Introduction
Point-of-care ultrasound (POCUS) has found numerous applications in ambulances, helicopters, wilderness, and other resource-limited settings and provides valuable insights into a patient’s disease severity, injury pattern, and underlying health conditions, which reduces time-to-diagnosis and ultimately affects clinical decision making and patient outcomes. Reference Rudolph, Sørensen, Svane, Hesselfeldt and Steinmetz1 In recent years, the technology has become more accessible and increasingly implemented in the prehospital setting, especially in Europe where it has proven to be feasible in ground transport, air medical services, and other limited-resource environments. Reference Press, Miller and Hassan2,Reference Quick, Uhlich, Ahmad, Barnes and Coughenour3 Numerous protocols that incorporate POCUS are now used to rapidly evaluate time-sensitive, life-threatening conditions (eg, Bedside Lung Ultrasound in Emergency [BLUE]/Fluid Administration Limited by Lung Sonography [FALLS] for respiratory distress; Reference Lichtenstein4 extended Focused Assessment with Sonography for Trauma [FAST]/Rapid Ultrasound for Shock and Hypotension [RUSH] exams for trauma in the thorax and abdomen Reference Netherton, Milenkovic, Taylor and Davis5 ). In addition to high-acuity and shock conditions that may benefit more from prehospital ultrasound-supported interventions, Reference O’Dochartaigh, Douma, Alexiu, Ryan and MacKenzie6 POCUS has uses in ultrasound-guided vascular access, Reference Egan, Healy, Neill, Clarke-Moloney, Grace and Walsh7,Reference Oliveira and Lawrence8 fracture detection, Reference Weston, Elmer, McIntosh and Lundgreen Mason9,Reference Waterbrook, Adhikari, Stolz and Adrion10 esophageal intubations, Reference Lema, O’Brien and Wilson11 endotracheal tube placement, Reference Hanlin, Zelenak, Barakat and Anderson12 and measurement of optic nerve sheath diameter in cases of traumatic brain injury. Reference Aletreby, Alharthy and Brindley13,Reference Houzé-Cerfon, Bounes, Guemon, Le Gourrierec and Geeraerts14
As a highly user-dependent technology, ultrasound operation and interpretation require sufficient training and knowledge. Prior to 2010, ultrasound was typically performed by physicians in the hospital setting or helicopter Emergency Medical Service (EMS) systems. Reference O’Dochartaigh, Douma, Alexiu, Ryan and MacKenzie6 More recently, evidence has shown that an acceptable standard of competency of prehospital ultrasound can be taught relatively quickly to non-physician personnel such as paramedics. Reference Brooke, Walton, Scutt, Connolly and Jarman15–Reference Heegaard, Hildebrandt, Spear, Chason, Nelson and Ho18 This is particularly important since most prehospital care teams consist of one or two non-physician personnel. However, few paramedics have had training in ultrasound. Training, skill retention, and continuing education can be laborious and involves a combination of theory, hands-on practice, and numerous clinical examinations, ideally with supervision. Reference Bøtker, Jacobsen, Rudolph and Knudsen19 Barriers to implementation of paramedic-performed prehospital ultrasound include costs of training, lack of consensus of a training regimen, and complexity involved in scaling up training to large prehospital systems. Reference Becker, Martin-Gill, Callaway, Guyette and Schott20,Reference Taylor, McLaughlin, McRae, Lang and Anton21
One solution to address these obstacles and increase access to prehospital ultrasound is to harness real-time data transmission technology, Reference Adams, Burbridge, Obaid, Stoneham, Babyn and Mendez22 which would enable a paramedic to communicate with a remote provider with ultrasound experience. Utilizing off-site experts can be useful in environments that are resource-constrained or restricted due to strict isolation precautions. For instance, tele-guided ultrasound has been used by non-physician astronauts on the International Space Station. Reference Kwon, Bouffard and van Holsbeeck23,Reference Hamilton, Sargsyan and Martin24 The concept of tele-ultrasound in the prehospital setting was initially devised in 2008 by Robosoft Inc. (Udupi, India) who developed a portable robot remotely controlled by physicians