You ask - what is normal blood pressure and what does it mean? Blood pressure varies greatly from individual to individual. Even after extensive scientific research, experts have differing opinions on the guidelines for blood pressure and when to treat it. 

The purpose of this post is to define, explain, and simplify blood pressure and the proper way to take it (see video).  The blood pressure guidelines from various organizations will also be presented.

If by the end of the post, you still have questions, feel free to ask away in the comment section.  We will do our best to answer them.

What is blood pressure?
Blood pressure is a quantitative measurement of blood pumping from the heart to the body.

What do the blood pressure numbers mean?
The top number represents systole. The bottom number represents diastole.  Systole occurs when the heart is contracting or pumping blood out to the body.  Diastole occurs when the heart is relaxing or filling with blood.

What is the United States Preventative Services Tasks Force (USPSTF)?
An independent, volunteer board of experienced medical professionals who first convened in 1984.  The Task Force makes recommendations based on current peer-reviewed evidence and helps primary care providers and patients make a shared decision about whether patients need a preventative service or not. The USPSTF designates a letter grade to each recommendation where the cost of the preventative service does not influence the grade.  A & B grade recommendations should be offered to patients, while C grade is offered to select patients, and D grade is discouraged. An I statement means there is inadequate evidence to evaluate the benefit to harm ratio of the preventative service. The USPSTF recommendations only apply to healthyindividuals who do not have symptoms/signs of disease.  From 1998 onward, Congress approved the Agency for Healthcare Research and Quality (AHRQ) to meet the Task Force and give continuing organizational, objective, and distribution assistance to the Task Force. Every year, the Task Force reports to Congress a rundown that identifies holes in evidence-based research connected to clinical preventative services and advises important areas that merit more analysis.For a list of the USPSTF A and B recommendations, click here: https://www.uspreventiveservicestaskforce.org/Page/Name/uspstf-a-and-b-recommendations/

When do we screen children and adolescents for abnormal blood pressure?
The USPSTF determined there is insufficient evidence to make a recommendation for screening asymptomatic children and/or adolescents for primary hypertension to prevent cardiovascular disease.

When do start checking blood pressure in adults?
The United States Preventative Services Task Force (USPSTF) recommends screening for high blood pressure in adults aged ≥18 years old and obtaining measurements outside of the clinical setting to confirm the diagnosis before initiating treatment. This is a Grade A (best) recommendation.

What are the bell and diaphragm on the stethoscope and what are they used for?
First off - not all stethoscopes have a bell. The bell has a smaller diameter and is used to listen to low-frequency sounds such as when examining the artery in the neck (carotid artery). The diaphragm has a larger diameter and is used to listen to high-frequency sounds. The stethoscope pictured below can be converted to a bell on the smaller/pediatric side when the diaphragm is removed.  To switch from the smaller to larger diaphragm or vice versa, turn the chestpiece, then tap the side while the ear tips are in your ears to see which side is on.

What happens to blood pressure with age?
The systolic blood pressure (top number) increases because the arteries stiffen as one gets older.

What conditions have low blood pressure?
Endocrine problems - such as parathyroid disease, adrenal insufficiency/Addison's disease, or low blood sugar
Dehydration
Major blood loss
Poor diet (B12 and folate deficiency)
Pregnancy
Heart problems - such as bradycardia or heart failure
Septicemia
Anaphylaxis
Medications - such as diuretics such as furosemide (Lasix), alpha blockers such as prazosin (Minipress), beta blockers such as propranolol (Inderal), tricyclic antidepressants such as imipramine (Tofranil), and drugs for erectile dysfunction such as sildenifil (Viagra) especially when sildenifil is combined with nitroglycerin

What is it called when a patient has high blood pressure, but there is no attributable cause?
Primary or Essential hypertension

What is called when a patient has high blood pressure caused by an underlying condition?*
Secondary hypertension
*Secondary hypertension develops faster and causes higher blood pressure numbers than primary hypertension

What are some of the most common causes of secondary hypertension?
Kidney problems, adrenal gland tumors, thyroid problems, congenital defects in the blood vessels (coarctation of the aorta), some over the counter, prescription, or illicit medications (such as oral contraceptive pills, cold/cough/pain medicines, amphetamines, or cocaine), and obstructive sleep apnea

A more detailed list of some of the causes and the associated clinical clues/features are shown below:

What is renovascular hypertension?
Suspect renovascular hypertension is patients with resistant hypertension (age of onset >55) with diffuse atherosclerosis, asymmetric kidney size (small atrophic kidney), recurrent flash pulmonary edema, or an acute increase in serum creatinine >30% after starting blood pressure medication with an ACE inhibitor (ACEI) or angiotensin receptor blocker (ARB). A central abdominal bruit is highly specific for this condition.

