Chapter 4. Ultrasound in Prehospital and Austere Environments

The term “out-of-hospital ultrasound” refers to sonographic examinations performed in a wide variety of settings outside of traditional hospital departments, laboratories, and freestanding imaging centers. “Prehospital ultrasound” is synonymous, even though this term is mostly used in reference to EMS and tactical medicine applications. Prehospital ultrasound examinations are generally not performed by radiologists or clinicians; caregivers incorporate the use of ultrasound into the initial patient assessment at the point of care in the prehospital setting. The images obtained provide real-time morphologic and functional clinical information. In the emergency and critical care literature, “point-of-care ultrasound” most commonly refers to “bedside emergency ultrasound” since the scientific debate has been originally focused on patients being cared for in the ED; the resuscitation, operative, or recovery room; the intensive care unit; the diagnostic imaging department; or other medical and surgical wards. Diagnostic and therapeutic advances have allowed “critical care” to be taken outside of the hospital setting to the scene of illness and injury in a wide variety of settings (Table 4-1).

In all of these settings, ultrasonography provides a visual extension of the clinical examination, permitting more accurate assessment of anatomic and physiologic integrity in complex states of illness and injury (Figures 4-1 and 4-2). Prehospital applications are generally incorporated into defined problem-based clinical pathways rather than organ-based categorizations (i.e., “shock assessment” rather than “liver assessment”).

Clinical accuracy and timeliness are essential for successful decision making and problem-solving in the prehospital environment. The prehospital use of ultrasonography can improve initial data gathering, which enhances the delivery of acute care in a timely and effective fashion. Efforts are being made to identify its most appropriate applications in the prehospital setting, the technical feasibility and reliability of its use, prehospital provider training and competency requirements, and the impact of prehospital ultrasound on patient outcomes and community health.1–10

To highlight the growing evidence in support of prehospital ultrasound, this chapter will review the experience of the German, Austrian, French, and American helicopter and ground-based EMS. This chapter will also review ultrasound in tactical medicine, remote telementored ultrasound, and the use of ultrasound in under-resourced settings.

Felix Walcher, Franziska Brenner, Marco Campo dell'Orto, Thomas Kirschning, Ingo Marzi, and Raoul Breitkreutz

The German emergency system takes advantage of a close alliance between emergency physicians and the rescuing service staff prior to transportation to the hospital. The overriding principle of on-scene care is “stay and play” in nontraumatized patients and “treat and run” in traumatized patients; however, this is in contrast to the “scoop and run” principle of most international prehospital systems. The implementation of ultrasonography into such a system is supported by the development of two major concepts and training programs: Prehospital Focused Assessment with Sonography for Trauma (P-FAST) and Focused Echocardiographic Evaluation in Life Support (FEEL) for emergency and critical care physicians, and partially paramedics. Those protocols are embedded as “understand, treat and run” into the prehospital workflow.

P-FAST is related to prehospital trauma care. Clinical estimates of intraperitoneal bleeding at the trauma scene are difficult to accurately assess. A blunt trauma patient with normal vital signs and an unremarkable physical examination may have massive intraperitoneal bleeding that requires urgent operative management for hemorrhage control. Data from several studies support the role of prehospital ultrasound in enhancing detection of intraperitoneal hemorrhage.10,11

The 2001 Frankfurt/Main pilot study and a subsequent prospective multicenter study of P-FAST investigated its feasibility in trauma care.10,11 Five air rescue centers in southwestern Germany and one ground ambulance rescue team in Frankfurt/Main took part in these studies. The entire P-FAST examination took about 2 minutes when results were negative, whereas positive intraperitoneal sonographic findings could be detected within seconds. Prehospital diagnosis of intraperitoneal injury by ultrasound was made approximately half an hour prior to arrival at the ED. In more than 90% of the cases, there was enough time to complete the P-FAST examination on the scene or during transportation. In a few cases, ultrasound could not be completed because of suboptimal conditions (e.g., subcutaneous emphysema, patient obesity, or lack of time). The P-FAST examination had a sensitivity of 93% for the detection of intraperitoneal hemorrhage. The investigators concluded that P-FAST had potential as a useful, reliable diagnostic tool in surgical triage at the trauma scene.11

