Chronic hypertension blood pressure measurement

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editor-In-Chief: Yazan Daaboul; Serge Korjian; Arzu Kalayci, M.D. [2]

Overview

The use of a sphygmomanometer in the clinic to measure blood pressure is the most accurate technique to diagnose hypertension. Blood pressure measurements must be performed appropriately according to a standardized technique that involves adequate device and cuff choice and comfortable positions. Sources of error, involving the sphygmomanometer, the patient, and the technique itself must also be considered and avoided. Other techniques for diagnosis, such as ambulatory and self blood pressure measurements may also be helpful, particularly for the follow-up of patients with hypertension.

Blood Pressure Measurement

See also: Blood pressure

Clinical practice guidelines address measurement

Retracted!(): For the prediction of cardiovascular death, 24-hour ambulatory blood-pressure measurements are a better predictor than are office measurements. Regarding the hazards ratio of cardiovascular death associated with each pattern of blood pressure elevation:

• Masked hypertension (normal clinic and elevated 24-hour ambulatory blood pressure): 2.83
• Sustained hypertension (elevated clinic and elevated 24-hour ambulatory blood pressure): 1.80
• "White-coat" hypertension] (elevated clinic and normal 24-hour ambulatory blood pressure): 1.79

The Rationale Clinical Examination concluded:

• "Office measurements of BP may not be accurate enough to rule in or rule out hypertension; HBPM may be helpful to confirm a diagnosis. When there is uncertainty around threshold values or when office and HBPM are not in agreement, 24-hour ABPM should be considered to establish the diagnosis"

Physiology

Blood pressure measurement using the sphygmomanometer yields two values that assess the pressure exerted by the blood on the walls of the arteries at two points in time:

• Systole is the maximum exerted pressure during a ventricular contraction and during expulsion of blood from the heart chambers into the aorta and corresponding arteries. The corresponding value measured by the sphygmomanometer is the systolic blood pressure.
• Diastole is the minimum exerted pressure directly before the next heartbeat. The corresponding value measured by the sphygmomanometer is the diastolic blood pressure.

Conventionally, blood pressure is frequently denoted as systolic and diastolic pressures and expressed in mmHg. Another way to denote blood pressure is using the mean blood pressure, calculated by:

Mean Blood Pressure = [Systolic Blood Pressure + (2 x Diastolic Blood Pressure)] / 3

Nonetheless, blood pressure is a continuously fluctuating hemodynamic parameter with various factors leading to such fluctuations other than the cardiac cycle. Those include the respiration, the baroreceptor loop, hormones, in addition to others. Therefore, experts do not rely solely on static blood pressure parameters but also on dynamic ones, such as pulse pressure, defined as the pressure difference in systolic and diastolic blood pressure, in the evaluation of blood pressure curve. Hence, accurate, precise, and reproducible measurements are pre-requisites for the evaluation of blood pressure. The level of blood pressure plays a major role in the diagnostic, therapeutic, and prognostic decision-making processes of various disease states.

Blood pressure readings in practice are lower than in the SPRINT trial.

Blood Pressure Measurement Technique

According to “Practice Guidelines of the European Society of Hypertension for Clinic, Ambulatory, and Self Blood Pressure Measurement” and JNC 7 , the optimal procedure to measure blood pressure is the following:

Selecting an Accurate Device

A systematic review found that automated office blood pressure measurement better matches awake ambulatory blood pressure than manual office readings and average 14.5 mm Hg lower than manual office readings.

List of devices, protocol for use, and details of validation status can be obtained on www.dableducational.org.

Cuff and Bladder Choice

Cuff bladder must enfold ≥ 80% of the measured arm circumference. Miscuffing is a common error during blood pressure measurement. The cuff and the bladder should be chosen according to the size of the arm circumference, as usually detailed by the device protocol. Commonly, such errors target obese patients where cuff size is too small for arm circumference, leading to a phenomenon called “Cuff Hypertension”.

Patient Profile

Special populations require special attention while measuring blood pressure. This includes children, elderly, obese individuals, patients with arrhythmias, and pregnant women. In the latter group, Korotkoff sounds may be heard down to zero mmHg, in which the fourth phase or muffling of sounds should be used to assess diastolic blood pressure.

Explanation to the Patient

This attempts to eliminate patient’s fear that might contribute to a phenomenon called “White Coat Effect”, whereby patients’ blood pressure values are elevated only in the clinic setting. Ambulatory blood pressure measurement helps in identifying the white coat effect (WCE) and white coat hypertension (WCHT).

Comfortable Positioning

Patients should relax silently for a few minutes before blood pressure is measured. Individuals should sit with the back supported, legs uncrossed and cuffed arm positioned at heart level. Likewise, the person conducting the measurement should also be seated comfortably to prevent rapid deflation of the cuff that might underestimate and overestimate systolic and diastolic blood pressures, respectively.