What is resistant hypertension?
Blood pressure that is persistently elevated despite treatment with ≥3 anti-hypertension medications from different classes with one medication being a diuretic

How long should the patient be resting before blood pressure is taken?
About 5 minutes.  More importantly, if you rush into the doctor's office and immediately have your blood pressure taken, your heart has not had a chance to normalize and could be falsely elevated.

What should one refrain from doing immediately before blood pressure is taken?
Eating (especially salty foods), drinking (including alcohol), smoking, and/or exercising These greatly influence blood pressure readings and could give a false reading.

What is white coat hypertension?
A patient with normal blood pressure who gives blood pressure readings in the hypertension range at the doctor's officeor in the clinical setting

How can white coat hypertension be distinguished from persistent hypertension?
Ambulatory blood pressure monitoring (a portable device that measures blood pressure at regular intervals) - typically every 20-30 minutes - over a 24 hour period
If the patient's blood pressure is elevated outside the clinical setting, it is less likely his/her hypertension is due to white coat hypertension.

How is blood pressure properly taken?
1. Allow the patient to rest for 5 minutes before beginning
2. Make sure the patient's arm is resting on a table or in the examiner's hand at the level of the patient's heart
3. Make sure the blood pressure cuff is the appropriate size - the width of bladder is about 40% the upper arm circumference and the length of bladder about 80% of the upper arm circumference.
4. Secure the cuff around the upper arm above the crease of the elbow (antecubital fossa) and ensure that it is tight enough so that no more than 1 finger can fit between the cuff and the patient's skin.
5. To estimate the systolic blood pressure (top number), palpate the radial pulse (at the wrist on the thumb side), tighten the dial on the pump, and pump the cuff until you no longer feel a pulse at the wrist. Mentally record the number on the blood pressure gauge and then release the dial on the pump to deflate the cuff. Wait 15-30 seconds before taking the blood pressure.
6. Place the diaphragm of the stethoscope (larger round chestpiece) on the brachial artery (located above the elbow crease/antecubital fossa and towards the mid-line). Make sure the stethoscope has full contact with the skin surface. You may palpate the brachial artery before placing your stethoscope there.
7. Tighten the dial on the pump and inflate the cuff to 30 mm Hg above the estimated systolic blood pressure (from before).
8. Slowly turn the knob to release the pressure in the cuff at a rate of about 2-3 mm Hg per second. The first tapping sound is the systolic blood pressure (top number). The last tapping sound you hear before the sound disappears is the diastolic blood pressure (bottom number).

What is an auscultatory gap?
A silent interval between the systolic and diastolic pressures

What happens to the blood pressure reading if the midpoint of the patient's upper arm is BELOW the level of his/her heart?
The blood pressure will be falsely elevated

What happens to the blood pressure reading if the midpoint of the patient's upper arm is ABOVE the level of his/her heart?
The blood pressure will be even more falsely elevated

What happens to a patient's blood pressure if the cuff is too small?
The systolic (top number) and diastolic (bottom number) blood pressures will be inflated

What happens to the blood pressure if the cuff is too big?
The systolic and diastolic blood pressures will be underestimated

What lifestyle factor reduces blood pressure the most?
Weight loss - Essentially for every 2.2 lb weight loss (1 kg), one can decrease his/her blood pressure by 1 mm Hg

What are the cut offs for waist circumference to reduce your risk of high blood pressure?
Men<40 inches (<102 cm)
Women<35 inches (<89 cm)

How much regular exercise does a person with hypertension need to do in order to reduce his/her blood pressure?*
150 minutes per week or 30 minutes/day 5 days a week can reduce blood pressure by 5-8 mm Hg in hypertensive individuals
*Regular exercise is important because if exercise is stopped, one's blood pressure could revert to being high

What type of eating regimen is recommended for patients with hypertension?
Dietary Approaches to Stop Hypertension (DASH) dietThe DASH diet includes food abundant in fruits, vegetables, whole grains, and low fat dairy. Food high in saturated fats and cholesterol are eaten sparingly. A plant-based diet is likely the best diet to lower blood pressure.

