“It must be confessed that there is something even ludicrous in the picture of a grave physician formally listening through a long tube applied to the patient’s thorax, as if the disease within were a living being that could communicate its condition to the sense without.” — Dr. John Forbes, 1821
As the Covid-19 pandemic reshapes how medicine is practiced in the U.S., one iconic tool could be relegated to the dustbin of medical history: the stethoscope.
For generations, there has been no better physician archetype than the quintessential black rubber stethoscope donned confidently over a crisp white coat. This highly recognizable image evolved from experiments conducted in 1816, when Dr. René Laennec listened through a paper cylinder placed on a patient’s chest, revealing a treasure trove of muted thumps, crackles, and wheezes that comprise the cacophony of physical exam findings clinicians rely on today.
Two centuries later, as the world suffers through a cataclysmic pandemic, many hospitals and clinicians have conspicuously decided that the ratio of useful information to infection risk does not favor employing a stethoscope on any patient with even a whiff of Covid-19 related illness. In its place has risen a budding dark horse of modern bedside medicine: the portable, and increasingly affordable, ultrasound.
We are entering the era of point-of-care ultrasound, which relies on higher-frequency sound waves than its stethoscope predecessor. It is a hand-held device equipped with the ability to both emit sound waves and interpret them as they reflect off structures of interest, similar to how a bat uses sonar to navigate its surroundings.
This technology could usher in an epoch in health care that does not rely on the spectrum of audible noise that the ears of aging doctors increasingly cannot discern. Instead, we should be looking ahead to the widespread use of a pocket-sized and radiation-free device that peers into the body in real time and explores the inner organs in a “Magic School Bus“-like fashion. Point-of-care ultrasound enables a clinician to digitally peel back the skin and observe the ecosystem of internal organs functioning in real time, an ability our forefathers and stethoscope-monogamous colleagues could infer only through skin changes, audible noises, and subjective symptoms.
So far, point-of-care ultrasound has been embraced mainly by emergency and intensive care clinicians, and has yet to crack my internal medicine colleagues’ morning rounds. Lack of formal training and cost — a basic point-of-care ultrasound system costs between $2,000 and $50,000, compared to $400 for a top-of-the-line stethoscope — are certainly barriers to adoption. Yet if medical students with only 18 hours of ultrasound training can more accurately diagnose heart problems with point-of-care ultrasound than experienced cardiologists can with a stethoscope, it is time to admit that our trusty analog listening device should be put out to pasture.
The art of auscultation using a stethoscope is a right-of-passage skill learned by all medical trainees on their journeys to becoming clinicians. Yet as with any other medical test or physical exam, auscultation requires adequate scrutiny and understanding of its limitations. The American Roentgen Ray Society once published 10 criteria for an ideal screening test. Two of them, affordability/availability and high accuracy, are most relevant to the stethoscope vs. point-of-care ultrasound debate. While the stethoscope is certainly more available and affordable, it fails to provide accurate data, the most crucial measure of a good screening assessment.
While there are many clinical scenarios in which point-of-care ultrasound provides more and better information than a stethoscope, the lung examination may be the most telling.
Take as an example pulmonary edema, a buildup of fluid in the lungs often caused by congestive heart failure. When this fluid is present, it can cause a crackling sound to be present as the patient takes a breath. Listening for these characteristic “crackles” picks up only about 4 out of 10 cases, and only 67% of patients in whom crackles are heard actually have congestive heart failure. In contrast, point-of-care ultrasound is almost perfect, accurately detecting 97% of cases with only 2% of false positives. Point-of-care ultrasound also outperforms auscultation in diagnosing asthma, COPD, and pleural effusion, a buildup of fluid between the lung and chest cavity (see table).
|Fluid buildup in the lungs due to congestive heart failure||46%||67%||97%||98%|
|Asthma / COPD||30%||90%||89%||97%|
|Pleural effusion with 200 or more milliliters of fluid||42%||90%||100%||100%|
|Pleural effusion with less than 200 milliliters of fluid||Cannot detect||Cannot detect||93%||96%|
As the authors of a meta-analysis on lung auscultation published in the journal Nature concluded, “When better diagnostic modalities are available, they should replace lung auscultation. Only in resource limited settings, with a high prevalence of disease and in experienced hands, lung auscultation still has a role.” Point-of-care ultrasound could certainly represent one of those “better diagnostic modalities.”
On top of their poor utility for screening and diagnosis, stethoscopes have already been linked to a Covid-19 outbreak in a South African hospital, are known to carry dangerous Staphylococcus aureus and MRSA bacteria, and the majority of them are cleaned rarely — or never.
In this ultra-heightened era of infection prevention, these shortcomings certainly beg the questions: Why are we clinging to this medical relic with minimal utility and known infection risk? If it does not provide enough useful information to warrant its risk in Covid-19 infections, then does it ever?
In the Covid-19 era, point-of-care ultrasound has proven invaluable. While it also carries significant risk of transmitting infection, multiple studies have confirmed that there are ultrasound lung findings for Covid-19 that can be used to triage patients with respiratory symptoms. It is more sensitive than the chest X-ray in detecting Covid-19 and conserves PPE and limits health care worker exposure by allowing one physician to both assess the patient and perform the imaging. In patients with a high suspicion for Covid-19 but a negative nasal swab test, ultrasound provides valuable objective information to determine if that negative test warrants a repeat, as these tests still have notoriously high false negative rates.
The art and tradition of medicine should be learned and respected. But with the high-stakes, time-sensitive decisions that physicians make on a daily basis, art and tradition should take a backseat to precision and certainty. Interventional cardiologists like to say that “time is heart” when referring to how quickly they need to open a blocked coronary artery. Neurologists prefer the “time is brain” axiom when referring to treating strokes. For the ultrasound-wielding clinician who can peer inside you with near-perfect accuracy for many diseases and see your fate as soon as you barge through the hospital doors with shortness of breath, “time is life.”
Time is life when you can find in a patient with plummeting blood pressure a large pericardial effusion compressing the heart, making it difficult for it to pump blood to the body and brain. Time is life when you can detect a large blood clot brewing in the leg before it has broken off and traveled to the lung, causing a life-threatening pulmonary embolism.
I believe that given the remarkable diagnostic accuracy of point-of-care ultrasound, every patient presenting to a clinic or hospital should have a focused ultrasound to augment their clinician’s physical exam findings. There is just no excuse not to.
With the advent of small ultrasound probes that connect to a smartphone and cost 20 times less than their traditional ultrasound counterparts, we are finally in a position where we can make point-of-care ultrasound as routine as auscultation. That means pivoting residency training and continuing education to ensure that all clinicians in every health care setting worldwide have this skill so one day soon we can see the adored stethoscope reach its final resting place: collecting dust inside the medical exam room drawer labeled “wheeze-detector.”
Larry Istrail is a hospitalist physician and is point-of-care ultrasound certified by the Society of Hospital Medicine. He is a champion of point-of-care ultrasound and a contributor to pocusmeded.com. He has no financial ties with any standard or point-of-care ultrasound companies.