The View Between Two Ribs
Point-of-care ultrasound (POCUS) and the future of our physical exam
In a 1968 episode of Star Trek, Captain Kirk is kidnapped by humanoid aliens, tortured unrelentingly, and shackled to the ceiling by his wrists. Science officer Spock and Dr. McCoy find him disheveled and minimally responsive. They release him from the chains and set him on a nearby table for examination. Dr. McCoy urgently takes out his medical tricorder, a device that can check organ function and detect disease with a wave of its detachable probe. He hovers it just above Captain Kirk’s chest and within seconds he notes “severe heart damage, signs of congestion in both lungs,” and “evidence of massive circulatory collapse.”
This scene was featured in a YouTube video from 2009 (above), which cuts to the video’s narrator discussing this “powerful, compact medical scanner,” that has been a key tool for the science fiction doctors of Star Trek. “I should think the tricorder will be a real thing in the future,” pondered Alexander Siddig who played Dr. Julian Bashir in the early 1990s. “A diagnostic device which is really based on scanning. How on earth they are going to do that is for them to work out.” That episode aired just three years after Dr. Feigenbaum, the father of echocardiography, for the first time figured out how to visualize a pericardial effusion with ultrasound, at a time when the only way to diagnose thoracic disease at the bedside was still with Dr. Rene Laennec’s stethoscope and the field of auscultation he pioneered.
The path toward medical progress is neither linear, trivial, or certain, and often snowballs out of humble solutions to unexpected conundrums. A case in point was Laennec’s clinical exam of an obese female patient in 1816. His normal routine of placing the ear directly on the chest in what was called immediate auscultation was “rendered inadmissible by the age and sex of the patient” and percussion was not possible due to “the great degree of fatness.” He recollected the experience of an “augmented impression of sound when conveyed through certain solid bodies - as when we hear the scratch of a pin at one end of a piece of wood, on applying our ear to the other.” Laennec proceeded to roll some paper into a cylinder, and with one ear on one side he placed the other on her chest wall, revealing a treasure trove of thumps, wheezes, and murmurs he detailed extensively in his immortal text.
Through his exhaustive exam-to-autopsy correlations of thousands of patients, he perfected the stethoscope design and developed the field of auscultation to accompany it; a field that to this day still relies on the principles Laennec first described, that a diseased organ emits an SOS signal in its native tongue of wheezes and rales, and it is the clinician’s job, with the help of a stethoscope, to translate these sounds into actionable diagnoses. This bicentennial tool and technique are quite a testament to the influence this brilliant young doctor from Quimper has had on our current medical practice.
For 149 years the only practical method of diagnosing diseases of the thorax was still Laennec’s audible portal into the chest until Dr. Feigenbaum published Ultrasound Diagnosis of Pericardial Effusion in 1965, sending shockwaves across the pond of bedside diagnostics. Here, for the first time, was a teaser of a visual window into the chest of a living human, a pie-in-the-sky pipe dream for the likes of Laennec and other physical exam pioneers. Yet it was met with bitter opposition and heel-digging, a response not unlike what Laennec experienced when introducing his tool over a century prior.
As Feigenbaum’s heart ultrasound was evolving into the field of echocardiography, ultrasound machines were rarely spotted outside radiology departments, and even less frequently at the patient’s bedside. Dr. Jos Roelant, a dutch cardiologist from the 1970s, was one of the first physicians to incorporate point-of-care ultrasound (POCUS) in his physical exam as early as 1978. He and his colleagues “constructed a hand-held battery-powered ultrasound imager” they named “the ultrasound stethoscope,” that he used in his patient examinations. He was able to diagnose pericardial effusions (fluid around the heart), estimate heart size, and look for valvular disease. But the real origin of evidence-based, empirical POCUS came a decade later, arising from the tireless work of another Frenchman by the name of Daniel Alexandre Lichtenstein.
At the time, the idea of ultrasound at the bedside was unheard of and forbidden. Lichtenstein learned sonography basics from a radiologist a few years prior and during one of his night shifts, those lessons would prove their worth. One of his patients was getting worse, and a chest X-ray revealed near white-out of both lungs, a sign of impending respiratory doom. Yet was this pneumonia? Was it infectious fluid accumulating around the lungs and preventing them from expanding? The chest X-ray resolution was not sufficient to tell. When midnight struck and the radiologists left, Lichtenstein snuck into the radiology department, unplugged the ultrasound machine, and rolled it into the patient’s room. He squirted ultrasound gel on the surface of the probe, gently placed it on the patient’s flank, and the diagnosis revealed itself. Centered on the screen was a compressed lung bobbing in the pleural fluid like a buoy in the ocean. This pleural effusion was drained and the patient improved.
