Are you aware of Why is first bp reading inaccurate??

The first blood pressure reading should not be discarded. The American Heart Association recommends taking at least two or more measurements and using all of them. Two to three readings minimize random errors and provide more accuracy for blood pressure estimation.

You may be thinking if the first reading is always higher, why should it be used? This blog post will answer that question and explain how it can be corrected. In addition, I’ll explain why the first reading is high and how long you should wait between the readings.

BP Tip: Did you know you can lower BP naturally by changing how you breathe a few times a day? There’s a device approved by the FDA and The American Heart Association gave it the thumbs up. It simply guides your breathing for you a few minutes a day which has been proven to lower blood pressure. You can check it out in the manufacturer’s website by clicking here.

Disclaimer: Some links in this article are affiliate links which means I may earn a small commission at no extra cost to you. As an Amazon associate I earn from qualifying purchases.

If you prepare for the first blood pressure reading and follow all the appropriate steps, the first measurement is beneficial for you to use. The blood pressure guidelines states at least two or more measurements should be taken. They recommend this for both medical staff and you at home 1.

Blood pressure can fluctuate throughout the day and even a few minutes apart 2. Measuring three times gives you more information to use while estimating your pressure and can eliminate a random error. The errors can be caused by the monitor or how you prepared or took your measurement.

Later, read my blog post on fluctuating blood pressure and learn 15 reasons for inconsistent readings, Fluctuating Blood Pressure and Inconsistent Readings.

Not only do they recommend at least two measurements, but what they recommend to estimate an individuals level of BP may surprise you. To estimate a person’s blood pressure level, they say to use an average of two or more readings obtained on two or more different occasions.

The importance of using multiple readings on different days to diagnose a person’s blood pressure is crucial. This tells you how you can’t rely on just one reading or day alone.

Therefore, the next time you take your pressure and get a higher reading than typical, don’t get so discouraged. Measure two more times and average the measurements over the longer-term.

It happens to me also. The first reading is often higher than the second 3. By now, you’re probably wondering, why is my first blood pressure reading always high?

The first blood pressure reading is always higher for the following reasons:

I think the first reason is the most common. People are typically in a hurry or impatient. This makes it extremely difficult to sit down and have five minutes of quiet time 4.

Without having quiet time, a persons heart rate hasn’t had time to slow down or the stress level is elevated more. Subsequent readings give the person a chance to relax and calm down.

Another major reason is the distractions. Many of my clients have admitted to me even though they sat down for five minutes they were still checking their phones or reading up on the news. Sitting down for five minutes is good but checking social media while doing it is not considered quiet time.

I wrote a blog post on this topic in complete detail. I even discuss how the majority of physician offices are making a huge mistake when measuring your blood pressure 5. You can read about it by clicking here, First Blood Pressure Reading Always High.

( Get my free Ebook which includes a breathing technique proven to lower BP 6 mmHg. Click the photo above or here for the free PDF )

Now you know the first reading shouldn’t be discarded and how many times you should be taking your measurements. In addition, how to avoid some errors with the first reading but, how long should you wait between blood pressure readings?

The blood pressure guidelines recommend you should wait one-minute between blood pressure readings. A one minute interval between readings allows your arm, blood vessels and blood flow a chance to recuperate.

There are some studies showing it’s beneficial to wait one minute after the first blood pressure reading and others.

One study measured blood pressure every 10 seconds and compared it to measurements taken every minute. The researchers concluded the one minute interval gave a closer agreement with the participants daytime average blood pressure then the 10 second interval 6.

BP TIP: In addition to preparing properly for the first reading, using an accurate monitor may be more important. I use and recommend the monitor having the fewest errors while measuring blood pressure under less than ideal conditions. Check out my detailed review by clicking here, Blood Pressure Monitor Review.

