Can ultrasound replace a stethoscope?

The patient, a man in his early 20s, walked into the emergency room Wednesday morning, anxious and panting, his shirt covered in blood. Minneapolis in the 1980s was experiencing an increase in violent crime that would later earn it the nickname Morderapolis. At Hennepin County Medical Center, stabbings and gunshot wounds have become commonplace at the city’s safety net hospital. Doctors there treated dozens of patients with chest wounds, with dismal results: nearly half died, and many of the survivors suffered brain damage.

The chest contains the heart, lungs, and the largest blood vessels in the body. The challenge for the clinician is to know which organs have been affected, if any, as each must be treated differently. For decades, medical texts have called for the use of a stethoscope for this task: In theory, doctors could use a patient’s breathing pattern to detect a collapsed lung, or hear the muffled sounds of a heart filling with blood. But in reality, the stethoscope performed poorly in the emergency room. It was dangerous just to treat and hope for the best: by acting without a clear diagnosis, a doctor could harm or kill a patient who might turn out to have only a superficial injury.

If the bloodied man in Hennepin had arrived a day earlier, he might have died while his doctors continued to monitor him. But he entered into a temptation. A small group of Hennepin doctors decided to put an ultrasound machine in the trauma room of the ER to see if they could quickly diagnose a bleeding heart. Ultrasound allows doctors to see inside the body in the same way that echolocation allows bats to navigate at night: The probe emits sound waves with a frequency beyond human hearing, and these waves bounce off bones but pass through fluid, allowing the probe, which is also a receiver, to sense The inner part of the body. On the ultrasound screen, bones appear bright white, flowing blood appears black, and most other body tissues are visible in various shades of gray.

When the doctors and nurses descended on the injured man, one of them rolled the half-ton ultrasound machine and placed its probe on his chest. Sound waves imperceptibly spread through his body, and a moment later his heart filled the screen. He was surrounded in light gray: the blood was beginning to choke him. The man was taken to the operating room, where surgeons quickly drained out the creeping blood and repaired the wounds in his heart. He recovered without major impairment.

Ultrasound is an ancient technology, with roots in the sonar scanners used during World War II. For decades, it was mainly used to scan fetuses while they were still in the womb and to examine diseased hearts. But in the past few decades, rapid advances in computer technology, combined with the trial and error work of physicians, have turned ultrasound into a powerful diagnostic tool for everything from damaged organs to tuberculosis. If ultrasound missionaries are right, it may soon replace the stethoscope as the doctor’s tool of choice. Meanwhile, its rise reveals something about how technology works. In some cases, the inventions reach out completely. But others reveal their true potential slowly, truly realizing their abilities over time.

Sonar uses sounds that humans can hear. Ultrasonic frequencies, which are louder and inaudible, were first used in metal flaw detectors – machines used by shipbuilders to detect defects in their hulls. At first, it was not clear how to adapt the technology to medicine. A pioneer tried using ultrasound to scan the brain. Unfortunately, this is one of the organs least suitable for ultrasound imaging, as it is covered with a skull of reflective bone. The first ultrasound machines were enormous, in part because because air causes ultrasound waves to propagate, patients had to be immersed in water. (Today, doctors use the gel to create an airless interface between the probe and the patient.)

Most of the pioneers of ultrasound were medical engineers hungry for experimentation. As a young Royal Air Force medical officer during World War II, Ian Donald, a British obstetrician, witnessed firsthand the power of both sonar and radar; Later, he wondered if ultrasound might be more effective than a physical examination in differentiating between benign cysts and cancerous masses. He persuaded the Glasgow Boilermaker to allow him to run a metal flaw detector on two stumps of tumors, cysts and fibroids that had recently been removed. In 1956, Donald and another young physician, John MacVicar, used a rudimentary ultrasound machine of their own design on a patient diagnosed with inoperable cancer. Diagnosis was based on x-rays and physical examinations. Conversely, the ultrasound indicated that the mass was a large ovarian cyst – a benign tumor that could easily be removed through surgery. Doctors removed the cyst and the patient’s symptoms disappeared.

