INTRODUCTION

Historical Development of Diagnostic Ultrasound

The diagnostic ultrasound (US) journey began in the 20th century and gained significant momentum in the 1960s and 1970s. This period saw the emergence of two primary methodologies:

• Technician-Based Ultrasound: In some regions, this approach relied heavily on technicians for image acquisition, with radiologists and cardiologists interpreting the images. This often led to limited practical ultrasound skills among physicians and necessitated standardized imaging protocols, which could result in less adaptable examinations.

• Physician-Performed Ultrasound: In other areas, physicians such as internists, gynecologists, surgeons, and cardiologists managed both image acquisition and interpretation. This integration allowed for real-time, dynamic adjustments during examinations.

These divergent approaches resulted in varying levels of ultrasound proficiency among physicians. By the 1990s, in regions favoring physician-performed ultrasound, primary care physicians and specialists routinely used ultrasound during patient visits, recognizing its significant diagnostic value.

Emergence of Emergency Medicine Ultrasound (EMUS)

The 1980s marked the advent of portable and mobile ultrasound machines, catalyzing the rise of Emergency Medicine Ultrasound (EMUS). Initially adopted by surgeons and emergency medicine physicians for trauma patients, EMUS quickly expanded to other emergency scenarios. This method involved focused, real-time diagnostic ultrasounds performed at the bedside, substantially enhancing acute patient care. EMUS became particularly popular in regions with technician-based systems.

EMUS involves bedside diagnostic and interventional sonography conducted and interpreted by trained physicians. It has proven to enhance diagnostic accuracy, expedite consultations, and integrate seamlessly into clinical pathways. Although evidence of its impact on clinical outcomes like mortality is still limited, studies underscore its efficiency and superior diagnostic capabilities in emergency settings.

Current Concepts and Classifications of EMUS

EMUS aims to answer specific clinical questions in emergencies through sonographic findings, guiding therapeutic decisions. Examinations are categorized into two types:

• Basic (Primary) Exams: Simple and straightforward, requiring minimal technical expertise.

• Advanced (Secondary) Exams: More complex and technically demanding, often necessitating specialized equipment.

These exams are classified based on their clinical relevance, technical difficulty, frequency, and availability of probes and software. The American College of Emergency Medicine provides a widely recognized classification system, grouping EMUS applications into five categories: Resuscitative, Diagnostic, Procedural guidance, Symptom- or sign-based, and Therapeutic.

Evolving EMUS Concepts

Recent developments in EMUS are driven by a deeper understanding of the physical examination, particularly the stethoscope's role, and by correlating sonographic capabilities with physical and pathophysiological processes. Advances in technology and competence-centered education are propelling new concepts and applications poised for integration into emergency medicine practice.

Examples of New EMUS Application Possibilities and Concepts

Recent years have seen numerous articles on novel EMUS applications across nearly all human organs and systems. However, only a few have been widely adopted. Notable examples include the E-FAST exam and pulmonary embolism (PE) diagnosis.

Advancements in Trauma Care

The initial goal of FAST was to quickly detect internal bleeding in unstable trauma patients, with E-FAST expanding this to include pneumothorax detection. Over time, FAST and E-FAST have been extended to stable trauma patients and additional indications like ruptured ectopic pregnancy and undifferentiated shock. Technological advances now enable the detection of small fluid collections, solid organ injuries, retroperitoneal hematomas, and free air using high-sensitivity color Doppler or contrast-enhanced ultrasound (CEUS). Further applications include detecting fractures, musculoskeletal issues, and vascular injuries, and guiding invasive procedures.

Emergency physicians now have a comprehensive range of sonographic examination options to aid in the primary survey, including endotracheal intubations, pulmonary contusions, hemodynamic evaluations, cerebral hypertension, and cerebral perfusion in traumatic brain injury (TBI). Hemodynamic monitoring is particularly beneficial for guiding fluid therapy, vasopressor use, and invasive procedures.

In summary, the traditional E-FAST exam for unstable patients and an expanded version for stable patients now encompass:

• Expanded E-FAST: Including additional views of the abdomen, retroperitoneum, solid organ injuries, and free air.

• PoCUS Applications: Beyond traditional E-FAST during the primary trauma survey.

• Hemodynamic Monitoring: Including cerebral perfusion in TBI, to guide fluid and vasopressor treatment.

• Detection: Of musculoskeletal, soft-tissue, and vascular injuries.

