Could Handheld Ultrasound Replace the Stethoscope?

Laurie Barclay, MD

April 01, 2014

Point-of-care, handheld ultrasound (HHUS) is already a valuable adjunct to the stethoscope and plays an important and increasing role in medical education and physical diagnosis. Whether it will become the stethoscope of the future, however, is a bit more uncertain.

"[A] generation of physicians will need to be trained to view this technology as an extension of their senses, just as many generations have viewed the stethoscope," write Scott D. Solomon, MD, and Fidencio Saldana, MD, from the Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, in a commentary published in the March 20 issue of the New England Journal of Medicine. "That development will require the medical education community to embrace and incorporate the technology throughout the curriculum."

French physician René-Théophile-Hyacinthe Laennec designed the first primitive "stethoscope" in 1816. Nearly 2 centuries later, the stethoscope is still used by virtually all physicians. With the exception of electronic stethoscopes providing amplification and filtering, this diagnostic tool has undergone few developments in style and technology.

The authors note, however, that in the last 5 decades, diagnostic ultrasound has largely replaced auscultation in cardiology, obstetrics, and gastroenterology, thanks to the anatomic and functional information it provides without exposure to ionizing radiation. Echocardiography is currently the most used and cost-effective imaging method in cardiovascular medicine.

"HHUS technology is far superior to the stethoscope in the ability it provides to an experienced user in rapidly 'ruling out or ruling in' certain key diagnoses, immediately, at the patient's bedside," Dr. Sharon L. Mulvagh, MD, FRCP(C), and Dr. Anjali Bhagra, MBBS, told Medscape Medical News.

Dr. Mulvagh is professor of medicine; director, Women's Heart Clinic; associate director preventive cardiology; and consultant in cardiovascular diseases, and Dr. Bhagra is associate professor of medicine, director of Ultrasound Mini Institute in Anatomy, and consultant in general internal medicine at the Mayo Clinic and College of Medicine in Rochester, Minnesota.

"This rapid fine-tuning and triaging of the differential diagnosis [obtained by the age-old traditional means of history, physical examination, and auscultation] enables optimization of the next steps for confirmatory diagnostic testing and treatment initiation," Dr. Mulvagh and Dr. Bhagra said. "HHUS permits expedient, efficient, and cost-effective diagnosis and initiation of an appropriate treatment plan."

"People like to compare ultrasound to the stethoscope, but ultrasound is actually a much more powerful tool when used well," Christopher L. Moore, MD, RDMS, RDCS, associate professor of emergency medicine at Yale University School of Medicine in New Haven, Connecticut, told Medscape Medical News. "Like the stethoscope, the contribution to diagnosis is directly related to the skill of the operator."

Cost and Feasibility Issues

Previous impediments to widespread use of ultrasound have included their cost and size. The development of faster microprocessors and better miniaturization has recently allowed fully functional ultrasound machines in laptop computers, or even as handheld devices that fit in a coat pocket. As the price of HHUS devices has fallen, they are now more accessible to physicians other than radiologists and cardiologists.

For example, Dr. Moore estimates the cost for a reasonable-quality HHUS at $8000 to $10,000 and from $30,000 to $60,000 for the compact cart-based units currently used in emergency departments and intensive care units. He expects the cost of HHUS to decline to about $2000 during the next decade.

"The cost of some rubber tubing and gaskets will likely always be less than ultrasound devices," said Jagat Narula, MD, PhD, Philip J. and Harriet L. Goodhart Chair in Cardiology, professor of medicine, and associate dean for global health, and Bret P. Nelson, MD, RDMS, director, Emergency Ultrasound Division, Department of Emergency Medicine, in an interview with Medscape Medical News. "However, in the next few years, it is reasonable to expect that the cost of HHUS devices would reach a price point where individual physicians would consider their purchase." Dr. Narula and Dr. Nelson lead the teaching program for HHUS at Icahn School of Medicine at Mount Sinai in New York City.

Greater availability of these devices raises the question of proper training in their use. Emergency physicians are now trained in basic abdominal, cardiac, and obstetrical ultrasound examination and in ultrasonographic catheter placement. Use of HHUS is also becoming more widespread among intensivists and anesthesiologists.

Ultrasound in Medical School Training

Dr. Solomon and Dr. Saldana note in their commentary that HHUS can outperform the stethoscope. For example, a recent study showed that first-year medical students who received some training in use of HHUS correctly diagnosed cardiac abnormalities more frequently than specialists using stethoscopes. The authors emphasize, however, that the information obtained from HHUS depends on operator skill.

Dr. Narula and Dr. Nelson echo that point. "Ultrasound devices require training and practice, but so do stethoscopes. Multiple studies have demonstrated superior diagnostic accuracy of ultrasound over physical examination or stethoscope use."

The University of South Carolina; University of California, Irvine; Harvard University; Mayo Medical School; and Mount Sinai medical schools have all recently begun ultrasound training early in the undergraduate curriculum.

"While HHUS is easy to use, it is difficult to learn really well," Dr. Moore said. "This is why it is important to expand ultrasound education earlier in the medical school curriculum."

A recent randomized trial of 3 different medical school educational programs showed that first-year medical students could modestly improve their ability in focused cardiac ultrasound interpretation and acquire limited scanning skills, and that third-year medical students could learn focused cardiac ultrasound image acquisition and interpretation skills. Self-directed electronic modules were effective for teaching introductory focused cardiac ultrasound interpretation skills, but expert-guided training was important for developing scanning techniques.