Correct Arm Position For Wrist Blood Pressure Monitor

Blood Pressure Cuff Bladder Width

Unfortunately, BP measurement is often suboptimally performed in clinical practice, which can lead to errors that inappropriately alter management decisions in 20% to 45% of cases. This inaccuracy has persisted despite extensive education and efforts to raise awareness on the adverse consequences of incorrect clinic BP measurement, according to the Lancet Commission on Hypertension Group position statement. That statement was co-written by AMA Vice President of Health Outcomes Michael Rakotz, MD, and Gregory D. Wozniak, PhD, who is vice president of outcomes analytics at the AMA.

“Many measurement errors can be minimized by appropriate patient preparation and standardized techniques. Validated semi-automated or automated upper arm cuff devices should be used instead of auscultation to simplify measurement and prevent observer error,” the consensus document says.

The consensus document cites multiple causes of inaccuracy in measurement. Here are four ways BP measurement goes wrong and how to address them.

There are instances in which the BP-measurement accuracy is affected by patients’ habits or behaviors. Acute meal ingestion, caffeine or nicotine use can all affect BP readings, leading to errors in measurement accuracy. If the patient has a full bladder, that can lead to an error in systolic BP of up to 33 mm Hg, and the white-coat effect can have an error of up to 26 mm Hg.

It is important for the patient to rest comfortably in a quiet environment for five minutes in a chair. The patient should also have an empty bladder and not have eaten, ingested caffeine, smoked or engaged in physical activity at least 30 minutes before the measurement.

Inaccuracies in BP measurement can also occur due to errors related to the procedure. For example, having the patient’s arm lower than heart level can lead to an error of 4 mm Hg up to 23 mm Hg. Procedure related error might also occur if the patient’s legs are crossed at the knees or if talking occurs during BP measurement. A fast cuff deflation rate also can contribute to inaccuracy.

The AMA has developed online tools and resources created using the latest evidence-based information to support physicians to help manage their patients’ high BP. These resources are available to all physicians and health systems as part of Target: BP™, a national initiative co-led by the AMA and American Heart Association.

If a cuff is too small or too large, errors in measurement can occur. Adding to inaccuracy are automated devices that have not been tested for accuracy, which can account for errors in systolic BP.

“An important issue with automated devices is that many have not been clinically validated for measurement accuracy,” says the statement. “Clinical validation involves demonstrating that the device meets the accuracy requirements of international BP measurement standards.”

The process of clinical validation involves performing a protocol-based comparison using multiple measurements against blinded, two-observer auscultatory reference standard. For greater accuracy, only validated devices should be used.

One common error in the clinical setting is failure to include a five-minute rest period. Errors can also include talking during the measurement procedure, using an incorrect cuff size and failure to take multiple measurements.

Time constraints are also quite common for casual measurements. This is because a casual reading takes about two minutes to perform compared with eight minutes for a standardized measurement. Physician readings were also found to be higher than nurse readings, which is the white coat effect in action.

The physician, nurse or other health professional is responsible for performing proper BP measurement while ensuring—to the greatest extent possible—that all potential causes of inaccuracy are avoided.

The organization is using May - National High Blood Pressure Education Month – to bring to light these measurement mistakes – all of which can lead to an artificially high reading:

“These simple things can make a difference in whether or not a person is classified as having high blood pressure that requires treatment,” said Michael Hochman, M.D., MPH, Associate Professor of Clinical Medicine at the Keck School of Medicine of USC and a member of the AHA’s Blood Pressure Task Force. “Knowing how to measure blood pressure accurately at home, and recognizing mistakes in the physician’s office, can help you manage your pressure and avoid unnecessary medication changes.”

In clinics, proper measurement may be the exception to practice rather than the norm. At a high blood pressure symposium in Pittsburgh this January, healthcare professionals and clinicians were tested on accurately measuring blood pressure. Of 30 participants, only three passed. “This suggests we must better educate our clinicians and healthcare professionals regarding the proper techniques to accurately measure blood pressure. More accurate blood pressure measurements will empower our clinical teams to aggressively reduce hypertension prevalence and improve overall cardiovascular health in our country,” said Sean Stocker, Ph.D., who chaired the symposium. Stocker is director of Basic and Translational Research at the University of Pittsburgh Hypertension Center and president-elect of the AHA Great Rivers affiliate.

