Scholarly article on topic 'Role of chest ultrasonography in the diagnosis of lung contusion'

Role of chest ultrasonography in the diagnosis of lung contusion Academic research paper on "Clinical medicine"

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{"LC lung contusion" / "CXR chest X-ray" / "CT computed tomography" / "AIS alveolointerstitial syndrome" / "PPL peripheral parenchymal lesion" / "ARDS acute respiratory distress syndrome"}

Abstract of research paper on Clinical medicine, author of scientific article — Shadia Helmy, Bassem Beshay, Mohamed Abdel Hady, Abdelmenam Mansour

Abstract Objective In this study we assessed the diagnostic performance of chest ultrasonography in lung contusion (LC). The study investigated the possible clinical applicability of chest ultrasonography for the diagnosis of LC in comparison to chest X-ray (CXR) and chest computed tomography (CT) (as a gold standard). Design: a screening cross-sectional study. Setting: Critical Care Department, Emergency Department, Alexandria main university hospital. Patients 50 patients of both genders admitted to the Emergency Department and the Critical Care Department presented with isolated blunt chest trauma or polytrauma with chest involvement. Methods 50 patients admitted for blunt chest trauma were investigated using ultrasonography to detect LC. After the ultrasound study, all patients were submitted to chest X-ray and CT. The sonographic patterns indicative of LC included the following: (1) the alveolointerstitial syndrome (AIS) [defined by increase in B-line artifacts]; and (2) peripheral parenchymal lesion (PPL) [defined by the presence of C-lines: hypoechoic subpleural focal images with or without pleural line gap]. Results The diagnosis of LC was established by CT scan in 40 patients. If AIS is considered, sensitivity of lung ultrasonography in detection of AIS was 97.50%, specificity was 90.0%, PPV 97.50%, NPV 90.0% and accuracy was 96.0%. If PPL is alternatively considered, sensitivity of lung ultrasonography in detection of PPL was 92.50%, specificity was 100.0%, PPV was 100.0%, NPV was 76.92% and accuracy was 94.0%. As a whole sensitivity of lung ultrasonography in detection of lung contusion was 97.50%, specificity was 90.0%, PPV was 97.50%, NPV was 90.0% and accuracy was 96.0%. Chest X-ray had sensitivity of 40.0%, specificity was 90.0%, with PPV 94.12%, NPV 27.27% and accuracy of 50.0%. Conclusion Lung ultrasound is a bedside, reliable, dynamic, rapid, and non-invasive technique and may be of significant value in the diagnosis of lung contusion in blunt chest trauma patients.

Academic research paper on topic "Role of chest ultrasonography in the diagnosis of lung contusion"

Egyptian Journal of Chest Diseases and Tuberculosis (2015) xxx, xxx-xxx

The Egyptian Society of Chest Diseases and Tuberculosis Egyptian Journal of Chest Diseases and Tuberculosis

www.elsevier.com/locate/ejcdt www.sciencedirect.com

ORIGINAL ARTICLE

Role of chest ultrasonography in the diagnosis of lung contusion

Shadia Helmy a, Bassem Beshay b, Mohamed Abdel Hady b, Abdelmenam Mansour b'*

a Radiodiagnosis Department, Faculty of Medicine, Alexandria University, Egypt b Critical Care Medicine Department, Faculty of Medicine, Alexandria University, Egypt

Received 12 November 2014; accepted 25 November 2014

HOSTED BY

KEYWORDS

LC lung contusion; CXR chest X-ray; CT computed tomography; AIS alveolointerstitial syndrome;

PPL peripheral parenchymal lesion;

ARDS acute respiratory distress syndrome

Abstract Objective: In this study we assessed the diagnostic performance of chest ultrasonogra-phy in lung contusion (LC). The study investigated the possible clinical applicability of chest ultra-sonography for the diagnosis of LC in comparison to chest X-ray (CXR) and chest computed tomography (CT) (as a gold standard). Design: a screening cross-sectional study. Setting: Critical Care Department, Emergency Department, Alexandria main university hospital.

