Emergency. 2018; 6 (1): e55 OR I G I N A L RE S E A RC H Screening Performance of Ultrasonographic B-lines in De- tection of Lung Contusion following Blunt Trauma; a Diag- nostic Accuracy Study Saeed Abbasi1, Hossein Shaker1, Fariba Zareiee1, Davood Farsi1, Peyman Hafezimoghadam1, Mahdi Rezai1, Babak Mahshidfar1, Mani Mofidi1∗ 1. Emergency medicine management research center, Iran University of Medical Sciences, Rasoul Akram Hospital, Tehran, Iran. Received: March 2018; Accepted: August 2018; Published online: 2 September 2018 Abstract: Introduction: Chest ultrasonography is routinely used in evaluation of chest trauma for diagnosis of pulmonary injury. This study aimed to evaluate the accuracy of B-Lines for diagnosing lung contusion in patients with blunt trauma of the chest. Methods: Trauma patients who met the inclusion criteria were enrolled in the study and underwent ultrasonography by trained emergency medicine residents. Ultrasound results were recorded in terms of number of B-lines and the existence of peripheral parenchymal lesion (PPL). After ultrasound, the patient underwent chest x-ray and chest CT scan (as reference test) and screening performance of B-lines and PPL were evaluated. Results: 147 patients underwent chest ultrasound. The mean age of the patients was 40.74 ± 18.6 (78.9% male). B-lines>3 had 94.0% (95% CI: 83.45-98.75) sensitivity and 57.7% (95% CI: 47.3-67.7) speci- ficity, B-lines>6 had 90.0% (95% CI: 78.2-96.7) sensitivity and 93.81% (95% CI: 87.0-97.7) specificity, and PPL had 34.0% (95% CI: 21.2-48.8) sensitivity and 100% (95% CI: 96.3-100.0) specificity. Composite findings of B-lines>6 + PPL had 92.0% (95% CI: 80.8-97. 8) sensitivity and 93.8% (95% CI: 87.0-97.7) specificity in the diagnosis of lung contusion. Conclusion: PPL and B-Lines>6 had the highest accuracy in detecting lung contusion. B-Line>6 had high sensitivity and specificity and was easy to perform; thus, it seems that B-Line>6 could be considered as an alternative screening tool in detection of lung contusion. Keywords: Diagnosis; emergency service, hospital; diagnostic imaging; ultrasonography; thoracic injuries © Copyright (2018) Shahid Beheshti University of Medical Sciences Cite this article as: Abbasi S, Shaker H, Zareiee F, Farsi D, Hafezimoghadam P, Rezai M, Mahshidfar B, Mofidi M. Screening Performance of Ultrasonographic B-lines in Detection of Lung Contusion following Blunt Trauma; a Diagnostic Accuracy Study. Compr J Emerg Med. 2018; 6(1): e55. 1. Introduction Chest trauma and its complications are responsible for about 25% of deaths due to blunt trauma. Lung contusion is a com- mon complication of blunt chest trauma as it happens in 30 to 75% of the cases (1). Lung contusion is an independent risk factor of acute respiratory distress syndrome (ARDS), pneumonia, long-term respiratory failure and is associated with 10 to 25% mortality rate (2-4). Early and accurate di- agnosis and proper management of pulmonary contusion in emergency department have a significant influence on mor- bidity and mortality of these patients (3). In the beginning, ∗Corresponding Author: Mani Mofidi; Emergency medicine management research center, Rasoul Akram Hospital, Tehran, Iran. Email: mani- mofidi@yahoo.com Tel: 00989122263218 Chest Radiography (CXR) is traditionally done to diagnose probable lung contusion, but identification of opacity and its size needs time and generally takes 6 to 48 hours, so lung contusion usually can’t be diagnosed in the early phase via CXR (4, 5). Chest Computed Tomography (CT) scan is more sensitive than CXR and is considered as the gold standard technique for detecting lung contusion (6). Chest CT scan reveals the exact distribution and size of pulmonary injury (7). Lung ultrasound is increasingly used as standard trauma care in emergency departments (ED). It can detect alveolar consolidations, interstitial syndrome, pulmonary embolisms and pneumothorax (8). Prompt and accurate bedside detec- tion of thoracic disorders is its advantage compared to other diagnostic modalities (9). Ultrasound is a method with high precision for detecting interstitial edema, which is used in di- agnosis of lung contusion based on local