All rescue teams involved in the multicenter study stated that P-FAST had an important impact on decision making. In approximately one-third of the cases, the findings of P-FAST had an influence on trauma management at the scene. Whenever intraperitoneal bleeding was detected, the prehospital phase of care was minimized to enable immediate transportation, either by ground or by helicopter. In contrast, if the findings of P-FAST were negative, the routine algorithm for trauma care at the scene was followed by completion of the primary and secondary surveys in accordance with the principles of advanced trauma life support (ATLS). The ultrasound findings led to a change in the choice of admitting hospital in approximately 20% of the cases. In addition, the results of P-FAST gave surgeons additional information that allowed appropriate planning of the hospital phase of care.

FEEL is an ACLS-compliant echocardiographic assessment and also addresses the development of skills for acute and critical care physicians in time-dependent scenarios.1 The aim of FEEL is to elucidate treatable conditions and not to terminate CPR. Entities such as pulmonary embolism, pericardial tamponade, global left ventricular failure, and hypovolemia should be identified during the initial resuscitation. A major challenge is recognizing return of spontaneous circulation when no central pulse is palpable and differentiating pulseless electrical activity (PEA) states with or without wall motion. New evidence suggests that echocardiography can identify a “subclinical” return of spontaneous circulation (i.e., mechanical cardiac output).

The FEEL algorithm is a structured workflow within the ACLS clinical management approach that can be applied in real time. The 2010 American Heart Association resuscitation guidelines recommend high-quality CPR with minimal interruptions to reduce no-flow intervals. The 2010 European Resuscitation Council guidelines have now incorporated suggestions for ultrasound concepts for identification and treatment of reversible causes or complicating factors and training of ALS-conformed ultrasound.

Studies have evaluated the FEEL concept for its ease of implementation into the CPR process and its ability to identify characteristic pathologies.12–14 The FEEL examination is a 10-step procedure (Table 4-2) designed to be performed during CPR cycles in order to reduce unwanted interruptions. Prehospital indications for performing FEEL are listed in Table 4-3.

A prospective, observational trial in the prehospital setting tested (a) the capability of FEEL to differentiate PEA states and (b) the feasibility of FEEL using a mobile, battery-powered ultrasound system. Trained emergency physicians applied the FEEL examination as described. A total of 230 patients were included, with 204 undergoing a FEEL examination during ongoing cardiac arrest (100) and in a shock state (104). Images of diagnostic quality were obtained in 96%. In 35% of those with an ECG diagnosis of asystole, and 58% of those with PEA, cardiac motion was detected, and associated with increased survival. Echocardiographic findings altered management in 78% of cases.12

Before 2001, a uniform course to teach P-FAST was unavailable in Germany or other parts of Europe. Prior to the P-FAST studies, it was necessary to set up a structured educational program for emergency physicians and paramedics. A P-FAST course concept was developed on the basis of several studies that had been performed in the 1990s with respect to the use of ultrasound in the clinical setting. Some groups had investigated which type of education programs were required to gain competency in performing the FAST examination and had assessed the learning curve. The recommended duration of didactic training, including hands-on experience, ranged from 2 to 30 hours.

The main goal of the P-FAST training is to prepare participants for uncommon situations in trauma scenarios under field conditions. The 1-day course in P-FAST includes both didactic and hands-on training. The didactic session includes a general introduction to ultrasound, physics of ultrasound, and the causes and relevance of artifacts and shadows that may be encountered during an ultrasound examination. Participants are introduced to the rationale for performing ultrasound as part of trauma management and are taught how to integrate P-FAST into the prehospital algorithm for trauma care. Numerous images and videos provide an overview of the physiologic and pathologic situations. Hands-on training is the main focus of the course. Participants perform the P-FAST examination under the supervision of clinicians experienced with ultrasound. The ratio of instructors to students is 1:2 or 1:3. During the course, a trainee performs 30–40 ultrasound examinations under the supervision of the instructors.

