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Advanced trauma life support radiographic trauma series: Part 2--the chest radiograph.

The chest radiograph is used as a screening test to exclude significant thoracic injuries in cases of major trauma. A systematic approach to reviewing chest radiographs is necessary for accurate interpretation. Radiographic findings should be considered together with clinical assessment.

KEYWORDS Trauma series / Chest radiograph / Thoracic trauma / Advanced Trauma Life Support

In this series of papers we review the radiographs performed as part of the Advanced Trauma Life Support (ATLS) trauma series; this paper deals with chest radiographs.

Thoracic trauma is a significant cause of morbidity and mortality (Gavelli et al 2002, Peters et al 2010). A portable chest radiograph may be carried out in the resuscitation room and is the first-line radiological investigation used to diagnose thoracic injuries. Chest radiography is indicated for all major trauma patients as part of the ATLS protocol. It is a useful screening test that facilitates prompt detection of potentially life-threatening injuries that may require rapid intervention. In the case of critically ill patients, the chest radiograph may be the only investigation that may be performed without the risk of further decompensation (Ho & Gutierrez 2009).

The review of the chest radiograph should be guided by findings from the clinical examination. In turn, the radiographic findings may then be used to focus further clinical examination and to direct decisions regarding the need for further investigations such as thoracic computed tomography (CT), arteriography or echocardiography. Clinical re-evaluation and repeat chest radiographs may be required if the patient's clinical status changes (ATLS 2004).

Mechanisms of thoracic injury

Most thoracic injuries may be classified as blunt or penetrating injuries. Blunt trauma refers to a closed injury that may be due to direct impact from moving solid objects, sudden deceleration, or compressive or shear forces. Most blunt thoracic injuries in the developed world are caused by road traffic accidents (Mayberry 2000, Zinck & Primack 2000). Falls, physical attacks and crush injuries are other causes of blunt trauma. Penetrating injuries occur when the skin and tissues are pierced by items such as knives, glass, bullets. These items enter the body and may damage organs and vascular structures. Less common mechanisms include burns, radiation and blast injuries (Ho & Gutierrez 2009, Ursic & Curtis 2010).

Thoracic anatomy

A clear understanding of the normal anatomy of the thoracic cavity is essential for accurate interpretation of the chest radiograph. Figure 1 shows a normal chest radiograph with the main anatomical features labelled. The thoracic cavity is the superior part of the trunk between the neck and the abdomen. It extends from the supraclavicular fossae to the diaphragm. It contains several vital organs and structures.

The thoracic wall surrounds the cavity and consists of skin, fasciae, nerves, muscles and bone. The skeleton of the thoracic wall includes 12 thoracic vertebrae and intervertebral discs, 12 pairs of ribs and costal cartilages, and the sternum. This osteocartilaginous cage protects the heart and lungs as well as some abdominal organs such as the liver (Moore & Dalley 1999).

The thoracic cavity is divided into two compartments that contain the lungs. The right lung is divided into three lobes by horizontal and oblique fissures. The left lung has two lobes separated by an oblique fissure (Moore & Dalley 1999). The bronchi and vessels enter and leave the lung at the hilum (Raby et al 2005). Each lung is surrounded by a pleural sac that consists of two serous membranes called the pleurae. The parietal pleura lines the thoracic wall and the visceral pleura the surfaces of the lungs. The pleural cavities are potential spaces between the layers of pleura that become visible on a chest radiograph only when abnormal, e.g. when fluid, blood or air collects within the pleural cavity.

The mediastinum is a central compartment within the thoracic cavity located between the two pleural sacs. It contains the heart, which is enclosed by the pericardial sac, great vessels related to the heart such as the aorta and vena cava, and the azygous venous system. The distal part of the trachea and the oesophagus are also located within the mediastinum (Moore & Dalley 1999).

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Interpretation of the chest radiograph for identification of thoracic injuries

It is important to have a structured, consistent approach for interpretation of chest radiographs. A useful mnemonic for reviewing a chest radiograph is 'ABCDEF' (see Medicalmnemonics.com). Useful approaches for the preliminary assessment of the chest radiograph and the systematic assessment of the main regions of the chest are summarised in Tables 1 and 2, respectively.

