Introduction
Background
Handheld ultrasound (US) devices are portable, wireless devices that do not require a separate screen and are a developing technology that has been applied since the beginning of the 2000s. Reference Stock, Klein and Steubl1,Reference Sforza, Mancusi and Carlino2 The cheaper prices of these devices as compared with those of conventional devices facilitate their access and wide-spread use. Ultrasound examinations are performed during the prehospital evaluation of patients by emergency health care personnel and significantly contribute to the triage of patients along with the wide-spread use of portable devices. Several studies have compared the performance of handheld devices with that of traditional devices and revealed that the Rapid Ultrasonography for Shock and Hypotension (RUSH) protocol shows high accuracy rates when performed with handheld devices. Reference Dewar, Wu and Hughes3
The RUSH protocol was defined in 2009. It is used to guide the treatment plan, while determining the possible cause in patients with shock. Reference Perera, Mailhot, Riley and Mandavia4 The performance of the RUSH protocol by paramedics, emergency medicine technicians, and nurses in the prehospital period may contribute to the early initiation of the diagnosis and treatment process and accurate referral of the patient.
Many studies have reported the accuracy of prehospital US evaluations by nurses and paramedics; however, data showing the accuracy of the examinations performed in a moving ambulance are limited. Reference Varndell, Topacio, Hagness, Lemon and Tracy5,Reference Unlüer, Yavaşi and Kara6
Objectives
This study aimed to examine the performability of the RUSH protocol with handheld US devices in a moving ambulance along with correct diagnostic views within an appropriate time.
Methods
Study Oversight and Design
This prospective study was conducted after receiving approval of the Health Sciences University Fatih Sultan Mehmet Training and Research Hospital Ethics Committee (Istanbul, Turkey; FSMEAH-KAEK_2022/49) on May 26, 2022. Informed consent of the volunteers who were included in the study was acquired.
Subjects, Participants, and Materials
The participants were selected from volunteer paramedics working in different institutions. The inclusion criteria were as follows: (1) being a paramedic, (2) participating in the didactic training and practical performances before the study, and (3) having performed the RUSH protocol correctly at least five times after the training. On the other hand, the exclusion criteria were as follows: (1) having a medical condition that limits US practice in the ambulance (ie, vertigo) and (2) having previous experience with using US.
The participating paramedics performed the RUSH protocol using the Sonosite IViz (FUJIFILM Sonosite, Inc.; Bothell, Washington USA) handheld US device with a 3–5 MHz curvilinear probe and 7–11 MHz linear probes.
Studies were conducted on two different healthy, volunteer, and alive models. Both models in the study were male. The first model was 18 years old, 188cm tall, and weighed 80kg. The second model was 19 years old, 185cm tall, and weighed 82kg. The models were examined by expert sonographers before the study, and it was determined that there were no windows for the RUSH protocol and no conditions that limited the acquisition of optimal images.
The ambulance in which the examinations were performed was rented from a private ambulance company, and certain maneuvers, such as fast cornering on a pre-determined route during the cruise, sudden braking, overturning, and sudden acceleration during patient transfer, were performed. The same maneuvers were performed on the same route at a standard speed for each practitioner. The maximum speed of the vehicle was 50km/h to ensure the safety of the participants.
A previous study reported that the duration to reach the scene after the call of ambulances in Istanbul, Turkey was 9.23 (SD = 8.6) minutes, whereas the duration to reach the hospital after the call was 22.75 (SD = 19.7) minutes. Reference Karakuş, Çevik, Doğan, Sam and Kutur7 According to these data, the ambulance was on the road for a maximum of 10 minutes for each participant, and when the inspection was completed in <10 minutes, the vehicle returned to the starting point.
Sample Size
The G*Power analysis software (version 3.1; Düsseldorf, Denmark) was used for sample size calculation. When the power was 0.8 to α = 0.05, the effect size was 0.88 and the sample size was calculated as at least 34 RUSH protocols. In total, 36 RUSH protocols were performed in two groups (station group/mobile group); 36 RUSH protocol reviews were recorded in two different models; and nine paramedics were included in the study. Each paramedic performed two RUSH protocols in each model, during cruise and at station, and four RUSH protocols in total in two models. A total of 36 examinations were performed by nine paramedics.
