Chest injury

Introduction

• chest injuries are second only to head injuries as a cause of traumatic paediatric mortality  

• most paediatric chest injury arise from blunt force trauma 

• the most common paediatric chest injuries are pulmonary contusions, rib fractures, pneumothoraces and haemothoraces 

• a lack of external signs does not preclude major underlying thoracic injury

• paediatric chest trauma is commonly associated with injuries to the head and/or abdomen 

• most paediatric chest injuries can be successfully managed with a combination of supplemental oxygenation, analgesia, fluid resuscitation and intercostal drain placement.

Pathophysiological differences between paediatric and adult chest trauma

Children have different anatomic and physiologic properties that influence the diagnosis and management of chest trauma. 

• the paediatric chest wall is much more compliant, and often has less muscle mass thereby allowing for a greater transmission of energy through the chest wall to the deeper structures with little or no external sign of injury  

• a child’s body-wall thickness is less than that of an adult therefore a penetrating thoracic injury is more likely to injure an internal structure 

• chest wall disruption is poorly tolerated in children due to their increased oxygen consumption, diaphragmatic breathing and low functional residual capacity  

Penetrating chest trauma

Penetrating thoracic injuries account for less than 10% of the total reported incidence of paediatric chest trauma worldwide. 

Any penetrating injury to the “Cardiac Box” should raise concern about cardiac injury. The Cardiac Box is the area bounded anteriorly by the clavicles, bilaterally by the mid-clavicular line and inferiorly by the costal margins. 

Due to its position, the right ventricle is the most lacerated area of the heart. 

Assessment

The priority in the management of all paediatric trauma patients is the identification and management of imminent life threats by completion of the Primary Survey.  

Primary survey

The following IMMINENT LIFE THREATS should be actively excluded during the primary survey. If these conditions are detected they should be immediately treated.

• Airway obstruction  

• Tension pneumothorax 

• Open pneumothorax 

• Massive haemothorax 

• Flail chest 

• Cardiac tamponade 

Imaging

Point of care ultrasound (POCUS)

• can be a useful adjunct in rapidly identifying intrathoracic life threats such as pneumothorax, haemothorax and hemopericardium 

• is more sensitive than a supine chest x-ray in detecting a pneumothorax 

For more information refer to both the Starship EFAST guideline and the Children’s Emergency Department Focused Ultrasound website.

Chest x-ray

• is the primary investigation for chest trauma 

• is useful in identifying pneumothoraces/haemothoraces, gross mediastinal injuries, flail chest and rib fractures (note that not all rib fractures are visible on x-ray)

• is a useful tool for determining the need for CT imaging  

Computed Tomography (CT)

• not ROUTINELY performed in paediatric trauma  

• indicated in patients with abnormal chest x-ray findings or those in which there is a high clinical suspicion of significant chest trauma 

Specific chest injuries

Tension pneumothorax

A tension pneumothorax occurs when injury to the pleural parenchyma creates a one-way value allowing air to accumulate in the pleural space. Initially the rise in intra-thoracic pressure impedes ventilation, while the collapsed lung impairs gas exchange. As air continues to accumulate the resultant mediastinal shift causes compression of the SVC and IVC leading to decreased venous return, hypotension and eventual PEA arrest.

Open pneumothorax

An open pneumothorax results from penetrating chest trauma that creates an air passage directly into the thoracic cavity. Air will preferentially flow through the chest wall deficit when the deficit is greater than two thirds the diameter of the trachea . If the air is unable to escape during expiration a tension pneumothorax will develop. 

Example of a three-way dressing

Haemothorax

A haemothorax is a collection of blood in the pleural space that can arise secondary to either penetrating or blunt thoracic trauma.

A massive haemothorax is the rapid accumulation of a large volume of blood in the pleural space. It is possible for a patient to lose up to 40 % of their total blood volume into each hemithorax.  

A haemothorax can cause impaired ventilation and oxygenation, along with hypotension and shock. Immediate chest decompression via thoracostomy and intercostal drain placement and restoration of blood volume are vital. 

An undrained haemothorax can lead to retained clot and formation of an empyema.

Some studies have even shown that smaller pigtail drains might be as efficacious as larger drains, however more research is needed. At present, it is still recommended that a larger bore drain be inserted for patients with traumatic haemothoraces.

Flail chest

A flail chest occurs when part of the chest wall is fractured in such a way as to create a floating segment that moves paradoxically with respiration (inward movement with inspiration and outwards with expiration). A peripheral flail segment arises when adjacent ribs are broken in two or more places. A central flail segment occurs when the sternum is separated from the chest wall from multiple fractures around the costochondral junctions.  

