How Does Blood Pressure Work?

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Your heart is the master pump for all the blood in your body. With every heartbeat, your heart pushes your blood to all the vital parts of your body, such as muscles and bones, through a network of arteries, capillaries, and veins. As blood flows through the tube-like arteries, it presses up against the walls of the blood vessels with varying degrees of strength. The strength or weakness of this pressure is called your blood pressure (BP).

Each time your heart squeezes, moving your blood to its various destinations, your blood pressure goes up—this number is referred to by a blood pressure reading as systolic. Then, as the heart relaxes after each contraction, your blood pressure goes down; that is called the diastolic reading. Together, these two numbers are presented as a score, systolic over diastolic: Your doctor might tell you that your BP is “120 over 80.”

According to the American Heart Association (AHA), normal blood pressure should reflect systolic pressure between 90 and 120, over a diastolic pressure between 60 and 80. Your doctor may take this measurement with a fancy-named instrument called a sphygmomanometer—an inflatable rubber cuff attached to a manual air pump. When the doctor inflates the cuff at your arm with air, it temporarily cuts off blood flow, and when it releases, the blood starts flowing again, revealing those two key numbers.

Nowadays, though, doctors are recommended to use an automatic blood pressure cuff, which relies on a different method and seems to be more accurate. While the manual cuff relies on auscultation, in which the doctor listens for the correct pressures using a stethoscope/microphone, automatic blood pressure cuffs are usually oscillometric. When blood passes under the cuff, the arm increases in circumference ever so slightly. And by measuring the amplitude of the oscillations (hence oscillometric) at a continuous interval of pressures, blood pressure can be calculated in much the same way.

If you have high blood pressure, a.k.a. hypertension—approximately 130/80 or higher in a person of average health—your heart is working too hard to pump the blood through your body, which becomes dangerous. According to the AHA [PDF], elevated blood pressure is 120–129/less than 80; hypertension stage 1 is 130–139 (systolic) or 80–89 (diastolic); and hypertension stage 2 is 140 or higher (systolic) or 90 or higher (diastolic). If your blood pressure hits 180/120, you're in hypertensive crisis, and you should get help.

If you fall into the above categories, your doctor will recommend changes to diet and exercise and probably medication. High blood pressure is often a precursor to heart disease or a heart attack and can be a side effect of other diseases, such as diabetes. However, your blood pressure can temporarily rise due to stress, pregnancy, and even some common medications, including over-the-counter pain relievers and antidepressants. One high reading will not necessarily mean you have hypertension—but it’s good to keep vigilant.

Editor's note: This story was updated in July 2018 to reflect new blood pressure guidelines from the AHA.

A Custom Wheelchair Allowed This Brain-Injured Baby Raccoon to Walk Again

фотограф/iStock via Getty Images
фотограф/iStock via Getty Images

Animal prosthetics and wheelchairs allow dogs, cats, and even zoo animals with limited mobility to walk again, but wild animals with disabilities aren't usually as lucky. Vittles, a baby raccoon rescued in Arkansas, is the rare example of an animal that was severely injured in its natural habitat getting a second shot at life.

As Tribune Media Wire reports, Vittles came to wildlife rehab specialist Susan Curtis, who works closely with raccoons for the state of Arkansas, with a traumatic brain injury at just 8 weeks old. The cause of the trauma wasn't clear, but it was obvious that the raccoon wouldn't be able to survive on her own if returned to the wild.

Curtis partnered with the pet mobility gear company Walkin' Pets to get Vittles back on her feet. They built her a tiny custom wheelchair to give her balance and support as she learned to get around on her own. The video below shows Vittles using her legs and navigating spaces with help from the chair and guidance from her caretaker.

Vittles will likely never recover fully, but now that she's able to exercise her leg muscles, her chance at one day moving around independently is greater than it would have been otherwise. She now lives with her caretaker Susan and a 10-year old raccoon with cerebral palsy named Beetlejuice. After she's rehabilitated, the plan is to one day make her part of Arkansas's educational wildlife program.

[h/t Tribune Media Wire]

Why You Should Never Shower With Your Contact Lenses In

belchonock/iStock via Getty Images
belchonock/iStock via Getty Images

Contact lenses offer a level of convenience for those with less-than-perfect vision that glasses can hardly compete with, but that doesn’t mean the daily struggle of taking them in and out of your eyes doesn’t wear on you. If you get a little lazy and decide it’s fine to leave them in your eyes during showers or pool parties, think again.

According to Popular Science, a 41-year-old woman in the UK lost sight in her left eye as a result of frequently showering and swimming without removing her contacts. The culprit was Acanthamoeba polyphaga, a protozoa that crawled into her eye and caused a cornea infection called Acanthamoeba keratitis. After two months of pain, blurry vision, and light sensitivity, the woman sought medical attention at the Manchester Royal Eye Hospital, where doctors discovered a ring shape in her left eye and a hazy layer covering her cornea. Upon testing her vision, they found that her left eye was now 20/200, which counts as legally blind in the United States.

Leela Raju, an ophthalmologist and cornea specialist at New York University, told Popular Science that the single-celled organisms “can be anywhere,” including pools, hot tubs, showers, dirty saline solution containers, and even tap water. Lens-wearers make up around 85 percent of those who get infected, and experts think it may be because the amoeba can latch onto a contact lens more easily than a bare eye.

Though Popular Science reports that Acanthamoeba keratitis only affects one or two people out of every million contact wearers each year, that’s no reason not to be careful. If you do catch it, you’ll likely need a cornea transplant, and even that won’t necessarily restore your eyesight to its previous state—after her transplant, the UK woman’s left eye now has 20/80 vision.

“It’s just a long road, for something that’s totally preventable,” Raju says. In addition to removing your contacts before swimming, showering, or sleeping, you should also refrain from reusing saline solution, make sure your contact case is completely clean and dry before filling it with more solution, and check out these other tips.

[h/t Popular Science]

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