Patients: 50 patients of both genders admitted to the Emergency Department and the Critical Care Department presented with isolated blunt chest trauma or polytrauma with chest involvement.

Methods: 50 patients admitted for blunt chest trauma were investigated using ultrasonography to detect LC. After the ultrasound study, all patients were submitted to chest X-ray and CT. The sonographic patterns indicative of LC included the following: (1) the alveolointerstitial syndrome (AIS) [defined by increase in B-line artifacts]; and (2) peripheral parenchymal lesion (PPL) [defined by the presence of C-lines: hypoechoic subpleural focal images with or without pleural line gap].

Results: The diagnosis of LC was established by CT scan in 40 patients. If AIS is considered, sensitivity of lung ultrasonography in detection of AIS was 97.50%, specificity was 90.0%, PPV 97.50%, NPV 90.0% and accuracy was 96.0%. If PPL is alternatively considered, sensitivity of lung ultrasonography in detection of PPL was 92.50%, specificity was 100.0%, PPV was 100.0%, NPV was 76.92% and accuracy was 94.0%. As a whole sensitivity of lung ultrasonography in detection of lung contusion was 97.50%, specificity was 90.0%, PPV was 97.50%, NPV was 90.0% and accuracy was 96.0%. Chest X-ray had sensitivity of 40.0%, specificity was 90.0%, with PPV 94.12%, NPV 27.27% and accuracy of 50.0%.

* Corresponding author.

E-mail address: mon3emmansour@gmail.com (A. Mansour). Peer review under responsibility of The Egyptian Society of Chest Diseases and Tuberculosis.

http://dx.doi.org/10.1016/j.ejcdt.2014.n.021

0422-7638 © 2014 The Egyptian Society of Chest Diseases and Tuberculosis. Production and hosting by Elsevier B.V. All rights reserved.

Conclusion: Lung ultrasound is a bedside, reliable, dynamic, rapid, and non-invasive technique and may be of significant value in the diagnosis of lung contusion in blunt chest trauma patients. © 2014 The Egyptian Society of Chest Diseases and Tuberculosis. Production and hosting by Elsevier

B.V. All rights reserved.

Introduction

Pulmonary contusions are typically the result of blunt trauma to the chest wall. Motor vehicle and motorcycle crashes are the most common causes of this injury pattern, but it can also be seen with blast trauma. Approximately 25-35% of blunt chest traumas involve injury to the lung itself. The lungs are the second most common organ injured in blast injuries [1].

After the initial blunt or blast thoracic trauma, the edem-atous phase is notable for worsening interstitial edema and infiltrates, occurring within the first 1-2 h after injury. The air spaces become inundated with blood, inflammatory markers, and tissue debris, as there is an increase in alveolar and capillary permeability along with a reduction in surfactant production. Within 24-48 h after the onset of injury, there is alveolar collapse and further consolidation due to the extravasation of blood into the alveoli. Lung consolidation can lead to increased vascular pressures causing pulmonary hypertension and retention of blood. The resulting ventilation/perfusion mismatch, increased pulmonary shunting, decreased gas exchange, and decreased compliance can predispose patients to clinically apparent symptoms such as hypoxia, hypercarbia, tachypnea, hemoptysis, and wheezing. It is also these mechanisms of consolidation, shunting, and mismatch that predispose patients with pulmonary contusions to pneumonia and acute respiratory distress syndrome (ARDS) [2].

Initial signs of pulmonary contusion on chest X-ray are focal or diffuse lung opacities, which classically appear within the first 6 h after injury, but may take 24-48 h to demonstrate maximum consolidation. During that time, the acute phase inflammatory response is driving the underlying cellular and sub-cellular injury with activation of the coagulation and complement cascades and release of multiple inflammatory mediators such as cytokines, chemokines, and free radicals. Much of the acute phase mechanisms have yet to be fully elucidated, but researchers believe that inflammation is responsible for much of the morbidity and mortality associated with pulmonary contusions. These markers are likely present with any lung parenchymal injury and predispose patients to delayed complications such as pneumonia, ARDS, and long-term disability. Despite these effects to the lung parenchyma from pulmonary contusions, most resolve within 7-14 days with overall minimal long-term effects [3,4].

