When patients with a new disease called COVID-19 started pouring into his hospital, pulmonary and critical care physician Bilal Jalil found himself turning to a pocket-size device he had been using to quickly check heart function in his private practice. It was a handheld point-of-care ultrasound, or POCUS, which consists of a simple probe that can broadcast ultrasound images to a display tablet or phone. The tool proved invaluable in making critical triage choices: within minutes Jalil, who works in the intensive care unit in the Baylor Scott & White Health system in Texas, could see if someone’s lungs were affected enough to require intensive care.

Many emergency care doctors around the world have begun relying on POCUS units as a first line of defense in confronting COVID-19. Blood tests sometimes take 24 hours, and CT scan rooms have long waits. But these little ultrasound gadgets can reveal lung damage on the spot, showing doctors whether individuals can breathe independently or need to be immediately put on ventilators.

“Some patients didn’t have very severe symptoms, but the ultrasound showed that lungs were really damaged,” says Alexandra Gonçalves, chief medical officer of strategy and partnerships at Philips, which makes a handheld ultrasound device called Lumify. At least one study found another POCUS unit diagnosed COVID-19 more accurately than the standard nasal-swab test, she says. Even when a swab test showed a false negative for coronavirus, ultrasound could prove that the lungs were inflamed. Handheld machines will not replace the existing diagnosis standards but should be part of the toolbox, doctors say.

Such small ultrasound devices can also help doctors monitor people who are already known to be infected with COVID-19. Bringing highly contagious patients to radiology departments for scans often means taking them to different floors, thus increasing the chances of spreading an infection around a hospital. Gurneys used for this procedure have to be covered. And radiology machines have to be disinfected after every use, which causies delays. Larger ultrasound units can be wheeled between individuals’ rooms, but they also take a relatively long time to disinfect. Health workers can wrap handheld probes and tablets in protective plastic sleeves, however, which makes taking scans regularly faster and easier. As a result, doctors can compare today’s images with those taken yesterday—or hours ago—to track COVID-19’s often-unpredictable progression.

A Brief History of Ultrasound

A longtime staple in medical diagnostics, ultrasound devices bounce high-frequency sound waves off the soft tissues of internal organs, such as the heart and liver, and of an embryo or fetus in utero to generate images. “Unlike with ionizing radiation from x-rays and CT scans, ultrasound has no side effects,” says radiologist Yale Tung Chen of the University Hospital of La Paz in Madrid. He says he monitored his own lungs daily after he contracted COVID-19 at the hospital.

When doctors first began using this technology in the mid-20th century, however, it did not seem like a natural tool for screening the lungs. Normally the sound waves dissipate in the air within a lung and do not produce an image. But more recently, scientists realized that for certain conditions, ultrasound can generate enough of a picture to tell doctors something is wrong. A 2008 paper in CHEST suggested it can be used to diagnose acute respiratory failure. A later paper in Cardiovascular Ultrasound noted that it can also detect built-up fluid or a solid mass such as a tumor within the lungs.

Full-scale ultrasound machines range in size from that of a large computer to a small wardrobe on wheels. A few years ago the first handheld devices appeared on the market. Scientist and entrepreneur Jonathan Rothberg started the company Butterfly Network in 2011 when his daughter developed a kidney growth. Monitoring it required visits to an imaging facility, so Butterfly Network created the Butterfly iQ—a POCUS that displays images on doctors’ smartphones via a secure app. Over the past decade, several other companies started selling pocket-size ultrasound units as well.

The machines’ quality has since improved substantially, says Jean-Jacques Rouby, a professor emeritus at Pitié-Salpêtrière Hospital and Sorbonne University, both in Paris. He says he used ultrasound imaging for 15 years and has compared the old and new devices. “The screens are smaller, of course. But image quality compares quite well,” he adds.

Popular in a Pandemic

Like larger ultrasound devices, handheld ones can show visual signs that lungs are ailing. To check for them, doctors look at the pleura, the membrane that envelops each lung. Under normal conditions, viewers see a reflection of the pleura as a series of equidistant horizontal lines, called A lines, throughout those organs. “When you scan healthy lungs, you see nice, beautiful A lines lined up very symmetrically,” says John Martin, chief medical officer at Butterfly Network. But when fluids build up, vertical streaks, called B lines, appear. As a condition worsens and lungs lose air, their tissue starts to look compressed and dense. “In the early stages you see scattered B lines, and later the pleural line becomes broken and irregular,” Martin explains. “You see consolidation [of fluid] beneath that pleura.”

Spotting this built-up fluid can help ultrasound users diagnose COVID-19 pneumonia, a common and potentially deadly complication that serves as a marker of severe coronavirus infection. Before the disease emerged, the adoption of point-of-care ultrasound technology had been relatively slow. Then the pandemic struck, and demand surged.

Philips says it has had an increase in orders for Lumify. And Martin has been hosting Webinars with hundreds of medical professionals who want to learn how to use Butterfly iQ and other POCUS devices. An “e-learning” company called iTeachU also offers a free COVID-19 lung ultrasound course for doctors, nurses and paramedics. Rouby first proposed making handheld ultrasound units standard equipment at his hospital six years ago, but “the idea was ahead of its time,” he says. “Now we just bought 14 of them.”

This increase in popularity began at the ground level. “Interested physicians and clinicians are purchasing these devices on their own,” says radiologist Rasu Shrestha, chief strategy officer and executive vice president of Atrium Health, a health care network that includes hospitals and urgent care centers in North and South Carolina and Georgia. Now larger health care systems are following suit: Atrium Health just bought more than 60 Butterfly devices for 30 locations, Shrestha says. “We were really the first heath system in the country to deploy it at scale,” he says.

The company chose the Butterfly iQs because they are easy to use—and relatively cheap: they cost about $2,000 each, compared with $50,000 or more for a full-scale ultrasound system. Jalil says he likes to use a device called GE Vscan, which comes with a dedicated display. He likens POCUS units to stethoscopes that let caregivers not only listen to the body but also see inside it.

Read more about the coronavirus outbreak from Scientific American here. And read coverage from our international network of magazines here.