Focused echocardiography in intensive care unit (ICU) patients with compromised cardiorespiratory function aims at rapid differential diagnosis of hemodynamic problems by detection of pericardial effusion, severe right and left ventricular (RV and LV) failure, and severe valvular abnormalities, and by evaluation of volume status.1–6 The use of focused echocardiography has been suggested to be the preferred modality for the initial assessment of circulatory shock as opposed to more invasive monitoring technologies.7 Serial focused echocardiography allows for monitoring of the evolution of circulatory compromise and the response to therapeutic intervention.7,8 Critical Care Societies worldwide therefore recommend focused echocardiography to be included in the training of ICU physicians.9–13
Critical care echocardiography mainly relies on transthoracic echocardiography (TTE), whereas transesophageal echocardiography (TEE) is less frequently performed.14 Nevertheless, TEE provides a consistently higher image quality than TTE as it is not hampered by the numerous limitations of surface ultrasonography such as obesity, emphysema, mechanical ventilation, and dressings or drains.15 TEE bypasses these barriers. Proficiency in TEE requires manual skills, in-depth knowledge of the 3-dimensional cardiac anatomy, and experience in image interpretation. Traditionally, these skills are acquired by repetitive, supervised hands-on training. While the number of performed examinations to achieve sufficient proficiency for focused TEE is not very high,16 training in TEE is often impeded by time constraints in busy ICUs, limited numbers of appropriate cases, and the lack of experienced teachers. Performing TEE for training purposes only is generally precluded by the invasiveness of the procedure and the associated risks.17
Commercially available TEE simulation systems, which allow for patient-independent teaching of TEE skills, have recently been introduced. Previous studies reported that the use of a TEE training simulator improves both the development of psychomotor skills18–20 and the trainee’s ability to obtain more examinations with a better image quality.21 TEE simulators also offer the possibility to simulate pathological conditions of the heart and thus may facilitate training in image interpretation.22 However, the acquisition of a TEE simulator system represents a substantial financial burden for already stretched hospital budgets.
The objective of this study was to determine the impact of TEE simulator-based training on the ability of novice operators to perform a focused critical care TEE and to compare the achieved skill level with TEE experts. We hypothesized that the use of a TEE simulator during training would enable TEE operators to obtain more views with better image quality, and improve their ability to quantify detected pathologies and interpret the findings in the clinical context.
The Ethics Committee of the Canton of Berne reviewed and approved the study (294/2015). All TEE examinations in the context of the study were part of the routine care and need for patient or proxy consent was waived.
This was a prospective, randomized controlled, nonblinded study with blinded outcome assessment in a single tertiary university hospital in Switzerland.
Forty-four ICU trainees without previous hands-on TEE experience were enrolled in the study. Restricted random allocation of participants to the intervention and control groups was performed to obtain equally sized groups before the start of lectures and hands-on training sessions using a standard software package (SPSS Statistics for Windows, Version 22.0; IBM Corp, Armonk, NY). A group of 3 experts in TEE supervised all TEE examinations and served as a reference group.
All study participants received 4 hours of lectures focusing on the techniques for acquiring 11 basic TEE views (Supplemental Digital Content 1, Table, http://links.lww.com/AA/B940). Additionally, normal cardiac anatomy and findings related to LV and RV dimensions and function, gross valvular pathologies, pericardial effusion and tamponade, filling status, and focused hemodynamic assessment were part of the theoretical lectures.2,23–25 Before and immediately after the lectures, the study participants were presented with 20 different TEE loop videos using PowerPoint (Microsoft Corporation, Redmond, WA) and answered multiple-choice questions relating to the lectured content. The pre- and postlecture knowledge assessment consisted of 20 questions related to the lecture content and referring to anatomy, echocardiographic view identification, and the identification of pathologies. The participants were given 90 seconds for choosing the best answer out of a choice of 5. Subsequently, the intervention group participated in a 4-hour simulator-based training in acquiring the basic TEE views in a heart without pathology using a mannequin-based TEE simulator (HeartWorks; Inventive Medical Ltd, London, United Kingdom). Training was performed in groups of 3 participants and 1 tutor. The participants took turns handling the probe with the same allocated time each, while the other 2 participants observed. The simulator displayed the real-time ultrasound views simultaneously with a second window showing a 3-dimensional heart, the TEE probe, and the active imaging plane in corresponding positions. This allowed the participants to visualize and understand the effect of changes of the probe position and rotations of the imaging plane on the echo image. The hands-on training started with a demonstration and teaching of the basic movements of the TEE probe. Thereafter, each view was repeatedly obtained by the participants and advice was offered at all times by the tutor on how to optimize imaging. Finally, the acquisition of the whole examination involving all 11 views was repeatedly practiced by each participant.