in France to conduct paramedic-assisted prehospital ultrasound examinations on remote patients in the Mediterranean Sea. Reference Fonte, Essomba and Vieyres25 Since then, tele-ultrasound has been evaluated for the assessment or diagnosis of numerous clinical indications, including fetal structural abnormalities, Reference Rabie, Sandlin and Barber26–Reference Whittington, Hughes and Rabie28 cardiac dysfunction, Reference Salerno, Kuhn, El Sibai, Levine and McCurdy29–Reference Jensen, Weile and Aagaard31 acute trauma, Reference Eder, Reime, Wurmb, Kippnich, Shammas and Rashid32,Reference Al-Kadi, Dyer and Ball33 coronavirus disease 2019/COVID-19, Reference Wu, Wu and Ye34 hepatic and biliary diseases, Reference Marini, Oppenheimer and Baran35 thyroid nodules, Reference Marini, Weiss and Gupta36 breast abnormalities, Reference Sun, Li and Wang37 dermatologic lesions, Reference Alfageme, Minguela and Martínez38 and spinal alterations. Reference Marshburn, Hadfield, Sargsyan, Garcia, Ebert and Dulchavsky39 In addition, tele-ultrasound has primarily been studied in low-income rural communities Reference Marini, Oppenheimer and Baran35,Reference Marini, Weiss and Gupta36 and resource-constrained settings, Reference Kaneko, Kagiyama and Nakamura30,Reference Marshburn, Hadfield, Sargsyan, Garcia, Ebert and Dulchavsky39–Reference Pian, Gillman and McBeth44 but also in the intensive care unit (ICU) Reference Duan, Liu and Chen45,Reference Levine, McCurdy, Zubrow, Papali, Mallemat and Verceles46 and emergency department (ED). Reference Jensen, Weile and Aagaard31,Reference Jensen, Duvald and Aagaard47,Reference Zennaro, Neri and Nappi48 Acceptable standards of ultrasound can be taught successfully via tele-guidance to ICU nurses and other non-physician personnel, including ultrasound-naïve firefighters and even non-medical undergraduate students. Reference Douglas, Levine and Olivieri49–Reference Ramsingh, Ma and Le51
Because of the increasing interest in tele-ultrasound coupled with a limited understanding of the current evidence on prehospital tele-ultrasound involving paramedics, the authors sought to conduct a scoping review to provide an overview of the literature. This review qualitatively analyzes literature from January 1, 2010 – December 31, 2021 in the MEDLINE (US National Library of Medicine, National Institutes of Health; Bethesda, Maryland USA), EMBASE (Elsevier; Amsterdam, Netherlands), and Cochrane (Wiley; Hoboken, New Jersey USA) online databases on prehospital, paramedic-acquired tele-ultrasound. In addition to assessing image acquisition, image quality, training of tele-ultrasound, and the quality of scientific evidence available, the goals of this review are to summarize current evidence and evaluate the feasibility of paramedic-performed tele-ultrasound in the prehospital setting. The review is geared toward prehospital personnel considering the benefits and costs of implementing tele-ultrasound in their practice and standards of care.
Methods
A systematic article search (Figure 1) was conducted in the MEDLINE, EMBASE, and Cochrane databases for articles during the period from January 1, 2010 – December 31, 2021 using search terms with variations of “ultrasound,” “tele-ultrasound,” “paramedic,” “emergency,” “sonography,” and “prehospital.” The complete search string is provided in the Supplementary Material (available online only). Two reviewers screened articles for inclusion. Included articles pertained to paramedic-performed ultrasound in the prehospital setting and had a tele-medicine component (ie, some form of real-time communication between the paramedic and a remote provider during the ultrasound examination). Retrospective, prospective, and randomized trials and review articles were included because of the lack of randomized controlled trials in the field. All patient ages were included as were all medical and trauma patients. Articles published outside of the range or those with no paramedic on the team were excluded. Case reports/series, abstracts only, editorials, and letters to the editor were excluded. Subsequently, a qualitative synthesis of data was performed, examining study methodology, image acquisition, image quality, and amount of training.
