Page 90 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars

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Chapter 3
ble to a telemedicine setup in which the US operator could be at a different physical location than the observer of the images. Therefore, we agree that lung ultrasound can be successfully used in telemedicine setups.18
Strengths and limitations
We chose a unique approach to select VATS patients with a freshly induced and visually confirmed pneumothorax as the gold standard. Also, we included the video clips of the same patients with normal anatomy before surgery. Another unique aspect was the cropping of the video clips so transducers couldn’t be identified by any text or image or sector shape.
A limitation of this study is that it might be underpowered because we couldn’t demonstrate a difference in diagnostic performance between transducers. It could also mean the differ- ence is close to none.
Another limitation is that we informed the observers that all patients were ventilated sim- ilarly and that besides a pneumothorax in half of the video clips, no other pathology was present. This could be an advantage for them judging the clips and might have resulted in an overestimation of the diagnostic performance and time needed. The performance could have been even better when we acquired M-mode clips looking for lung pulse or clips that included the lung point.14
Conversely, most observers were uncomfortable with the fact that they had to assess video clips and that they were therefore unable to reposition or adjust the transducer, adjust the gain or depth, or compare with the contralateral chest. Also, it was regarded a disadvantage that no additional clinical parameters were provided. The setting of pulmonary surgery in- troduced some minor challenges. In some clips, lung sliding was minimal, probably due to the lung-protective ventilator settings. B-lines were still present, obviously. In contrast to the normal clips, the pneumothorax clips were recorded with the transducer wrapped in a sterile cover. In theory, this might result in a slightly degraded US image.
Image quality might be overstated in video clips in which the diagnosis was made fast and perceived to be easy. Those clips might be scored good quality because they were ‘easy’ to assess.
A suggestion for future studies comparing ultrasound transducers might be to include sub- jects of all BMIs to better represent the general population of critically ill and injured pa- tients.