How much can the DASH diet reduce blood pressure in hypertensive individuals?
Up to 11 mg Hg if you have high blood pressure

How does alcohol affect blood pressure?
Drinking alcohol in moderation can reduce blood pressure by 4 mm Hg.  Moderate alcohol intake means 1 drink/day for women and 2 drinks/day for men.  One drink means 12 oz of beer, 5 oz of wine, or 1.5 oz of 80 proof liquor/40% alcohol by volume. More than moderate alcohol intake eliminates the potential blood pressure lowering and can greatly increase blood pressure. Increased alcohol intake also makes blood pressure medications less effective.

How does smoking affect blood pressure?
Blood pressure increases with every cigarette smoked and for several minutes after you finish smoking. Smoking cessation helps bring blood pressure back to normal.

How does caffeine affect blood pressure?
People who rarely consume caffeine are more sensitive to blood pressure changes when they actually consume caffeine.  Blood pressure may increase up to 10 mm Hg in such individuals.  Those who consume caffeine on a regular basis may have little to no change in their blood pressure.  Long term effects of caffeine consumption on blood pressure are unclear, but may potentially raise it. If you think you may be sensitive to caffeine, check your blood pressure within 30 minutes of consuming caffeine. If your blood pressure increases 5-10 mm Hg after having caffeine, you could be sensitive to it.

A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines - the most recent guideline for blood pressure is shown below: 2017 Adult Blood Pressure Guidelines:

World Blood Pressure Guidelines

References:
James, P. A., & Oparil, S. (2014). 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, 507-520. doi:10.1001/jama.2013.284427

Karnath, B. (2002). Sources of Error in Blood Pressure Management. Hospital Physician, 33-37. Retrieved May 13, 2018, from http://studylib.net/doc/8856290/sources-of-error-in-blood-pressure-measurement

Mayo Clinic, S. (2018, April 10). 10 Ways to Control Blood Pressure without Medication. Retrieved from https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/high-blood-pressure/art-20046974Mayo Clinic, S. (2018, May 12). High Blood Pressure (Hypertension). Retrieved May 20, 2018, from https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/symptoms-causes/syc-20373410

Mayo Clinic, S. (2018, March 10). Low Blood Pressure (Hypotension). Retrieved May 20, 2018, from https://www.mayoclinic.org/diseases-conditions/low-blood-pressure/symptoms-causes/syc-20355465

Mohrman, D. E., & Heller, L. J. (n.d.). Cardiovascular Physiology (6th ed., Lange Physiology). The McGraw Hill Companies Moyer, V. A. (2013, November 5).

Screening for Primary Hypertension in Children and Adolescents: U.S. Preventive Services Task Force Recommendation Statement*. Retrieved May 13, 2018, from https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/blood-pressure-in-children-and-adolescents-hypertension-screening

Prabhu, F. R., & Bickley, L. S. (2002). Bates' Guide to Physical Exam and History Taking (8th ed.). Lippincott Williams and Wilkins.

Siu, A. L. (2015, October). Screening for High Blood Pressure in Adults: U.S. Preventive Services Task Force Recommendation Statement. Retrieved May 13, 2018, from https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/high-blood-pressure-in-adults-screening

USMLE World ABFM Question Bank. (n.d.). Retrieved February 1, 2016, from http://www.uworld.com

USPSTF A and B Recommendations. U.S. Preventive Services Task Force. April 2018. https://www.uspreventiveservicestaskforce.org/Page/Name/uspstf-a-and-b-recommendations/

Whelton, P. K., & Carey, R. M. (2018). 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. Journal of the American College of Cardiology,71(19). doi:10.1016/j.jacc.2017.11.006