40 Fun Facts About Blood Pressure

Which African mammal's heart must generate roughly double human blood pressure to keep its brain supplied?

Giraffe hearts weigh about 11 kg, with walls up to 7.5 cm thick, because every beat has to push blood up a neck some two metres long.

The first ACE inhibitor, a common type of blood pressure drug, was modelled on a peptide in which animal's venom?

A pit viper from Brazil, the jararaca, kills partly by making its prey's blood pressure collapse. Chemists copied the venom peptide to make captopril in 1975.

Which Pfizer drug, launched in the 1990s, was first studied as a treatment for high blood pressure and angina?

Viagra, or sildenafil, did little for angina in early trials, but the volunteers reported an unexpected side effect. Pfizer switched its target to erectile dysfunction.

What nickname does the WHO give high blood pressure, since most people who have it feel no symptoms?

The silent killer is a major cause of early death worldwide, yet hundreds of millions of adults who have it are unaware. The only way to know is to have a reading taken.

Which fruit's juice can dangerously boost the dose of some blood pressure pills, such as felodipine, in the bloodstream?

Grapefruit juice was caught doing this by accident in 1989, when researchers used it to hide the taste of alcohol in a drug study. One small glass can be enough.

Which piece of medical clothing names the effect where blood pressure reads higher in a clinic than at home?

White coat hypertension is put down to the anxiety of a clinic visit. The reverse pattern, fine at the clinic but raised in daily life, is called masked hypertension.

Clergyman Stephen Hales gauged blood pressure by letting blood climb a nine-foot glass tube from which animal?

Horse blood climbed more than eight feet up the tube, which Hales had fixed to an artery in a mare's leg. He published his results in 1733.

Which sweet contains glycyrrhizin, a compound that can raise blood pressure when a lot is eaten for weeks?

Licorice gets much of its sweetness from glycyrrhizin, which is 30 to 50 times sweeter than sugar. Overindulging is a recognised cause of unexplained hypertension.

The Hg in mmHg, the unit printed on every blood pressure reading, is the chemical symbol for which element?

Mercury takes the symbol Hg from its Latin name, hydrargyrum. One mmHg was defined as the pressure that holds up a column of the metal one millimetre high.

Which US president was found to have high blood pressure and heart failure a year before dying in office?

Franklin D. Roosevelt was examined at Bethesda Hospital in March 1944, then ran for and won a fourth term that November. He died the following April, aged 63.

Which instrument, devised by Samuel von Basch in 1881, is the standard cuff-and-gauge tool for taking blood pressure?

Sphygmomanometer is the formal term for what most people call a blood pressure monitor or gauge. Versions with a dial need regular calibration checks to stay accurate.

In a blood pressure reading such as 120 over 80, the lower number captures what moment in the heart's cycle?

Between heartbeats the heart relaxes and refills, so the diastolic figure is the minimum in the cycle. The higher systolic figure is the peak as the heart pumps.

Which pair of organs helps control blood pressure by releasing renin, an enzyme that starts a pressure-raising cascade?

Kidneys release renin when they sense the pressure of the blood flowing into them falling. Disease in these organs is one of the most common identifiable causes of hypertension.

Which mineral is linked to lower blood pressure when people eat more of it?

Potassium is so abundant in fruit and vegetables that eleven bananas would cover a full day's needs. Studies tie higher intakes to lower readings.

Which everyday ingredient does the WHO advise adults to keep under five grams a day to hold blood pressure down?

Salt intake worldwide averages more than double that limit, which is about one teaspoon. Much of it arrives hidden in processed foods such as bread and snacks.

High blood pressure is the biggest single risk factor for which sudden, often disabling brain emergency?

Stroke risk is 35 to 50 percent attributable to high blood pressure. One review found that trimming the lower number by just 5 mmHg cut the danger by about a third.

Orthostatic hypotension is a fall in blood pressure, often felt as a head rush, triggered by which everyday action?

Standing up shifts about 700 ml of blood out of the chest. Vessels in the lower body normally tighten at once to make up for it; when they lag, the reading dips.

What is the everyday name for vasovagal syncope, when blood pressure plunges at a trigger like the sight of blood?

Fainting happens when the nervous system slows the heart and widens blood vessels together, starving the brain of blood. Falling flat restores the flow, so people come round quickly.

Which type of blood pressure medicine, nicknamed water pills, works by making the body produce more urine?

Diuretics have a quirk: the thiazide kind lowers blood pressure at doses too small to cause much extra urine, so fluid loss is not the whole story.

Which organ should be emptied before a blood pressure reading, since a full one can skew the result?

Bladder fullness is easy to overlook, so the advice is to go first if there is any urge. It also helps to sit upright for five minutes, feet flat on the floor and limbs uncrossed.