Assessment of training effects occurred within 2 weeks after the training. Basic TEE examinations2 were performed by every study participant in 2 different intubated and sedated ICU patients with existing cardiorespiratory compromise. The examinations were performed on request by the treating physician for clinical reasons. All examinations were supervised by a TEE expert for safety reasons but no help in acquiring or interpreting the views was provided. Patients were examined by 1-3 study participants and 1 TEE expert without removing the probe. Due to restriction in patient and study participant availability, patients were not examined by equal numbers of trainees from each group. Study procedures precluded the participants from observing the expert or the other participants performing a TEE study or to discuss TEE findings before all examinations were completed. At the beginning of each patient examination, the TEE probe was placed by the TEE expert in the gastric position, and rotated anteriorly at an imaging plane of 0°. After completion of the TEE, the study participants had to report the TEE findings using a study-specific case report form (Supplemental Digital Content 2, Table, http://links.lww.com/AA/B941). The time requirement for performing TEE (TEE time) was measured. A maximum of 25 minutes per examination plus 5 minutes for reporting was allowed. The quantification of study findings encompassed assessment of LV function and dimensions, identification pericardial effusion, grading of valvular function, whereas the interpretation skills included identification of hypovolemia, LV and RV failure, pericardial tamponade, and significant valvulopathy. For comparison purposes, the basic TEE with completion of the study case report form was performed by the TEE expert in each patient before supervising the study participants. After completion of study assessments, the TEE expert performed a standard comprehensive TEE24 which was reported to the physician treating the patient.
All TEE examinations were independently graded offline by 2 board-certified TEE specialists (assessors) who were blinded to the identity of the TEE operator. The image quality of each view was graded using a scale consisting of a maximum of 5 categories (angle and depth, overall clarity, and visualization of up to 3 distinguishing anatomical structures) resulting in a maximal achievable examination quality score per TEE of 100 points and a maximum of 28 visible anatomical structures (Figure 1).26,27 To establish a measure of clinical utility of an examination, a dichotomous clinical judgment of the visibility of the 28 anatomical structures of interest in the 11 views of the American Society of Echocardiography (ASE) examination was used. Each structure was classified as either being visible in sufficient quality for clinical use or not. The clinical utility was expressed as the percentage of the 28 anatomical structures which were visible in sufficient quality for clinical use per TEE examination. The quantification of TEE findings encompassed eyeballing of LV function (normal, moderately decreased, severely decreased), measurement of LV fractional area change (>45%, 20%–45%, <20%), presence or absence of LV and RV dilation and pericardial effusion, and grading of aortic, mitral, and tricuspid insufficiency (none, not significant, significant). The interpretation of the study required the identification of hypovolemia, LV and RV failure, pericardial tamponade, and clinically significant valvulopathy. The comparator for the quality of quantification and interpretation skills of the study subjects was obtained by the assessors who independently reviewed the comprehensive TEE examinations. In the case of assessor disagreement on ordinal or scaled parameters, a consensus was established after jointly reviewing the TEE study.
Assuming a difference in means of 10 and an equal standard deviation of ±20 when comparing TEEs allocated to 1 of 3 operator categories, we calculated a necessary minimum sample size of 96 TEEs to achieve a power of 0.95 for the main analysis (α error .05). The performed sample size calculation is an approximation to the full study design, with a potential underestimation of sample size needed due to the repeated measures. To account for possible study drop outs and inaccuracy in sample size calculation, additional study subjects were recruited, to obtain a maximum possible number of TEEs of 120.
Data are shown as mean and 95% confidence interval (CI) or median and range or interquartile range as indicated. Time to completion of TEE stratified by operator group affiliation (intervention/control/expert) was compared using Kruskal-Wallis test followed by Dunn’s procedure to demonstrate differences between pairs.
