Correct BP Measurement vs Hypertension

It seems so easy, after all we do it everyday. I one of the common medical procedures done in clinics. There is a say that goes as this “ don’t overlook small things” in this topic nothing can be further from the truth of the saying.

First things first

Definition: Is the force exerted by the circulating blood against the walls of the arteries. The results are given in two numbers. The first is SBP or systolic blood pressure which is the pressure caused by the heart contracting and pushing out blood. The second number is DBP or diastolic blood pressure which is the pressure when your heart relaxes and fills with blood.

?Blood pressure is measured by a BP measuring device. They come in different types and mechanisms of measurements. These includes manual sphygmomanometers, which include mercury and anaeroid devices; and automated sphygmomanometers (O'brien et al 2001) . Mercury devices are now rarely used due to the health risk that mercury carries.

So in many clinics we use aneroid devices and automated ones. Aneroid devices requires to listen for Korotkoff's sounds and reading the number at which these sounds are heard thus requiring good eye hand coordination and good hearing for correct measurement. This obviously increase the risk for errors. Automated devices uses oscillometric technique which involves conversion of the signals obtained by using a set of algorithms set in the device. They allow little margin of errors when are validated, functional and well maintained e.g. regular battery changes.

Types of BP measuring devices, mercury device, aneroid device and automated devices.

Does it matter?

One can rightfully ask the question “does it matter how we measure BP, why all the fuzz?”. The answer is yes it does matter! We know that hypertension or elevated blood pressure significantly increases the risks of heart, brain, kidney and other diseases. An estimated 1.28 billion adults aged 30-79 years worldwide have hypertension, two-thirds living in low- and middle-income countries. An estimated 46% of adults with hypertension are unaware that they have the condition. Less than half of adults i.e. 42% with hypertension are diagnosed and treated. Approximately 1 in 5 adults i.e. 21% with hypertension have it under control. Hypertension is a major cause of premature death worldwide (WHO, 2021).

BP measurement is where hypertension is first diagnosed, treatment initiated and monitored and through BP measurement decisions are made to increase doses or add antihypertensive if the BP remains uncontrolled. Therefore BP measurement is the gateway through which hypertension and cardiovascular disease is managed. This means errors in BP measurement can have huge consequence on an individual patient, healthcare system and the public at large.

Overestimating BP equates to about 30 million American adults receiving unwarranted antihypertensive treatment leading to uneeded labelling, side effects and costs. Wheras underestimating leads to missing about 21 million people who probably have hypertension leading to missed opportunities for cardiovascular risk reduction (Jones DW et al 2003). Data is lacking for our country Tanzania and the African region of how much underestimation or overestimation of BP readings.

All of these emphasize on the importance of correct BP measurement in?clinical practice so that patients gets proper diagnosis and management.

?

What does the evidence says:

The problem starts at the grassroots! The magnitude of this can captured in the study done in United States of America.?One hundred fifty-nine students from medical schools in 37 states attending the American Medical Association’s House of Delegates Meeting in June 2015 were assessed on an 11-element skillset on BP measurement. Only one student demonstrated proficiency on all 11 skills.

The mean number of elements performed properly was 4.1.?These 11 skills included (1) resting the patient for 5 minutes prior to the measurement or expressing intent to do so; (2) legs uncrossed; (3) feet on floor; (4) arm supported; (5) correct cuff size; (6) cuff placed over bare arm; (7) no talking; (8) no mobile phone use or reading; (9) BP measurement taken in both arms; (10) correctly identifying BP from the arm with the higher reading as being clinically more important when asked; (11) correctly identifying which arm to use for future readings (the arm with higher BP) (Rakotz M K et al 2016)

A study done in Spain reported ?on the level of knowledge about correct blood pressure (BP) measurement procedures among 175 third-year and 176 sixth-year students at a medical faculty, and 58 third-year students at a nursing college. Only 51.8% of all students thought that they knew how to measure BP correctly (28.6% in the third year, and 61.9% in the sixth year at the medical faculty, and 91.4% at the nursing college).

Among sixth-year medical students, 12.5% knew the appropriate cuff size, 35% that the stethoscope diaphragm should not be placed under the cuff, and 43% that the cuff deflation rate affects BP measurement. Among nursing students, 33% knew the appropriate cuff size, 22% that an outpatient’s BP should be measured more than once during each visit, and 55% that a diagnosis of hypertension can only be made if the BP is elevated on more than one visit (González-López J J et?al 2008).