The standard upper-arm cuff reads blood pressure from which artery, which runs down to the crook of the elbow?

Brachial artery pressure is what the phrase blood pressure means whenever nothing else is specified. The listener's stethoscope goes on the inner elbow, just below the cuff.

The thumping sounds heard as a blood pressure cuff deflates carry the name of which Russian physician?

Korotkoff reported the sounds in 1905 while working in St Petersburg. The first thump marks the upper number, and the moment they fade out marks the lower one.

A blood pressure cuff that is too small for the patient's arm tends to have what effect on the reading?

Too high is the usual error from an undersized cuff, while an oversized one may read low. Clinics are meant to keep three or four sizes to hand.

Ambulatory blood pressure monitoring uses a wearable cuff that takes automatic readings over what span?

24 hours of readings capture both the daytime pattern and the fall that normally comes with sleep. People whose pressure fails to dip overnight tend to have poorer outcomes.

Which type of blood pressure gauge, named like the liquid-free barometer, shows its reading on a mechanical dial?

Aneroid gauges are considered safer than the liquid-column type they largely replaced, although inexpensive ones are less accurate.

Which chamber of the heart produces the upper blood pressure number when it pumps blood into the aorta?

Left ventricle walls are three to six times thicker than those of its right-hand twin by young adulthood, because it pumps against far greater resistance.

In which tiny vessels, known as the main site of vascular resistance, does blood pressure drop the most?

Arterioles have muscular walls that tighten or relax to steer the flow. The steep fall across them protects the one-cell-thick capillaries from bursting.

Which stretch-sensing nerve endings in the carotid sinus and aortic arch alert the brain to blood pressure changes?

Baroreceptors are slightly misnamed, since they detect the stretching of the vessel wall rather than pressure itself. Older textbooks call them pressoreceptors.

What name is given to the gap between systolic and diastolic readings, about 40 mmHg in a healthy adult?

Pulse pressure for a textbook 120 over 80 is 40 mmHg. Doctors watch it because a gap of less than a quarter of the upper figure counts as abnormally narrow.

Why does the upper blood pressure number tend to climb as people grow older, even when the lower one stays normal?

Arteries stiffen with the years and lose their give, so each beat lands harder. A high top figure over a normal bottom one is common enough to have its own name, isolated systolic hypertension.

Which pregnancy complication, arising after 20 weeks, brings new high blood pressure and often protein in the urine?

Pre-eclampsia usually causes no symptoms at first, which is why it is picked up by routine screening. Unchecked, it can progress to eclampsia, an emergency marked by seizures.

Which part of the eye do doctors examine for vessel damage caused by years of high blood pressure?

Retina damage from hypertension shows up as narrowed vessels, tiny flame-shaped bleeds and pale patches known as cotton wool spots.

Which disorder, usually confirmed by an overnight study, is a common hidden cause of high blood pressure?

Sleep apnea causes repeated drops in blood oxygen through the night, and hypertension that resists treatment can be one of its subtle signs. A bed partner often notices the pauses in breathing first.

Which eating plan, promoted by the US National Institutes of Health, was designed to control high blood pressure?

DASH diet is short for Dietary Approaches to Stop Hypertension. It is built around fruit, vegetables, whole grains and low-fat dairy foods.

Portal hypertension, raised pressure in the vein draining the gut, is most often caused by scarring of which organ?

Liver cirrhosis is the most common cause. Blood that cannot get through the scarred organ backs up into swollen veins in the gullet, which can bleed heavily.

Propranolol, developed by James Black in the 1960s, was the first major success in which class of blood pressure drugs?

Beta blockers shield the heart from adrenaline, so it beats slower and with less force. Some performers take propranolol to calm the physical signs of stage fright.

Which gas do blood vessel linings release to relax the vessel and lower blood pressure, a 1998 Nobel-winning discovery?

Nitric oxide was proclaimed Molecule of the Year in 1992. The lining of a vessel uses it to tell the surrounding muscle to relax, which widens the channel.

Which hormone, formed when the enzyme ACE trims a longer peptide, narrows blood vessels and pushes blood pressure up?

Angiotensin II is made mostly in the lungs, where the enzyme is abundant. Slowing its production, or blocking its receptors, is how two major families of blood pressure drugs work.

Which Italian physician introduced the arm-encircling inflatable cuff for measuring blood pressure in 1896?

Scipione Riva-Rocci gave one of his devices to the visiting American surgeon Harvey Cushing in 1901, who went on to popularise it across the Atlantic.

Which manoeuvre, a hard breath out against a closed airway as when straining, makes blood pressure jump and then drop?

Valsalva was a professor of anatomy at Bologna whose main interest was the ear. The strain first adds chest pressure to the aorta, then cuts the blood returning to the heart.