These U-turns in a patient’s clinical trajectory after a bedside ultrasound exam are such a common experience among POCUS-wielding clinicians that they even have a name. Dr. Nilam Soni, a pioneer in the field of internal medicine POCUS and co-author of the seminal point-of-care ultrasound textbook, calls it the “POCUS Kiss,” or PO-kiss for short.
Dr. Lichtenstein’s PO-kiss that night in the ICU ignited a fire inside him that would forever change bedside diagnostics. A few years later, Lichtenstein went to work at Ambroise Pare Hospital under the famed Dr. Francois Jardin. He chose this ICU “because it was the only ICU in the world which was equipped with ultrasound. We can say he created ‘echocardiography in the ICU.’” It was exclusively used for cardiac ultrasound until Lichtenstein began experimenting with imaging of other portions of the body. At the time (and still to this day for clinicians not familiar with Lichtenstein’s work), since the lungs are filled with air, the general consensus was that lung ultrasound is not possible. As recently as 2008, Harrison’s Principles of Internal Medicine, the seminal modern medical textbook, incorrectly reported that lungs are a major hindrance to ultrasound imaging.
Yet Lichtenstein noted various sonographic artifacts arising from the lung surface that until that point was not thought of as anything other than useless noise. Through his research challenging the status quo of the time, Lichtenstein showed that not only are these artifacts useful, but in fact map directly to various pulmonary diseases, much in the same way Laennec demonstrated with various lung sounds. He showed that just by using a standardized protocol to detect the presence or absence of three basic lung findings called lung sliding, A-lines, and B-lines, he could arrive at the correct diagnosis almost every time.
Lichtenstein’s work revolutionized the bedside evaluation of a patient with cardiopulmonary disease. Yet outside the intensive care unit or emergency department, this technique is seldom used in place of our stethoscopes. Despite the strong clinical evidence to support his findings corroborated by multiple studies around the world, the bedside deployment has been hindered by misguided preconceptions, cost, portability, and lack of training for the busy clinicians expected to adopt it. This juxtaposition of highly accurate clinical techniques to diagnose our most common diseases combined with a lack of training or affordable pocket-sized devices creates a chasm between idealism and practicality which has played out repeatedly in the medical literature and mainstream media.
For example, in 2016 Dr. Sanjiv Kaul, the head of the division of cardiovascular medicine at the Oregon Health and Science University, thought it was “time to discard the inaccurate, albeit iconic, stethoscope and join the rest of mankind in the technology revolution,” he explained in a Washington Post article, arguing instead that we should focus on the abilities of handheld ultrasound. “We are not at the place, and probably won’t be for a very long time,” countered Dr. W. Reid Thompson, an associate professor of pediatrics at Johns Hopkins University School of Medicine, “where listening to the body’s sounds is replaced by imaging.” This may have been true at the time, yet just 20 months later on September 6, 2017, the FDA would approve the Butterfly IQ, the first handheld full-body, smartphone-connected ultrasound device, ushering the field of bedside diagnostic medicine - kicking and screaming - into the POCUS Era that Dr. Kaul presciently described.
POCUS is the natural progression of what Laennec started over 200 years ago, a tool he would undoubtedly add to his diagnostic repertoire were he able to, as he did with Auenbrugger’s percussion or Hippocrates’s succussion. It enables a clinician to digitally peel back the epidermis and observe the ecosystem of internal organs functioning in real-time, an ability our forefathers, foremothers, and stethoscope-monogamous colleagues could infer only through skin changes, audible noises, or subjective symptoms. The pocket-sized ultrasound probe is a non-fiction device of today that was a science-fiction device of the 1960s, a handheld scanner that enables us all to be modern-day Dr. McCoys and instantly diagnose disease. With the introduction of multiple portable ultrasound probes on the market coupled with a 20x reduction in cost, the financial barrier to wide adoption is quickly being flattened. To achieve an ionizing-radiation-free diagnostic utopia our patients need and our clinicians desire, we must continue to cross this chasm, one Po-kiss at a time.
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Dr. Larry Istrail is an internal medicine physician and author of The POCUS Manifesto: Expanding the limits of our physical exam with point-of-care ultrasound. You can buy it on Amazon here.
Despite the (relatively recent) reduction in cost, it seems that still the stethoscope is the tool of choice.