|Year : 2022 | Volume
| Issue : 2 | Page : 39-44
A comparative analysis of thoracic ultrasound with radiography in the detection of lung pathologies among patients in intensive care units
Ogenyi Obande1, Janet Adetinuke Akinmoladun2, B Babatunde Osinaike3, M Atinuke Agunloye2, O Ayotunde Ogunseyinde2
1 Department of Radiology, University College Hospital, Ibadan, Oyo State, Nigeria
2 Department of Radiology, University College Hospital; Department of Radiology, University of Ibadan/University College Hospital, Ibadan, Oyo State, Nigeria
3 Department of Anaesthesia, University of Ibadan/University College Hospital, Ibadan, Oyo State, Nigeria
|Date of Submission||22-Apr-2022|
|Date of Decision||10-Jun-2022|
|Date of Acceptance||05-Jul-2022|
|Date of Web Publication||17-Dec-2022|
Janet Adetinuke Akinmoladun
College of Medicine, University of Ibadan/University College Hospital, Ibadan, Oyo State
Source of Support: None, Conflict of Interest: None
Introduction: Chest X-ray (CXR) is a common study in intensive care unit (ICU) and to a lesser extent, chest computed tomography. Both studies use ionizing radiation. Bedside ultrasound (US) avoids exposure to ionizing radiation or potentially hazardous movement of the patient. Materials and Methods: This was a prospective, cross-sectional, comparative study of B-mode thoracic ultrasound (TUS) with CXR in the detection of lung pathologies in ICU patients. M-mode was further used in suspected pneumothorax (PTX). Patients with clinical suspicion or diagnosis of lung pathologies were recruited. CXR with portable machine and TUS using mobile US machine were done. Results: Seventy patients were recruited; 38 (54.3%) were female. Pleural effusion was detected in 17 patients, 15 (88.2%) by TUS and 11 (64.7%) by CXR. TUS and CXR detected lung consolidations in 11 (84.6%) and 9 (69.2%) patients, respectively. PTX was seen by CXR in 6 (85.7%) patients and 5 (71.4%) were seen on TUS. Both modalities diagnosed equal numbers of alveolar and interstitial edemas. Conclusion: Overall, there was no statistically significant difference in imaging diagnosis of lung pathologies by TUS and CXR. However, TUS detected more pleural effusion and consolidations; hence, it may be considered an alternative in the management of pediatric patients and pregnant women to avoid ionizing radiation.
Keywords: Chest X-ray, intensive care unit, lung pathologies, thoracic ultrasound
|How to cite this article:|
Obande O, Akinmoladun JA, Osinaike B B, Agunloye M A, Ogunseyinde O A. A comparative analysis of thoracic ultrasound with radiography in the detection of lung pathologies among patients in intensive care units. J Radiat Med Trop 2022;3:39-44
|How to cite this URL:|
Obande O, Akinmoladun JA, Osinaike B B, Agunloye M A, Ogunseyinde O A. A comparative analysis of thoracic ultrasound with radiography in the detection of lung pathologies among patients in intensive care units. J Radiat Med Trop [serial online] 2022 [cited 2023 Feb 5];3:39-44. Available from: http://www.jrmt.org/text.asp?2022/3/2/39/364181
| Introduction|| |
Critically ill patients in the intensive care unit (ICU) are usually predisposed to various chest pathologies which include pleural effusion, lung consolidation, alveolar–interstitial syndrome (AIS), and pneumothorax (PTX). They are at increased risk because of their prolonged use of mechanical ventilators, prolonged stay in the hospital, respiratory distress syndrome, and fluid overload.,
Bedside chest X-ray (CXR) has been the routinely performed investigation in the ICU and is considered a reference for assessing lung status in critically ill patients. However, several studies have reported limited diagnostic information and efficacy of bedside portable CXR. Factors accounting for this diminished reliability include the breathing movement of the chest during the acquisition procedure which decreases the spatial resolution of the radiological image from motion blurring. Second, the film cassette is placed posterior to the thorax for an anteroposterior (AP) view image which can give an apparent cardiomegaly, making accurate assessment of the cardiac size technically difficult in some patients. Third, the radiograph beam originates anteriorly, at a shorter distance than recommended, and quite often not tangentially to the diaphragmatic cupola, thereby leading to a misdiagnosis of the silhouette sign. These technical difficulties may lead to misdiagnosis of pleural effusion, lung consolidation, AIS, and other pathologies.,,