"It is imperative to educate our trainees in these basic focused ultrasound examinations within the context that HHUS is not meant to replace basic diagnostic skills, but to augment them," Dr. Mulvagh and Dr. Bhagra said. "Missed diagnoses and/or misdiagnosis are potential pitfalls that can be avoided with appropriate training, guidance, and acquisition of experience."

Will HHUS Replace the Stethoscope?

"We can't find any evidence that the stethoscope introduced major improvements in patient outcomes, [which] may be because in the early 1800s there were no antibiotics for lung infections, no diuretics for congestive heart failure, etc," Dr. Narula and Dr. Nelson said. "Prior to this, patients were observed; now they could be examined. Illnesses were described as syndromes, collections of described symptoms, but now illness could be described based on physical manifestations of disease, some of which would be invisible or inaudible to the unaided clinician."

In contrast, Dr. Narula and Dr. Nelson expect significant outcome differences with the introduction of HHUS. For example, midwives in rural Africa have been trained to use HHUS to identify abnormal fetal presentations necessitating referral for high-level obstetric care, thereby improving survival of the mother and child through timely cesarean delivery.

Dr. Mulvagh and Dr. Bhagra gave the example of HHUS allowing rapid diagnosis of pulmonary embolism in an elderly patient admitted for presumed non-ST segment elevation myocardial infarction, allowing immediate triage to chest computed tomography and appropriate treatment.

"Wasted dollars and excess risk to the patient were avoided by the appropriate next test being rapidly selected through guidance by the handheld device immediately at the initial patient contact," they explained. "It would potentially have been very expensive, both in terms of dollars and risk to patient, if [the patient] had been sent instead to the cardiac catheterization laboratory for a coronary angiogram, [which is] the wrong and potentially dangerous test to do (in this setting)."

Dr. Solomon and Dr. Saldana note 2 major developments needed before HHUS is likely to replace the stethoscope. Technological advances must include smaller size, more ergonomic design, and additional functionality, such as the ability to amplify lung or bowel sounds. In addition, educational advances must include training physicians to view HHUS as an extension of their senses, as well as continued incorporation of ultrasound throughout the curriculum.

"We are advocating that HHUS devices be used as an extension of the stethoscope, and not a replacement for the stethoscope," Dr. Mulvagh and Dr. Bhagra said. "HHUS is intended to enhance the physical examination by actually 'seeing,' or 'not seeing' (ruling in or out) the suspected pathophysiology from a carefully performed clinical assessment."

Barriers to Widespread Use

Barriers to widespread HHUS use include possible reservations by specialists already trained in ultrasound use and interpretation, issues regarding medical records and billing, false-negative as well as false-positive results, and potential distraction of medical students from the core principles of physical diagnosis.

"It is important that when ultrasound is used as a focused diagnostic test in an appropriate situation that it be reimbursed appropriately, even when done by nonradiologists," Dr. Moore said. "This will help to ensure quality and provide the resources for equipment and teaching that are needed to do it well."

He noted that false-negatives and false-positives caused by less-experienced operators will decrease with more practice and exposure and should not unnecessarily limit HHUS use.

"At the same time, it is important that people using ultrasound receive good training and understand their limitations, that strong policies are in place about what can and should be done with ultrasound [and] by whom, particularly when ruling in or ruling out a diagnosis, and that patients also are made aware of the difference between a point-of-care ultrasound and a comprehensive study," Dr. Moore added.

Dr. Narula and Dr. Nelson also recommend supervision for any diagnostic decisions made by trainees, whether for ultrasound or for physical examination.

"Overconfidence in ultrasound results could lead to unnecessary additional testing or premature diagnostic closure when test results are misinterpreted or not placed in the proper clinical context," they said. "But we believe that this would be a technology which will uniquely improve both sensitivity and specificity of diagnosis."

Outcomes Research Is Needed

In terms of additional research, Dr. Narula and Dr. Nelson recommended determining whether HHUS use can reduce patient exposure to tests that are more expensive, invasive, or involve ionizing radiation, as well as time to diagnosis.

"We need quality (funded) research on what training is required and how and when point-of-care ultrasound can impact patient-centered outcomes," Dr. Moore said. "Unfortunately, many of the traditional research funding routes (such as [the National Institutes of Health]) do not have institutes that are directly interested in this area. Hopefully, other organizations, such as the Patient-Centered Outcomes Research Institute...or the Agency for Healthcare Research and Quality...or even private foundations may be able to help fund needed research."

Dr. Mulvagh and Dr. Bhagra recommended research on how to implement and integrate ultrasound into medical training programs and to assess learning and competence. "As this technology is adopted, an important area of research will not only be outcomes studies, exploring cost-effectiveness parameters (length of stay, cost of episode of care), but also patient satisfaction, leveraging the immediacy of the available feedback in the context of our current health care environment, which emphasizes high value and quality care," they concluded. "Indeed, it will be interesting to see if patients will soon begin to expect that their health care providers are proficient in use of HHUS."

The authors have disclosed no relevant financial relationships. Dr. Moore consulted once during the last 3 years for Philips Medical on development of an educational ultrasound product. Dr. Narula is also director of the Cardiovascular Imaging Program at the Zena and Michael A. Wiener Cardiovascular Institute and Marie-Josée and Henry R. Kravis Center for Cardiovascular Health, New York City, and editor-in-chief of the Journal of American College of Cardiology–Imaging. He has received research grants from GE Healthcare, and Philips Healthcare. Dr. Nelson is a consultant for Simulab Corporation. Dr. Mulvagh and Dr. Bhagra have disclosed no relevant financial relationships.

N Engl J Med. 370;12:1083-1085. Extract

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