In the first part of hands-on training, participants perform the standardized procedure of P-FAST on healthy and patient volunteers. Patient volunteers have positive findings for free intraperitoneal fluid secondary to peritoneal dialysis or ascites. In the second part of the hands-on training, students learn how to perform the ultrasound examination under difficult circumstances, such as on patients found in challenging prehospital conditions. In the third part, real-time scenarios are presented with healthy or patient volunteers found in critical situations following a traumatic event. These scenarios include surgical triage of three or more victims or volunteers trapped in the wreckage of a vehicle. Evaluation of the course program is consistent with data from other training evaluations in the literature, which have shown that these programs produce competent examiners and are associated with a steep learning curve. No significant differences were found between emergency physicians and paramedics in terms of sensitivity, specificity, and accuracy of P-FAST examinations.

A 1-day course was established on focused echocardiography for emergency physicians and critical care physicians who had no previous experience in performing echocardiography.13 The course emphasizes basic echocardiography, rapid evaluation, and communication skills. In addition, a real-time 3D-ultrasound simulation combined within a full-scale ACLS training system as well as web-based learning and tests are included. We also evaluated an emergency physician's ability to obtain a correct subxiphoid 4-chamber view and to interpret a 5-second echocardiogram of normal and pathologic findings. We found that emergency physicians could learn to identify some simple pathologic findings on very short video clips, and for the combined ultrasound and ACLS trainer there were high positive ratings. In 2011, P-FAST and FEEL became incorporated into the nationwide certified training programs of the German Society of Ultrasound in Medicine (DEGUM) and German Society of Anesthesiology, Intensive and Emergency Care (DGAI) as extended-FAST (E-FAST) (including lung ultrasound) and cardiosonography modules.

Prior to the German P-FAST multicenter study, the fire department of the city of Frankfurt and the Department of Trauma Surgery at the University of Frankfurt used a device based on Esaote Tringa. The compact ultrasound machine SonoSite 180 Plus is used by the German Army and in the MedEvac system operating worldwide. The SonoSite NanoMaxx is standard of care in an increasing number of prehospital care services. Up to 35 German air rescue helicopter services, Lufthansa German Airline, and fire department-based emergency services of several metropolitan areas are equipped with General Electric Vscan.

These mobile devices can be held with one hand; the adjustments necessary during an examination can be made with the thumb. It is now very well received that our concepts also apply to many acute care settings for point-of-care exams within the hospital.

Since 2003, the German Air Rescue Organization (Deutsche Rettungsflugwacht) has incorporated P-FAST into the algorithm for trauma management. By 2012, 35 helicopters and 3 fixed-wing aircrafts were equipped with portable ultrasound devices and most of the emergency physicians and paramedic crews were trained. The other main provider of air rescue services, the German Automobile Club, also partially adopted P-FAST.

Some air rescue centers of the German federal police have implemented P-FAST; in addition, the German Air Force also have equipped their international mobile medical crews and supplied their aircraft for multinational flights with mobile ultrasound devices. Their crews have been trained in our courses.

P-FAST and FEEL have been integrated into ground-based services as well. The region of Darmstadt adopted the prehospital FEEL examination in 2002. In Frankfurt/Main, the five ground-based ambulances staffed by emergency physicians have been equipped with portable ultrasound devices with financial support from the city's public health department.

Peter M. Zechner, Gernot Aichinger, Raoul Breitkreutz, Gernot Wildner, and Gerhard Prause

In Austria, physicians, who staff ambulances, treat prehospital patients. As a result, prehospital portable ultrasound as well as other specialized point-of-care diagnostic tools, such as blood gas analysis systems, invasive blood pressure monitoring, and fiberoptic bronchoscopy, have become available. The first emergency vehicle in Graz was equipped with portable ultrasound (SonoSite 180 Plus) in 2000. Today, up to three emergency vehicles in Graz are equipped and some other emergency systems have also implemented its use. While prehospital ultrasound was almost exclusively applied to detect free intraabdominal fluid in trauma patients in the initial years, its applications have been extended. An increasing number of emergency physicians have begun using prehospital ultrasound for differentiation between cardiac and pulmonary causes of dyspnea with the evaluation of B-lines, the prediction of outcome in cardiac arrest patients, the detection of pneumothorax, and ultrasound-guided venous and arterial line insertion. A report published by the Graz group studied the prognostic value of prehospital emergency echocardiography in cardiac arrest and the ability of optic nerve ultrasound to detect elevated intracranial pressure.14 Although prehospital emergency ultrasound is still in its infancy in Austria, the results and improvement in patient care have been promising and ground-breaking.

