Here are a few reasons why Aktiia may differ from the values you see with a regular cuff:
Continual vs. Snapshot / Aktiia’s 2-hrs average vs. single on-demand cuff reading
In the detailed Blood Pressure screen of the Aktiia mobile application (located in the “Insights” tab and accessible by clicking anywhere on the blood pressure card or on the arrow in the top-right corner of the card), each circle and diamond displayed on the main graph represents the average of all measurements taken within the selected timeframe. Circles represent systolic blood pressure, while diamonds represent diastolic blood pressure. Due to averaging and depending on the amplitude of your BP variations within this timeframe, the values displayed may differ from a single measurement taken with another BP cuff.
We use measurement averaging because this is the standard practice that physicians and hypertension guidelines recommend.
Your blood pressure (BP), even at rest, is not static. Your blood pressure is dynamic and can change every time your heart beats. By its very nature, the oscillometric BP cuff enables only episodic measurements, providing a low-resolution, static snapshot of your BP pattern.
Acute meal ingestion and caffeine or nicotine use can affect BP readings negatively, leading to errors in measurement accuracy of the one-off cuff. A full bladder can lead to an error in systolic BP of between 4 mm Hg and 33 mm Hg, compared with the white-coat effect, which can have an error of up to 26 mm Hg.
Not all cuffs are made the same
Electronic blood pressure units, also called Non-Invasive Blood Pressure (NIBP) machines, sense air pressure changes in the cuff while “listening” for the changes in the blood flowing through the brachial artery. Sensors in the Cuff estimate the Mean Arterial Pressure (MAP) and your pulse rate. Software in the machine then uses these two values to calculate the systolic and diastolic BP. Differences of more than 10 percent in pulse readings will seriously alter the unit’s calculations and produce incorrect systolic and diastolic values on the display screen.
Inflating a regular cuff has also been demonstrated to elevate a wearer's blood pressure. Aktiia's optical measurement is automated, and you do not know or feel when the reading occurs. This can often lead to lower values using the Aktiia product because we minimize the stress effect.
Incorrect body position, cuff placement, and sizing
Blood pressure tends to drop in the standing position compared with sitting or lying down. Your Systolic BP is highest when lying down compared to the other positions. When measuring BP with a Cuff, you should be sitting, with your arm supported at mid-heart level, legs uncrossed, and not talking. Measuring BP with your arm positioned above heart level will produce a false BP. Falsely high readings will be obtained whenever your arm is positioned below heart level. Crossing your legs while sitting increases systolic BP by 2 to 8 mm Hg.
Blood pressure measurements can be made at other locations, such as the wrist, fingers, feet, and calves but will produce varied readings depending on the distance from the heart. This is due to the naturally occurring hydrostatic pressure drop in your body.
An incorrectly sized cuff is also a common error. If the BP cuff is too large, it will give falsely low readings, while an overly small cuff will provide falsely high readings.
It is important to note that Aktiia is accurate in different body positions. The Aktiia monitor can perform reliable BP measurements irrespective of the body position - standing up, sitting, or even lying down.
In summary
While there may be minor differences between Aktiia and a regular cuff, you can have confidence that Aktiia has rigorously tested its technology in multiple clinical studies across a broad range of people. We have the endorsement of leading hypertension experts and have been granted the CE Mark as a Class IIa medical device. You can find more about the clinical trials that supported the commercialization of Aktiia on our dedicated page here: Evidence - Clinically Validated Blood Pressure Monitoring - AKTIIA.