Hypertension

"Elevated blood pressure" is defined by the the American College of Cardiology/American Heart Association (ACC/AHA) Clinical Practice Guidelines [1] as above 120 mmHg systolic or above 80 mmHg diastolic (120/80). "Hypertension" is defined as blood pressure (BP) above 130/80. The diagnosis of high blood pressure should be based on both clinic and home readings, since they may be different due to the phenomena of white coat and masked hypertension. White coat hypertension refers to blood pressure readings that are elevated in the clinic but normal at home. According to UpToDate [2]:

On average, blood pressure readings are 5 to 10 mmHg lower with digital, unattended, or out-of-office methods of measurement (ie, AOBPM, daytime ABPM, home blood pressure) than with routine/standard methods of office measurement (ie, manual auscultatory or oscillometric measurement), presumably due to the "white coat effect." However, it is critical to realize that this average difference in blood pressures according to the methodology of measurement applies to the population and not the individual. Some patients do not experience a white coat effect, and, therefore, there is some uncertainty in setting goals that are specific to the method of measurement.

Conversely masked hypertension refers to normal clinic but elevated home readings. Also, blood pressure should be measured throughout the day and night, since readings may differ significantly by time of day. Whereas the normal 24-hour mean blood pressure is  below 125/75, the normal daytime awake mean is below 130/80, and nighttime asleep mean below 110/65 [1]. Furthermore, BP should be measured periodically in both arms to ensure they are approximately equal. BP should also be measured standing as well as sitting in the elderly and in people with dizziness, since BP may fall significantly with standing.

Each individual patient should discuss their appropriate BP target with their healthcare provider, because the target may vary depending on a patient's age and medical condition.

The most convenient method to take a BP reading is to use an oscillometric instrument. According to an American Heart Association scientific statement [3]:

Oscillometric devices are commonly used to measure BP in clinic, ambulatory, home, and hospital settings, with readings based on the amplitude of the oscillations recorded in the
lateral walls of the upper arm. Most oscillometric devices estimate BP when the cuff is being deflated, but some devices obtain estimates on inflation. Mean arterial BP is estimated to be the cuff pressure when the oscillation amplitude is maximal, and then the SBP and DBP are computed. SBP and DBP estimation from mean arterial BP is commonly performed via fixed ratios of the maximal oscillation amplitude. Each oscillometric device uses a proprietary algorithm that is known only to the manufacturer. These algorithms can be modified by the device manufacturer, and there are no requirements for such changes to be reported. Therefore, different devices, even from the same manufacturer, are not interchangeable, and only those that have been independently validated with an established protocol should be used (see the Protocols for the Validation of BP Monitors section).

The most accurate method to diagnosis hypertension is ambulatory blood pressure monitoring (ABPM). This is performed by equipment that automatically measures blood pressure every 15-20 minutes throughout the day and night. However, this equipment is expensive and not widely available.

A reasonable alternative to ambulatory blood pressure monitoring is home blood pressure readings. 

In contrast to ABPM, HBPM is better tolerated, more widely available, and associated with lower cost. Several studies have shown that BP on HBPM maintains a stronger association with CVD risk than office BP. HBPM also can be used to identify patients with white-coat hypertension and masked hypertension, and it can be used more easily to monitor BP levels over time [3].

Home blood pressure readings correlate well with ambulatory blood pressure monitoring. Home BP was more predictive of mortality than clinic BP [4]. Home readings are best performed using an upper arm digital device with the appropriate size cuff, which is more accurate than wrist devices. The monitor should be validated and calibrated periodically.

Healthcare providers should advise their patients to use only upper-arm cuff oscillometric devices that have successfully passed validation protocols (see the Protocols for the Validation of BP Monitors section) because many nonvalidated devices do not provide accurate measurements of BP [3].

BP should be taken after five minutes of rest while sitting with back and arm support and uncrossed legs. At least 12-14 measures should be obtained over one week. It is important to measure nighttime as well as daytime blood pressure. Blood pressure should decline by at least 10% during the night. Failure to decline at night is termed nondipping, and seems to be an independent risk factor for some hypertensive complications [2].

[The] diagnosis of hypertension with HBPM should be based on 2 measurements taken in the morning and 2 taken at night over a preferred period of 7 days (ie, 28 scheduled readings). A minimum of 3 days (ie, 12 readings) for estimating mean home BP has also been recommended because the mean of morning and evening measurements obtained over this period may provide a sufficiently accurate assessment of home BP [3].

Rickerby reviewed the role of home BP measurement and concluded:

Home measurement of BP gives results which are equivalent to the accepted 'gold standard' measure of ambulatory BP values, whilst using a simpler and much less expensive technique which is therefore more widely available [5].

The Clinical Practice Guidelines states [1]:

Out-of-office BP measurements are recommended to confirm the diagnosis of hypertension and for titration of BP-lowering medication, in conjunction with telehealth counseling or clinical
interventions.

Home BP monitoring results should be periodically sent to and reviewed by a healthcare provider.

The Omron 10 Series BP 786N blood pressure monitor has received the best rating from Consumer Reports in 2018 [6], which judged it excellent for accuracy and convenience, and very good for comfort. Wirecutter also found that the Omron 10 Series monitor was the most accurate and comfortable [7]. Besides measuring BP, this monitor has an irregular heartbeat detector and includes a one-size-fits-most cuff. BP readings are stored in memory, can be blue-toothed to your phone, and sent to your physician for review.

1. Whelton PK, Carey RM, Aronow WS, et al. ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2018; 71: 313.

2. https://www.uptodate.com/contents/ambulatory-and-home-blood-pressure-monitoring-and-white-coat-hypertension-in-adults.

3. Muntner P, Shimbo D. Measurement of Blood Pressure in Humans. Downloaded from http://ahajournals.org on March 4, 2019

4. Ohkubo T, Imai Y, Tsuji I et al.  Home blood pressure measurement has a stronger predictive power for mortality than does screening blood pressure measurement: a population-based observation in Ohasama, Japan. J Hypertens 1998. 16(7): 971.

5. Rickerby J. The role of home blood pressure measurement in managing hypertension: an evidence-based review. J Human Hypertension 2002: 16, 469.

6. https://www.consumerreports.org/products/blood-pressure-monitor/ratings-overview/

7. https://thewirecutter.com/reviews/best-blood-pressure-monitors-for-home-use/

Disclaimer: Since healthcare is complicated and personal, you should discuss these topics with your healthcare provider before applying this information to your own health. This website does not intend to diagnose or treat any disease or medical condition. Its only purpose is to assist people to monitor their health at home under the supervision of their healthcare provider.

diagnosis of hypertension with HBPM should be based on 2 measurements taken in the morning and 2 taken at night over a preferred period of 7 days (ie, 28 scheduled readings).166 A minimum of 3 days (ie, 12 readings) for estimating mean home BP has also been recommended because the mean of morning and evening measurements obtained over this period may provide a sufficiently accurate assessment of home BP.176,177