Tomislav Petrovic, Frédéric Lapostolle, and Frédéric Adnet

The feasibility and usefulness of prehospital ultrasound have expanded since the early 1980s in France. Bulky ultrasound machines requiring very skilled operators were used back then; as a result, they had limited applicability to most prehospital systems. In the early 1990s, technological advances produced lighter ultrasound machines that were much more practical to use in the prehospital setting.

French prehospital clinicians have been interested in broad applications of prehospital ultrasound. Investigators have studied the detection of free intraperitoneal fluid, assessment of cardiac function in shock and arrest states, evaluation of thoracic injuries, detection of deep venous thrombosis, assessment of long diaphysis fractures, and detection of optic nerve enlargement.

The methods of training and the level of performance of emergency physicians using ultrasound in prehospital settings in France were evaluated. The ultrasound training was scheduled for one half-day session that included didactic and practical instruction. Like our German colleagues, didactic sessions reviewed the guiding principles of ultrasonography and normal and pathological images. The practical training consisted of performing examinations on healthy subjects or on patients with pertinent findings on ultrasound examinations (e.g., patients with ascites). The training focused on examinations pertinent to the French prehospital setting, which included the assessment for pneumothoraces, pleural effusions, abdominal or pericardial effusions, or deep venous thrombosis of the lower limbs.

Eight physicians of the SAMU 93 (EMS department) were trained on the emergency use of a portable ultrasound device (SonoSite 180). The number of training sessions varied from 1 to 6, according to the experience level of the operators. Each operator determined a clinical diagnostic probability (before ultrasonography) noted on an analog visual scale from 0 (absence of lesion) to 10 (presence of lesion). According to the same principle, the operator determined a second probability after ultrasound. The hospital follow-up of the patients made it possible to obtain the final diagnosis (0 for absent and 10 for present lesion) that was compared with the pre- and posttest probabilities.3

The initial analysis of 83 ultrasound examinations carried out on 40 patients revealed a median time of examination of 5 minutes, 100% sensitivity, 98% specificity, a positive predictive value of 92%, and a negative predictive value of 100%. In our analysis of the learning curve for ultrasound proficiency by prehospital providers, we found that the number of ultrasound examinations required to achieve desired proficiency was approximately 25 examinations.

The absolute difference between the probabilities before and after ultrasound was calculated and compared with the final diagnosis (0 or 10). When ultrasound had brought the operator closer to it, a positive value was allotted to the obtained number; conversely, a negative value was allotted when ultrasound had moved the operator away from the final diagnosis. For example, if a diagnostic probability was 3 before and 8 after ultrasonography, the absolute difference was 5 (8 − 3). If the final diagnosis was positive (presence of a lesion), ultrasound would have brought the operator closer to the final diagnosis. The value allotted to ultrasound would then be +5. Conversely, if the final diagnosis was negative (absence of lesion), ultrasound would not have been helpful in making the final diagnosis. The value allotted to ultrasound would then be −5.

The results of 302 ultrasound examinations were analyzed. The median impact of ultrasound on the final diagnosis was +2. The diagnostic performance was improved by ultrasound in 67% of the cases; it was not modified in 25% of the cases and it was degraded in 8% of the cases. Our results were consistent with the use of ultrasound as a “complement” to the clinical assessment.3

In France, prehospital ultrasound has established itself as a legitimate clinical adjunct. Just as the stethoscope serves as an extension of the physician's ears, the ultrasound transducer serves as an extension of her hands and eyes. If the indications are focused, the procedure is codified, and the operators are properly trained, then the level of performance approaches that of a medical imaging expert. The rapidity of the examinations provides additional diagnostic information without delaying transport or definitive care. As experience with this modality increases and technological advances produce improved portability and resolution, we believe that the use of ultrasound will gain broad acceptance in prehospital venues around the world.

