## 4 Discussion
The same provider performs and interprets the study, immediately integrates the findings into the clinical setting, and repeats the study as needed to identify changes associated with bedside interventions. In this case, the raters did not have the opportunity to explore the patients or adapt the ultrasound exploration according to their preferences and findings. Therefore, despite allowing us to evaluate the scans in a very controlled setting (same device, same image quality, etc. ), this type of patient observation is not realistic. This fact may have caused some errors in the interpretation of some particular cases. The impact of this was evaluated by performing a comparison of the evaluations the sonographer who collected the videos during the examination with respect to those observed in the surveyed videos. The moderate agreement found (Cohen's kappa 0.68) in this case is a good indication of the differences that might be expected between in situ evaluations and those performed with a recorded video. Furthermore, in this study, there were no patients who suffered extremely severe conditions. This reduced the number and size of the consolidations (if present), making them more difficult to identify (see Figure 7). As shown in Figure 5 and Table 1, the cases with score = 2 were those with significantly higher disagreements. In terms of which is the best way to perform LUS, i.e., whether to use longitudinal or transversal view, our results show that there is a very good correlation between both types of examination (R\({}^{2}\) = 0.87), although, on average, the transversal view provides slightly higher scores (1.12). This was expected as avoiding the ribs provides a larger field of view of the lungs and, therefore, a higher probability of detecting pneumonia-related artifacts. The difference is small and does not impact the classification of patients into subgroups for most patients. However, in our case, 4 out of 20 patients changed their subgroup, with 3 increasing their subgroup classification with a transversal view and one decreasing the subgroup (Figure 6). This does not necessarily mean the two orientations are similarly useful, especially since we only examined a type of interstitial lung disease. In certain pathologies, such as pneumothorax, the visualization of the ribs provides a depth landmark  
Figure 7: Pie chart with the distribution of findings observed by the participants in all the videos considered. A reduced number of severe cases can be observed. and helps to better identify the pleural line. Consequently, our group believes that each patient might benefit most from a different approach, which has been adapted to a flexible scanning protocol subject to the clinical scenario. We would like to acknowledge that, as in all cases, the 12 videos of the transversal view of each patient were evaluated right after the 12 videos of the longitudinal view, this may have created some undesirable correlation between both evaluations. This was chosen to mimic the original in situ study, but a more randomized order of the videos could have been a better choice. Furthermore, pathological findings such as B-lines may have been better represented than others (consolidations and pleural effusions). Despite these limitations, this study represents one of the most controlled studies into the inter-observer agreement of LUS findings for COVID-19. Other studies could be conducted with the gathered data. For instance, a study of variability by region (i.e., anterior vs lateral vs posterior), upper and lower, left and right, etc., could be conducted. Furthermore, we did not include AI tools, which are able to evaluate the acquired videos and compare them with human observers. In this work, the AI tool used in [8; 16] was not compared but will be part of future work.