in a blood pressure machine from the local pharmacy. Additionally, blood pressure machines are generally covered by private health insurance with supporting letter from the GP.

While these machines need to be calibrated occasionally, over the long term they prove an invaluable tool to help us diagnose and manage hypertension. In short, it gives the patient more control in monitoring their own condition and helps us consistently track how their actual blood pressure is going.

In future weeks, I will discuss how home blood pressure monitoring is performed, and some broader thoughts on its role in managing hypertension.

Broader Reading: Beyond the Basics

• Quite an old but interesting Australian study, showing that 16 of 62 patients newly diagnosed with hypertension in fact had normal blood pressure on ambulatory monitoring and did not actually require blood pressure medication.

• Some more recent findings show that untreated white coat hypertension may cause increased risk of heart disease, which directly contradicts suggestions from a previous study. While this doesn't mean GPs should overtreat individuals who don't need medication, it does present some nuance to monitoring of individuals with white coat hypertension. This can be an interesting point of discussion with your GP.

• What do patients feel about undergoing ambulatory blood pressure testing? Can we predict what demographic has white coat hypertension? This article provides some interesting insights.