Computed tomography (CT) of the chest is now considered the gold standard for the diagnosis of lung pathologies such as PTX, pleural effusion, lung consolidation, atelectasis, and AIS as well as image-guided therapeutic procedures in critically ill patients. However, performing a CT scan of the chest requires transporting the patient to the department of radiology, which can be risky in an unstable patient necessitating the presence of trained physicians and sophisticated cardiorespiratory monitoring in most settings with good health care system. Ultrasound (US) examination of the chest is a real-time, noninvasive imaging technique that gives information about the lungs and pleura as well as the chest wall without the risk of exposure to radiation. In the past, US was only performed in the department of radiology and by specialized hands, but in the past decade, as technology advanced, it can now be done at the point of care, usually at the patient's bedside. This was first introduced in the emergency departments where US was used as an adjunct in the trauma bay for the detection of pericardial or free intra-abdominal fluid in what is known as Focused Assessment with Sonography in Trauma. Its role has since advanced to the point of care diagnosis of basic intra-abdominal pathology, safer line, and tube insertion as well as confirming pregnancy, among many other uses.,
Because US waves are nearly completely reflected by an air–tissue interface, it was initially thought that US imaging is not useful for the evaluation of the pulmonary parenchyma. However, recent evidence reveals that an examination of the artifacts produced by thoracic ultrasound (TUS) results in a wealth of information about the underlying lung. For instance, beyond just knowing that there is pleural effusion, US would most likely characterize it as exudative or transudative fluid. Pneumonia and PTX can also be detected at the bedside with US.,,,,,
This study evaluated the use of US in ICU patients with suspected lung pathologies and compared the findings in them to that seen in their respective chest radiographs.
| Materials and Methods|| |
This was a prospective, cross-sectional study carried out in the ICU of University College Hospital, Ibadan, Nigeria. The study spanned a period of 7 months, from August 2020 to March 2021. Consenting adult patients/those whose relatives consented with clinically diagnosed or suspected lung pathology admitted to the ICU of UCH Ibadan were included in the study, whereas nonconsenting ones and ICU patients without clinical suspicion for lung pathology were excluded from the study. Informed consent was obtained from all participants, and institutional ethical approval was obtained from the UI/UCH Institutional Review Board.
Chest X-ray technique
Each patient recruited underwent CXR examination before or after TUS using the mobile GE® X-ray machine in the ICU. The AP view was done with patient in either supine or sitting positions. The detector is carefully positioned under the patient's chest with the upper edge of the detector above the lung apices. The collimated vertical beam is angled caudally until it is at right angles to the sternum and centered midway between the sternal notch and the xiphisternum.
The radiographs were reported by radiologists who were not privy to the US findings.
Thoracic ultrasound technique
TUS examinations were done using a mobile LOGIQ V2 GE® Medical System (China) Co., Ltd., US machine. All patients had real-time gray scale US with a 3–5 MHz and 5–10 MHz transducers. M-mode (motion mode) was a supporting imaging mode in all patients that required it.
Each hemithorax was divided into six regions bordered by the anterior and posterior axillary lines, three in upper fields (anterior, posterior, and lateral) and three in lower fields (anterior, posterior, and lateral).
The interval between these two investigations (CXR and TUS) did not exceed 24 h to minimize interval changes that could occur following treatment in the ICU.
Determination of pathologic findings on thoracic ultrasound
When performing TUS, some specific ultrasound features are usually of importance. These include the following; lung sliding, A-lines and B-lines on B-mode as well as Sky-ocean-beach/Seashore sign on M-mode.
Lung sliding: This is a normal sliding movement at visceral parietal pleural interphase (VPPI) of the lung. This is a normal finding and is usually absent in the presence of PTX.
A-lines are horizontal, repetitive reverberation artifacts originating from the pleural line, which is also known as the VPPI. It is seen in normal lungs as well as in the setting of PTX. A-lines are equidistant lines between the skin line and the pleural line. Absence of A-line in a patient means that the air in the lung is replaced by a substance that can transmit sound waves.