William G. Heegaard

The advancement of prehospital ultrasound in the United States has been significant. While no large randomized prehospital study has yet to be completed in the United States, the body of literature is increasing. Four broad areas are utilizing prehospital ultrasound: helicopter EMS, ground EMS, tactical, and tele-transmission of ultrasound. While the American EMS system has not swayed from expeditiously transporting ill or injured patients to the receiving medical center for definitive care, ultrasound may expand the traditional tools that prehospital providers use in their care of patients.

Point-of-care ultrasound use in helicopter EMS is growing. This growth is not surprising given the critical and time-sensitive nature of helicopter EMS patients. Helicopter EMS transport in the United States has consistently grown each year for the past two decades. Approximately 867 rotor-wing air ambulances currently operate out of 714 bases across the country.15 For millions of rural Americans prompt emergency care is only accessible through the use of helicopter EMS.

Numerous United States helicopter EMS programs are now utilizing or have utilized ultrasound. Some programs include Oregon Health & Science University, Portland, Oregon; MetroHealth Medical Center, Cleveland, Ohio; Medical College of Georgia, Augusta, Georgia; University of San Diego, San Diego, California; several USA-based military helicopter EMS programs; and Life Link III, Minneapolis, Minnesota.

It has been demonstrated that the FAST examination can be performed rapidly and with relative ease in the helicopter.8 Using a SonoSite 180 ultrasound machine with a 3.5 MHz transducer, 10 flight clinicians performed 21 FAST examinations on 14 patients. Nine patients were simulated. They reported no effect on avionics and were able to complete the standard FAST examination in a mean time of 3 minutes. In 2004, Heegaard and coinvestigators applied a focused template for didactic ultrasound training with additional hands-on training in an ED.2 They found that flight clinicians could perform a wide variety of ultrasound examinations with good long-term retention (>90%) over 1 year. Ultrasound examinations were performed proficiently in the helicopter, although time and space constraints limited the clinicians' ability to perform the complete FAST examination. One study analyzed the use of ultrasound to perform a screening examination on obstetric patients transported by helicopter.7 The Fetal Evaluation for Transport with Ultrasound (FETUS) is a screening examination that evaluates fetal heart rate, position, and movement and general condition of the placenta. The examination can be performed serially in flight with no acoustic distortion from rotor noise. In 2011, a study examined the feasibility of using M-mode to detect pneumothoraces during helicopter transport.16 Earlier studies on helicopter EMS ultrasound in the United States utilized the SonoSite 180, a 2.4-kg compact ultrasound machine with 3.5 MHz transducer. One helicopter EMS program (Life Link III, Minneapolis, Minnesota) utilized the SonoSite iLook ultrasound machine (1.4 kg) with a 3.5 MHz transducer, which was mounted in the helicopter for ease of use. Other studies have been utilizing newer generation ultrasound machines that have both M-mode and video recording capability.

Ultrasound use in ground ambulances has gained traction. In 2010, Heegaard reported on 104 FAST and abdominal aortic ultrasound examinations performed by 9-1-1 paramedics in the prehospital environment (Figure 4-3).17,18 Of the FAST exams performed, 7.1% were positive for intraperitoneal/pericardial fluid. Paramedics were unable to obtain adequate images in 7.7% (8/104) patients. All exams recorded 6-second video clips of each portion of the exam. FAST and aortic ultrasound exams performed by the paramedics had a 100% agreement with an independent emergency medicine physician ultrasound expert.

It remains to be seen whether the European experience will impact the implementation of ultrasound in ground ambulances in the United States. The first American ground EMS system to utilize prehospital ultrasound was in Odessa, Texas. Currently, there are multiple United States prehospital agencies utilizing ultrasound in various capacities on their ground ambulances. Obstacles to implementing prehospital ultrasound programs include lack of reimbursement for ultrasound imaging, difficulty in maintaining ultrasound competency among numerous EMS personnel, and the cost of ultrasound machines.

Potential applications of helicopter EMS and ground ambulance ultrasound in the United States include, but are not limited to:

• E-FAST examination on trauma patients to expedite definitive care and early operating/radiological intervention suite activation, especially in rural areas;
• Focused cardiac ultrasound examination in hypotensive patients to place them in one of four shock states (severe hypovolemia, cardiogenic, pericardial tamponade, or right ventricular obstruction), which helps guide therapy;
• Fetal monitoring and evaluation in obstetrical patients;
• Early detection of mainstem intubations;
• Early detection of pneumothorax with the E-FAST examination;
• Early evaluation of cardiac arrest and PEA;
• Confirmation of out-of-hospital death (cardiac standstill).