Role of chest ultrasonography in diagnosis of lung contusion

• Ultrasonography is now becoming an accurate method for detecting interstitial edema. Based on this statement, it is assumed that chest ultrasound may be able to find pulmonary contusions at an earlier stage than CXR, therefore reaching a higher sensitivity in the ED [5,6]. The normal

sonographic appearance of the lung [6]: a longitudinal scan of an intercostal space, with the ribs as topographic reference:

(1) The gliding sign is present when the visceral pleura slides are on the parietal pleura, excluding pneumothorax.

(2) Horizontal artifacts—the A-lines appear cyclically at an interval that reproduces the distance of the transducer to the pleural line. The gliding sign is not always evident, and the pleural contact and lung movement may be shown in the M mode, this image is called the seashore sign, characterized by horizontal lines ("waves") representing the static chest wall and by a scattered region ("sand"), formed by the dynamic artifacts beyond the pleural line, which would be absent in the case of pneumothorax.

(3) Eventually, a type of vertical artifact-B-lines-(formerly called comet tails) can be found in normal examination.

• The recognition of a few other artifacts must be mastered when looking for B-lines:

- Z-line artifacts are lines that arise from the pleural line and fade away vertically, do not reach the edge of the screen.

- E-lines are generated by subcutaneous emphysema; they are vertical laser-like lines that reach the edge of the screen but do not arise from the pleural line.

• An examination was considered normal in the presence of the gliding sign, the presence of fewer than three B-line artifacts in the entire scanned surface, and the absence of peripheral consolidations [6,7].

LC is diagnosed in the presence of the following: Alveolo-interstitial syndrome (AIS), ultrasonographically defined as

Figure 1 Left: normal image, with one isolated B-line (arrows). Right: ultrasonographic pattern of AIS.

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J -î^i'.

, «f Si»

Figure 2 Sonographic pattern of parenchymal lung consolidation.

the presence of multiple B-lines (Fig. 1) arising from the pleural line, in a patient with no clinical suspicion of cardiogenic pulmonary edema [5].

Or by the presence of a peripheral parenchymal lesion (PPL) (Fig. 2), defined as the observation of C-lines, confluent consolidations ("hepatization"), or the presence of parenchymal disruption with localized pleural effusion [5].

The aim of this work was to evaluate the role of chest ultra-sonography in diagnosis of lung contusion in comparison to chest X-ray and the gold standard CT chest. It was expressed in sensitivity, specificity, positive predictive value, negative predictive value and accuracy.

Patients and methods

This study was carried out in Alexandria main university hospital on 50 patients of both genders according to sample size study which was calculated using a power of 80% to detect sensitivity of ultrasound in diagnosing lung contusion relative to CT as a standard diagnostic method. Patients were admitted to the Emergency Department and the Department of Critical Care presenting with isolated blunt chest trauma or polytrauma with chest involvement. Patients were excluded for reasons such as: pregnancy, morbid obesity, pneumothorax, multiple fractured ribs, surgical emphysema, open chest wounds, and aspiration [8]. Formal written consent was taken from first degree relative of every patient. The research was approved from the Ethics Committee of Alexandria faculty of medicine.

All patients included in the study were subjected on admission to the following routine examination and investigations.