B-lines are well-defined, hyperechoic vertical comet-tail artifacts that extend down from the pleural line and erase the A-lines. One to four B-lines are normal findings, whereas multiple diffuse B-lines are abnormal and are seen in pulmonary edema. Multiple B-lines, about 7 mm apart, are characteristics of interstitial edema. In contrast, B-lines 3 mm or less apart are seen in alveolar edema. Interstitial edema and alveolar edema aare grouped together as alveolar–interstitial syndrome (AIS).
Sky-ocean-beach/seashore sign is a normal appearance of the lung on M-mode and it gives a typical sky-ocean-beach sign. PTX is diagnosed when there is absence of the normal Sky-ocean-beach sign and it gives a typical sky-ocean-ocean (no beach) appearance.
Furthermore, in the setting of PTX, A-lines are visualized, but there is absence of B-lines as well as lung sliding at the VPPI.
In the setting of pneumonia, diagnostic features of lung consolidation are seen as hypoechoic, wedge shaped or poorly defined lung parenchyma (hepatization) with linear echogenic structures within it in keeping with air bronchograms.
Pleural effusions were classified as either transudates or exudates on TUS. Transudates were anechoic collection without any internal echoes, whereas pleural effusions with septations, internal echogenicity, or associated pleural thickness were classified as exudates.
The data were entered into a standard pro forma and analyzed using the Statistical Package for the Social Sciences (SPSS version 20) Inc., Chicago, Illinois. All results were presented in texts, frequency tables, and figures/charts as necessary.
Continuous variables were expressed as means with standard deviations (SDs), whereas categorical variables were expressed as proportions and percentages. Appropriate tests of significance were carried out. The relationship between qualitative variables (lung pathologies) using TUS and CXR was evaluated using Chi-square test. Statistical significance level was defined as P < 0.05 for all tests.
| Results|| |
A total of 70 adults, 32 (45.7%) males and 38 (54.3%) females, were recruited for the study. The age range of the participants was 18–86 years with a mean ± 1 SD of 54.8 ± 14.3 years. The most affected age group involved was the age range of 49–58 with a frequency of 19 participants, whereas the least affected age group was the 18–28 years' age group with only two participants [Figure 1]. Nineteen (27.1%) participants were recruited on account of a clinical suspicion for aspiration pneumonitis, 16 (22.9%) on account of chest infection, breathlessness in 13 (18.6%), chest injury in 14 (20%), suspicion of pulmonary embolism in 6 (8.6%), and other causes in 2 (2.9%) participants [Table 1].
|Table 1: Clinical indications for radiological investigations in the intensive care unit patients|
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All participants had TUS performed not later than 24 h of having the CXR. The interval between the CXR and TUS studies ranged between 1 h and 23 h with a mean time of 10.76 ± 6.71 h. The Glasgow Coma Score of patients as at the time of TUS ranged between 4 and 15 with a mean of 10.61 ± 3.61. Their duration of stay in ICU as at the time of CXR/TUS ranged between 1 day and 17 days with a mean of 2.9 ± 2.26 days.
Thirty-eight (54.3%) participants had normal CXR, whereas 37 (52.9%) had normal TUS. Twenty-nine (41.4%) participants had normal findings on both CXR and TUS. Six (8.6%) participants had abnormal findings on CXR alone, whereas 8 (11.4%) participants had abnormal findings on TUS alone. Twenty-four (34.3%) participants had abnormal findings in both modalities.
Pleural effusion [Figure 2] was detected in a total of 17 patients, of which 15 (88.2%) were detected by TUS and 11 (64.7%) were detected by CXR. Nine participants (52.9%) had pleural effusion on both modalities. Two (11.8%) cases were detected by CXR but missed on TUS, whereas 6 (35.3%) cases were detected by TUS but missed on CXR. Overall, TUS picked more cases of pleural effusion. TUS diagnosed more cases of pleural effusion. Fourteen (82.4%) of the diagnosed cases of pleural effusion were transudaes while 3 (17.6%) were exudatives. There was no significant difference between the findings of the TUS and the CXR, P = 0.404 [Table 2].
