BPM Measurement Guidance
Variability & Best Practices
The following notes were taken from a variety of sources including several PubMed™ publications, the CDC, and the American Heart Association.
Tenovi also a list of Best Practices and Tips on our Tenovi Blood Pressure Monitor Support Page.
Variability
Blood pressure is not a fixed number—it is highly variable and changes from beat to beat as well as throughout the day based on multiple factors. A fluctuation of up to 20 mmHg is expected and completely normal. Many things influence these changes, including time of day, food and drink (especially caffeine), stress levels, body position, and even whether you’re talking while measuring.
“Blood pressure and its variability: classic and novel measurement techniques”
The intrinsic dynamic nature of BP remains underappreciated. On a beat-to-beat basis, BP levels can vary markedly (from –24 mmHg to 33 mmHg) in response to usual extrinsic and behavioral factors4 (Table 1). The degree of BP variability (BPV) also differs between individuals in the short term and long term.
“Factors Affecting Blood Pressure Variability: Lessons Learned from Two Systematic Reviews of Randomized Controlled Trials” – Vijaya M Musini
Blood pressure (BP) measurements are highly variable. This is a fact that is commonly not appreciated and variability of blood pressure in an individual could be as important as the magnitude of the blood pressure.
Measured blood pressure varies due to a large number of factors such as measurement technique, accuracy of equipment, and multiple patient factors such as anxiety. Even if these factors are controlled, blood pressure is subject to biological variation from beat to beat, minute to minute, and day to day.
Each blood pressure measurement is therefore analogous to a single sample from a population of blood pressures. However, it is a patient’s mean blood pressure over months and years that are thought to determine his or her risk of cardiovascular disease.
In order to increase the precision of the estimated blood pressure, clinical diagnosis is based on the average of 2 to 3 measurements taken after resting for 5 minutes in a non-stimulating environment. Despite such standardized procedures, BP remains highly variable both within and between individuals.
“Sources of inaccuracy in the measurement of adult patients’ resting blood pressure in clinical settings: a systematic review” – Noa Kallioinen
As demonstrated by these studies, the accuracy of BP measurement can be affected by many factors. A single BP value outside the expected range should therefore be interpreted with caution and should not be seen as a definitive indicator of clinical deterioration or lead to an alteration in clinical care without the support of other evidence.
Where a BP measurement indicates an abnormally high or low level, further measurements should therefore be taken and the average used (instead of the original reading) before deciding on appropriate clinical interventions.
Tips for Accurate Blood Pressure Measurement
- Take Multiple Readings: Where a blood pressure measurement indicates an abnormally high or low level, further measurements should be taken and the average used (instead of the original reading) before deciding on appropriate clinical interventions.
- Consistent Conditions: Try to measure your blood pressure under similar conditions each time (e.g., same time of day, same body position).
- Avoid Caffeine and Stress: Avoid consuming caffeine or engaging in stressful activities before taking a measurement.
- Stay Still and Quiet: Sit quietly for a few minutes before and during the measurement to avoid fluctuations caused by movement or talking.
Measuring Your Blood Pressure – CDC
Learn the correct way to have your blood pressure taken, whether you’re getting it checked at the doctor’s office or checking it yourself at home. Use this checklist:
- Take your blood pressure at the same time every day.
- Take at least two readings, 1 or 2 minutes apart.
- Don’t eat or drink anything 30 minutes before you take your blood pressure.
- Empty your bladder before your reading.
- Sit in a comfortable chair with your back supported for at least 5 minutes before your reading.
- Put both feet flat on the ground and keep your legs uncrossed.
- Rest your arm with the cuff on a table at chest height.
- Make sure the blood pressure cuff is snug but not too tight. The cuff should be against your bare skin, not over clothing.
- Do not talk while your blood pressure is being measured.