(1) Chest sonography was performed in all patients on the first day of admission. Using ultrasound unit Digital ultrasonic imaging model DP-3300, Shenzhen mindray biomedcal electronics .co. ltd., with macroconvex probe 5 MHZ. The chest was scanned in search of signs of LC: • Patients were investigated in a semirecumbent position and if patients were intubated, the study had been accomplished in supine position. Scans were longitudinal. As in Fig. 3: scanning was divided

into three stages. Stage 1 defines the investigation of the anterior chest wall (zone 1). Stage 2 adds the lateral wall (zone 2). Stage 3 adds the posterolateral chest wall, moving the patient only minimally (zone 3). Each wall is divided into upper and lower halves, resulting in six areas of investigation [7]. • LC was diagnosed in the presence of the following:

(A) Alveolointerstitial syndrome (AIS), ultrasono-graphically defined as the presence of multiple B-lines arising from the pleural line, in a patient with no clinical suspicion of cardiogenic pulmonary edema; or

(B) By the presence of a peripheral parenchymal lesion (PPL), defined as the observation of C-lines, confluent consolidations ("hepatization"), or the presence of parenchymal disruption with localized pleural effusion [5,6].

(2) After the ultrasound examination bedside had been completed, X-ray anterio-posterior of the chest was obtained.

(3) Chest computed tomography was done to evaluate the extent of lung consolidation to establish the diagnosis of LC by the presence of consolidation or ground-glass areas.

After radiological assessment of the studied cases, CT chest was used as a gold standard [9] to evaluate the sensitivity, specificity and accuracy of both plain X-ray and bedside chest ultrasonography.

Statistical analysis

Data were fed to the computer and analyzed using the IBM SPSS software package version 20.0. Qualitative data were described using number and percent. Quantitative data were described using range (minimum and maximum), mean and standard deviation and median. Agreement of the different predictives with the outcome was used and was expressed in sensitivity, specificity, positive predictive value, negative predictive value and accuracy. Receiver operating characteristic curve (ROC) was plotted to analyze a recommended cutoff,

Figure 3 Method of lung ultrasonography examination.

the area under the ROC curve denotes the diagnostic performance of the test. Area more than 50% gives acceptable performance and area about 100% is the best performance for the test. Significance of the obtained results was judged at 5% level.

Results

This study included 50 patients admitted to the Emergency department and the Department of Critical Care presented with isolated blunt chest trauma or polytrauma with chest involvement.

Table 1 shows the distribution of the studied cases according to the demographic data. This study included 35 male and 15 female patients, their age ranged from 18.0 to 67.0 years.

Table 2 shows descriptive data of the patients, as regards the clinical presentation of 70.0% of the patients presented by polytrauma with blunt chest trauma and 30.0% of them had isolated blunt chest trauma, vital signs of the patients showed that mean arterial blood pressure ranged from 50.0 to 115.0, heart rate ranged from 85.0 to 140.0 beats/min, respiratory rate ranged from 18.0 to 38.0/min and temperature ranged from 37.0 to 38.50 0C, by chest auscultation 56.0% of the patients had decreased air entry and 36.0% of them had

Table 1 Distribution of the studied cases according to demographic data.

Min-Max 18.0-67.0

Mean ± SD 39.74 ± 12.78

Median 39.0

Male 35 70.0

Female 15 30.0

Table 2 Descriptive data of the studied patients.

No. (%)

Clinical presentation Isolated blunt chest trauma 15 30.0

Polytrauma with 35 70.0

blunt chest trauma

Min-Max Mean ± SD Median

Mean arterial blood pressure 50.0-115.0 81.0 ± 14.25 80.0

Heart rate 85.0-140.0 107.52 ± 14.39 105.0

RR 18.0-38.0 26.36 ± 5.42 26.0

Temperature 37.0-38.50 37.62 ± 0.38 37.70

No. (%)

