In choosing a blood pressure monitor the accuracy of the device should be the most important consideration. Secondly, the reliability of the readings should be considered. Thirdly, the ease of use of the device should be taken into account.

 Accuracy refers to the degree to which the blood pressure readings obtained actually reflects the true pressure within the arteries at the time that readings are performed. Reliability on the other hand, refers to the degree to which blood pressure readings reflect the average arterial pressure within a 24-hour period of time.

The technique of the individual performing the measurements, the attributes of the measuring device, and arm selection are the main variables that determine accuracy. The frequency of readings, the recording of the readings and understanding the many factors that can affect blood pressure are the main variables that determine the reliability of the readings.

One of most common reasons for an inaccurate reading is malpositioning of the arm in relationship to the heart when a reading is being taken. If the reading is taken with the arm hanging down well below the level of the heart the reading is likely to be spuriously higher than the true pressure, and if the arm is positioned higher than the level the heart the reading is likely to be spuriously low. Parenthetically, if the arm is not supported by a stationary structure such as a stand or another person if someone else is performing the reading, but is held in position against gravity by the individual on whom reading is being performed, a certain degree of isometric exercise is being performed which can have an effect on the reading.  If achieving proper arm positioning is a problem, a wrist monitor with the Omron patented advanced positioning sensor technology is a likely solution. The device will alert you with a characteristic beep signal and will not begin to read at all if the arm is not in proper position. It allows you to take readings sitting and lying, knowing that at the accuracy of your readings is not being compromised by improper arm position.  Since sitting readings are performed with the arm flexed at the elbow and supported by the hand of the contralateral arm isometric exercise is not performed during the readings.

Another very common cause of an invalid blood pressure reading is an improper cuff size in relationship to the circumference of the upper arm. Generally, if the cuff size is too small relative to the upper arm circumference the reading will be higher than the true arterial pressure. Conversely, if the cuff size is too large for the circumference of the arm the reading will be lower than the true pressure. The cuffs used for upper arm measurements come in several adult sizes. There is no standardization of the sizes between manufacturers, but for the sake of practicality the primary sizes are adult, adult large and thigh. Some manufacturers also produce an extra large adult size which is the size in between adult large and thigh.  To ensure use of the appropriate cuff size the American Heart Association recommends that you measure your upper arm circumference and select a cuff with a specified arm circumference range that includes your measurement. If your arm circumference exceeds that of the largest cuff available you should consider one of the wrist monitors which generally accommodate wrist circumferences between 13.5 cm to 21 cm or 5.25 inches to 8.5 inches.

If the cuff is not inflated high enough before deflation is begun the systolic reading might be lower than the true arterial pressure. If the inflation and deflation process is interrupted and repetitive the overall reading is likely to be inaccurate. To eliminate the inaccuracies associated with these technical flaws, an automated unit, particularly one with the IntelliSense technology is a likely solution. IntelliSense is an exclusive technology developed by Omron which allows monitors to automatically inflate and deflate at a level optimal for each individual user, thus assuring accuracy and comfort. It requires no adjustments.

There are generally a few and sometimes several point differences in blood pressure readings between arms.  The dominant arm i.e. the right arm in a right-handed person and the left arm in a left-handed person usually has the higher reading, which is considered to be the reading most reflective of the pressure within the arteries of the body in general. Thus, that arm should be arm in which readings are taken. Some of the blood pressure devices, particularly the wrist monitors are designed to take readings from left arm or wrist respectively, which means that your readings might be invalid if your are right-handed. A likely solution to this problem, even if you are left-handed but have higher readings in the right arm would be one of the units that can be adjusted to take readings from the desired arm or wrist.

 If you are visually impaired and have difficulty reading the screen of a blood pressure measuring device there are some quality talking units that will give you an audio reading in addition to an LCD display.

 The American Heart Association recognizes certain blood pressure monitors as approved, tested and validated by The Association for the Advancement of Medical Instrumentation, the British medical Society and The International Protocol for the Validation of Automated Blood Pressure Measuring Devices.  A list of validated monitors is available at the Dabl Educational Trust Web site* and the British Hypertension Society Web site*.

The fact that a particular brand or model monitor is not on the list means that it either did past the tests or has never been subjected to the approval and validation testing protocol, which is the case with many of the newer devices which have been launched since the last lists were generated in 2008. Based on my experience with blood pressure monitors, the low-end priced units, i.e. $24.99- $39.99 range tend to be somewhat erratic in their readings whereas units that began at the intermediate $50 price range tend to be much more accurate and consistent. The higher-priced units are not necessarily any more accurate than the medium priced units but do provide some of the aforementioned benefits as well as the benefit described in the following paragraph.

The sine qua non for reliable blood pressure readings is performing multiple readings in a 24-hour period which is the basis for experts’ in the field of hypertension current recommendation to perform three readings in rapid succession in the morning and three readings in rapid succession at night. There are monitoring machines that will do this, average the readings, and allow downloading of the information into an accompanying software program installed on your PC. The information can then be presented to your doctor for analysis and proper integration into your treatment course.