Figure 1. PRISMA Flow Diagram of Article Selection Process.
Results
There were 10 articles (Table 1) that met inclusion criteria. Except for one qualitative survey, the articles could be classified into three major groupings (Table 2): (1) tele-ultrasound involving a specialized tele-echography robot; (2) tele-guidance of an ultrasound-naïve examiner; and (3) remote interpretation of ultrasound images acquired independently by a paramedic. The tele-echography robot system enabled paramedics to quickly attach the robot to the patient so that a FAST exam could be completed by a physician remotely operating the ultrasound probe. Reference Ito, Tsuruta, Sugano and Iwata52,Reference Ito, Sugano, Takeuchi, Nakamura and Iwata53 While the robot-assisted scans would free the paramedic to provide other forms of medical care, it was the most resource-intensive method and difficult to replicate.
Table 1. Prehospital Paramedic-Performed Tele-Ultrasound Study Features
Abbreviations: FAST, Focused Assessment with Sonography for Trauma; US, ultrasound; EMT, emergency medical technician; ALS, Advanced Life Support; EMS, Emergency Medical Services; ED, emergency department; COPD, chronic obstructive pulmonary disease.
Table 2. Comparing Three Approaches to Paramedic Prehospital Tele-Ultrasound
The tele-guidance system involved ultrasound-naïve paramedics performing FAST examinations under the remote guidance of experienced emergency physicians. Reference Boniface, Shokoohi, Smith and Scantlebury54–Reference Leviter, Auerbach and Amick56 Tele-guidance would entail less training for the paramedics, but would require strong communication between the “mentor” and paramedic. In particular, a good understanding of anatomic relationships and a “common language” for fanning the probe, switching locations, and probe adjustments in the different views would be key to more successful tele-guidance. In addition, the tele-mentoring studies all utilized healthy volunteers in a stationary setting with reliable network connection, so there was not the added stressor of providing time-sensitive care in a moving ambulance, which could affect communication and internet signal.
Finally, in the approach using remote interpretation, paramedics independently performed the ultrasound scan while images or video were transmitted in real time to a remote physician or ultrasound expert who would interpret the findings. Reference Becker, Martin-Gill, Callaway, Guyette and Schott20,Reference Song, Shin and Hong57–Reference Nadim, Laursen and Pietersen59 Remote image interpretation appeared to be the safest method, but required physicians who were available to interpret, which was not always possible in busy EDs. This complication could be addressed by asking paramedics to limit discussion to a brief pre-alert if the ED is busy.
Image Acquisition
All studies reported that images could be obtained successfully by paramedics. The majority of images could also be transmitted successfully to remote physicians (the lowest value being 73.5%). Reference Becker, Martin-Gill, Callaway, Guyette and Schott20 The vast majority found that images were clinically useful or could aid in the diagnosis of the disease of interest. Of the studies that measured the amount of time to scan, the average time spent for paramedics to scan was less than five minutes, which was deemed an adequate amount of time in the prehospital setting. Reference Boniface, Shokoohi, Smith and Scantlebury54
Technology
There was tremendous heterogeneity in technological equipment used across the studies (Table 3). For instance, methods of transferring the ultrasound image data included consumer-level smartphones, Reference Becker, Martin-Gill, Callaway, Guyette and Schott20,Reference McBeth, Crawford and Tiruta55–Reference Song, Shin and Hong57 Live-U (LiveU Inc.; Hackensack, New Jersey USA) device, Reference Morchel, Ogedegbe and Chaplin58 MPEG-2 compression technology, Reference Ito, Tsuruta, Sugano and Iwata52,Reference Ito, Sugano, Takeuchi, Nakamura and Iwata53 Skype (Skype Technologies; Luxembourg City, Luxembourg) streaming, Reference McBeth, Crawford and Tiruta55 GrandTec (GrandTec USA; Dallas, Texas USA) frame grabber, Reference Song, Shin and Hong57 or the Lumify app (Philips; Amsterdam, The Netherlands) and React-Secure-app (Meta Platforms, Inc.; Menlo Park, California USA). Reference Nadim, Laursen and Pietersen59
Table 3. Additional Prehospital Tele-Ultrasound Study Features
Abbreviations: US, ultrasound; EMT, emergency medical technician.