To assess differences in examination quality score, we used a linear mixed-model including a fixed effect for operator group affiliation and crossed random intercepts for individual physicians and patients. The probability of imaging to be of sufficient quality was analyzed using a generalized linear mixed-effects model with a binomial distribution and logit-link. The model included a fixed effect for the operator group affiliation random intercepts for physician, patient and view, as well as random slopes for groups by view (ie, a random intercept for every view/operator group combination).
Agreement with the assessor’s evaluation of the comprehensive TEE examinations for quantification or interpretation of findings was calculated by fitting generalized linear mixed-effects models using a binomial distribution and logit-link. Operator groups were treated as fixed effect with random intercepts for patient and finding. Agreement was expressed as percent of agreement with the assessor plus odds ratio (OR) using a binary outcome (rating by operator agrees or disagrees with rating by the assessor). To perform multiple comparisons between operator groups for single echocardiographic findings, an individual model for each TEE finding was calculated with group affiliation as fixed effect and random intercepts for patient. Comparisons were expressed as estimates of percent agreement with CI as predicted from fixed effects of the models, with CI corresponding to the predicted value ±1.96 times the standard error of predictions. A P < .05 was considered significant.
Analysis was performed using R version 3.3.228 (including packages lme4 for fitting mixed-effects models29 and multcomp for multiple comparisons using Holm P value adjustment30) and IBM SPSS Version 22 (including an SPSS extension command31).
This manuscript adheres to the applicable Equator guidelines.
Forty-four ICU trainees registered for the advertised TEE course and were randomized. One subject decided not to participate at short notice and could not be replaced. All trainings and TEE examinations were conducted during May and June 2016. Forty-three trainees completed the group-specific training and performed 2 TEE examinations in ICU patients. Demographic and professional baseline characteristics and performance levels in the multiple-choice examinations pre- and postlectures of the control and intervention group did not differ (Table 1). A total of 114 TEE examinations in 28 ICU patients were included in the final analysis (44 TEEs intervention group, 42 TEEs control group, 28 TEEs expert group; Figure 2). The relative frequencies and severities of TEE findings detected by the assessors based on the comprehensive TEE examinations are reported in Table 2.
The examination quality scores differed significantly between the TEEs performed by the control, intervention, and expert groups (χ2 37.6; P < .001; Figure 3). The multiple comparisons of the examination quality scores between TEEs stratified by operator group allocation revealed significant differences between all groups (19.7 [95% CI, 12.8–26.6], adjusted P < .001 for intervention versus control; 32.6 [95% CI, 23.0–42.3], adjusted P < .001 for expert versus control; 12.9 [95% CI, 3.4–22.5], adjusted P = .008 for expert versus intervention). The percentage of the 28 anatomical structures which were visible in sufficient quality for clinical use per TEE examination differed significantly between TEEs stratified by operator group allocation (χ2 = 22; P < .001; Figure 3). Multiple comparisons revealed significant differences between all operator groups (OR of a structure image being usable versus not-usable 2.8 [95% CI, 1.2–6.2], P = .015 for intervention versus control; OR 20.1 [95% CI, 6.7–60.2], P < .001 for expert versus control; OR 7.3 [95% CI, 2.7–19.5], P = .008 for expert versus intervention). Table 3 reports the percentage of useable anatomical structures in groups stratified by operator group allocation.
The TEE acquisition time was significantly lower in the intervention compared to the control group (19.5 minutes [11–25] for intervention group; 24 minutes [16–25] for control group; P < .001). Compared to the intervention group, the expert group acquired the views in significantly shorter time (13.5 minutes [7–22]; P < .001).
The overall percentage of agreement in quantification and interpretation of findings between TEEs stratified by operator group allocation in comparison to the assessors evaluation differed significantly (χ2 34.5, P < .001 for quantification; χ2 13.9, P < .001 for interpretation) and was lower for TEEs of the control than the intervention group, while TEEs performed by the expert group demonstrated the highest percentage of agreement (Table 4). Multiple comparisons revealed significant differences in agreements in quantification of findings of TEEs; agreement was lower for TEEs of the control than the intervention group, while TEEs performed by the expert group demonstrated a significantly higher percentage of agreement than examinations of both the intervention and control groups. Similarly, agreement of interpretation findings was significantly lower for TEEs of the control than the intervention group, but did not differ between the intervention and expert TEEs (Table 5). The level of agreement for interpretation and quantifications stratified by operator groups and single clinical findings is represented in Figure 4.