“We need to raise awareness among clinicians about the overall benefit of getting an accurate measurement. If we make a concerted effort to get good measurements, that can lead to correct diagnoses, faster treatment and improving blood pressure control rates,” Hochman said.

Across the country, local experts are tackling their community’s blood pressure problems by encouraging healthcare providers, clinics and health systems to enroll in a national program called Target: BP. The program was created through a collaboration between the AHA and American Medical Association.

Target: BP includes a blood pressure improvement program that starts with helping healthcare providers identify and correct errors in blood pressure measurement. The program also provides guidance for creating a clear treatment plan and partnering with patients to enable ongoing self-management – including teaching them to measure their blood pressure accurately at home.

Have you ever wondered why blood pressure is the first thing your doctor or nurse takes during a medical appointment?

High blood pressure (hypertension) is the leading worldwide risk factor for death.¹ Around half of all deaths related to heart disease and stroke are caused by high blood pressure, and the condition affects around one billion people.

Your first blood pressure reading will almost always be higher than the second due to a wide range of factors, both environmental and psychological. These factors include white coat syndrome, stress, and having a full bladder.

• Wrong cuff size.
• Cuff positioning.
• Patient preparation.
• Incorrect patient positioning.
• Talking.

To make the best use of blood pressure monitoring equipment, it is helpful to have an insight into how the equipment works and the likely sources of error that can affect readings. Download a guide to these tips to keep with you for quick reference.

The most common blood pressure reading mistakes are:

Here’s what many of us do wrong, and how to take a blood pressure reading:

The most common error when using indirect blood pressure measuring equipment is using an incorrectly sized cuff. A BP cuff that is too large will give falsely low readings, while an overly small cuff will provide readings that are falsely high.

The American Heart Association publishes guidelines for blood pressure measurement [2]. recommending that the bladder length and width (the inflatable portion of the cuff) should be 80 percent and 40 percent respectively, of arm circumference. Most practitioners find measuring bladder and arm circumference to be overly time consuming, so they don’t do it.

The most practical way to quickly and properly size a BP cuff is to pick a cuff that covers two-thirds of the distance between your patient’s elbow and shoulder. Carrying at least three cuff sizes (large adult, regular adult, and pediatric) will fit the majority of the adult population.  Multiple smaller sizes are needed if you frequently treat pediatric patients.

Korotkoff sounds are the noises heard through a stethoscope during cuff deflation.  They occur in 5 phases:

In their 1967 guidelines, the AHA recommended that clinicians record the systolic BP at the start of phase I and the diastolic BP at start of phase IV Korotkoff sounds. In their 1981 guidelines, the diastolic BP recommendation changed to the start of phase V [2].

The second most common error in BP measurement is incorrect limb position. To accurately assess blood flow in an extremity, influences of gravity must be eliminated.

The standard reference level for measurement of blood pressure by any technique — direct or indirect — is at the level of the heart. When using a cuff, the arm (or leg) where the cuff is applied must be at mid-heart level. Measuring BP in an extremity positioned above heart level will provide a falsely low BP whereas falsely high readings will be obtained whenever a limb is positioned below heart level.  Errors can be significant — typically 2 mmHg for each inch the extremity is above or below heart level.

A seated upright position provides the most accurate blood pressure, as long as the arm in which the pressure is taken remains at the patient’s side. Patients lying on their side, or in other positions, can pose problems for accurate pressure measurement. To correctly assess BP in a side lying patient, hold the BP cuff extremity at mid heart level while taking the pressure. In seated patients, be certain to leave the arm at the patient’s side.