Studies involving tele-guidance through verbal communication utilized two-way radio, Reference Boniface, Shokoohi, Smith and Scantlebury54 Skype, or the React-Secure-app, which had interactive video conferencing capability. In this way, some of the ultrasound mentors could view the paramedic’s probe position in addition to the ultrasound image on the screen while others could only see the scan. Communication was affected by the amount of background noise, and scanning efficiency was improved when the paramedic had a good understanding of anatomic relationships and when there was a “common language” for a pre-determined starting point, fanning the probe, and switching locations.
Image Quality
The majority of studies found that paramedics minimally trained in ultrasound could obtain images with adequate quality for interpretation. Reference Boniface, Shokoohi, Smith and Scantlebury54,Reference McBeth, Crawford and Tiruta55,Reference Song, Shin and Hong57–Reference Nadim, Laursen and Pietersen59 Morchel, et al specifically compared the quality of images performed by emergency medical technicians (EMTs) minimally trained in FAST ultrasound to images obtained by in-hospital physicians, and the EMT-acquired images were rated essentially as good as the hospital images. Only one study noted the majority of images (58.8%) obtained by paramedics to be uninterpretable. Reference Becker, Martin-Gill, Callaway, Guyette and Schott20
Amount of Training
There were differences in the amount of ultrasound training that paramedics received based on the tele-ultrasound approach. Robot-assisted tele-ultrasound and tele-mentoring studies involved paramedics with minimal training (20 minutes or less), while paramedics who independently scanned had at least two hours of ultrasound training (range: 2-12 hours of training). An average could not be calculated because some studies did not report the number of paramedics who performed scans or the specific number of hours of ultrasound training the EMTs received. Reference Song, Shin and Hong57,Reference Morchel, Ogedegbe and Chaplin58
One study found that tele-ultrasound with remote guidance was a helpful activity in prehospital ultrasound training for paramedics, which would be applicable for training in any resource-constrained environment without access to on-site ultrasound instructors. Reference Leviter, Auerbach and Amick56
Paramedic Perspectives on Tele-Ultrasound
One qualitative study explored the perspectives of a small sample of eight paramedics on tele-ultrasound. Reference Marsh-Feiley, Eadie and Wilson60 The paramedics were optimistic about the technology and saw tele-ultrasound as logical progression from standard POCUS, given advancements in telemetry of other diagnostic tests, such as electrocardiogram/ECG telemetry. On the other hand, physicians were concerned about cost-effectiveness, skill atrophy in rural settings, and usefulness in urban environments with short transport times. Overall, there was a call toward bridging “research enthusiasts and clinical pragmatists” as there is a clear research-practice gap in opinions on tele-ultrasound.
Feasibility
A list of criteria for determining feasibility of tele-ultrasound was devised by Becker, et al and is shown below:
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Paramedics must successfully obtain images in >80% of attempted cases;
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Expert sonographers must deem images interpretable in >80% of cases;
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Real-time image transmission must be successful in >80% of scans;
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Scans will be clinically useful (ie, ultrasound images correlate with ED diagnosis in >80% of patients).
Only three of the ten studies involved patients in the prehospital setting and could have the criteria applied. One of those studies used tele-ultrasound solely in the prehospital setting, and the data successfully met the first three threshold criteria, but the patients were not seen in the ED and did not have an ED diagnosis to correlate with the prehospital interpretation. Reference Nadim, Laursen and Pietersen59 There were mixed results with data from Becker, et al meeting none of the feasibility criteria and reporting many technical issues that considerably limited patient size. On the other hand, data from Morchel, et al suggested that ambulatory images transmitted in real time were essentially as good as the quality of hospital-acquired images. Overall, there was tremendous heterogeneity in methods and technology used and the amount of ultrasound training for paramedics, which limited additional cross-comparisons.