Arm Choice

On the first consultation, patient’s blood pressure must be measured in both arms. Consecutive readings showing differences of > 20 mmHg or > 10 mmHg for systolic and diastolic pressures respectively might suggest an underlying arterial disease that should be ruled out, such as subclavian stenosis. Further blood pressure measurements should be conducted in the arm with the highest values at first assessment if the difference between right and left readings was within normal limits.

Timing

Repeat at the end of the visit after rest may lower the pressure by 17/2

Assessment of Postural Hypotension

Due to increasing prevalence, postural hypotension must be assessed by measuring blood pressure when the patient assumes an erect position . Postural hypotension is defined as a systolic blood pressure drop of ≥ 20 mmHg or diastolic blood pressure decrease of ≥ 10 mmHg when the patient stands from a seated position. The presence of postural hypotension suggests in most of the cases impairment in the baroreceptor (firing of afferent nerves and consequential dysfunction of the initiation of autonomic cardiovascular reflex. It is most commonly present in diabetics and elderly. According to the Honolulu Heart Program in 1998, it carries a prognostic value with 64% increase in age-adjusted mortality compared to control population . Intensive blood pressure control then might be compromised due to the presence of orthostatic hypotension, making control of hypertension a bigger challenge in such patients.

Common Sources of Error

Technical sources of error include, but are not limited to:

• Misconfigured sphygmomanometer
• Use of low quality or unclean or non-fitting stethoscope
• Inappropriate positioning of the arm
• Inappropriate cuff size for the arm or cuff placed too tight over the arm
• Too rapid deflation of the cuff
• Observer error, digit preference, prejudice, or bias

Auscultatory methods are subject to error and bias, moreso in recording the systolic pressure. Problems include rounding values to "0", less so in more recent years.

Comparison of measurement and cost-effectiveness of methods

AHA vs Roerecke estimates of relationship between routine, auscultated BP measurement and gold standard ambulatory measurement.

Clinic (routine) AHA, 2017	Clinic (routine) Roerecke, 2018	Clinic (automated) Roerecke, 2018	Home (self) AHA, 2017	Daytime, ambulatory †	Nighttime ambulatory AHA, 2017	24 hour ambulatory AHA, 2017 †
120/80	125/82	120/80	120/80	120/80	100/65	115/75
130/80	145/85	130/80	130/80	130/80	110/65	125/75
140/90	150/90	135/85	135/85	135/85	120/70	130/80
160/100	160/95	145/90	145/90	145/90	140/85	145/90
Notes: † The IDACO Investigators found that the 24-hour ambulatory systolic pressure may better predict mortality than the daytime systolic blood pressure.

Cost effectiveness studies favor ambulatory monitoring. These studies were performed before the IDACO and Banegas (Retracted) cohorts were published.

Ambulatory Blood Pressure Measurement

• Usually 24-hour blood pressure measurement that allows repetitive blood pressure measurement at specified intervals.
• Diagnosis of hypertension is based on average systolic blood pressure ≥ 130 mmHg and/or diastolic blood pressure > 85 mmHg.
• Can identify hidden phenomena like white-coat hypertension (elevated blood pressure only during patient’s visit to clinic) or masked hypertension (normal blood pressure only during patient’s visit to clinic).
• Considered superior to all other techniques in its association with hypertension complications such as target organ damage.
• Most expensive, but still cost-effective.
• Requires interpretation by skilled medical personnel.

Regarding whether the ambulatory pressure should guide treatment, there is uncertainty. One trial, using "After 5 minutes of rest in the sitting position, patients performed 3 consecutive self-measurements of BP twice daily" with an automated cuff, found that the office pressure may be a better to treatment.

Self Blood Pressure Measurement

• Normally, two measurements should be obtained each morning and evening for seven consecutive days. First day measurements are to be eliminated. Remaining 24 blood pressure measurements averaged to obtain mean arterial blood pressure
• Diagnosis of hypertension is done based on average systolic blood pressure ≥ 135 mmHg and/or diastolic blood pressure > 85 mmHg
• Can identify hidden phenomena like white-coat hypertension or masked hypertension.
• Superior only to office blood pressure measurement in assessing hypertension complications, such as target organ damage
• More expensive than office blood pressure measurement but less expensive than ambulatory blood pressure measurement

Medical personnel assistance used to be recommended; however with currently available accurate and validated electronic devices, blood pressure measurement became feasible, easy, and dependent only on patient education.

2017 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

The 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA recommendations are below.

