We found that LUS had a high diagnostic accuracy in common pulmonary abnormalities in critically ill patients; indeed, LUS showed a higher percentage of correct diagnosis of consolidation, interstitial syndrome, and pleural effusion than when using CRX as a diagnostic tool and a similar percentage of correct diagnosis pneumothorax at 99.1% when compared to CRX. In our study, LUS had a sensitivity of 90% and an accuracy of 88.4% for the detection of consolidation, which was comparable to previous studies [5, 6, 10]. The same occurred with the LUS accuracy for the detection of interstitial syndrome and pleural effusion when compared with CRX; LUS was significantly better, as reported in the literature [5, 6, 11]. Indeed, CRX showed low sensitivity for these abnormalities, with 59%, 48%, and 64% sensitivity for consolidation, interstitial syndrome and pleural effusion, respectively [5, 6, 11]. It has also been suggested that LUS was better than CRX in differentiating forms of pleural effusions on the basis of internal echogenicity, homogeneity, and pleural thickness . With pneumothorax, however, LUS and CRX were both very accurate. This finding is in contrast with a previous comparable study, in which CRX could not identify this abnormality . It has been shown that LUS outperforms CRX when detecting residual pneumothoraxes after drainage and that residents can learn to operate on LUS after only two hours of training [13, 14].
Replacing CXR with LUS in the ICU reduces radiation exposure, which is a substantial improvement in patient safety . Indeed, the carcinogenic effects of X-rays are well known; one chest CT scan has an effective radiation dose equivalent to 400 CXRs . indeed, medical radiation from CRX and nuclear medicine is the most important source of radiation exposure in Western countries . In our study, we performed 610 CRXs, and some patients spent several days in the ICU with substantial radiation exposure. Routine daily CXRs for critically ill patients have been the standard practice in many institutions. A recent intervention to promote a change in CXR ordering practice contributed to a decrease in routine CXRs and a two-thirds decrease in patients receiving CRXs .
Other studies have shown that the use of LUS reduced the use of CRX  or CRX and CT [21, 22]. Brogi et al. evaluated the influence of routine use of LUS on costs and the usage of CXRs in the ICU and found a significant reduction in the number of CXRs and in costs without affecting the outcome . Additionally, the point-of-care LUS protocol led to a significantly lower utilization of chest radiography, ultrasound performed by non-intensivist specialists, and CT scans, leading to lower radiation exposure, less intrahospital transportation of unstable patients, and cost savings .
We found LUS to be a useful method to inform intensivists on the decision to prescribe a diagnostic and/or therapeutic procedure. LUS proved to inform the decision correctly in the vast majority of patients. In 76% of patients, performing CT did not provide any additional information that would change the decision based on the LUS findings. Agreement between LUS and CT was high, and coinciding with the literature, LUS alone informed the decision-making process . This saved time and provided a better use of healthcare resources by avoiding unnecessary CRXs and CTs. Similar to other studies, we also found LUS to be superior to CRX .
This study has limitations that need to be acknowledged. First, we studied a small number of patients, which led to some constraints in the analysis. The location of the pathological finding and the analysis to identify factors associated with a subsequent action were both affected by the sample size. Second, the time interval between LUS and CT was minimized but could not be controlled. Third, this is a single center study, which could limit the transferability of our findings to other settings, especially those related to decision-making.
In conclusion, in ICU patients, bedside LUS, which can be performed by ICU specialists, offers better diagnostic performance than radiography for the diagnosis of common pathologic conditions and could be an alternative to CT scans.