Jeffrey D. Ho

Tactical Medicine, often referred to as Tactical Emergency Medical Support (TEMS), is an evolving niche of out-of-hospital medical practice with origins based on military medical knowledge. TEMS is specifically designed for use in austere, often hostile situations, usually in support of high-risk civilian law enforcement operations (LEOs).19 TEMS has become important because of decades of experience demonstrating a breakdown in standard operations by EMS personnel during high-risk, unsecured situations. One only has to search the Internet for “active shooter incidents” to find numerous examples of situations with multiple casualties where standard civilian EMS personnel were not able to enter the scene to treat, evacuate, or transport the injured. In situations such as these, the only personnel generally operating within a secured perimeter are suspects, innocents, LEOs, and specially-trained TEMS personnel. Depending on the type of incident, the perimeter can be as small as a few hundred yards to as large as several miles around. Without TEMS availability, especially during prolonged operations, it is likely that casualties within these perimeters will go untreated.

TEMS providers can come from different training backgrounds, ranging from basic first aid provider to physician levels of training. Many TEMS physicians may already have adequate ultrasound training. Paramedic-level providers can also be trained to perform prehospital ultrasound.18 Regardless of medical training background, TEMS personnel are generally taught specialized topics not normally found in standard care and resuscitation classes.20 These areas of competency may seem obscure to most but are vital in tactical situations and include topics such as Remote Patient Assessment, Evaluation of Injury due to Lethal and Less-Lethal Weapons, and Care Under Fire. These topics generally assume that treatment decisions may need to be made rapidly based on consideration of risk versus survival, ability to perform immediate lifesaving interventions, as well as ability to evacuate in a timely manner to an appropriate facility. The introduction of ultrasound into the prehospital care setting is beginning to gain support and is likely to have significant ramifications for use in the TEMS arena as this support increases.

Ultrasound use in a TEMS scenario by a qualified operator for rapid diagnosis of pneumothorax or pericardial tamponade is extremely helpful in shortening decision time to perform a potentially lifesaving procedure. A FAST exam performed within the perimeter demonstrating rapidly worsening intraperitoneal hemorrhage would likely cause a specific hasty evacuation plan to be followed, leading to an appropriate trauma-receiving destination. These skills and preplans are generally put in place by TEMS providers before an operation unfolds, but may not be acted upon unless absolutely necessary because of the danger to the providers if they are enacted unnecessarily (e.g., if actively under fire, it may be safer to leave a person with minor injuries in place behind cover rather than attempt a rescue extraction and evacuation that places numerous LEOs at unnecessary risk).

The working environment of a TEMS operator is foreign to most clinicians. They carry large amounts of portable medical equipment, cumbersome protective gear, and often tools of law enforcement that may include a firearm. They may have their attention divided between patient care and personal safety/security during an operation. The development of small, portable ultrasound machines has recently made the use of ultrasound in the tactical medical practice arena even more of a reality. Because of the amount of equipment carried by TEMS operators and the environment for use, any ultrasound machine needs to be lightweight, durably rugged, battery-operated, and rapid and simple to use. A single microconvex transducer could suffice for almost every necessary field application. An ultrasound machine that cannot tolerate being knocked around in a field pouch or one that requires numerous keystrokes or time delays to function is not acceptable.

The niche specialty of TEMS is growing as the benefit of having TEMS providers present is recognized to improve casualty outcomes.21,22 Use of ultrasound by TEMS providers is an emerging area of diagnostic interest. It has the potential for enabling more rapid, accurate decisions to be made about diagnostic uncertainties. This, in turn, allows for more informed decisions to be made with regard to injury care, taking into account risk versus benefit in high-risk tactical situations.