“From this point on, there’s no going back,” Donald reportedly said. But his colleagues were not convinced. Early ultrasound machines were difficult to use and made fuzzy images. Donald’s team took the positive step of replacing the water bath with a probe, but used olive oil to bridge the gap between the probe and the body—a messy proposition for both patient and practitioner. For many physicians, ultrasound seemed like a crutch for those who hadn’t mastered the art of the physical examination. One doctor told MacVicar that the ultrasound would only be of value to “a gynecologist who was blind and had lost the use of both hands.”

The stethoscope, the most totem medical object, faced similar obstacles. In 1816, physician René Laennec was treating a young woman with a heart condition. Fearing the mistake of placing his ear directly on her chest, he rolled a piece of paper into a tube, placing his ear at one end and his patient’s at the other. To his surprise, he found that he could hear heart and lung sounds much more clearly than with his ear alone. Link spent years refining and improving the stethoscope — the name is derived from the Greek words for “looking” and “rib cage” — before publishing a book describing his findings. But adoption has been slow. Critics argued that the tool was too difficult to use, and that the training required was too specialized. Even the Scottish physician John Forbes, who translated Link’s dissertation into English, wrote that he doubted the stethoscope would “ever enter general use”. It took several revisions to the device’s design—early models still resemble coiled tubes—and show meaningful, repeatable results for Laennec and his collaborators to overcome these objections.

in his bookSpread of innovationsSince 1962, sociologist Everett Rogers has identified five characteristics that explain the success or failure of new technologies. The most obvious advantage is the comparative advantage: the new invention must provide a clear improvement over what came before. But it also has to be in line with current practice patterns, be easy to use, and be easy to experiment with. On those scores, early ultrasounds failed miserably. Even into the 1960s, ultrasound machines remained large and difficult to move, requiring specially trained operators. They produced grainy still images, initially taken on Polaroid film. Obstetricians were open to ultrasound, because they wanted to avoid exposing fetuses to radiation from X-rays. Other doctors have adopted a wait-and-see attitude.

The first wave of substantial improvements came through digitization. When silicon wafers replaced vacuum tubes, ultrasound made use of Moore’s Law; Image quality has improved dramatically even as machines have shrunk in size. Manufacturers have simplified their user interfaces, making the machines more accessible to non-techies. in the nineties, DarpaThe Defense Advanced Research Projects Agency awarded a grant to design an ultrasound unit that was portable and rugged enough to be taken to the battlefield. In 1999, a company called Sonosite released a commercial version—the first portable ultrasound machine. The race for miniaturization continues: today, there are ultrasound machines that can be attached to your smartphone.

As technology spreads, so does experimentation, refinement and systematization of new ideas. In the early 1990s, Grace Rosicky, a surgeon at Grady Memorial Hospital in Atlanta, studied how ultrasound could be used in the evaluation of trauma patients. “Surgeons have realized that speed is the most important quality of an ultrasound,” Rozycki told me. She and her colleagues helped pioneer the use of Quickly – For focused ultrasound assessment with trauma – to allow them to make treatment decisions sooner.

I learned to perform Quickly Exam as a trainee in emergency medicine. I will never forget my first patient to receive a positive scan—a 50-year-old who was hit by a car after lying on the road, in a possible suicide attempt. The stretcher came swinging through the double doors of the ambulance entrance; When she crossed the threshold, a nurse rushed to place an IV in a patient’s arm, while another hooked her up to a monitor that began showing her vitals. In a worrying sign, the patient became increasingly disoriented.

I rolled the ultrasound machine to the side of the bed, squirted some gel across the probe, and placed it on the right side of the patient’s abdomen. Most probes radiate ultrasound outward in an arc, and as a result, the images have a fantastical quality, as if a spotlight is being shined through murky water. When the patient’s kidney appeared, it was surrounded by a black puddle – abdominal bleeding. In an instant, we knew that surgery and a blood transfusion could make the difference in life.

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