No adverse events occurred during any of the TEEs in the context of the study.
The results of our study indicate that in the context of a TEE introductory course, novice operators are able to acquire TEE views faster and with better quality after additional TEE simulator training in comparison to lecture-based training alone. After a 1-day course comprising of each, 4 hours of lectures and simulator training, the participants quantified and interpreted cardiac pathologies of ICU patients based on a focused TEE in substantial accordance with the assessment of a comprehensive study by board-certified experts.
The limitations of this study pertain to the single-center design and the fact that the study participants were not blinded to their training group after random allocation. We only evaluated short-term effects of simulator training and only included echocardiographic novices in our study. Not all basic pathologic findings were present in the cohort of examined ICU patients and several outcome parameters were based on ordinal data with its inherent disadvantages. Timing of TEE examinations were subject to the necessity to perform a TEE on clinical grounds and study participant availability, making it impossible to ensure that each patient was assessed by a trainee from each group. This was accounted for by the applied statistical methods, but a potential bias due to patients’ characteristics cannot be completely excluded. The study featured a pragmatic randomized controlled design in the context of an actual TEE training course in an ICU setting and was sufficiently powered to obtain highly significant results for the assessment of TEE quality. In contrast to previous studies comparing simulator-based TEE training with traditional TEE teaching methods,20,26,32 we did not focus exclusively on differences in manual skills to obtain sufficient imaging quality but included the ability to correctly quantify and interpret imaging results—thus encompassing the complete work flow of an echocardiographic examination.
Basic competency in TTE and TEE is rapidly becoming an important component of intensivist training.33 While TTE is less invasive and can be performed in healthy volunteers or patients for training purposes, disadvantages include limited view quality due to patient factors (eg, obesity, presence of chest drains and dressings, high positive end-expiratory pressure, and hyperinflation). TEE requires a shorter training period to acquire sufficient competency to acquire images of good quality and is less operator dependent.16,33 However, time pressure when assessing hemodynamically compromised patients and the varying availability of appropriate cases limit TEE training opportunities in the ICU.
TEE is a complex imaging modality, necessitating the manual skills of probe manipulation to acquire defined echo views and the cognitive skills to interpret the 2D representation of the 3D cardiac anatomy. TEE simulators allow to simultaneously obtain an anatomic view of the heart, the relative position of the TEE probe, and the corresponding ultrasound image. This feature allows to better understand the effects of probe manipulation and positioning on the ultrasound plane within the surrounding anatomic structures34 and leads to improvements in terms of precision and speed of the TEE probe motions.20,32 Few studies have assessed the transferability of manual and cognitive skills from simulated TEE to patient examinations. Prat et al22 compared the performance of ICU trainees in the periods before and after the introduction of a simulator-based training program and demonstrated that the addition of simulator sessions to a standardized TEE training curriculum accelerated the acquisition of manual skills in performing TEE. Ferrero et al26 performed a randomized controlled trial assigning anesthetics trainees to either lecture-based training only or a simulator group who received a 45-minute hands-on session and found that simulator training correlated to improvements in overall image quality and number of acquired acceptable views when examining patients.
The reported advantageous effects of simulator-based training are confirmed by our results in an ICU setting, and show significantly higher imaging quality in TEEs performed by trainees after having participated in the simulator training. The design of the study at hand additionally allows for the comparison of the TEE quality between study groups and experienced TEE experts. It has to be emphasized that even if the quality of TEEs of both study groups was rated to be significantly inferior to that achieved by the TEE experts, the majority of imaging results of the intervention group featured sufficient quality to be used in a clinical context.
