Should You Use a Simple Pulse Oximeter to Detect COVID-19 Symptoms?
Patients who are having trouble breathing from a COVID-19 infection are showing up at the hospital long after a normal pneumonia infection is detected. That trend means more ventilators need to be used and more people are dying from the infection than need to. Lives could be saved if the infections were caught earlier. Now, an emergency doctor says in The New York Times that a simple pulse oximeter could slow down the number of patients needing ventilators and succumbing to the disease.
The opinion piece by Dr. Richard Levitan argues that since many patients have COVID-19 pneumonia but have not complained of breathing problems, they are not aware that something is slowly attacking their lungs. The infection is causing something called "silent hypoxia," a form of oxygen deprivation that is difficult to detect.
"But when COVID pneumonia first strikes, patients don't feel short of breath, even as their oxygen levels fall," Levitan wrote. "And by the time they do, they have alarmingly low oxygen levels and moderate-to-severe pneumonia (as seen on chest X-rays). Normal oxygen saturation for most persons at sea level is 94 percent to 100 percent; COVID pneumonia patients I saw had oxygen saturations as low as 50 percent."
He says that a simple, over the counter pulse oximeter will detect silent hypoxia. He argues that the simple device is reliable, simple to use — just attach it to a fingertip and turn the machine on — and "could provide an early warning system for the kinds of breathing problems associated with COVID pneumonia."
"When we see low oxygen readings, we would bring patients in [and] we would treat them with oxygen. And a variety of positioning maneuvers where we lay people on their stomach," Levitan said to CBS Boston. "We monitor their blood tests for inflammatory markers and we would reach many more patients earlier in the disease."
Pulse oximeters usually run from $25 to $100 and work by passing a small beam of light through your finger to measure how much oxygen your blood is carrying, according to Consumer Reports. When your blood oxygen levels start to trend downwards, it could be a sign that your lungs are faltering.
"In COVID-19 patients, we often see that they look comfortable, but their oxygen saturation is significantly worse than normal," said Elissa Perkins, M.D., associate professor of emergency medicine at Boston Medical Center, to Consumer Reports. For that reason a home pulse oximeter "could provide valuable additional information about their disease."
However, the American Thoracic Society and the American Lung Association feel that most people do not actually need one, but should have one if they have specific respiratory conditions that would require it. In the absence of those conditions, frequently checking a pulse oximeter could lead to increased anxiety, according to ABC News.
"There is no good role for a pulse oximeter for an otherwise healthy person who doesn't have access to [supplemental] oxygen," said Jamie Garfield, a volunteer medical spokesperson at the American Lung Association and an interventional pulmonologist at the Temple Lung Center in Philadelphia, as Quartz reported.
Some doctors warn that the value of a pulse oximeter during the pandemic is limited. Furthermore, most are not intended for medical use and have not been put through the same rigorous testing and review as medical-grade oximeters, according to Lex Schultheis, M.D., research professor of bioengineering at the University of Maryland in College Park, who spoke to Consumer Reports.
"Most infected people will survive this infection, and will never need a visit with their doctor, let alone hospitalization," said Mark Levy, a family physician in Seattle, to Quartz. "For those who are sicker, monitoring pulse, respiratory rate, and other low-tech things like how someone looks and feels may be all that is needed."
For his part, Levitan recognized some of those problems. "People using the devices at home would want to consult with their doctors to reduce the number of people who come to the E.R. unnecessarily because they misinterpret their device," he wrote. He believes that everyone who has tested positive for COVID-19 should have pulse oximetry for two weeks to see if an acute lung infection develops.
He added, "All persons with cough, fatigue and fevers should also have pulse oximeter monitoring even if they have not had virus testing, or even if their swab test was negative, because those tests are only about 70 percent accurate. A vast majority of Americans who have been exposed to the virus don't know it."
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The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.
"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."
The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.
They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.
They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.
But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.
"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.
What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.
It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.
To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.
First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.
Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.
University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.
"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."
Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.
"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.
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