interstitial edema This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com S. Abbasi et al. 2 due to trauma. Two studies conducted by Soldati and Sha- dia found that chest ultrasonography had a high sensitivity and precision in diagnosis of lung contusion in patients with blunt trauma (10, 11). B-lines are the important finding in chest sonography of lung contusion, but the number of B- lines that can be used to diagnose is not known. One study believed that less than 3 B-lines could be seen in an unin- jured lung (9) and the other one stated the lung ultrasound would be normal in presence of less than 6 B lines (10). A recent meta-analysis study has shown ultrasonography is a preferred screening modality in detection of pulmonary con- tusion compared to chest radiography, but the eligible stud- ies didn’t mention the number of B-lines that indicated pul- monary contusion (12). The aim of this study was to evaluate the accuracy of B-Line in diagnosing of lung contusion in pa- tients with blunt trauma to the chest. 2. Methods 2.1. Study design and setting This diagnostic accuracy study was conducted in the EDs of Rasool-e-Akram and Sina Hospitals, Tehran, Iran, from 1 Au- gust 2014 to 1 June 2014. The study was approved by the ethics committee of Tehran University of Medical Sciences with the code number of 142, 2013. Informed consent was obtained from patients or their relatives. 2.2. Participants The study participants included patients with blunt chest trauma brought to EDs of the mentioned hospitals. We con- secutively enrolled eligible patients in the study. Patients suf- fering from chest trauma or multiple traumas with chest in- volvement who were aged more than 18 years old and gave consent to participate in the study were included. In addi- tion, patients with hemodynamic instability, patients with diagnosis of pneumothorax, subcutaneous emphysema in- terfere with the ultrasound images, patients with a Body Mass Index (BMI) >30, pregnant patients, patients without co-operation for ultrasonography, and patients did not give consent to participate in the study or refrained from contin- uing to cooperate with investigators were excluded. 2.3. Imaging Bedside lung ultrasound was performed during the initial as- sessment with simultaneous resuscitation after the arrival of the patient with blunt chest trauma to the ED and then all patients were sent for CXR and CT scan immediately. We used ultrasound scanner (SonoAce X8, Samsung Medison, Seoul, Korea) equipped with a 7.5 to 10 MHz convex trans- ducer with 5-inch wide field. Ultrasound was performed by six emergency medicine residents who were familiar with ultrasound. First, a one-hour theoretical course was held Figure 1: A: Lung zones in chest ultrasound (with permission from Credit A, Tozer J, Vitto M, Joyce M, Taylor L. Clinical ultrasound, A Pocket Manual. Springer, 2018). B: lung contusion with more than 6 B-lines (arrow). for them. Thereafter, bedside tutoring was given by a fac- ulty member of emergency medicine, including at least 25 chest ultrasounds. Each patient was scanned by one of emer- gency residents. Ultrasonography was done according to the method described by Lichtenstein (13, 14). Each lung area was divided into 4 regions. The upper and lower parts of the anterior and postero-lateral regions of chest walls were scanned with the patient in supine position. We could only examine patients in supine position because of trauma con- dition. The multiple zones that were examined in ultrasonog- raphy are shown in figure 1-A. In the normal lung, ultrasound was carried out with the probe longitudinally placed in the spaces between the ribs; these indicators can be seen as lung sliding on a line with echogenic view that synchronizes with ventilation. This sign can be seen when visceral pleura moves on the pari- etal pleura, which rules out pneumothorax. Lung sliding is not always evident and pleural contact and lung movement may be demonstrated by M mode, which is called seashore sign, and is characterized by horizontal lines (“waves”) rep- resenting the static chest wall and a scattered region (“sand”) formed by the dynamic artifacts beyond the pleural line, for which