Andrew W. Kirkpatrick, Paul B. McBeth, Innes Crawford, and Corina Tiruta

Ultrasound offers an almost unlimited scope for enhancing the bedside care of the critically ill or injured patient. With the ever-increasing availability of ultrasound machines, however, there is often a gap between the education and experience of care providers and the needs of the critical patient. This paradigm is no more pertinent than in space medicine, where a state-of-the-art ultrasound machine is the only potential imaging capability onboard the International Space Station (ISS), yet a nonphysician such as a geologist may be required to make time-sensitive critical diagnoses and provide invasive therapies to a fellow crewmate.23–25 This quandary has led investigators working on behalf of the National Aeronautics and Space Administration (NASA) to pioneer remote guidance techniques wherein a novice care provider onboard the ISS is mentored to obtain meaningful ultrasound images that can be interpreted by terrestrial experts to guide diagnosis and therapy. Using such an approach a wide variety of specific ultrasound examinations have been conducted, including the FAST examination, demonstrating that with advanced informatics, even inexperienced but motivated novice operators can generate meaningful images.26–28

Terrestrially, although telemedicine, and specifically tele-ultrasound, becomes more extensively utilized every year in clinical care,29,30 its use in real-time trauma resuscitation remains limited. One study examined guiding paramedics remotely via two-way radio communication through solely viewing the ultrasound images without viewing the on-site examiner's hand or transducer movements.31 The study noted that 51 paramedics were able to generate 100% of the required FAST views, after 20-minute didactic sessions without hands-on scanning.31 Another study utilized the NetMeeting software application from the Microsoft Corporation to transmit 50 patient images from Serbia to the United States, concluding that there was potential to further investigate these techniques.32 To our knowledge the first use of real-time remote telementored ultrasound for trauma resuscitation was reported in 2008.33 This involved trauma surgeons at a tertiary care trauma center viewing the resuscitative bay of a rural referral center in the Rocky Mountains with both a macro-field camera and real-time display of the rural ultrasound machine on a console in the ED. Using this somewhat complex system, remote telementored ultrasound was found to be not only feasible and accurate, but it also impacted patient triage, educated novice operators, and increased collegiality.33,34 The system, however, was unsustainable for 24/7 immediate responses, as it required the responding trauma surgeons who mentored the remote examiners to physically respond to the tele-ultrasound console.

Newer efforts have centered on attempting to make tele-ultrasound simpler and to reduce the infrastructure required to facilitate communication. One group has championed the use of a stand-alone video compression device to stream through a secure satellite modem to allow one-way ultrasound and video transmissions and two-way audio from challenging environments such as Mount Everest and the Canadian Arctic.35–37 In this manner, remote lung examinations for high altitude pulmonary edema and joint examinations were performed by novice operators, guided by Henry Ford Medical Center in Detroit, Michigan.35–37 Efforts in Calgary, Alberta, have attempted to simplify remote telementored ultrasound even further. This group has used freely available but password protected voice over Internet Protocol (VOIP) software to transmit from a portable head mounted video camera and portable handheld ultrasound devices, thus providing the remote mentor with an ultrasound image produced by the novice and simultaneous real-time views of the novice's handling of the ultrasound transducer.38–40

Once the macro scene and ultrasound images have been assembled and transmitted using VOIP, the device used by the remote mentor can be any that receives a password-protected secure Internet signal such as desktop or laptop computer, a tablet device, or a smartphone. Pilot investigations have demonstrated the ease of using such systems from essentially anywhere that the Internet can be received through fixed lines, wireless networks, or tethered to cellular phone networks. Thus, remote telementored ultrasound can be conducted from rural mountainsides, within small airplanes, and from buildings while remote mentors can respond from anywhere they can use a smartphone.40 While technically feasible, the next level of evaluation is to demonstrate that such technologies benefit decision making and patient outcomes. As a great percentage of the developing world lacks adequate medical services, including medical imaging, the ability to remotely diagnose, teach, and guide seems to offer a remote outreach with limitless potential.

Daniel D. Price

According to the United Nations, over 60% of the world's population has no access to medical imaging.41 Most people will never have access to plain film radiography, let alone CT, MRI, or PET. In challenging under-resourced settings, ultrasound offers a solution.

