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Fig. 3.9 Flail chest. The diagnosis is made by observing paradoxical chest wall movement in combination with multiple right-sided rib fractures on the chest X-ray. Note the surgical emphysema and lung contusion.

framework of the upper limb. The scapula, humerus, and clavicle, along with their muscular attachments provide a barrier to rib injury. Fractures of the scapula, first or second ribs, or the sternum suggest a magnitude of injury that place the head, neck, spinal cord, lungs and great vessels at risk for serious associated injury. Because of the severity of the associated injuries, mortality can be as high as 35%. Pain from rib fractures can precipitate hypoventilation and atelectasis. Adequate analgesia is essential.

In a flail chest injury paradoxical motion of the free-floating segment of chest wall occurs during respiration. This means that during inspiration the affected segment moves inwards in the opposite direction to the rest of the thoracic cage. Lateral chest wall injuries are the commonest cause and the injury usually consists of fractures in at least two sites in multiple adjacent ribs. If the pulmonary condition worsens, the paradoxical movement of the chest wall becomes more severe, making respiration more inefficient. In the unconscious patient the chest wall muscles do not splint the area and the flail effect is more pronounced.

The diagnosis is clinical and depends upon recognising paradoxical chest wall movement in the presence of multiple fractures on the chest X-ray. Ventilation is impaired, coughing is ineffective and the injuries are usually very painful. This injury should not be underestimated, assisted ventilation may be necessary. The patient should be monitored and observed in an HDU or ITU. Thoracic epidural analgesia is often used to provide pain relief to facilitate respiration and clearing of secretions.

Thoracic spine

Make a point of tracing the contour of the thoracic spine on the frontal 134 radiograph. Reconstructions can be performed from spiral CT (see Fig. 3.6).

The most common fractures are anterior compression fractures and burst fractures, most of which occur at the thoraco-lumbar junction.

Check for shoulder dislocation, clavicle or scapulae fractures and sternal injuries.

Pulmonary contusion

Pulmonary contusion is defined as focal injury with oedema, alveolar and interstitial haemorrhage. It is the most common potentially lethal chest injury. The respiratory failure may be subtle and develops over time rather than occurring instantaneously. Patients need careful monitoring and re-evaluation for several days after the injury.

The initial presentation is usually with hypoxia and on the X-ray or CT, the pattern is of air space shadowing (Fig. 3.9). This is normally non-segmental, often peripheral and adjacent to the area of trauma. Other causes of air space shadowing seen in trauma patients include aspiration, atelectasis and pulmonary oedema (cardiogenic and non-cardiogenic). Management is with oxygen therapy either with a positive pressure mask or mechanical ventilation. Due to the high force required to cause contusion there are often other accompanying injuries. In contrast, due to the increased compliance of the chest in children, pulmonary contusion can occur in the absence of rib fractures.

Pulmonary laceration can occur secondary to shear forces in blunt trauma (Figs 3.7 and 3.8) or in penetrating injury. This is easy to miss if there is surrounding contusion. It is characterised by collections of air within surrounding contusion.

Pneumothorax

There must be a high index of suspicion for pneumothorax in blunt chest trauma - it occurs in over one-third of cases. If there are clinical suspicions of tension (tracheal deviation, dilated neck veins, hyper-resonant percussion note over one hemithorax and absent breath sounds, hypoxia and hypotension) then the chest must be decompressed immediately by inserting a large bore needle into the second intercostal space in the mid-clavicular line of the affected hemithorax. This must be done before obtaining a chest X-ray. Subsequent chest drain insertion is usually performed in the fourth or fifth interspace in the mid-axillary line. Even small pneumothoraces can be clinically relevant in the setting of trauma, as ventilation or general anaesthesia may become necessary.

Haemothorax

Large volumes of blood can accumulate in the pleural space and this can cause hypovolaemia as well as ventilatory problems from the mass effect.

Sites of bleeding include intercostal vessels, internal mammary artery the mediastinal great vessels or abdominal viscera in the presence of diaphragmatic rupture. The diagnosis is made by identifying fluid on the

X-ray and sampling the fluid in the pleural space. 135

Massive haemothorax results from a rapid accumulation of more than 1500 ml of blood in the chest cavity. It is most commonly caused by a penetrating wound that dirupts the systemic or hilar vessels. It may also result from blunt trauma.

Cardiac injury

The most anterior of the heart chambers - the right ventricle and right atrium are the most frequently injured. A combination of cardiac enzyme elevation, ECG changes (usually significant conduction abnormalities), echocardiography and thallium scintigraphy can be used to assess cardiac contusion.

B Pericardial tamponade

This is seen more often in association with penetrating trauma. Clinical signs are unreliable in the resuscitation setting but can include venous pressure elevation, hypotension and muffled heart sounds. Prompt transthoracic echocardiography may be a valuable way of assessing the pericardium but has a false negative rate of about 5%. Examination of the pericardial sac may form part of a focused abdominal ultrasound examination performed by a trauma team properly trained in its use. If found, pericardial tamponade frequently requires drainage. Underlying causes include cardiac rupture, aortic disruption and cardiac contusion.

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Essentials of Human Physiology

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