Discussion
Tele-ultrasound potentially allows for novice prehospital providers to rapidly triage patients with the assistance of a remotely located ultrasound expert and make prompt decisions on patient transport to appropriate facilities. Tele-ultrasound performed by paramedics shows potential to improve ultrasound accessibility and care in the prehospital setting. Research on prehospital tele-ultrasound by paramedics is nascent, and additional studies are needed to address technological challenges and determine feasibility as well as benefit to patients. This screening only found ten relevant articles, which may limit the usefulness of the current evidence. Most of the studies had a high degree of bias and were small-scale studies in simulated settings. The between-study heterogeneity and the lack of control groups and randomized controlled trials hindered cross-study comparisons and meta-analyses. Overall, there was considerable heterogeneity of clinical models, communication methods, and amount of ultrasound experience in the paramedics. The current lack of sufficient and quality evidence on paramedic prehospital tele-ultrasound indicates a pressing need for additional investigation to provide clarity on its feasibility.
Barriers to real-world implementation are numerous and include cost of equipment, difficulties in training, the absence of a remote image receiver and interpreter at the time of examination, uninterpretable images, possibility of equipment failure, patient refusal, and patient acuity. Reference Becker, Martin-Gill, Callaway, Guyette and Schott20 Common concerns about tele-ultrasound with their respective potential solutions are shown in Table 4. To work around the issue of equipment complexity specifically, some studies are adapting existing broadcast technology for medical diagnostics and rescue. For instance, the same Live-U unit for digital video stream in one tele-ultrasonography study is used in over 60 countries to cover major news and sports events. Reference Ogedegbe, Morchel, Hazelwood, Chaplin and Feldman61 In addition, commercial transmission equipment (eg, Live-U) may be better optimized to prevent system overloading (associated with mass-casualty events) and signal dropouts compared to consumer-level smartphones and other non-robust transmission systems.
Table 4. Concerns about Prehospital Tele-Ultrasound
The real-time image transmission rate and time to complete the FAST scan in the studies analyzed in this review appear to be consistent with that of other tele-ultrasound studies. Reference Ogedegbe, Morchel, Hazelwood, Chaplin and Feldman61 Other studies have reported no difference in image quality between images transmitted under cellular versus satellite networks. Reference Ogedegbe, Morchel, Hazelwood, Chaplin and Feldman61 The studies that reported duration of the FAST scan found that paramedics could complete scans on average under five minutes, which is similar to the time to complete an examination in ED. Reference Nelson and Chason62 It is important to note though that the paramedics scanned under simulated, idealized conditions with healthy volunteers.
The implementation of prehospital tele-ultrasound in different organizations/standards of care depends on numerous factors related to the patient, ultrasound operator, interactions between the operator and remote mentor, technology available, and environment (Figure 2). One framework of understanding the complex integration of novel health care interventions, especially within telehealth and multidisciplinary fields, is normalization process theory. The theory considers different aspects of the technology: coherence (differentiating the technology from existing practices), internalization (seeing benefit or value in the technology), communal and individual specification (how individuals make sense of the technology), cognitive participation (the training and implementation), and collective action (contextual and relational integration, effects on workflow, use of resources). Reference Marsh-Feiley, Eadie and Wilson60 The likelihood of success in implementing prehospital tele-ultrasound is influenced by these interconnected factors.
Figure 2. The 5 Pillars of Prehospital Tele-Ultrasound.
Limitations
This study is a descriptive analysis without a formal bias assessment, and meta-analysis could not be conducted due to study heterogeneity. English-only literature focus and publication bias in the screening could have failed to capture international or unpublished studies.
Conclusion
Portable tele-ultrasonography could be a solution to save time by providing immediate real-time ultrasound that reduces time-to-diagnosis. With potential applications in resource-limited settings, global health, disaster situations, and acute trauma, where reducing time to definite care is of the essence, prehospital tele-ultrasound may not only reduce time to diagnosis, but also help with accurate patient treatment or referral. Research on prehospital tele-ultrasound by paramedics is nascent, and additional studies are needed to address technological challenges and determine feasibility, benefit to patients, and long-term skill retention.
Conflicts of interest
The authors declare none.
Supplementary Material
To view supplementary material for this article, please visit https://doi.org/10.1017/S1049023X23006234
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