Study Protocol
A 120-minute theoretical lecture, including US physics, device orientation, RUSH protocol, and technique, was given to the paramedics participating in the study; videos and photographs containing pathological and normal images were shown. The participants completed the pre-test and post-test consisting of 12 multiple-choice questions in the didactic part. Practices were then performed on the living model. Each participant performed the RUSH protocol at least six times during the practices. The participants who completed the didactic performance and practices made at least five reviews, wherein they correctly followed the entire protocol until the study began, as indicated in previous studies.
Review Design of the Model
The performances were evaluated in two groups. Eighteen performances in the moving ambulance were included in the MOVE group, whereas 18 performances in the stationary ambulance were included in the STATION group.
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Step 1: Model 1 fixed; Model 2 mobile inside the vehicle.
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Step 2: Model 2 fixed; Model 1 mobile inside the vehicle.
All paramedics included in the study first performed the RUSH protocol in the first model on the vehicle at the station. Moreover, they performed the RUSH protocol on healthy volunteer models in a moving ambulance. The participants performed the RUSH protocol by obtaining cardiac views (parasternal long/short axes [PSLA and PSSA]), apical/subxiphoid) for the pump function and evaluating visual ejection fraction (EF) estimation and right chambers for the tank, Morrison’s pouch, inferior vena cava (IVC) collapsibility index and lungs (A lines, B lines, lung sliding), and the aorta for the pipes.
Data Registration
The individuals who conducted the study were in the ambulance and noted the duration and video recordings of the practice. The review times were recorded for each participant; the duration was started at the moment when the probe touched the model and stopped when the participant stated that she/he had finished the examination. Clip images were obtained from the US device at each step during the review, and these were saved to an external memory (Figure 1). However, the performances of the participants were video recorded, time spent on the video recordings was determined, and actual performance times were calculated by subtracting them from the total performance time.
Figure 1. Ultrasound Images Obtained on the Move and at the Station.
Note: (1a) IVC, Stationary; (1b) IVC, Moving Ambulance; (2a) Pleura, Stationary; (2b) Pleura, Moving Ambulance; (3a) Aorta-LA, Stationary; (3b) Aorta-LA, Moving Ambulance; (4a) PSLA, Stationary; (4b) PSLA, Moving Ambulance.
Abbreviations: IVC, inferior vena cava; LA, long axes; PSLA, parasternal long axes.
Since it would take time to undress to reach the popliteal and femoral regions of the patients in the ambulance and unbuckling the seat belt of the stretcher to give the knee a flexion position created a safety violation, the popliteal vein and femoral vein examinations for deep venous thromboembolism were excluded from the routine protocol.
Image Quality and Interpretation by the Reviewers
The recorded images were reviewed by two emergency medicine physicians with at least 12 years of bed-side US experience and at least six years (four Basic US courses/year) of bed-side US instructor experience. The accuracy of the frames was evaluated by watching the videos. The recorded images were analyzed under three titles, including the tank, pump, and pipes, as in the RUSH algorithm. The accuracy, quality, and diagnostic evaluability of the images obtained by the participants were evaluated in accordance with the current RUSH protocol guidelines and noted on the previously prepared RUSH Protocol Practitioner Control Form.
Outcomes
The primary outcomes of the study were performing the RUSH protocol accurately by the paramedics in a moving ambulance using handheld US devices, obtaining views, and interpreting the findings accurately, whereas the secondary outcome of the study was performing the protocol within an adequate duration in a moving ambulance.
Statistical Analysis
The conformity of the variables to normal distribution was analyzed using the Shapiro–Wilk test. The continuous variables were expressed as mean (standard deviation [SD]) under the normality assumption. The categorical variables were expressed as n (%) values. Independent sample t-test was used for comparing the two independent groups under the normality assumption. The association between categorical variables was analyzed using chi-square test and Fisher–Freeman–Halton test. Statistical analysis was conducted using the SPSS (IBM SPSS, 25.0; IBM Corp.; Armonk, New York USA) program, and any P value below 0.05 (P <.05) was considered statistically significant.