• Guidance: For invasive procedures.

From the Stethoscope to PoCUS

René Laennec's invention of the stethoscope over 200 years ago revolutionized heart auscultation, eventually extending to the lungs, intestines, and vessels. Despite its widespread use, its diagnostic value is often limited due to poor usage. While digital stethoscopes with smartphone apps might not significantly improve skills, many institutions now recommend point-of-care ultrasound (PoCUS) devices, which have proven superior for diagnosing cardiac, pulmonary, and abdominal issues compared to traditional methods like the stethoscope and X-rays.

Although some debate PoCUS's efficacy, it's evident that many physicians lack proficiency with the stethoscope, which requires substantial training. Thus, the shift from auditory to visual diagnostics using ultrasound is becoming more plausible. PoCUS integrates heart, lung, abdomen, and vessel examinations, as well as palpation and percussion, redefining physical examination. Portable or handheld ultrasound devices could replace significant portions of traditional auscultation exams, reducing reliance on other imaging modalities, and decreasing costs, infrastructure needs, and resource demands. Implementing this shift in resource-limited areas poses challenges, but tailored curricula and tele-ultrasound training can help.

In well-resourced countries, this paradigm shift might begin with medical education. Students already use ultrasound in anatomy, physiology, and pathophysiology courses, and clinical examination courses should incorporate PoCUS training. Continuing education for emergency medicine should focus on specific aspects of PoCUS, with competence-based supervision being crucial. In regions with limited resources, PoCUS can be a feasible alternative to hospital-based imaging, using cost-effective mobile devices suitable for austere environments.

PoCUS Visualization of Pathophysiological Processes

Emergency medicine topics like fluid therapy, pulmonary edema, and viral pneumonias benefit from correlating ultrasound physics with pathophysiology, leading to improved diagnostic concepts. For instance, cardiac output increase with fluid is closely tied to venous return, which can be described by the Doppler spectrum of large veins. Lung sonography concerns, such as B-lines (vertical ultrasound artifacts), are increasingly understood in relation to conditions like interstitial lung pathologies versus water retention in the lungs.

Technical Innovations

• Elastography: With over 20 years of use in advanced regions, elastography has applications in trauma, musculoskeletal diseases, and pulmonary conditions.

• Advanced Color Doppler Technology: High sensitivity enables visualization of small peripheral blood vessels, aiding in detecting hemorrhages, hematomas, and infarcts, potentially replacing contrast-enhanced ultrasound (CEUS).

• Artificial Intelligence (AI): AI-assisted diagnosis in ultrasound devices, using deep learning and convolutional neural networks, shows promise in areas like lung artifact sonography and quantitative echocardiography.

• Cloud-Based PoCUS: Utilizing 5G technology, cloud-based PoCUS platforms facilitate real-time imaging transmission, offering low-cost, high-performance diagnostic solutions.

• Smart Glasses: These wearable devices enhance PoCUS by allowing hands-free adjustments and real-time ultrasound projection during procedures, showing potential in improving ultrasound-guided vascular access.

Future research will likely expand the use of technologies like elastography and high-sensitive flow in PoCUS. AI applications in PoCUS are growing rapidly, requiring ethical considerations and further studies to understand their best implementation.

Conclusions

Emergency sonography involves bedside PoCUS by attending physicians to address time-sensitive issues in emergency patient care. EMUS encompasses five domains: resuscitative, diagnostic, procedural guidance, symptom- or sign-based, and therapeutic, with applications divided into basic and advanced levels. Technological advances and practical research findings open many new possibilities for integrating PoCUS into emergency medicine.

• New Indications: Numerous potential applications for all organs and systems await routine use, exemplified by trauma ultrasound, which should extend beyond E-FAST and pulmonary embolism diagnosis.

• Educational Shift: As financial barriers diminish, the transition from stethoscopes and traditional examination methods to PoCUS should be implemented widely. Medical education must be revolutionized to include comprehensive PoCUS training.

• Pathophysiological Insight: Combining knowledge of pathophysiology with ultrasound physics can improve the management of hemodynamics and lung artifact sonography.

• Technical Innovations: Emerging technologies like elastography, advanced Doppler, AI, cloud-based PoCUS, and smart glasses have significant potential in emergency settings.

These advancements necessitate tailored curricula, competency-based supervision, and innovative training methods to integrate PoCUS effectively into emergency medicine practice.