The correct quantification of cardiac pathologies and interpretation of findings is an integral and highly important part of every echocardiographic examination. Misjudgement of TEE findings could lead to incorrect assumptions regarding the patients’ hemodynamic status and have a detrimental effect on treatment decisions. The impact of a TEE simulator training on the ability of trainees to interpret TEE findings of actual patients has so far only been investigated in the previously mentioned study of Prat et al.22 As in our study, trainees had to identify the presence of left and right ventricular failure and hypovolemia. The authors did not find a difference between the simulator and the control groups, and hypothesized that training using a TEE simulation of a normal heart does not offer a significant benefit for evaluation and interpretation skills of pathologic findings. In our study, we found a significant agreement beyond chance between quantification and interpretation of basic TEE and assessment of a comprehensive study by the experts in both TEEs of the control and intervention groups. The difference in rating agreements with the assessment of a comprehensive study by the experts of the intervention and the control groups reached statistical significance for the quantification, but not the interpretation skills. Our results indicate a trend for a higher level of agreement for each assessed TEE finding, although the study was not sufficiently powered to establish the significance in difference. The fact that training using the simulation of a normal heart improved quantification skills of pathologic findings might be explained by the superior image quality in the intervention group facilitating correct quantification. Second, the intervention group was significantly faster in acquiring the requested views indicating that the participants had more time to focus on image interpretation instead of acquisition.
Multiple comparisons of agreement in quantification of findings of focused TEEs stratified by operator group allocation in comparison to the assessors’ evaluation-based on comprehensive TEE did detect significantly higher agreement in the intervention than in the control group TEEs, while agreement was best for TEEs of the expert group. We did not find a significant difference of agreement in interpretation of focused TEE findings between the intervention and the expert groups. It can be argued that our study was not sufficiently powered to reliably detect differences in interpretation skills between study groups, as it is unlikely that novice operators could achieve the same competency as trained experts after only 8 hours of training. However, we detected a substantial accordance between the quantification and interpretation of cardiac pathologies with the comprehensive study by the experts for the focused TEEs of our intervention group, while TEEs of the control group only achieved moderate agreement.
It can be argued that the reported outcome differences between the study groups are solely caused by the differing duration of the training period (4 vs 8 hours) and that any additional exposure to TEE topics—such as additional lectures or viewing video material—would potentially cause the same or a similar learning effect. We are convinced that manual skills are an integral part of TEE training which can only be adequately acquired by either using a simulator or by examining real patients. It is conceivable that training interventions other than simulator or patient examinations might offer a varying degree of knowledge gain and therefore have some effect on manual skills. However, the aim of the study was to assess the net effect of simulation training.
Our results suggest that simulation-based TEE training enhances the acquisition of manual skills and ability to correctly quantify cardiac pathologies in comparison to lecture-based education only. Eight hours of combined simulator and lecture-based training enable novice operators to achieve a 2–3 times higher level in obtaining TEE views of good quality and to correctly quantify and interpret imaging results compared to novice operators with only lecture-based training. We suggest that the use of a TEE simulator should be considered, especially in the early phase of an ICU echocardiography training curriculum, followed by frequent supervised hands-on practice in patients.
Name: Andreas Bloch, MD.
Contribution: This author helped design the study, analyze and interpret the data, draft the manuscript, establish the TEE training course and provided lectures and TEE simulator training. This author helped revise the manuscript critically for important intellectual content, and read and approved the final manuscript.
Name: Robert von Arx, MD.
Contribution: This author helped establish the TEE training course and provided lectures and TEE simulator training. This author helped revise the manuscript critically for important intellectual content, and read and approved the final manuscript.
Name: Reto Etter, MD.
Contribution: This author helped establish the TEE training course and provided lectures and TEE simulator training. This author helped revise the manuscript critically for important intellectual content, and read and approved the final manuscript.
Name: David Berger, MD.
Contribution: This author helped revise the manuscript critically for important intellectual content, and read and approved the final manuscript.
Name: Heiko Kaiser, MD.
Contribution: This author helped establish the TEE training course, provided lectures and TEE simulator training, revised the manuscript critically for important intellectual content, and has read and approved the final manuscript.
Name: Armando Lenz, PhD.
Contribution: This author helped analyze and interpret the data and drafted the manuscript. This author helped revise the manuscript critically for important intellectual content, and read and approved the final manuscript.
Name: Tobias M. Merz, MD.
Contribution: This author helped design the study, analyze and interpret the data, and draft the manuscript. This author helped establish the TEE training course and provided lectures and TEE simulator training. This author helped revise the manuscript critically for important intellectual content, and read and approved the final manuscript.
This manuscript was handled by: Roman M. Sniecinski, MD.
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