Decreased air entry 28 56.0

Crepitations or wheezes 18 36.0

Min-Max Mean ± SD Median

HB 6.0-15.0 10.29 ± 2.28 10.0

WBC 8.0-18.0 12.45 ± 2.55 12.0

Platelets 13.0-354.0 206.32 ± 80.86 201.50

Creatinine 0.80-4.60 1.42 ± 0.69 1.20

Urea 20.0-170.0 59.14 ± 23.70 55.50

RBS 112.0-350.0 189.18 ± 63.82 180.0

Hypoxic index

<300 43 86.0

P300 7 14.0

Ischemia 7 14.0

Arrhythmia 9 18.0

AIS 40 80.0

PPL 37 74.0

X-ray positive 17 34.0

CT positive 40 80.0

Negative Positive Sensitivity Specificity PPV NPV Accuracy

AIS (alveolointerstitial Negative 9 1 97.50 90.0 97.50 90. 96.0

syndrome) in ultrasound Positive 1 39

PPL (peripheral parenchymal Negative 10 3 92.50 100.0 100.0 76.92 94.0

lesion) in ultrasound Positive 0 37

Table 3 Sensitivity, specificity and accuracy of ultrasound in diagnosis of lung contusion as regards the CT.

CT Negative Positive Sensitivity Specificity PPV NPV Accuracy

Ultra-sound Negative Positive 9 1 1 39 97.5 90.0 97.5 90.0 96.0

Figure 4 ROC curve for ultrasound with CT.

crepitation or wheezes, as regards laboratory investigations hemoglobin ranged from 6.0 to 15.0 g/dL, WBC ranged from 8.0 to 18.0 x 103/mcL, platelets ranged from 13.0 to 354.0 x 103/mcL, creatinine ranged from 0.80 to 4.60mg/dL, urea ranged from 20.0 to 170.0 mg/dL and RBS ranged from 112.0 to 350.0 mg/dL, regarding hypoxic index 86.0% of the patients were hypoxic with hypoxic index <300 and 14.0% of them were not hypoxic. ECG findings showed that ischemic changes were found in 14.0% and 18.0% of the patients had arrhythmia in the ECG, by ultrasound signs of alveolointersti-tial syndrome (AIS) were detected in 80.0% of the patients and signs of peripheral parenchymal lesion (PPL) were found in 74.0% of them, 66.0% of the patients had normal chest X-ray and 34.0% of them had X-ray opacity, lung contusion was diagnosed in 40 patients (80.0%) by CT chest, sensitivity of lung ultrasonography in detection of AIS as regards the CT chest was 97.50%, specificity was 90.0%, PPV was 97.50%, NPV was 90.0% and accuracy was 96.0%. sensitivity of lung ultrasonography in detection of PPL was 92.50%, specificity was 100.0%, PPV was 100.0%, NPV was 76.92% and accuracy was 94.0%.

Table 3 shows the sensitivity, specificity and accuracy of lung ultrasonography in detection of lung contusion as regards CT, sensitivity of lung ultrasonography was 97.50%, specificity

Figure 5 ROC curve for X-ray with CT.

Table 5 Sensitivity and specificity for ultrasound and X-ray in diagnosis of lung contusion.

Sensitivity Specificity

Ultrasound 97.50 90.0

X-ray 40.0 90.0

was 90.0%, PPV was 97.50%, NPV was 90.0% and accuracy was 96.0% (see Fig. 4).

Table 4 shows the sensitivity, specificity and accuracy for chest X-ray as regards the CT chest in diagnosis of lung contusion, sensitivity of X-ray chest in detection of lung contusion was 40.0%, specificity was 90.0%, PPV was 94.12%, NPV was 27.27% and accuracy was 50.0% (see Fig. 5).

Table 5 shows the sensitivity and specificity for chest X-ray and lung ultrasonography in detecting lung contusion, sensitivity of lung ultrasonography in detection of lung contusion was 97.50% and specificity was 90.0%, compared to chest X-ray which showed 40.0% sensitivity and 90/0% specificity (see Fig. 6).

Table 4 Sensitivity, specificity and accuracy for X-ray in diagnosis of lung contusion as regards the CT.