Thoracic injuries and associated radiological findings

Chest wall

Subcutaneous emphysema is the presence of air within the subcutaneous soft tissues (Figures 2-4). It may result from airway injury, lung injury or chest wall infection.

The air appears on the chest radiograph as radiolucencies within the subcutaneous tissues. This may be seen as the 'gingko leaf' sign, which is the presence of radiolucent striations outlining the fibres of the pectoralis major muscles. Subcutaneous emphysema is usually self-limiting, but the underlying injury must be addressed (ATLS 2004, Ho & Gutierrez 2009).

A subcutaneous haematoma is the collection of blood within the soft tissues. They may develop due to damage to the thoracic vessels, muscles or ribs.

Haematomas appear on chest radiographs as radiodense opacities overlying the chest wall. A lateral radiograph or a CT scan is useful to localise the presence of the haematoma to the chest wall. Subcutaneous haematomas usually resolve spontaneously (Collins 2000).

Thoracic trauma may lead to a variety of skeletal injuries. The ribs are commonly injured and may have significant consequences. Multiple rib fractures are seen in Figures 4 and 5. Pain results in splinting of the thorax, reducing the effectiveness of ventilation, oxygenation and effective coughing. These factors increase the risk of atelectasis (collapse of part of or the entire lung) and pneumonia, especially if there is pre-existing lung disease. Fractures to the upper ribs (first to third) are uncommon because they are protected by the shoulder girdles and musculature (Collins 2000). Fractures of these ribs indicate significant energy transfer and may be associated with injuries to the great vessels, brachial plexus, lungs, head and neck. Fractures to the middle ribs (fourth to ninth) often occur due to anteroposterior compression of the thoracic cavity and may be associated with intrathoracic injuries such as pneumothorax. Young patients have more flexible chest walls and multiple rib fractures indicate high forces being applied to the chest. Lower rib fractures (tenth to twelfth) may be associated with injuries to the upper abdominal organs such as the liver, spleen and kidneys (ATLS 2004). A flail chest occurs when three or more adjacent segmental rib fractures or five or more contiguous single fractures are present. It results in paradoxical motion of the chest wall during inspiration or expiration and may lead to underlying lung injuries with pulmonary contusions. Treatment consists of adequate ventilation and fluid resuscitation (Ho & Gutierrez 2009).

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Fractures of the sternum and scapula may be identified on chest radiographs, although CT scans, and sternal or scapular radiographs, are more sensitive in diagnosing these injuries (Collins 2000, Ho & Gutierrez 2009). Clavicle fractures are common injuries easily identified on chest radiographs (Figures 6 and 7). These injuries require significant application of force to the thoracic cavity. Sternal fractures may be associated with blunt cardiac injury and lung injuries.

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Pleura

A pneumothorax occurs when air enters the potential space between the visceral and parietal pleurae. This may occur as a result of blunt or penetrating trauma. This appears as an apical lucent area without bronchial or vascular markings on a chest radiograph (Figures 7 and 8 and see Figures 2 and 3). A pneumothorax is generally treated with a chest drain placed in the fourth or fifth intercostal space, just anterior to the midaxillary line (ATLS 2004).

A tension pneumothorax (see Case study 1) occurs when air is forced into the thoracic cavity but cannot escape due to the development of a 'one-way-valve' air leak from the lung or through the chest wall. As the air collects, the affected lung collapses completely. The mediastinum is displaced to the opposite side, which decreases the venous return and compresses the opposite lung (ATLS 2004). Chest radiographic signs include a unilateral hyperlucent lung field with collapse of the lung, tracheal deviation and mediastinal displacement (see Figure 4) (Ho & Gutierrez 2009). As tension pneumothorax is a life-threatening emergency, time should not be wasted obtaining a chest radiograph. The diagnosis should be made on the basis of clinical findings of chest pain, respiratory distress, tachycardia, hypotension, tracheal deviation, unilateral absence of breath sounds and neck vein distension. Immediate treatment consists of insertion of a large-calibre needle into the second intercostal space in the midclavicular line in order to convert it to a simple pneumothorax. Chest drain insertion is the definitive treatment (ATLS 2004).