As a flail chest results from significant force being applied to the chest wall, significant underlying lung injury (e.g. pulmonary contusion, pneumothorax, haemothorax) should also be anticipated. 

Respiratory compromise from a flail chest is secondary to pain, underlying lung injury (if present) and the increased work of breathing created from the paradoxical chest wall movements.

A flail segment is rare in children due to the greater elastic properties of the paediatric ribcage which permits far greater plastic deformation on impact without resultant broken ribs.    

Cardiac tamponade

Traumatic cardiac tamponade is the compression of the heart by the accumulation of blood in the fibrous pericardial sac. As blood continues to accumulate, the volume available for cardiac filling during diastole is reduced, resulting in diminished cardiac activity. If blood continues to accumulate, shock and then cardiac arrest will occur.

*JVP is particularly difficult to identify in the setting of hypovolemia

Pulmonary contusions

Pulmonary contusions are often seen in moderate to severe blunt chest injury and are the most common thoracic injury in paediatric patients.  

The high incidence of pulmonary contusions in paediatric patients is due to energy being readily transmitted to the lungs as the ribs are elastic and do not easily dissipate energy by fracturing. If the ribs do fracture, the degree of force is such that associated pulmonary contusion is likely.

Complications of pulmonary contusions including decreased lung compliance, ventilation-perfusion mismatch/shunting and hypoxia, may lead to respiratory distress and failure. 

Uncomplicated contusions usually resolve within 36 hours.

Rib fractures

Despite the compliant nature of the paediatric chest wall, rib fractures are still common in paediatric chest trauma, however they are usually indicative of significant injury and the greater likelihood of associated multi-system trauma. 

Rib fractures are almost always associated with pulmonary contusions in the paediatric patient and lower rib fractures are often associated with liver, spleen and diaphragmatic injuries.

Simple pneumothorax

A pneumothorax occurs when air collects in the potential space between the visceral and parietal pleura. It can be caused by both blunt and penetrating thoracic trauma. The degree of compromise is related to both the size of the pneumothorax and any other associated thoracic injuries.  

*Traditionally patients with traumatic pneumothoraces, regardless of size, had an intercostal drain inserted. However, increasing evidence in adult trauma suggests that asymptomatic, hemodynamically stable patients with occult pneumothoraces (i.e. pneumothorax detected on CT but not seen on chest x-ray) can be observed without chest drain insertion. Additionally, “small” pneumothoraces that are visible on chest x-ray are now considered amenable to observation, however there is no universally accepted radiological measurement of what a “small” pneumothorax is.

It is therefore reasonable that clinically stable paediatric patients with asymptomatic pneumothoraces can be admitted for close monitoring without intercostal drain insertion. However, if the patient subsequently becomes symptomatic or hemodynamically unstable an intercostal drain should be placed without delay.  

Blunt cardiac injury

Blunt cardiac injury (BCI) is a challenging clinical diagnosis due to a lack of clear diagnostic criteria. It should be considered in all patients who have sustained blunt trauma to the torso, particularly in the setting of high impact trauma 

The incidence of blunt cardiac injury varies due to minor injuries often being asymptomatic 

* Whilst a normal ECG has a 95% negative predictive value, the value of troponin is less well established. However, some studies indicate that a normal troponin with a normal ECG increases the negative predictive value to 100% .

Tracheobronchial injuries

Tracheobronchial injuries are rare, potentially life-threatening injuries resulting predominantly from penetrating trauma. Delay in diagnosis is not uncommon. 

Aortic injury

Aortic injuries typically occur as a recent of significant deceleration forces such that occur in high-speed motor vehicle accidents. The most common area of aortic injury is at, or close to the ligamentum arteriosum which attaches to the proximal descending aorta just beyond the left subclavian artery. At this point the aorta is tethered and therefore prone to shearing forces. 

Types of aortic injuries:

• rupture (almost always fatal due to immediate massive blood loss) 

• pseudoaneurysm 

• intramural hematoma or dissection 

• intimal tear 

Diaphragmatic injury

Injuries to the diaphragm are rare but well recognised in children. In blunt trauma it is generally thought that left sided injury is more common.

Oesophageal injury

Most commonly due to penetrating injury but may occur following blunt injury to the upper abdomen causing forceful ejection of stomach contents into the oesophagus resulting in a tear in the lower oesophagus. Failure to treat can lead to significant morbidity and mortality from mediastinitis. 

Traumatic asphyxiation

Prolonged severe compression of the chest results in obstruction of venous return leading to extravasation of blood into the tissues.