In its most basic sense, the physical exam is a method of inferring the state of health of the internal organs. For two centuries, it has been accomplished through auscultation, inspection, palpation, and percussion. These techniques complement the taking of a detailed history, designed to flesh out uncertainties arising from the patient’s subjective report. However, such methods are often so imprecise that they do little to reduce uncertainty or narrow our differential diagnosis at all.
Consider the diagnosis of congestive heart failure (CHF), one of the most common causes of hospitalization in the United States. Since the 1800s the signs and symptoms of CHF and its downstream ramifications have been well understood. Dr. Rene Laennec, the inventor of the stethoscope and the field of auscultation to accompany it, knew these patients presented with a “habitually swelled state of the veins.” Likewise, Dr. James Hope, a cardiologist from the 19th century who wrote one of the first cardiology texts, understood that fluid backs up into the lungs and into the rest of the body through “a series of striking phenomena,” starting with lower extremity swelling that “gradually ascends ... over the whole surface of the body.” However, since these signs or symptoms are not unique to congestive heart failure, the direct diagnosis of CHF at the bedside has remained elusive.
This was evidenced by a recent study in JAMA analyzing medicare data of nearly one million patients from 2003 to 2019, looking at those who were first diagnosed with CHF in an emergency department visit or hospitalization. About 1 in 6 of them had heart failure-related symptoms such as edema or shortness of breath documented during outpatient clinic visits in the 6 months prior, suggesting they were likely in heart failure already, it was just not detected.
Timely diagnosis of CHF reduces suffering by starting diuretics earlier, preventing unnecessary treatments like antibiotics for presumed pneumonia, and enables guideline-directed medical therapy to be started earlier. Yet in the absence of using POCUS to augment our physical exam, even with the most adept clinician, this diagnosis is difficult to make with an exam and stethoscope alone. This is due mainly to the imprecise methods we have in our tool kit rather than any shortcomings of those who routinely employ them.
Take a hypothetical example of one of these roughly 170,000 patients who had symptoms resulting from undiagnosed heart failure presenting to an outpatient clinic. In the early stages of CHF, they may present with mild lower extremity swelling, shortness of breath when climbing stairs, or report using an extra pillow to keep their head elevated. While these vague symptoms may be the result of CHF, they could also be explained away by many other factors. To flesh out the root cause, a clinician could perform a thorough physical exam, starting with the neck vein exam to detect signs of excess fluid accumulation. Yet this iconic jugular vein exam has consistently poor diagnostic accuracy for detecting elevated pressures and is rendered futile in many patients who are overweight or obese. The next step would be listening to the lungs for crackles or examining the lower body for edema. Unfortunately, these are not very precise either. A meta-analysis in Nature found that lung auscultation could only detect this CHF-related pulmonary edema with sensitivity and specificity of about 60%, while in patients with severe pulmonary edema in another study, half had no detectable edema-related lung crackles and 80% had no lower extremity swelling.
In the setting of an outpatient visit, a clinician could then order an echocardiogram, yet this requires days or weeks to schedule and result, and inflicts a significant burden on the patient to take time off work, schedule the echo, and return to the clinic to discuss the findings. Alternatively, the medical provider could get a chest x-ray to look for evidence of pulmonary edema or enlarged heart, yet chest X-rays are often inconclusive and only detect 6 out of 10 patients with pulmonary edema.
This piecemeal diagnostic web of outsourced imaging studies to specialists not directly involved in the care can hamper our ability to diagnose CHF outside a hospital, limitations that can be easily overcome with point-of-care ultrasound.
Diagnosing CHF with POCUS
In contrast to our traditional physical exam which infers cardiopulmonary disease from secondary acoustic findings, the direct visualization of the heart, lungs, and neck veins themselves make a POCUS-augmented physical exam orders of magnitude more effective. For example, in a study of medical students and residents, using just signs and symptoms of congestive heart failure acquired through a traditional physical exam, they detected CHF patients with 25% sensitivity and 84% specificity. The addition of cardiac POCUS and only two hours of training increased these figures to 74% and 93.6% respectively. The researchers "found a dramatic improvement in trainees' sensitivity, [positive predictive value] and [negative predictive value] in detecting or ruling out moderate-to-severe LV systolic dysfunction and valvular disease when using [POCUS] on the top of physical examination."
Such abilities of non-cardiologists to evaluate heart function directly with bedside ultrasound has been seen in multiple studies, and would allow real-time diagnosis of heart failure with reduced ejection fraction and a more strategic approach to cardiology consultations and echo referrals.
Yet even without a reduced ejection fraction, CHF can be accurately inferred from other ultrasound findings. With POCUS the neck veins can be visualized and assessed in every patient regardless of their body size or neck girth, and highly accurate qualitative assessments can be done.
Lung ultrasound findings consistent with pulmonary edema (lung sliding with Rockets in two or more lung fields) gleaned from a few-minute exam increase the odds of having pulmonary edema by 53.7 times compared to just 5-times when detecting pulmonary edema with lung crackles, and basic protocols can be employed to consistently diagnose it with over 95% sensitivity and specificity.
With this level of diagnostic accuracy, a clinician with training in POCUS can effectively rule in or out CHF with near certainty, a skill set that our patients need and our clinicians desire. Yet outside the intensive care unit or emergency department, these techniques are seldom used in place of our stethoscopes.
Despite the strong clinical evidence to support POCUS-augmented physical exams, 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 has created a chasm between idealism and practicality, relegating these skills to those that learned during residency or are intrinsically motivated to become certified on their own.
Fortunately, there are promising signs that our medical behemoth is adapting. The cost of an ultrasound device has dropped exponentially. Medical schools are giving new students ultrasound probes to complement their stethoscopes, and 72% of medical schools have some amount of ultrasound training incorporated into the curriculum. These trends paint an exciting future of bedside diagnostic medicine that offers our clinicians new powerful tools and our patients the precise and timely diagnoses they deserve.
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Dr. Larry Istrail is a 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 now.