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A haemothorax (see Case study 2) can result from lung laceration or vascular injury. The chest radiograph appearance of a small haemothorax consists of layering of fluid and blunting of the costophrenic angles. Figure 6 shows the appearance of a haemothorax on an erect chest radiograph. Figures 9 and 10 show the appearance of haemothoraces in supine patients. Small haemothoraces resolve spontaneously. A large haemothorax may appear radiographically as complete opacification of the hemithorax. Large haemothoraces are treated with chest drainage and fluid resuscitation or blood transfusion in hypovolaemic patients (Ho & Gutierrez 2009). If 1,500 ml of blood is immediately evacuated on insertion of the chest drain, or if haemorrhage continues at a rate of 100-200 ml/hour for more than 2 hours, thoracotomy by a suitably trained surgeon is indicated (ATLS 2004).

Lungs

Pulmonary contusions occur when lung injuries result in leakage of blood and oedema into the interstitial and alveolar spaces. Areas of air-space shadowing are seen within the lung fields (see Figure 5). Contusions are usually evident within 6 hours after trauma and usually resolve within a week (Ho & Gutierrez 2009).

Mediastinum

Pneumomediastinum is the presence of air within the mediastinal structures. It may be due to tracheobronchial, pharyngeal or oesophageal rupture. Chest radiographs show air outlining the mediastinal soft-tissue structures and the parietal pleura (Zinck & Primack 2000).

Mediastinal widening and irregularity are signs of aortic injury (Figure 11). This is often difficult to identify and chest radiographs may be normal. Clinical suspicion of aortic dissection is more important than chest radiograph appearances (Raby et al 2005). Traumatic aortic dissection may show non-specific signs on radiographs such as an irregular aortic silhouette, discontinuous calcification of the arch of the aorta or intraluminal displacement of a calcified aortic intima (Ho & Gutierrez 2009). CT or arteriography is required for further investigation of aortic injury (Fishman 2000).

Oesophageal rupture and foreign body injury may lead to mediastinitis (mediastinal infection). Chest radiographs may show oedema, haemorrhage and gas production in the mediastinum. Pleural effusions and lower lobe consolidation may also occur (Ho & Gutierrez 2009).

Cardiac tamponade occurs when the pericardium fills with blood from the heart, great vessels or pericardial vessels. A relatively small amount of blood may impair cardiac filling and result in venous pressure elevation, decline in arterial pressure and muffled heart sounds on auscultation (Beck's triad) (ATLS 2004). Chest radiography may occasionally show a global enlargement of the cardiac silhouette (Ho & Gutierrez 2009). Echocardiography is the usual method of making the diagnosis. Prompt removal of small amounts of fluid by needle periocardiocentesis may result in immediate haemodynamic improvement (ATLS 2004).

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Diaphragm

Diaphragmatic rupture may be identified on chest radiographs as hemidiaphragmatic elevation, irregular diaphragmatic contours and the presence of upper abdominal organs within the thoracic cavity. A CT scan has a considerably greater sensitivity and is usually required to make the diagnosis. The treatment for diaphragmatic rupture is surgical repair (Shanmuganathan et al 2000).

