This is the first study that aimed to validate whether a focused training program designed to achieve essential competences in extended basic CCE including Doppler capabilities for residents with no prior ultrasound experience was adequate. Basic critical care echocardiography by physicians inexperienced in ultrasound has been previously investigated, using training programs of 6–15 h [4–7]. Of note, these programs did not include the use of Doppler and the training objectives were limited to a 2D approach that may considerably narrow the scope of the examination [4–6]. The scanning times of our trainees was 10–15 min longer than these earlier series, related to more assessments using Doppler examination, which goes beyond the scope of basic critical care echocardiography. Even if our longer training program allows acquiring some essential competences for establishing diagnoses and guiding the management of critically ill patients, it seems to be insufficiently to perform a complete extended basic critical care transthoracic echocardiography.
The shorter training program blending approximately 4-h theory and 3-h practical allowed residents to acquire only two important skills using 2D imaging including global systolic LV function and pericardial effusion assessment. However, residents failed to achieve others skills using 2D imaging and Doppler capabilities. The longer training program blending approximately 4 h theory and 12 h practical allowed residents to acquire to a good or very good degree of some essential competences in extended basic CCE, using 2D imaging (global systolic LV function and pericardial effusion assessment, RV size evaluation) and Doppler capabilities (detection of significant left-sided valve including aortic stenosis, mitral stenosis, aortic regurgitation and mitral regurgitation). As expected, LV filling pressure and diastolic function were more adequately assessed by residents trained by the long program than by those trained with the short program, with a good reproducibility but a moderate agreement. Lastly, some skills such as the measurement of the stroke volume, the detection of heterogeneous LV contraction and of paradoxical septum and the assessment of respiratory variation of IVC diameter probably require more in-depth training.
For the first time, our study shows that a focused training program in ICU setting allows to reach competences using Doppler capabilities. Using color and continuous Doppler, the residents trained by the long program adequately detected significant left-sided valve disease, as only 6 % of the evaluated patients were misclassified. Consistent with our results, Mjølstad et al.  found that residents undergoing a training program with 4-h theoretical and 95 echocardiograms adequately detected moderate aortic or mitral valve diseases (and missed no severe ones) using a pocket-size handheld echocardiography machine in a non-ICU setting. Conversely to the valve diseases, LV filling pressures and diastolic function assessments using pulsed and tissue Doppler were more challenging, even for the expert in 23 % of the patients, because of no sinus rhythm, tachycardia or low imaging quality. Despite a good reproducibility for the E/A and E/e′ Doppler indices on patients with normal sinus rhythm between the residents (trained with the long program) and the expert, the limits of agreement (bias ± 1.96, SD −0.7 to 0.6 and −4 to 5, respectively) are too large for us to be confident that the measure of residents can be used for clinical purposes. Our results are in the same range as in previous study that reported a moderate interobserver agreement for E/e′ ratio in patients with septic shock, possibly reflecting the difficulty in assessing diastolic function in critically ill patient . Since we found considerable interobserver variability between residents and the expert in stroke volume measurement requiring aortic pulsed-flow Doppler and detailed 2D imaging, our results imply the need for additional training in using these to guide management in critically ill patients.
Some essential basic skills using only 2D imaging seem easier to achieve since, in keeping with recent series [4–7], both groups of residents adequately evaluated global LV systolic function and identified pericardial effusion. Residents trained by the longer training program accurately diagnosed the two cases of tamponade encountered in the current study. Our results indicate that RV size may be more difficult to evaluate, especially when the dilatation RV is moderate, requiring the longer training program. Similarly, DeCara et al.  noted substantial differences in the performances of handheld devices to detect RV dysfunction when used by physicians with limited training, compared with an expert in echocardiography. However, some competences using 2D imaging probably require more training, as previously reported [6, 13, 15]. According to our results, Vignon et al.  showed that residents who underwent a 12-h training program tended to underestimate respiratory variations of IVC size. In the same way, Mjølstad et al.  reported that recently trained residents inadequately assessed the inferior vena cava diameter in a non-ICU setting. Although the visual detection of regional wall motion abnormalities is defined as a basic competence in critical care echocardiography, no previous study in ICU setting has validated the level of training required for its acquisition. Similar to our results, previous studies in a non-ICU setting find that acquisition of this skill by physicians with limited training was particularly difficult [13, 15]. Assessing thickening of every LV walls requires a very good quality of imaging and probably a more important level of training. Lastly, our results confirm the consensus statement on competence in critical care ultrasonography which indicates that accurate identification of paradoxical septal motion may be challenging .
Compared to residents trained by the short program, the agreement between responses provided by residents trained by the long program and the expert was generally higher. This may be related to the longer training curriculum, which included more interactive clinical cases, but may also be related to a learning curve effect, since residents trained by the long program performed a mean of 27 examinations, compared with 10 in the short training program. Our learning rate estimates are consistent with the “European Society of Intensive Care Medicine” recommendations of approximately 30 TTEs in ICU patients to reach competence in basic critical care echocardiography . Despite scarce data, experts in echocardiography in the ICU have suggested that “a minimum of 100 full TTEs is required as part of training in advanced critical care transthoracic echocardiography” . It is clear that mastering the technique of advanced level requires a considerable investment in training . However, our study indicates that some essential competences at an advanced critical care transthoracic echocardiography level were achieved with approximately 30 extended basic critical care transthoracic echocardiography. One strength is that the training program required trainees to scan various ICU patients with and without mechanical ventilation, which provided a rich source of practical experience. Lastly, apart from the time taken by the expert to teach, we did not invest in additional training materials or echocardiography simulators. As such, others may readily replicate our program.
Our study has some limitations. First, the training programs were conducted in two different places, at different times. However, indications, conditions and global imaging qualities of “paired” extended basic CCEs were mainly similar between both study centers, and both trainings were conducted with non-cardiologist residents with no prior experience in ultrasound. Second, we have included a limited number of trainees because of our small number of residents, their 6-month rotation period and the exclusion of those who had experience in ultrasound. However, each recently formed resident performed a large number of CCE during the evaluation period. Third, the mean duration of extended basic CCE examination was very long, even after a larger number of “offline reviewed” extended basic CCEs. We consider this point to be crucial because hemodynamic evaluation has to be performed quickly in order to rapidly optimize treatment. Fourth, because of the workload in the ICU, the residents were often hard-pressed to find time to perform the CCEs. A rotation specifically dedicated to learning echocardiography might be one way to improve results substantially. Fifth, our study wasn’t designed to assess the learning curve of residents. Finally, because the simulation system was unavailable in our units, this very efficient learning modality was not been tested in the study.