In a descriptive cross-sectional study done in Nigeria, convenience sampling was used in selecting 211 respondents (82 doctors and 129 nurses). One hundred and fifty (71.1%) had not read the guidelines on BPM since graduation. A large proportion of the respondents had poor knowledge of BPM [n=155(73.5%)], and this was more pronounced among the nurses. The study concluded that the knowledge of BPM among doctors and nurses is suboptimal in the study’s practice setting. The poor knowledge spans across patients’ preparation, BPM technique, cuff selection and patients’ position (Ojo O S et al 2018).

It is clear that there is a problem in measuring BP accurately in clinical setting all over the world. The following are errors due to occur during BP measurement.

Errors encountered

Patient related: Meal intake, caffeine or nicotine intake. Full bladder can also interfere with BP readings. It is essential for the patient to rest for at least 5minutes and to not have taken caffeine, food or full bladder or any physical activity 30minutes prior BP measurements.

Procedure related: Inaccuracies during the procedure can include crossing legs at the knees, talking during BP measurement or having a patient heart below heart level. A fast deflation can also reduce accuracy.

Equipment related: If the cuff is too small or large errors are sure to occur. Using non-validated automated BP measuring devices means there is high chance of getting incorrect readings. A validated BP measurement involves demonstrating that the device meets the accuracy requiremnts of international BP measurement standards. To verify that the device you are using is validated you can visit the following website www.dableducational.org or similar sites found in the internet.

Manual BP devices should be regularly recalibrated to have accurate BP measurements. Automated Devices are preferred as they reduce the bias of the observer.

Physician or health professional related: Time constraints are one of the commonest source of errors. Failure to include a 5-minutes rest period is another common error as is the failure of taking multiple measurements, talking during measurement procedure and using an incorrect cuff size. Rounding off the reading should be avoided.

All these errors can lead to overestimation or underestimation of BP and thus inaccurate diagnosis and management:

?

?

How to correctly measure BP

From the 2020 International Society of Hypertension Global Hypertension Practice Guidelines the following are key areas when you want to correctly measure BP. They will be presented by images and tables:

There are several guidelines in how to measure BP. But as we have seen most of the times aren’t followed.

In this article I will share the 5 steps of accurate measuring BP I learned in the online course (one of strategies in educating healthcare workers on correct BP measurement) Fundamentals For Implementing A Hypertension Program provided by Johns Hopkins Bloomberg School of Public Health through Coursera:

Before measuring someone’s blood pressure, make sure they haven’t used any tobacco products or had caffeine-rich food or drinks for at least the last 30 minutes. You should also make sure that they don’t need to use the restroom and aren’t in any pain or discomfort - because these factors can raise the blood pressure. These are five essential steps for measuring blood pressure with any type of device.

Step 1. Make sure that the person is sitting on a chair with their back supported, legs uncrossed, and feet flat on the floor.

Step 2. Choose the correct cuff size for the person whose blood pressure you are measuring. Ideally, you should measure a person’s upper arm at the mid-point and choose the indicated cuff size. If this isn’t practical, use the range marks on the cuff as your guide.

Step 3. Wrap the cuff around the person’s bare arm. For this to happen, an individual may need to take off excess clothing or roll up long sleeves. If a sleeve is rolled up, you must make sure that the sleeve is not too tight on the upper arm because this can make the person’s blood pressure appear lower than it really is. In some circumstances, a bare arm may not be practical and in that case, thin clothing may be acceptable.

To place the cuff correctly, find the pulse at the bend in the elbow, and make sure you align the arrow on the cuff directly over it. The cuff should be wrapped snugly, and fastened with Velcro, with the lower edge about 2 to 3 cm above the bend at the elbow. There should be enough space to slip two fingers under the bottom edge of the cuff.

Step 4. Place the person’s arm on a flat surface like a table, with the middle of the blood pressure cuff about the same level as the person’s heart. With the person’s arm supported by the table, he or she should be relaxed. They should NOT have to hold their arm.

Step 5. Have the person completely rest for 2 to 5 minutes before and during the blood pressure measurement. This is important because talking, texting, and even reading can give a false reading of elevated blood pressure. Taking these five steps each time is necessary for accurate blood pressure measurements.

?

NUGGETS

Assess how BP is currently measured in your clinic and identify sources of errors.

Build knowledge in BP measurement. Attend CME activities regarding BP measurement e.g. take the free online course at coursera of Fundamentals for Implementing a Hypertension Program by Johns Hopkins University. Read and apply current guidelines on correct BP measurement one way to start is the 2020 International Society of Hypertension Global Hypertension Practice Guidelines.

Train care team on techniques. Train your fellow health care workers. Add posters in clini measuring area for reminders.

Maintain the culture of adherence to correct BP measurement techniques.

?

Evidence shows that as clinicians we need to review our skills in BP measurements. Furthermore we need to share the knowledge of accurate BP measurement in our places of work.