|Figure 2: (a) Supine AP CXR in a 57-year-old female patient showing a uniform soft tissue opacity obscuring both hemidiaphragms, the left lower lung zone and almost the entire right hemithorax. Inhomogenous opacities are also noticed in the visualized left lung field. The cardiac shadow is silhouetted. A submission of bilateral pleural effusion, worse on the right, was made. (b) TUS in the same patient showing pleural effusion with low level echoes. AP = Anteroposterior, CXR = Chest X-ray, TUS = Thoracic ultrasound|
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Lung consolidation was detected in a total of 13 patients, of which 11 (84.6%) were detected by TUS [Figure 3], whereas 9 (69.2%) were detected by CXR. Seven (53.8%) participants had lung consolidation detected on both TUS and CXR examinations. Two (15.4%) cases were detected by CXR but missed on TUS, whereas 4 (30.8%) cases were detected by TUS but missed on CXR. Overall, TUS picked more cases of lung consolidation. There was no significant difference between the findings of the TUS and the CXR, P = 0.462 [Table 2].
|Figure 3: B-mode sonogram showing underlying right lung consolidation evidenced by the demonstration of hepatisation on TUS. TUS = Thoracic ultrasound|
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|Table 2: Comparison of lung ultrasound with chest radiographs in detecting various pathologies in the intensive care unit patients|
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PTX was detected in a total of seven patients, of which 5 (71.4%) were detected by TUS, whereas 6 (85.7%) were detected by CXR [Figure 4]. Four participants (57.1%) had PTX detected in them on both TUS and CXR examinations. Two (28.6%) cases of PTX were detected by CXR but missed on TUS, whereas 1 (14.3%) case was detected by TUS but missed on CXR. Overall, CXR picked more cases of PTX. There was no significant difference between the findings of the TUS and the CXR, P = 0.714 [Table 2].
|Figure 4: Chest radiograph of a 59-year-old male patient with severe breathlessness showing a right sided pneumothorax (star) and collapsed lung (arrow). There is a subtle mediastinal shift to the contralateral side|
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Alveolar edema was detected in a total of 7 patients, of which 6 (85.7%) were detected by TUS and 6 (85.7%) were detected by CXR. Five (71.4%) participants had alveolar edema detected on both TUS and CXR examinations. One (14.3%) case was detected by CXR but missed on TUS, whereas another solitary case (14.3%) was detected by TUS but missed on CXR. Overall, both CXR and TUS picked equal number of alveolar edema. There was no significant difference between the findings of the TUS and the CXR, P = 0.857 [Table 2].
Interstitial edema was detected in a total of 7 patients, of which 6 (85.7%) were detected by TUS and 6 (85.7%) were detected by CXR. Five (71.4%) participants had interstitial edema detected on both TUS and CXR examinations. One (14.3%) case was detected by CXR but missed on TUS, whereas another solitary case (14.3%) was detected by TUS but missed on CXR [Table 2].
Overall, both CXR and TUS picked equal number of interstitial edema [Figure 5]. There was no significant difference between the findings of the TUS and the CXR, P = 0.857.
|Figure 5: Sonographic image of interstitial edema in the right lung in a patient demonstrating multiple long, vertical, well-defined hyperechogenicities consistent with B-lines (arrow) which are seen to erase the A-lines|
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| Discussion|| |
Different clinical indications have necessitated the performance of TUS worldwide; some of them agree with the clinical indications in the participants in our study. The most common indication for radiologic investigations in the patients studied was a clinical suspicion for aspiration pneumonitis, followed by chest infection and dyspnea. Bourcier et al., Cortellaro et al., and Nazerian et al. in their studies used TUS in the detection of pneumonias, whereas Cibinel et al. investigated the diagnostic accuracy and reproducibility of pleural and lung US in discriminating cardiogenic causes of acute dyspnea in the participants they studied. Frasure et al. and Lichtenstein et al. studied patients with acute heart failure whose indication for TUS was dyspnea.
Five main lung pathologies were detected in the studied patients, namely, pleural effusion, lung consolidation, PTX, interstitial, and alveolar edema. These findings are similar to Inglis et al.'s study conducted 5 years ago in Australia, where they detected pleural effusion, lung consolidation, and AIS. Barillari and Fioretti also alluded to similar findings in their publication on the use of lung US as a new tool for the emergency physician.
TUS detected relatively more abnormalities than CXR in our patients and this was similar to findings in some previous studies reviewed.,, The agreement between CXR and TUS in the participants studied was comparable, though TUS was substantially more effective in detecting pleural effusion than supine CXR. In addition, it was also possible to suggest the nature of an effusion being exudative or transudative using the sonographic appearance on TUS, as was the case in many other previous studies reviewed.,,
TUS detected considerably more pleural effusions than CXR and we believe that this reflects the previously reported accuracy and superiority of the technique, which was reported by Lichtenstein et al., Xirouchaki et al., and Rocco et al.