Alternative radiological tests for the initial investigation of thoracic trauma

CT of the chest is more sensitive and specific for the detection of lung lesions than plain chest radiographs (De Wever et al 2000, Traub et al 2007). It has been suggested that CT could be used as a routine screening test for patients presenting with chest trauma. However, as CT cannot be performed in the resuscitation room and takes longer to perform, its use as an initial screening test would be appropriate only in selected clinically stable patients who are alert and do not have evidence of chest wall tenderness, reduced air entry or abnormal respiratory effort (Traub et al 2007). Ultrasonography has also been found to be more sensitive than supine plain chest radiography and as sensitive as CT for the detection of traumatic pneumothoraces (Rowan et al 2002). Focused assessment sonography in trauma (FAST) may be performed rapidly at the patient's bedside to detect other traumatic thoracic lesions such as haemothoraces, pericardial effusions, pulmonary contusions and rib fractures (Rowan et al 2002, Chan 2003, 2009). It has the added advantage of enabling immediate ultrasound-guided pericardiocentesis in the presence of cardiac tamponade (ATLS 2004) or chest drainage for pneumothoraces or haemothoraces (Laws et al 2003). This is possible only if the facilities are available in the accident and emergency department and the operator has appropriate expertise.

Conclusion

Thoracic trauma is common and may lead to life-threatening complications. Diagnosis of thoracic injuries should be prompt to allow early intervention and prevent unnecessary deaths. Clinical assessment and accurate interpretation of plain chest radiographs is the basis of diagnosis. Some thoracic injuries may produce subtle clinical signs which may be missed in the accident and emergency department but is usually recognised on chest radiographs. Other thoracic injuries result in classic dramatic clinical signs and lead to rapid deterioration. Tension pneumothoraces, for example, should be diagnosed clinically and treated immediately without the delay of obtaining a chest radiograph. Some injuries may be underestimated or not easily diagnosed on plain chest radiography and require further investigations such as CT (Miller 2006).

References

Advanced Trauma Life Support (ATLS) Student Course Manual Seventh Edition 2004 103-130

Chan SS 2003 Emergency bedside ultrasound to detect pneumothorax Academic Emergency Medicine 10(1)91-94

Chan SS 2009 Emergency bedside ultrasound for the diagnosis of rib fractures American Journal of Emergency Medicine 27(5)617-620

Chest X-ray interpretation Medicalmnemonics.com

Collins J 2000 Chest Wall Trauma Journal of Thoracic Imaging 15(2) 112-119

De Wever W, Bogaert J, Verschakelen J 2000 Radiology of lung trauma. JBR-BTR 83(4):167-73

Fishman JE 2000 Imaging of Blunt Aortic and Great Vessel Trauma Journal of Thoracic Imaging 15(2) 97-103

Gavelli G, Canini R, Bertaccini P et al 2002 Traumatic injuries: imaging of thoracic injuries European Radiology 12(6) 1273-1294

Ho M, Gutierrez F 2009 Chest Radiography in Thoracic Polytrauma American Journal of Roentgenology 192 599-612

Laws D, Neville E, Duffy J; Pleural Diseases Group, Standards of Care Committee, British Thoracic Society 2003 BTS guidelines for the insertion of a chest drain. Thorax 2003 58 (Suppl 2)ii53-ii59

Mayberry JC 2000 Imaging in Thoracic Trauma : The Trauma Surgeon's Perspective Journal of Thoracic Imaging 15(2) 76-86

Miller LA 2006 Chest wall, lung and pleural space trauma Radiologic Clinics of North America 44(2) 213-224

Moore KL, Dalley AF 1999 Thorax Clinically Oriented Anatomy Fourth Edition Lippincott Williams & Wilkins 60-172

Peters S, Nicholas V, Heyer CM 2010 Multidetector computer tomography-spectrum of blunt chest wall and lung injuries in polytraumatized patients Clinical Radiology 65(4) 333-338

Raby N, Berman L, de Lacy G 2005 Chest Accident and Emergency Radiology Elsevier Saunders 256-269

Rowan KR, Kirkpatrick AW, Liu D 2002 Traumatic pneumothorax detection with thoracic US: correlation with chest radiography and CT--initial experience Radiology 225(1)210-214

Shanmuganathan K, Killeen K, Mirvis SE, White CS 2000 Imaging of Diaphragmatic Injuries Journal of Thoracic Imaging 15(2) 104-111

Traub M, Stevenson M, McEvoy S, et al. 2007 The use of chest computed tomography versus chest X-ray in patients with major blunt trauma. Injury 38(1)43-47