Arterial pressure transducers are subject to similar inaccuracies when the transducer is not positioned at mid-heart level. This location, referred to as the phlebostatic axis, is located at the intersection of the fourth intercostal space and mid-chest level (halfway between the anterior and posterior chest surfaces.

Note that the mid-axillary line is often not at mid-chest level in patients with kyphosis or COPD, and therefore should not be used as a landmark. Incorrect leveling is the primary source of error in direct pressure measurement with each inch the transducer is misleveled causing a 1.86 mmHg measurement error. When above the phlebostatic axis, reported values will be lower than actual; when below the phlebostatic axis, reported values will be higher than actual.

The standard for blood pressure cuff placement is the upper arm using a cuff on bare skin with a stethoscope placed at the elbow fold over the brachial artery.

The patient should be sitting, with the arm supported at mid heart level, legs uncrossed, and not talking. Measurements can be made at other locations such as the wrist, fingers, feet, and calves but will produce varied readings depending on distance from the heart.

The mean pressure, interestingly, varies little between the aorta and peripheral arteries, while the systolic pressure increases and the diastolic decreases in the more distal vessels.

Crossing the legs increases systolic blood pressure by 2 to 8 mm Hg. About 20 percent of the population has differences of more than 10 mmHg pressure between the right and left arms. In cases where significant differences are observed, treatment decisions should be based on the higher of the two pressures.

Prejudice for normal readings significantly contributes to inaccuracies in blood pressure measurement. No doubt, you’d be suspicious if a fellow EMT reported blood pressures of 120/80 on three patients in a row. As creatures of habit, human beings expect to hear sounds at certain times and when extraneous interference makes a blood pressure difficult to obtain, there is considerable tendency to “hear” a normal blood pressure.

Orthostatic hypotension is defined as a decrease in systolic blood pressure of 20 mm Hg or more, or diastolic blood pressure decrease of 10 mm Hg or more measured after three minutes of standing quietly.

There are circumstances when BP measurement is simply not possible. For many years, trauma resuscitation guidelines taught that rough estimates of systolic BP (SBP) could be made by assessing pulses. Presence of a radial pulse was thought to correlate with an SBP of at least 80 mm Hg, a femoral pulse with an SBP of at least 70, and a palpable carotid pulse with an SBP over 60. In recent years, vascular surgery and trauma studies have shown this method to be poorly predictive of actual blood pressure [3].

Noise is a factor that can also interfere with BP measurement.  Many ALS units carry doppler units that measure blood flow with ultrasound waves. Doppler units amplify sound and are useful in high noise environments.

BP by palpation or obtaining the systolic value by palpating a distal pulse while deflating the blood pressure cuff  generally comes within 10 – 20 mmHg of an auscultated reading. A pulse oximeter waveform can also be used to measure return of blood flow while deflating a BP cuff, and is as accurate as pressures obtained by palpation.

In patients with circulatory assist devices that produce non-pulsatile flow such as left ventricular assist devices (LVADs), the only indirect means of measuring flow requires use of a doppler.

The return of flow signals over the brachial artery during deflation of a blood pressure cuff in an LVAD patient signifies the mean arterial pressure (MAP). While a normal MAP in adults ranges from 70 to 105 mmHg, LVADs do not function optimally against higher afterload, so mean pressures of less than 90 are often desirable.

Clothing, patient access, and cuff size are obstacles that frequently interfere with conventional BP measurement. Consider using alternate sites such as placing the BP cuff on your patient’s lower arm above the wrist while auscultating or palpating their radial artery.  This is particularly useful in bariatric patients when an appropriately sized cuff is not available for the upper arm. The thigh or lower leg can be used in a similar fashion (in conjunction with a pulse point distal to the cuff).

All of these locations are routinely used to monitor BP in hospital settings and generally provide results only slightly different from traditional measurements in the upper arm.