Lung consolidation was also detected by TUS with much greater frequency than by CXR in the index study. This is shown in the absolute number of cases detected even though not statistically significant. This is similar to the findings by Inglis et al. who diagnosed lung consolidation in 102 (70%) of the 145 patients examined in the ICU with TUS while CXR only diagnosed it in 38 (26%) patients.
CXR, on the other hand, showed minimally higher sensitivity in the detection of PTX than TUS by detecting an extra case which TUS did not pick. This was similar to the finding by Xirouchaki et al., where CXR also detected relatively more PTX. It, however, differed from the finding by Bouhemad et al., where TUS diagnosed more pneumothoraces that were further confirmed by CT. Even though chest CT has been the gold standard for the diagnosis of pneumothoraces, in its absence, TUS and CXR are better alternatives that produce similar results in experienced hands.
Pleural effusions were detected on both CXR and TUS in this study. Several other workers,,,, evaluated the performance of TUS against other diagnostic techniques. Essentially, these studies repeatedly showed that TUS has superior sensitivity and diagnostic accuracy in detecting various pulmonary pathological changes, compared with CXR.
Lichtenstein et al. in their study compared TUS with CXR as well as auscultation and CT. Different clinicians examined all the participants using the variious modalities. Furthermore, the patients included in the study had already been diagnosed with, and were being treated for, acute respiratory distress syndrome. It was a well-designed study though it did not necessarily reflect how patients are assessed in an ICU. Similar to the findings in our study that pleural effusion and consolidation were well detected, Lichtenstein et al. showed that TUS performed extremely well when compared with CT in detecting effusion, consolidation, and AIS. Therefore, if one were to use TUS as a surrogate standard for each of these pathological states, it may be shown that the technique slightly outperforms CXR. A possible explanation may come from an understanding of the differences between the main pathological conditions examined in the study. Pleural effusion, lung consolidation, and AIS all involve excess extravascular fluid within the chest cavity, and a factor to consider is the distribution of that fluid.
Gazon et al.also performed an agreement analysis, comparing the detection of some pathological conditions (pleural effusion, lung consolidation, and AIS) using CXR and TUS. In their study of 50 patients, they performed independent interpretation of the TUS and CXR images. Only moderate agreement between the two imaging modalities was observed. However, in the index study, there was a significant agreement between the results of the two modalities. The disparity in findings in our study and that by Gazon et al. may have been due to the difference in sample size.
Due to the non- availability of CT, which is the gold standard for reference in lung pathologies, the index study and that of Gazon et a1., relied on the observed marginal total values of the contingency tables. These may serve as surrogates for prevalence. In the index study, TUS and CXR had relatively similar results in the detection of PTX, alveolar edema and interstitial edema but TUS showed a slight superiority over CXR in the diagnosis of pleural effusion and consolidation.
Similar to the study by Lichtenstein et al., inclusion of comparison with CT imaging would have allowed us to derive sensitivity and specificity data. That data would have allowed us to more objectively compare the performance of the two diagnostic modalities. However, as discussed earlier too, CT has its own disadvantages that preclude its more routine use, and it is instructive to know how consistently CXR and TUS agree with each other in the diagnostic assessment of a patient.
Given the already high sensitivity and specificity of TUS for many lungs, the current study showed that TUS slightly outperformed CXR in the detection of pathologies such as pleural effusion and lung consolidation. It, however, showed similarity in detecting interstitial and alveolar edema.
The major limitation in the study was the inability to compare the findings with CT imaging, which is regarded as the gold standard. We, however, hope to pursue further studies in that regard as the opportunity presents in future.
| Conclusion|| |
There was no statistically significant difference between thoracic USS findings and plain CXR findings of lung pathologies among ICU patients in this study. As such, TUS can be an attractive alternative to bedside CXR since it does not involve the use of ionizing radiation and can be easily repeated by the bedside of the patient if need be. It may also be considered an alternative imaging modality in lung pathologies like pneumonia and effusion especially in pediatric patients or pregnant women in whom exposure to ionizing radiation is not desirable.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]