Because clinical decisions are influenced by office BP readings, organizations should examine their BP measurement processes to identify areas for attention.

We also have to remember that knowledge alone although necessary but is insufficient to curb incorrect BP measurement. Strategies that involve systems change, technology, and education may be the most promising (Hwang et al 2018). Example of a system change includes curriculum changes on BP measurement in medical training to be emphasized, using 'validated' automated BP measuring devices to reduce observer bias, educating the healthcare sector by doing research to highlight the burden and areas for improvement locally and globally plus educating patients on the components of correct BP measurements.

The ideal and proper BP measurement requires an estimated 7 more minutes than a casual measurement (Ray G M et al 2012). Thus, effort have to be made to ensure that accommodation of proper BP measurement doesn’t interfere with work load and patient flow in a busy clinic. A supportive organizational culture (eg, endorsement from managers and physicians) is needed to establish and maintain improvements in BP measurement (Hwang et al 2018).

As time goes BP measurement will be simplified by the progressive use of automatic devices, this does not mean that healthcare professionals can cease to pay attention to patients’ posture, appropriate cuff size, condition in which BP is measured and multiple BP measurement in one visit.

We have seen that part of the problem arise since the medical school years of training. Rakotz MK et al concluded that their findings suggested that changes in medical school curriculum emphasizing BP measurement are needed for medical students to become, and remain, proficient in BP measurement. Measuring BP correctly should be taught and reinforced throughout medical school, residency, and the entire career of clinicians (Rakotz M K et al 2016).

It’s a high time now that our own curriculum gets reviewed and updated to include more vigorous training of healthcare professionals during college on how to properly measure BP. Patients should also be empowered to know their responsibilities during BP measurement like not talking over the phone or to the healthcare provider. Placement of images reminding the components of correct BP measurement on the clinic area is another efficient strategy to remind all of the importance of correct BP measurement.

CONCLUSION

We can therefore conclude that to achieve correct BP measurement to our patients we need a team cooperation between all health stakeholders including healthcare providers, managers of hospitals and the ultimate target of all, the patients themselves.

Thank you for reading up to here. Lets go make the necessary changes in wherever we are!

?

?

?

?

?

?

?

?

?

?

REFERENCES

2020 International Society of Hypertension Global Hypertension Practice Guidelines

American Heart Association. Scientific statement. Recommendations for blood pressure measurement in humans and experimental animals. AHA. 2005.

ESH (European Society of Hypertension) Guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring. J Hypertens. 2008; 26: 1505-1530.

Fundamentals For Implementing A Hypertension Program provided by Johns Hopkins Bloomberg School of Public Health through Coursera.

González-López JJ et al (2008). Knowledge of Correct Blood Pressure Measurement Procedures Among Medical and Nursing Students. Rev Esp Cardiol. 2009;62(5):568-71.

https://www.ama-assn.org/delivering-care/hypertension/quick-start-guide-measuring-bp-accurately-your-practice . Accessed on 29/03/2022.

https://www.ama-assn.org/delivering-care/hypertension/4-big-ways-bp-measurement-goes-wrong-and-how-tackle-them.Accessed on 29/03/2022 .

https://www.who.int/news-room/fact-sheets/detail/hypertension . Accessed 31/3/2022

Jones DW et al. Measuring blood pressure accurately: new and persistent challenges. JAMA 2003;289:1027-1030.

Kevin O. Hwang, Aitebureme Aigbe, Hsiao-Hui Ju, Victoria C. Jackson, and Emily W. Sedlock (2018). Barriers to Accurate Blood Pressure Measurement in the Medical Office. Journal of Primary Care & Community Health Volume 9: 1–7.

Michael K. Rakotz, Raymond R. Townsend, Jianing Yang, ?Bruce S. Alpert, Kathleen A. Heneghan, Matthew Wynia, Gregory D. Wozniak (2016). Medical students and measuring blood pressure: Results from the American Medical Association Blood Pressure Check Challenge. J Clin Hypertens. 2017;19:614–619. DOI: 10.1111/jch.13018

O'Brien E, Waeber B, Parati G, Staessen J, Myers MG. Blood pressure measuring devices: recommendations of the European Society of Hypertension. BMJ. 2001;322(7285):531-536. doi:10.1136/bmj.322.7285.531

Ojo OS, Sogunle PT, Malomo SO, Adeyemo AJ (2018) Knowledge of Blood Pressure Measurement (BPM) among Tertiary Hospital Staff in South West Nigeria and its Related Socio-Demographic Determinants. J Family Med Community Health 5(3): 1153.

Ray GM, Nawarskas JJ, Anderson JR. Blood pressure monitoring technique impacts hypertension treatment. J Gen Intern Med. 2012;27:623-629.