Chest Trauma
Pulmonary Contusion

Pulmonary contusion is an injury to lung parenchyma, leading to oedema and blood collecting in alveolar spaces and loss of normal lung structure & function. This blunt lung injury develops over the course of 24 hours, leading to poor gas exchange, increased pulmonary vascular resistance and decreased lung compliance. There is also a significant inflammatory reaction to blood components in the lung, and 50-60% of patients with significant pulmonary contusions will develop bilateral Acute Respiratory Distress Syndrome (ARDS).

Pulmonary contusions occur in approximately 20% of blunt trauma patients with an Injury Severity Score over 15, and it is the most common chest injury in children. The reported mortality ranges from 10 to 25%, and 40-60% of patients will require mechanical ventilation. The complications of pulmonary contusion are ARDS, as mentioned, and respiratory failure, atelectasis and pneumonia.

Diagnosis

Pulmonary contusions are rarely diagnosed on physical examination. The mechanism of injury may suggest blunt chest trauma, and there may be obvious signs of chest wall trauma such as bruising, rib fractures or flail chest. These suggest the presence of an underlying pulmonary contusion. Crackles may be heard on auscultation but are rarely heard in the emergency room and are non-specific.

Severe bilateral pulmonary contusions may present with hypoxia - but more usually hypoxia develops as the pulmonary contusions blossom or as a result of subsequent ARDS.

Chest X-ray

Most significant pulmonary contusions are diagnosed on plain chest X-ray. However the chest X-ray will often under-estimate the size of the contusion and tends to lag behind the clinical picture. Often the true extent of injury is not apparent on plain films until 24-48 hours following injury.

Pulmonary Contusion Admission CXR	Pulmonary Contusion 24 Hours

Computed Tomography

Computed tomography (CT) is very sensitive for identification of pulmonary contusion, and may allow differentiation from areas of atelectasis or aspiration. CT also allows for 3-dimensional assessment and calculation of the size of contusions. However, most contusions that are visible only on a CT scan are not clinically relevant, in that they are not large enough to impair gas exchange and do not worsen outcome. Nevertheless, CT will accurately reflect the extent of lung injury when pulmonary contusion is present.
 

CHEST TRAUMA INITIAL EVALUATION PNEUMOTHORAX TENSION PNEUMO OPEN PNEUMO HAEMOTHORAX CONTUSION RIB FRACTURE / FLAIL AORTIC INJURY CHEST DRAINS

PULMONARY CONTUSION PRIMARY SURVEY AIRWAY BREATHING CIRCULATION DISABILITY EXPOSURE ADJUNCTS CXR SECONDARY SURVEY

L pulmonary contusion
L pneumothorax

lung contusion at
thoracotomy

Management

Managment of pulmonary contusion is supportive while the pulmonary contusion resolves. Most contusions will require no specific therapy. However large contusions may affect gas exchange and result in hypoxaemia. As the physiological impact of the ocntusions tends to develop over 24-48 hours, close monitoring is required and supplemental oxygen should be administered.

Many of these patients will also have a significant chest wall injury, pain from which will affect their ability to ventilate and to clear secretions. Management of a blunt chest injury therefore includes adequate and appropriate analgesia. Tracheal intubation and mechanical ventilation may be necessary if there is difficulty in oxygenation or ventilation. Usually ventilatory support can be discontinued once the pulmonary contusion has resolved, irrespective of the chest wall injury.

The classic management of pulmonary contusion includes fluid restriction. Much of the data to support this comes from animal models of isolated pulmonary contusion. However, while relative fluid excess and pulmonary oedema will augment any respiratory insufficience, the consequences of the opposite - hypovolaemia are more severe and long-lasting. Prolonged episode of hypoperfusion in trauma patients will result in inflammatory activation and acute lung injury, and may result in ARDS and multiple organ failure. Hence the goal for management of patients with pulmonary contusion should be euvolaemia.

Complications

Pulmonary contusions will usually resolve in 3 to 5 days, provided no secondary insult occurs. The main complications of pulmonary contusion are ARDS and pneumonia. Approximately 50% of patients with pulmonary contusion develop ARDS, and 80% of patients with pulmonary contusions involving over 20% of lung volume. Direct lung trauma, alveolar hypoxia and blood in the alveolar spaces are all major activators of the inflammatory pathways that result in acute lung injury.

Pneumonia is also a common complication of pulmonary contusion, blood in the alveolar spaces providing an excellent culture medium for bacteria. Clearance of secretions is decreased with pulmonary contusion, and this is augmented by any chest wall injury and mechanical ventilation. Good tracheal toilet and pulmonary care is essential to minimise the incidence of pneumonia in this susceptible group.
 

R pulmonary contusion
(Chest wall injury)

ARDS after
R pulmonary contusions

References

Cohn SM. 'Pulmonary contusion: review of the clinical entity.' J Trauma 1997; 42:973–979

Trinkle JK, Furman RW, Hiushaw MA et al. 'Pulmonary contusion: pathogenesis and effect of various resuscitative measures.' Ann Thorac Surg 1973;16:568

Bongard FS, Lewis FR. 'Crystalloid resuscitation of patients with pulmonary contusion.' Am J Surg 1984;148:145

Miller PR, Croce MA, Kilgo PD et al. 'Acute respiratory distress syndrome in blunt trauma: identification of independent risk factors.' Am Surg 2002;68:845-50

Miller PR, Croce MA, Bee TK et al. 'ARDS after pulmonary contusion: accurate measurement of contusion volume identifies high-risk patients.' J Traum 2001;51(2):223-8

Tyburski JG, Collinge JD, Wilson RF et al. 'Pulmonary contusions: quantifying the lesions on chest X-ray films and the factors affecting prognosis.' J Trauma 1999;46(5):833-8