CT Sensitivity Specificity PPV NPV Accuracy

Negative Positive

X-ray Negative 9 24 40.0 90.0 94.12 27.27 50.0

Positive 1 16

Figure 6 ROC curve for X-ray and ultrasound with CT. Discussion

In our study chest computed tomography was used as a gold standard for diagnosing lung contusion, to assess the diagnostic value of chest radiography and lung ultrasonogra-phy. Regarding the role of ultrasonography in detection of AIS, in our study we assessed the diagnostic performance of lung ultrasonography in detection of AIS in comparison to CT chest, sensitivity was 97.50%, specificity was 90.0%, PPV was 97.50%, NPV was 90.0% and accuracy was 96.0%.

In a study of chest ultrasonography in lung contusion performed by Soldati [10], the sonographic alveolointerstitial pattern was observed in 35 CT-positive results and in 2 false-positive results, sensitivity was 94.6% and specificity was 96.0%. In a study performed by Daniel A [11] studying relevance of lung ultrasound in the diagnosis of acute respiratory failure, ultrasonography had 95% specificity and 97% sensitivity in diagnosis of AIS.

In another study by Lichtenstein [12] which was about the comet-tail artifact an ultrasound sign of alveolar-interstitial syndrome, where ultrasonography had a sensitivity of 92.5% and a specificity of 65.1% for diagnosing radiologic alveolar-interstitial syndrome. In a study of bedside lung ultrasound in the assessment of alveolar-interstitial syndrome performed by Volpicelli [13], ultrasonography showed a sensitivity of 85.7% and a specificity of 97.7% in recognition of radiologic AIS.

Ultrasound showed in our study high sensitivity and specificity for detection of AIS compared to the gold standard CT chest. Also the same in the above mentioned studies showed high sensitivity and specificity, so we can assume that ultrasound chest might be an accurate investigation tool for the diagnosis of AIS and its different causes.

Regarding the role of ultrasonography in detection of PPL, in our study we assessed the diagnostic performance of lung ultrasonography in detection of PPL in comparison to CT chest, sensitivity was 92.50%, specificity was 100.0%, PPV was 100.0%, NPV was 76.92% and accuracy was 94.0%.

In a study of chest ultrasonography in lung contusion performed by Soldati [10], the PPL pattern was observed in seven patients, all of them also positive for the alveolointerstitial

pattern. No false-positive results were found with this lesion pattern (sensitivity, 18.9%;specificity, 100%).

In a study by Lichtenstein [14] studying the dynamic air bronchogram, a lung ultrasound sign of alveolar consolidation ruling out atelectasis, ultrasonography had a specificity of 94% and a positive predictive value of 97%, the sensitivity was 61%, and the negative predictive value was 43%. In another study performed by Daniel A [11] which was about relevance of rung ultrasound in the diagnosis of acute respiratory failure, ultrasonography had 89% sensitivity and 94% specificity for PPL.

If we consider the ultrasound finding of consolidation compared to the gold standard CT, a specificity of 100% was achieved in the selected trauma population, also in the above mentioned studies it achieved a high specificity. Of course, these data cannot be extended to a clinical population, since there are other diseases that show the same consolidative pattern, such as pneumonia and correlation with the clinical data must be done.

Regarding the role of lung ultrasonography in diagnosis of lung contusion, in our study we assessed the diagnostic performance of lung ultrasonography in lung contusion in comparison to CT chest, sensitivity was 97.50%, specificity was 90.0%, PPV was 97.50%, NPV was 90.0% and accuracy was 96.0%.

In a study performed by Soldati [10] about chest ultraso-nography in lung contusion, sonography showed alterations suggesting a diagnosis of LC in 37 patients, with 2 false-positive results (sensitivity, 94.6%; specificity, 96.1%; positive predictive value, 94.6%; negative predictive value, 96.1%;and accuracy, 95.4%). In another study performed by Rocco [15] for studying diagnostic accuracy of bedside ultrasonography in the ICU: feasibility of detecting pulmonary effusion and lung contusion in patients on respiratory support after severe blunt thoracic trauma, sensitivity of ultrasound was 86.0% for LC while specificity 97.0%.