Results
Twelve paramedics were initially recruited for this study. However, three of them were excluded due to incomplete training and insufficient practical experience. The practices were completed by nine paramedics; 18 performances were performed in the station group and 18 in the moving group.
All participants obtained the PSLA view optimally in both groups in the evaluation of pump functions. No significant difference was observed between the groups in the optimal evaluation of the PSSA, apical, and subxiphoid views (P = .603, P = .092, and P = .804, respectively; Table 1). Moreover, no significant difference in the right ventricular evaluation was observed in both groups (P = .603). The pericardium was recognized and evaluated as optimal by all participants in both groups. A significant difference in the optimal evaluation of the entire pump component was observed between the station and movement groups (83.3% versus 44.4%; P = .015).
Table 1. Comparison of RUSH Protocols between the Station and Moving Groups
Note: Variables were expressed in n (%). Chi-square test was used when calculating the differences between the groups, and the significance value was expressed as P value.
Abbreviations: RUSH, Rapid Ultrasonography for Shock and Hypotension; EF, ejection fraction; IVC, inferior vena cava; Aorta LA, aorta long axes; PSLA, parasternal long axes; PSSA, parasternal short axes; Aorta SA, aorta short axes.
In the tank examination of the RUSH protocol, no significant difference in the optimal evaluation of the IVC, Morrison’s pouch, and lung (P = .421, P >.99, and P = 1.00) was observed between the groups. The lungs were evaluated as optimal by all participants in both groups.
In the examination of the pipes, the long axes (LA) and short axes (SA) of the aorta were correctly evaluated by all participants in both groups.
A statistically significant difference was observed between the station and movement groups in terms of duration (P = .047). The mean duration was calculated as 320.20 (SD = 94.46) seconds in the station group and 266.94 (SD = 52.81) seconds in the moving group. The station group showed a longer mean duration than the moving group (Table 2).
Table 2. Comparison of Performance Times between the Station and Moving Groups
Note: The variables were expressed as mean (standard deviation).
a Independent sampling t-test.
Discussion
Although several studies have measured the focused US skills of paramedics in and out of the hospital, no study has investigated the effect of ambulance movement on paramedics’ RUSH protocol performance. Although many studies reported that paramedics may perform thoracic, cardiac, aortic, and Focused Assessment with Sonography in Trauma (FAST) US examinations, which are components of the RUSH protocol, with higher accuracy rates, the present study is the first to evaluate the ability of paramedics to perform the RUSH protocol in an ambulance with a handheld device. Reference Unlüer, Yavaşi and Kara6,Reference Maloney, Williams and Reardon8–Reference Schoeneck, Coughlin and Baloescu12 This study revealed that the paramedics successfully performed the RUSH protocol in the stationary and moving ambulance after theoretical and practical training.