pneumothorax was ruled out. The pleural line was de- fined as a horizontal hyperechoic line visible at 0.5 cm be- low the rib line. Horizontal lines arising from and parallel to the pleural line were called A lines; roughly vertical lines aris- ing from and perpendicular to the pleural line were called B lines. During the ultrasound, the probe was placed in the an- terior and lateral wall and the rear area around the posterior axillary line. Those who could not move were placed in the supine position. The results were interpreted as follows: 1. Normal ultrasound: lung sliding in addition to less than This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 3 Emergency. 2018; 6 (1): e55 Figure 2: Study flow chart. *: equal or less than 6 B-lines, ∈: more than 6 B-lines, £: true negative, λ: true positive. 3 B-lines on the scanned surface and the absence of any pe- ripheral consolidation. 2. Lung contusion in ultrasound: the presence of one of the following criteria alone or both; a) Alveolo-interstitial syndrome (AIS) by the presence of mul- tiple B-lines (more than 3) that originate from pleural line in a person with no clinical cardiopulmonary signs (figure 1-B). b) Peripheral parenchymal lesion (PPL), defined by the pres- ence of C-lines: hypoechoic subpleural focal images with or without pleural line gap (10). The chest CT scan and CXR im- ages were analyzed and reported by an attending radiologist. Obviously, physicians performing ultrasound were unaware of the CT and CXR findings. The radiologist was also unaware of the result of the ultrasound performed by the emergency residents. All examinations were performed in the same se- quence for all patients. 2.4. Reference standard After the ultrasound, CXR and chest CT scan (lung and medi- astinal aspect) without contrast agent were performed. Tho- racic CT scan was performed from the apex of the chest to the diaphragm in a 5-mm interval with the patients in the supine position using a 16 Multi Detector Computed Tomography (MDCT) scanner (Sensation 16, Siemens, Erlangen, Ger- many). CT scanning can detect lung contusion almost im- mediately following chest trauma and it is the standard crite- rion for diagnosis of lung contusion. The evidence of contu- sion in CT images are non-segmental areas of consolidation and ground-glass opacification that predominantly involve the lung and are directed deeply into the area of trauma, of- ten sparing 1 to 2 mm of subpleural lung parenchyma adja- cent to the injured chest wall (15). 2.5. Data gathering Patients’ demographic data as well as ultrasonography, CXR, and chest CT scan findings were collected by trained emer- gency medicine residents using a predesigned checklist. 2.6. Statistical Analysis The sample size was calculated based on Hosseini et al. (12) study considering α-error equal to 0.05, power equal to 80%, prevalence of lung contusion equal to 30%, and presumed This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com S. Abbasi et al. 4 Table 1: Baseline characteristics of studied patients and imaging findings regarding the presence or absence of lung contusion Variable Values Sex Male 116 (78.9) Female 31 (21.1) Age (year) Mean ± SD 40.7 ± 18.6 Mechanism of trauma Accident 100 (68.0) Falling 32 (21.8) Direct impact 15 (10.2) Chest X-ray Positive 13 (8.8) Negative 134 (91.2) Chest CT scan Positive 50 (34.1) Negative 97 (65.9) Ultrasonography (Number of B-lines) Positive (3 – 6) 36 (24.5) Positive (> 6) 51 (34.7) Negative (≤ 3) 60 (40.8) Ultrasonography (PPL) Positive 17 (11.6) Negative 130 (88.4) Data are reported as mean ± standard deviation (SD) or fre- quency (%). PPL: Peripheral parenchymal lesion. sensitivity of 92%. The estimated sample size obtained was 140 patients. All statistical analyses were performed using SPSS 16.0 (SPSS Inc. Chicago, IL, U.S.A.). Quantitative de- scriptive data was reported using mean ± standard devia- tion (SD), and qualitative data as frequency (%). Quantita- tive variables such as age and time intervals were assessed re- garding normality using One-Sample Kolmogorov-Smirnov Test, and t-test was used for analytical examination. To de- termine the diagnostic value of ultrasound in lung contusion, sensitivity, specificity, positive predictive value, negative pre- dictive value, positive and negative likelihood ratio, as well as area under the receiver operating characteristic (ROC) curve were calculated. The level of significance was considered less than 5%. 