• Ultrasound systems can be hand-carried, which allows them to go to the patient. Ultrasound systems have been carried on horseback, motorcycles, boats, and on long hikes to extremely remote areas. Virtually all other imaging systems are built for stationary and controlled environments.
• Ultrasound systems can be battery operated, so patient care doesn't have to stop when the power is out. Patient care can also take place in health-care centers that have no electricity.
• Ultrasound is relatively straightforward to learn, but adequate training and experience are essential. Ultrasound has been used successfully by nurses, midwives, clinical officers (similar to physician assistants), and even health promoters with limited formal education, most of whom operate independently of physicians. Other imaging modalities require significantly more training.
• Ultrasound images are more accessible. Printing radiographs and CT images require film, silver, and other expensive and caustic ingredients, which add cost and complexity. Electronic viewing systems, such as PACS, are expensive and rely on unreliable infrastructure and vulnerable technology. Ultrasound images and clips can be viewed on the device and can be easily transferred wirelessly or via removable media.
• Ultrasound imaging is dynamic and can evaluate physiology over time, which is important in echocardiography, obstetrics, and other applications. Other imaging modalities provide only static images.
• In resource-limited settings, cost is paramount. An ultrasound system has only the fixed cost of purchase, which is much less than other imaging modalities. Furthermore, the costs of other imaging options are ongoing with respect to supplies and maintenance.
• Maintenance of a rugged ultrasound system is minimal, compared with the complexity and vulnerability of other imaging options. In many areas of the world, dust is ubiquitous and can easily damage equipment. This is also true for ultrasound systems not designed for austere environments, making maintenance an important consideration in purchasing decisions.
• Technical support can be challenging in under-resourced settings, which are generally remote. Lightweight, hand-carried ultrasound systems can be easily shipped to servicing centers, in contrast to other systems that require site visitation by a technician. Many health-care facilities in developing countries have broken devices sitting in closets. If a system becomes nonfunctional, the ultrasound program at that facility will be at risk for ceasing to function as well, as practitioners' skills degrade from lack of use and the flame of their enthusiasm dims.

The differential diagnosis in resource-limited settings often varies from the differential in more developed settings. Tropical diseases and illnesses related to tuberculosis, malaria, and HIV/AIDS are much more prominent on a differential, because prevalence is so high. Bedside ultrasound can help establish a firm diagnosis and guide appropriate management.42–44

One of the advantages of ultrasound is that it can help in the evaluation of many conditions. Appropriate ultrasound applications have been well elucidated in the Partners In Health Manual of Ultrasound for Resource-Limited Settings, which is available online free of charge.45 There is an excellent review of the literature regarding the use of ultrasound in the developing world46 and the breadth of applications. Novel applications of ultrasound not used in highly developed countries are emerging from under­-resourced settings.42–44 An important factor in considering the use of specific applications is that the information gained be actionable and lead the provider along a management algorithm.

A central question in the decision of whether to implement ultrasound in under-resourced settings is, “What difference does it make?” Studies have found that ultrasound led to changes in management in 17-68% of patients.47–52 Changes included the decision to perform a surgical procedure, medication changes, clinic referral, and canceling of a planned surgical procedure.47

Treatment in resource-limited settings may be more expensive, difficult, and dangerous to the patients than if they were treated in resource-rich settings. For example, a patient with tuberculosis misdiagnosed as having a pulmonary embolism could die from the use of heparin or warfarin.

Even if the use of blood thinners was correct, the warfarin may be expensive and difficult to find, and monitoring costly when available. For these reasons, it is necessary to have a high degree of diagnostic certainty before undertaking such treatment. A study in the Amazon found that the physician's differential diagnosis narrowed after the ultrasound results in 72% of cases, with diagnostic certainty achieved in 68%.50 In a study in Cameroon, about half of the confirmed diagnoses made by ultrasound had not been previously considered.52

A “magnet effect” has also been observed. The compelling nature of ultrasound draws patients from outside the health-care system to facilities where they can receive public health interventions known to be of benefit, such as immunization, HIV screening, and education. A study in Mali observed that women came to a health center from farther and farther away as word of the use of ultrasound spread.53

Ultrasound empowers health-care providers at the point of care. New skills with ultrasound have been shown to improve job satisfaction53 and can lead to better retention of skilled personnel, a common problem in under-resourced settings.