The evaluation of the components of the RUSH protocol individually revealed that no difference was observed in the feasibility of the views for evaluation in the examinations of the pump component between the groups. Considering the general evaluation of the pump component as EF+RV+pericardial space, the difference between the groups was significant compared with the moving group. The lack of significant difference between the groups in the visual EF evaluation is attributed to the fact that most of the participants opened the PSSA view correctly and provided the opportunity for a diagnostic evaluation. The PSLA view provides insights into E-Point Septal Separation (EPSS), which is one of the most important findings for EF estimation. The higher sensitivity of EPSS evaluation alone for left ventricular ejection fraction (LVEF) estimation makes the PSLA view by all paramedics in both groups more valuable in terms of EF estimation. In a study analyzing the most preferred cardiac view for LVEF estimation, PSLA was rated as the most useful view by the participants. Reference Mark, Ku and Carr13
Moreover, this study reported that the accuracy of the apical view was low in both groups and was affected by ambulance turbulence. The views that could be obtained at the lowest rate in the station group and the view that is most negatively affected by ambulance movement suggest that the examinations made by the paramedics from the apical view were not reliable. In a study evaluating the skills of participants after focused echocardiography training, it was reported that the PSSA and PSLA views were at a higher rate (85% of the participants) and the apical view was successfully at the lowest rate (57% of the participants), which is consistent with the current findings. Reference Chisholm, Dodge, Balise, Williams, Gharahbaghian and Beraud14
Several studies in the literature have shown that the IVC, thorax, and Morrison’s pouch, which are the components of the tank examination, may be evaluated with high accuracy by paramedics. A study conducted by Maloney, et al demonstrated that paramedics successfully obtained and interpreted simulated lung US images. In their study, no significant differences were identified in the application time and accuracy of lung US images under different driving conditions, especially during motion. Reference Maloney, Williams and Reardon8 In the present study, it was observed that they were evaluated with high accuracy in both the stationary and moving ambulances. Reference Unlüer, Yavaşi and Kara6,Reference Maloney, Williams and Reardon8,Reference Kowalczyk, Turkowiak, Piotrowski, Rosiak and Białas9
In a study by Snaith, et al, wherein the association between environmental factors and prehospital US performance was evaluated, 36 aortic ultrasonography (USG) performances were examined. A significant difference between the aortic diameter measurements made in the moving and stationary ambulances was observed, and the measurements made in the moving ambulance were on average 0.11cm larger; however, this difference was not the same as for all measurements made in the moving ambulance. This may have been caused due to performing all measurements before lunch. Reference Snaith, Hardy and Walker15 Similar to the current study, Snaith, et al reported that image quality and evaluability were not affected by environmental factors. In this study, it was observed that the aorta could be evaluated correctly in both groups by all participants in the LA and SA.
Furthermore, in the present study, the completion time of the RUSH protocol was significantly shorter in the movement group compared to the station group. Simmons, et al investigated the effect of ambulance movement on FAST examination and reported that although no statistically significant difference was observed, the average FAST completion time was shorter while in motion (stationary ambulance = 98.5 seconds, moving ambulance = 78.7 seconds; P = .23). Reference Simmons, Mack, Cronin, Monti, Perreault and Ahern16 However, Snaith, et al reported that FAST performance was completed in a longer time in a moving ambulance than that in a stationary ambulance, but this difference was not statistically significant (stationary land ambulance = 135-266 seconds versus moving land ambulance = 126-247 seconds; P = .15). Reference Snaith, Hardy and Walker15 Brun, et al reported that performing extended FAST (eFAST) in the field or during transfer did not affect the accuracy and duration of the examination (w = 0.68). Reference Brun, Bessereau and Chenaitia17 It was also reported in the abovementioned study that eFAST examinations performed during transfer took approximately one-third of the transfer time and did not affect the transfer time. Reference Brun, Bessereau and Chenaitia17 In this study, the RUSH protocol was completed in a shorter time than the ambulance arrival time in Istanbul. In the present study, the reason why the RUSH performance in the movement group was completed in a shorter time may be attributed to the fact that the movement of the ambulance and the sirens encouraged the participants to move a little faster.
Limitations
However, this study has some limitations. The lack of previous USG experience of the volunteer paramedics may have affected the accuracy of some cardiac views. Because the study was conducted with volunteer paramedics, a limited number of performances were examined. Moreover, the utilization of healthy volunteers restricts the study’s scope, as it did not assess the accuracy of US findings in models presenting with abnormal conditions. This omission is critical, as it could affect the applicability of these results to a broader patient population, including those with underlying pathologies.
Conclusion
The present study revealed that paramedics acquire the RUSH protocol skills after a standard theoretical and practical training, adapt quickly to handheld USG devices, obtain examination views with high accuracy, and evaluate sonographic anatomy in healthy volunteers. However, it is important to note that the study only involved healthy, live volunteer models and did not assess pathology. Further studies with more paramedics in the field are warranted to validate the findings of this study.
Conflicts of interest/funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with this article.