3. Results 3.1. Baseline Characteristics of participants One hundred sixty-one patients were evaluated, 14 patients were secondarily excluded, and finally 147 patients with blunt chest trauma were enrolled (figure 2). The mean age of the patients was 40.74 ± 18.6 (18 - 90) years (78.9% male). Baseline characteristics of patients as well as thoracic imag- ing findings are shown in Table 1. 96 (65.3%) cases had 6 or less B-lines and 51 (34.7%) had more than 6 B-lines. PPL in favor of lung contusion was observed in 17 (11.6%) patients, among them 16 cases had more than 6 B-lines and only one case had 3 to 6 B-lines. Chest CT scans of 50 (34%) patients showed definite lung contusion. In eighteen patients, one ninth to three ninths of lung were injured. Half of them (25 patients) had four ninths to six ninths involvement and 7 pa- tients were severely injured (seven ninths to nine ninths in- volvement). 3.2. Screening performance characteristics of tests Out of the 51 patients who had more than 6 B-lines on ul- trasound, 45 patients had definite contusion and six of them did not show any evidence of lung contusion on CT scan. Ta- ble 2 shows the sensitivity, specificity, positive and negative predictive values and likelihood ratios of sonographic B-lines and PPL in detection of lung contusion. 4. Discussion The current study showed acceptable sensitivity and speci- ficity of point of care ultrasound in chest trauma for diagno- sis of lung contusion. PPL and more than 6 B-lines had the highest sensitivity and specificity (92.0 and 93.81) in the di- agnosis of lung contusion. In addition, when the number of B-lines was >6, it had a good sensitivity and specificity (90.0 and 93.81) in diagnosis of lung contusion. PPL was seen on ultrasound in 17 patients in our study with the sensitivity of 34% (21.21-48.77), and specificity of 100%, which indicated that this is a specific finding in diagnosis of lung contusion. In a study conducted by Soldati et al. (10) out of 37 patients diagnosed with lung contusion, 7 had PPL with a sensitivity of 18.9% and specificity of 100%. The study by Helmy et al. (11) showed that sensitivity and specificity of PPL in diag- nosis of lung contusion were 92.5% and 100%, respectively. The Soldati study was more consistent with our results and the notable fact is that the specificity of all three studies was reported to be 100%. In our study, it was found that when more than 3 B-lines was considered as lung contusion, the sensitivity and negative predictive value of the test increased to 94%, but in parallel, specificity and positive predictive value decreased. Therefore, consideration of more than 3 B- lines leads to over-diagnosis of lung contusion. When more than 6 B-lines in ultrasound were considered as lung contu- sion, specificity and positive predictive value increased sig- nificantly; this reduced the probability of false positives. In this study, only 6 false positives were reported, which were di- agnosed in chest CT scans as one case of pulmonary fibrosis and one case of pneumonia. Patients with diffuse parenchy- mal lung disease (DPLD) had positive B-lines on ultrasound as defined in a study conducted by Reibig et al (7). Four other cases diagnosed as B-line by mistake could be Z and E lines. Z lines are vertical lines arising from the pleural line but not This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 5 Emergency. 