Ursic C, Curtis K 2010 Thoracic and neck trauma International Emergency Nursing 18 47-53

Zinck SE, Primack SL 2000 Radiographic and CT Findings in Blunt Chest Trauma Journal of Thoracic Imaging 15(2) 87-96

About the author

Mukai Chimutengwende-Gordon MBChB, MSc, MRCS

Academic Orthopaedic Registrar, University College London Institute of Orthopaedic and Musculoskeletal Sciences, Royal National Orthopaedic Hospital, Stanmore, Middlesex

Wasim S Khan MBChB, MRCS, PhD

Academic Orthopaedic Registrar, University College London Institute of Orthopaedic and Musculoskeletal Sciences, Royal National Orthopaedic Hospital, Stanmore, Middlesex

Jasmeet Sidhu MBBS, BSc

Senior House Officer Orthopaedics, Queen's Hospital, Romford

Umile G Longo Specialist in Orthopaedics

Shoulder Fellow, University Campus Bio-Medico of Rome

Nimalan Maruthainar FRCS (Orth)

Consultant Orthopaedic Surgeon, Royal Free Hospital, London

No competing interests declared

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Case study 1

Mrs RC, a 47-year-old journalist, was brought to hospital by ambulance after being crushed on her bicycle between a reversing bus and a wall. She was complaining of right-sided chest and right wrist pain. She was noted to have bruising over her right chest wall and a deformed right wrist.

The patient was managed in accordance with the ATLS guidelines. In the A&E department, the patient was found to be dyspnoeic, disoriented and agitated. Although her blood pressure was normal she was tachycardic and tachypnoeic. Her oxygen saturation was only 68% despite being on high-flow oxygen via a re-breather mask. On examination her trachea was deviated away from the right side, she had hyperresonance of the right chest wall on percussion and decreased breath sounds.

A clinical diagnosis of tension pneumothorax was made and it was decompressed with a needle in the right second anterior rib space. This was followed by a chest drain inserted into the fifth mid-axillary rib space.

The patient then had a chest radiograph confirming the pneumothorax and correct placement of the chest drain. It also showed the presence of associated rib fractures. A right sided distal radius fracture was identified and stabilised in the secondary survey. The chest drain was removed on day 4 after the patient had her distal radius fracture operation, and once the pneumothorax had resolved.

Case study 2

Mr AP, a 20-year-old student, was brought to hospital by ambulance after the car he was driving was hit from the right side by another car at a junction. He was unconscious and noted to have bruising over his right chest wall and a deformed right thigh.

The patient was managed in accordance with the ATLS guidelines and had been intubated and ventilated at the scene. In the A&E department, the patient was noted to be hypotensive and tachycardic but was responding to fluid resuscitation. On examination the trachea was in the midline but the right chest wall was dull to percussion and had decreased breath sounds. The deformed thigh was aligned and stabilised in a splint.

The patient then had a chest radiograph confirming a right-sided haemothorax. A chest drain was inserted in the fifth midaxillary rib space to drain the haemothorax. After an initial drainage of 700 ml of blood, the drainage stopped. A midshaft femoral fracture was identified in the secondary survey. The chest drain was removed on day 6 after the patient had intramedullary nailing of his femoral fracture, and after the haemothorax had resolved.

Mukai Chimutengwende-Gordon, Wasim S Khan, Jasmeet Sidhu, Umile G Longo and Nimalan Maruthainar

Correspondence address: Mr WS Khan, Academic Clinical Fellow, University College London Institute of Orthopaedics and Musculoskeletal Science, Royal National Orthopaedic Hospital, Stanmore, Middlesex, London, HA7 4LP. Email: wasimkhan@doctors.org.uk

Provenance and Peer review: Commissioned by the Editor; Peer reviewed; Accepted for publication June 2010.
Table 1 Preliminary assessment of the chest radiograph

A   Anteroposterior (AP) or   Most chest radiographs in trauma
    a posteroanterior         patients will be AP films. On an AP
    (PA) film                 chest radiograph, the heart will
                              appear slightly larger than on a
                              PA film

