The measurement of blood pressure has now become commonplace. Anyone can now buy or borrow a home BP monitor that is more accurate than anything that was produced in the last 100 years. However, it is important to use the device in the correct manner to get accurate and reliable results.
A few basics about blood pressure
There are a few undeniable facts and rules about digital BP monitors. These rules are very important but are often forgotten. They are worth repeating here.
Your digital blood pressure monitor does not magically transform you into a doctor.
Your BP monitor is probably really easy to use. It probably inflates automatically, makes cool sounds and then incredibly gives you a clinically accurate result. Isn’t that great? It’s child’s play to measure your BP… Well it certainly feels like it… However, your blood pressure monitor is not intended to replace regular medical examinations. It is there to be used together with your doctor as a tool to better manage your blood pressure. Only a physician is qualified to interpret changes in your BP.
When in doubt, ask your doctor for advice.
The first commercially usable BP monitor was manufactured at the turn of the century. In the 70ies digital devices made their appearance and by the 90ies they were commonly available to the untrained public. According to the statistics from our various service departments worldwide, an incredible 94% of all “faulty” devices sent back to manufacturers show absolutely no problem at all and are simply badly used. Faults can range from silly mistakes such as batteries being put in upside down to using the wrong size cuffs. We have even received devices where the batteries were still wrapped up in plastic. Your doctor has been working and studying blood pressure for most of his life and is an expert on the subject. Please ask him to show you how to correctly use your monitor.
Never make adjustments to your medication unless you are advised to do so by your physician.
As mentioned earlier, your BP monitor does not replace a regular medical examination. Your doctor has prescribed medication for you after a careful examination and it can be very dangerous to make your BP fluctuate by changing your medication or by reducing the dosage on your own. If you suspect that your blood pressure medication is wrong because you regularly get low or high BP readings on your device at home, please keep a regular record of your blood pressure for at least three days in a row and then contact your doctor. He will appreciate the fact that you present all the evidence to him in a clear format. To do so, use a BP passport. There is a multitude of blood pressure passports available out there. You can also download one that I have designed to fit in your wallet on my diabetes company website.
You should know that when the doctor at his office measures BP, there is a multitude of reasons why the BP measured by the doctor can be higher or lower than the one measured at home. One of the most common reasons is what is called “White Coat Hypertension” and occurs when the patient is subconsciously nervous at the medical examination and this makes his BP go up. On average, the systolic pressure will vary by about 30 points during the day, so it is normal for you to have a different blood pressure at home than at the doctor.
This is one of the main advantages of home monitoring, in that it gives you a much better overall picture of your blood pressure over time than the single BP reading that is taken at the doctor’s office.
Do not believe in urban legends or marketing hype when it comes to your health.
When making decisions about your health, question what is commonly believed. There are many “urban legends” about blood pressure, such as salt intake, anti-oxidants in grape seeds and drinking alcohol every day is good for the heart. Although there might be a grain a truth to these kinds of stories, they are not necessarily completely true and are certainly misunderstood. In some of my blogs, I try to demystify these stories.
Digital blood pressure monitors are for adults.
There are 2 main obvious reasons why children should not use digital BP monitors. The most important one is that it is sometimes very difficult to find a cuff that is of the correct size for a child. The second reason is much more subjective, but as important as the first. When you measure a blood pressure the cuff has to be inflated to 30 or 40 points higher than the systolic pressure and this can prove to be quite uncomfortable for children, especially infants who cannot express themselves. Often, as a result of this, they move their arm or cry or get stressed, and this negates any diagnostic value of the reading. Children should not use a digital BP monitor unless it is under the strict supervision of an adult.
Another reason why children should not use automatic blood pressure monitors is that the amplitude of the pulse waves generated by a child is very small (an infant has less than 1/2 liter of blood in his body so by definition his BP is quite low) and more often than not an oscillometric (digital) blood pressure monitor will not “hear” the first “Korotkov” sound on which the BP is calculated and will thus give an artificially low result for the blood pressure.
So what is blood pressure really?
Blood pressure is the measure of the force that the blood exerts on the inside walls of your arteries. BP is expressed as a ratio (e.g. 120/80). The first number is called the systolic pressure, and is the pressure in the heart when it is beating. The second number is the diastolic pressure, and is the pressure in the heart when it is resting (between beats). BP is historically expressed in mmHg, or millimeters of mercury, even though there is no longer any mercury used in electronic devices. It is interesting to note that in most French speaking countries, BP is expressed cm/Hg, or centimeters of mercury, which means that the doctor would express your BP as 12/8 (twelve over eight) instead of 120/80.
It is also interesting to note that most doctors use rounded figures for blood pressure and will use the number 120/80 for any value considered as being in the normal range, so instead of telling you that your BP is 134 over 76, he will quite often just tell you that you are 120 over 80. One could almost say that 120/80 is a generic number for normal BP. We have noticed over the years that this is often a cause of complaints from patients who do not understand that the doctor is using this number (120/80) as a reference only. Over the past 15 years, we have received hundreds of letters from patients telling us that they think that their device is inaccurate. An example is Patient X who states that she would like a refund on her blood pressure monitor because “it is giving me a result of 133 over 84 and my doctor told me that I was 120 over 80“. In fact the result of 133/84 of Patient X is much more accurate than the doctor’s estimation, but it is of no medical consequence because both results are perfectly normal. In this case, the doctor of Patient X just gave her the “generic” figure for a normal blood pressure, which is 120/80.
When the blood pressure is measured, it should ideally fall within a specific range. Knowledge of this range and of your BP should allow you to better manage your health. In general, it is better to have a lower blood pressure than a high one. With high blood pressure, the heart works harder, your arteries get damaged and your chances of a stroke, heart attack, or kidney problems are greater.
Your blood pressure fluctuates greatly in the course of a day. Many factors, such as exercise, conversation, alcohol, stress, movement, food or smoking can cause your BP to rise and fall temporarily. This is why it is important to always measure and record your blood pressure at the same time and under the same conditions every day and to be completely relaxed when you measure your blood pressure.