2018; 6 (1): e55 Table 2: Diagnostic accuracy of sonographic B-lines and peripheral parenchymal lesion (PPL) in detection of lung contusion considering non-contrast chest CT scan as gold standard Variable Specificity Sensitivity PPV NPV LR+ LR− B-line>3 TP=47 TN=56 57.73 94.0 53.41 94.92 2.22 0.10 FP=41 (47.28-67.7) (83.45-98.75) (42.46-64.12) (85.85-98.94) (1.74-2.84) (0.03-0.32) FN=3 B-line>6 TP=45 TN=91 93.81 90.0 88.24 94.79 14.55 0.11 FP=6 (87.02-97.70) (78.19-96.67) (76.13-95.56) (88.26-98.29) (6.67-31.76) (0.05-0.25) FN=5 PLL TP=17 TN=97 100.0 34.0 100.0 74.62 Infinite 0.66 FP=0 (96.27-100) (21.21-48.77) (80.49-100) (66.24-81.84) (0.54-0.81) FN=33 PPL + B-line>6 TP=46 TN=91 93.81 92 88.46 95.79 14.87 0.09 FP=6 (87.02-97.7) (80.77-97.78) (76.56-95.65) (89.57-98.84) (6.82-34.42) (0.03-0.22) FN=4 PPL + B-line>3 TP=46 TN=56 57.73 92 52.87 93.33 2.18 0.14 FP=41 (47.28-67.7) (80.77-97.78) (41.87-63.67) (83.8-98.15) (1.7-2.79) (0.05-0.36) FN=4 CXR TP=13 TN=97 100.0 26.0 100.0 72.39 Infinite 0.74 FP=0 (96.27-100) (14.63-40.34) (75.29-100) (64-79.76) (0.63-0.87) FN=37 Data are presented with 95% confidence interval. TN: true negative; TP: true positive; FP: false positive; FN: false negative; PPV: positive predictive value; NPV: negative predictive value; LR: likelihood ratio. reaching the distal edge of the screen. E lines are vertical lines that reach the distal edge of the screen but do not arise from the pleural line (10). The above-mentioned studies (10, 11) in traumatic patients reported the sensitivity and specificity of B-line>6 in diagnosis of lung contusion as “94.6% and 96%” and “97.5% and 90%”, respectively, which were consistent with our results. In a study by M. Rocco et al., patients with chest trauma who were under mechanical ventilation in the ICU were assessed for pleural effusion and lung contusion by ultrasound at the time of admission to the ICU. After 48 hours, the authors reported the sensitivity and specificity of ultrasonography in diagnosis of pulmonary contusion to be “86% and 97%” against “89% and 89%” on arrival (8). In our study, the diagnostic value of PLL with the B-line>6 was the highest in diagnosis of lung contusion, with only 2% higher sensitivity when compared to B-line>6 alone. Given that ed- ucation and diagnosis of B-line>6 is far easier than PPL, it is advised that B-line>6 alone be used as a reliable method for diagnosis of lung contusion. Our study showed that chest x- ray has low sensitivity and high specificity (26 and 100%) in diagnosis of pulmonary contusion. In a study by McGoni- gal et al. entitled “Supporting role of lung CT scan in man- agement of patients with blunt trauma”, sensitivity of chest x-ray for lung contusion was reported to be 40% (16). In ad- dition, Hemly et al. showed that chest x-ray has low sensitiv- ity and high specificity, 40% and 90%, respectively (11). Sol- dati et al. had also reported 27% sensitivity and 100% speci- ficity for chest x-ray, which are consistent with our results (10). Chest radiography is frequently used for evaluation of traumatic patients. Although chest radiography is valuable, based on existing studies, its sensitivity in diagnosis of lung contusion is low and needs several hours to diagnose the le- sion (12, 17). CT scan is the gold standard method in chest trauma, but generally needs the patient to be transferred; so, performing it is not possible in an unstable patient. In ad- dition, the cost and radiation of CT scan is high (18). High sensitivity and specificity is considered the advantage of Ul- trasound. It seems that sonographic B-lines > 6 could be con- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com S. Abbasi et al. 6 sidered as a reliable alternative tool in diagnosis of lung con- tusion. 5. Limitation One of the limitations of the current study was that we ex- cluded the patients with the BMI more than 30, thus the results of study could not be generalized to these patients. Sensitivity and specificity of Ultrasound could be affected by obesity and fat tissue. Also, ultrasound was performed by six emergency residents. They attended a similar educa- tion course (lecturing and hands on) but we did not compare them with each other and it could be basically a limitation. 6. Conclusion PPL and B-Lines>6 had the highest accuracy in detecting lung contusion. B-Line>6 had high sensitivity and specificity and was easy to perform; thus, it seems that B-Line> could be considered as an alternative screening tool in detection of lung contusion. 7. Appendix 7.1. Acknowledgements This article was part of Dr. Fariba Zareiee’s thesis, who was an emergency medicine resident at the time of the study. 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