B   Body position             It should be noted whether the
                              patient is supine or upright. In
                              trauma patients who are critically
                              ill, or when unstable spinal
                              fractures have not been excluded,
                              an upright chest radiograph may not
                              be possible (Gavelli et al 2002).
                              Erect chest radiographs increase
                              the sensitivity for detecting small
                              haemothoraces, pneumothoraces and
                              diaphragmatic injuries. Blunt upper
                              abdominal injury is an indication
                              for an erect chest radiograph
                              In the absence of any rotation of
                              the film, the medial ends of each
                              clavicle are equidistant to the
                              spinous process of the vertebra at
                              that level

C   Confirm the patient       It is important to confirm that the
    details                   film being viewed is that of the
                              correct patient

D   Date                      The date that the film was taken on
                              should be checked

E   Exposure                  The thoracic intervertebral disc
                              spaces are barely visible behind
                              the heart on an adequately
                              penetrated chest radiograph.
                              Slightly overpenetrated films allow
                              better visualisation of the
                              thoracic spine, paraspinal lines
                              and aortic outline

F   Films for comparison      Reviewing old films on the same
                              patient may be helpful

ABCDEF is a mnemonic to remember a systematic way of
going through chest radiographs. A stands for airway, which
includes the trachea and main bronchi, B for bones of the
chest, C for cardiac shadow, D for diaphragm, E for edges of
the lung fields and F for fields of the lung. This mnemonic
applies only to radiographs and should not be confused with
the ABCDE (airway, breathing, circulation, disability,
exposure) which is used in the primary survey of a trauma
patient.

Table 2 Systematic assessment of the main regions of the chest

A   Airways     The radiograph should be assessed for the presence
                of interstitial or pleural air that may indicate a
                large airway injury. Tracheal lacerations that may
                present as pneumomediastinum, pneumothorax, and
                subcutaneous emphysema of the neck should be
                looked for (ATLS 2004)

B   Bones       Fractures of the ribs, sternum, clavicle or
                scapula may accompany major thoracic injuries. The
                soft tissues should also be assessed, e.g. the
                presence of subcutaneous air or foreign bodies
                should be identified

C   Cardiac     An enlarged cardiac silhouette occurs when there
                is air or blood within the pericardium. A widened
                mediastinum suggests aortic rupture

D   Diaphragm   The radiograph should be carefully evaluated
                for evidence of diaphragmatic irregularity or
                obliteration. The right hemidiaphragm is usually
                slightly higher than the left. Excessive
                diaphragmatic elevation indicates diaphragmatic
                injury. The presence of stomach, bowel gas or
                a nasogastric tube above the diaphragm indicates
                rupture (Zinck & Primack 2000, ATLS 2004)

E   Edges       The apices should be assessed in particular for
                the presence of a pneumothorax. Abnormal fluid
                collections in the pleural space may represent a
                haemothorax

F   Fields      The lung fields are assessed for infiltrates that
                may suggest pulmonary contusion, haematoma,
                aspiration, etc. Pulmonary contusions appear as
                air-space consolidation that can be irregular and
                patchy, homogeneous, diffuse or extensive. The
                lung parenchyma should be assessed for evidence of
                laceration. Lacerations appear as a haematoma and
                areas of consolidation

ABCDEF is a mnemonic to remember a systematic way of going
through chest radiographs. A stands for airway, which includes
the trachea and main bronchi, B for bones of the chest, C for
cardiac shadow, D for diaphragm, E for edges of the lung fields
and F for fields of the lung. This mnemonic applies only to
radiographs and should not be confused with the ABCDE (airway,
breathing, circulation, disability, exposure) which is used
in the primary survey of a trauma patient.
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Title Annotation:CLINICAL FEATURE
Author:Chimutengwende-Gordon, Mukai; Khan, Wasim S.; Sidhu, Jasmeet; Longo, Umile G.; Maruthainar, Nimalan
Publication:Journal of Perioperative Practice
Article Type:Report
Geographic Code:4EUUK
Date:Dec 1, 2010
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