Electronic blood pressure units also called Non Invasive Blood Pressure (NIBP) machines, sense air pressure changes in the cuff caused by blood flowing through the BP cuff extremity. Sensors estimate the Mean Arterial Pressure (MAP) and the patient’s pulse rate. Software in the machine uses these two values to calculate the systolic and diastolic BP.

To assure accuracy from electronic units, it is important to verify the displayed pulse with an actual patient pulse. Differences of more than 10 percent will seriously alter the unit’s calculations and produce incorrect systolic and diastolic values on the display screen.

Given that MAP is the only pressure actually measured by an NIBP, and since MAP varies little throughout the body, it makes sense to use this number for treatment decisions.

A normal adult MAP ranges from 70 to 105 mmHg. As the organ most sensitive to pressure, the kidneys typically require an MAP above 60 to stay alive, and sustain irreversible damage beyond 20 minutes below that in most adults. Because individual requirements vary, most clinicians consider a MAP of 70 as a reasonable lower limit for their adult patients.

Increased use of NIBP devices, coupled with recognition that their displayed systolic and diastolic values are calculated while only the mean is actually measured, have led clinicians to pay much more attention to MAPs than in the past. Many progressive hospitals order sets and prehospital BLS and ALS protocols have begun to treat MAPs rather than systolic blood pressures.

Finally, and especially in the critical care transport environment, providers will encounter patients with significant variations between NIBP (indirect) and arterial line (direct) measured blood pressure values.

In the past, depending on patient condition, providers have elected to use one measuring device over another, often without clear rationale besides a belief that the selected device was providing more accurate blood pressure information.

In 2013, a group of ICU researchers published an analysis of 27,022 simultaneous art line and NIBP measurements obtained in 852 patients [4]. When comparing the a-line and NIBP readings, the researchers were able to determine that, in hypotensive states, the NIBP significant overestimated the systolic blood pressure when compared to the arterial line, and this difference increased as patients became more hypotensive.

At the same time, the mean arterial pressures (MAPs) consistently correlated between the a-line and NIBP devices, regardless of pressure. The authors suggested that MAP is the most accurate value to trend and treat, regardless of whether BP is being measured with an arterial line or an NIBP. Additionally, supporting previously believed parameters for acute kidney injury (AKI) and mortality, the authors noted that a MAP below 60 mmHg was consistently associated with both AKI and increased mortality.

Since 1930, blood pressure measurement has been a widely accepted tool for cardiovascular assessment.  Even under the often adverse conditions encountered in the prehospital or transport environment, providers can accurately measure blood pressure if they understand the principles of blood flow and common sources that introduce error into the measurement process.

Keep learning about blood pressure assessment by reading how to mitigate NIBP and auscultating innacuracies by watching the plethysmography waveform on your pulse oximeter and noting the mean arterial pressure.

Read next: Learn how to read a MAP.

References:

1. James PA, Oparil S, Carter BL, et al. 2014 Evidence-Based Guideline for the Management of High Blood Pressure in Adults: Report From the Panel Members Appointed to the Eighth Joint National Committee (JNC 8). JAMA. 2014;311(5):507-520.  (Available at: http://jama.jamanetwork.com/article.aspx?articleid=1791497)

2. Pickering TG, Hall JE, Appel LJ, et al. AHA Scientific Statement: Recommendations for blood pressure measurement in humans and experimental animals, part 1: blood pressure measurement in humans.  Hypertension.  2005; 45: 142-161. (Available at: https://hyper.ahajournals.org/content/45/1/142.full)

3. Deakin CD, Low JL.  Accuracy of the advanced trauma life support guidelines for predicting systolic blood pressure using carotid, femoral, and radial pulses: observational study.  BMJ. 2000; 321(7262): 673–674.  (Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC27481/)

4. Lehman LH, Saeed M, Talmor D, Mark R, Malhotra A. Methods of blood pressure measurement in the ICU. Crit Care Med. 2013;41:34-40.

This article, originally posted Apr. 9, 2014, has been updated.