Accurate Measurement of Blood Pressure (BP) in the Office

Class I

"1. For diagnosis and management of high BP, proper methods are recommended for accurate measurement and documentation of BP.(Level of Evidence: C-EO) "

If the goal is 130/80, proper measurement includes (distilled from Table 8 of the ACC/AHA guidelines, executive summary):

• having the patient sit quietly for 5 minutes before a reading is taken
• supporting the limb used to measure BP
• ensuring the BP cuff is at heart level
• using the correct cuff size
• for auscultatory readings, deflating the cuff slowly
• the timing of BP measurements in relation to ingestion of the patient’s medication should be standardized
• a single reading is inadequate for clinical decision-making. An average of 2 to 3 BP measurements obtained on 2 to 3 separate occasions will minimize random error and provide a more accurate basis for estimation of BP.

Out-of-Office and Self-Monitoring of Blood Pressure (BP)

Class I

"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.(Level of Evidence: A) "

Masked and White Coat Hypertension

Class IIa

"1. In adults with an untreated Systolic Blood Pressure (SBP) greater than 130 mm Hg but less than 160 mm Hg or Diastolic Blood Pressure (DBP) greater than 80 mm Hg but less than 100 mm Hg, it is reasonable to screen for the presence of white coat hypertension by using either daytime Ambulatory blood pressure monitoring (ABPM) or Home blood pressure monitoring (HBPM) before diagnosis of hypertension. (Level of Evidence: B-NR) "

"2. In adults with white coat hypertension, periodic monitoring with either ABPM or HBPM is reasonable to detect transition to sustained hypertension. (Level of Evidence: C-LD) "

"3. In adults being treated for hypertension with office BP readings not at goal and HBPM readings suggestive of a significant white coat effect, confirmation by ABPM can be useful. (Level of Evidence: C-LD) "

"4. In adults with untreated office BPs that are consistently between 120 mm Hg and 129 mm Hg for SBP or between 75 mm Hg and 79 mm Hg for DBP, screening for masked hypertension with HBPM (or ABPM) is reasonable . (Level of Evidence: B-NR) "

Class IIb

"1. In adults on multiple-drug therapies for hypertension and office BPs within 10 mm Hg above goal, it may be reasonable to screen for white coat effect with HBPM. (Level of Evidence: C-LD) "

"2. It may be reasonable to screen for masked uncontrolled hypertension with HBPM in adults being treated for hypertension and office readings at goal, in the presence of target organ damage or increased overall CVD risk. (Level of Evidence: C-EO) "

"3. In adults being treated for hypertension with elevated HBPM readings suggestive of masked uncontrolled hypertension, confirmation of the diagnosis by ABPM might be reasonable before intensification of antihypertensive drug treatment. (Level of Evidence: C-EO) "

Follow-Up After Initial BP Evaluation

Class I

"1. Adults with an elevated BP or stage 1 hypertension who have an estimated 10-year ASCVD risk less than 10% should be managed with nonpharmacological therapy and have a repeat BP evaluation within 3 to 6 months.(Level of Evidence: B-R) "

"2. Adults with stage 1 hypertension who have an estimated 10-year ASCVD risk of 10% or higher should be managed initially with a combination of nonpharmacological and antihypertensive drug therapy and have a repeat BP evaluation in 1 month.(Level of Evidence: B-R) "

"3. Adults with stage 2 hypertension should be evaluated by or referred to a primary care provider within 1 month of the initial diagnosis, have a combination of nonpharmacological and antihypertensive drug therapy (with 2 agents of different classes) initiated, and have a repeat BP evaluation.(Level of Evidence: B-R) "

"4. For adults with a very high average BP (e.g., SBP ≥180 mm Hg or DBP ≥110 mm Hg), evaluation followed by prompt antihypertensive drug treatment is recommended.(Level of Evidence: B-R) "

Class IIa

"1. For adults with a normal BP, repeat evaluation every year is reasonable. (Level of Evidence: C-EO) "

2013 ESH/ESC Guidelines For The Management of Arterial Hypertension (DO NOT EDIT)

Summary of Recommendations on Blood Pressure Measurement (DO NOT EDIT)

Class I

"1. Office BP is recommended for screening and diagnosis of hypertension. (Level of Evidence: B)"

"2. It is recommended that the diagnosis of hypertension be based on at least two BP measurements per visit and on at least two visits. (Level of Evidence: C)"

Class IIa

"1. Out-of-office BP should be considered to confirm the diagnosis of hypertension, identify the type of hypertension, detect hypotensive episodes, and maximize prediction of CV risk. (Level of Evidence: B)"

"2. For out-of-office BP measurements, ambulatory blood pressure monitoring; or home blood pressure monitoring may be considered depending on indicaton, availability, ease, cost of use and, if appropriate, patient preference. (Level of Evidence: C)"