Regarding the role of chest X-ray in diagnosis of lung contusion, in our study the sensitivity of chest X-ray in detecting lung contusion was 40.0% in comparison to chest computed tomography. The specificity was 90.0%, with PPV 94.12%, NPV 27.27% and accuracy of 50.0%.

In a study of chest ultrasonography in lung contusion performed by Soldati [10], standard CXR documented signs of LC in 10 patients (sensitivity, 27%). No false-positive results were found on CXR. In another study performed by McGON-IGAL [16] which was about supplemental emergent chest computed tomography in the management of blunt torso trauma, chest X-ray was less sensitive than chest computed tomography in the detection of pulmonary contusion (40% vs. 100%).

In a study performed by Elmal [17] about lung parenchymal injury and its frequency in blunt thoracic trauma, the diagnostic values of chest radiography and thoracic CT, such as the sensitivity, specificity, positive predictive value, and negative predictive value of chest radiography in determining parenchy-mal injury were 69%, 76%, 84%, and 57%, respectively.

Chest X-ray is a common method used for diagnosis in trauma patients; consolidated areas appear with white opacity on X-ray film. X-ray appearance of pulmonary contusion is similar to that of aspiration, and the presence of hemothorax or pneumothorax may obscure the contusion on a radiograph. Although chest radiography is an important part of the diagnosis, it is often not sensitive enough to detect the condition early after the injury. When a pulmonary contusion is appar-

ent in X-ray, it suggests that the trauma to the chest was severe and that a CT scan might reveal other injuries that were missed by X-ray. The conventional X-ray can detect contusion more when a confluent consolidation is established and this explains the low sensitivity of X-ray [18].

Ultrasonography is an accurate method for detecting interstitial edema. Based on this, we can assume that chest ultrasound may be able to find pulmonary contusions at an earlier stage than CXR, therefore reaching higher sensitivity [5]. Our study suggests this assumption is true, by finding an overall sensitivity of 97.50% for ultrasound and 40.0% for initial CXR. Of course, the interstitial sonographic pattern achieved a very high sensitivity in our study, with good specificity. There are several other diseases that present interstitial syndromes (ARDS, cardiogenic pulmonary edema) and, naturally one difference to be noticed is the focal pattern of the B-lines in LC found in our study. This localized pattern differs from the diffuse bilateral B-line pattern found in cardiogenic pulmonary edema, thus increasing the specificity of ultrasound in the diagnosis of pulmonary traumatic contusions.

One must keep in mind that ultrasound imaging is based on tissue density and resonance; therefore, diseases that present with similar anatomic densities will produce similar images. Aspiration or atelectasis will produce images generated by the structural alteration they inflict, appearing as B-line artifacts for interstitial syndromes and consolidations or C-lines for larger densities. In spite of this, we believe that a cautious correlation with the clinical picture must always be made [19].

Conclusion

• Lung ultrasound is a bedside, reliable, dynamic, rapid, non-invasive technique and may be of a significant value in the diagnosis of lung contusion in blunt chest trauma patients.

• Although CT is the gold standard for evaluation of lung parenchyma, the access to this examination is not always possible as in the case of hemodynamic instability or there are other priorities that would be overrun by the need of transportation to the CT laboratory, in these circumstances ultrasound may be of a great value for diagnosis of lung contusion.

• For obese patients visualization of lung parenchyma might be difficult.

• Thoracic ultrasound is an operator dependent technology. Focused and supervised training is needed to ensure that the operator correctly interprets the sonographic findings.

• Because the same probe serves multiple patients, it can be the vector of disseminate resistant pathogens in the intensive care unit and imposes special decontamination procedures.

• These limitations should be balanced against the benefits of lung ultrasonography, which has a direct diagnostic and therapeutic impact for critically ill patients [20,21].

Conflict of interest

There is no conflict of interest. References

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