Pulmonary contusion in children

INTRODUCTION — This topic will discuss the epidemiology, clinical features, and management of pulmonary contusion in children. The approach to thoracic trauma in children and other thoracic injuries are presented elsewhere. (See "Thoracic trauma in children: Initial stabilization and evaluation" and "Chest wall injuries after blunt trauma in children" and "Overview of intrathoracic injuries in children".)

DEFINITION — Pulmonary contusion is defined as pulmonary parenchymal damage with edema and hemorrhage, in the absence of an associated laceration of a large pulmonary vessel.

EPIDEMIOLOGY — While thoracic injury in children is uncommon, occurring in only 4 to 8 percent of injured children identified through trauma registries or as patients at trauma centers [1-3], pulmonary contusion is the most commonly identified thoracic injury.

The vast majority of pulmonary contusions are the result of blunt trauma, usually involving a motor vehicle. In one retrospective series, 56 percent of injuries occurred in a motor vehicle crash, while 39 percent were the result of auto-pedestrian collisions [4].

The majority of patients with pulmonary contusions have associated thoracic injuries (eg, pleural effusion, pneumothorax, hemothorax, and fractures of the bony thorax) [4,5]. While flail chest and scapular fractures are uncommon in children, when present, they are typically associated with pulmonary contusion as well. (See "Chest wall injuries after blunt trauma in children".)

More than 80 percent of children with pulmonary contusion also have extrathoracic injuries. While mortality for children with pulmonary contusion in one series was 22 percent, the cause of death was attributable to brain injury, hemorrhage, or multiple organ system injury in all cases rather than the contusion itself [4].

PATHOGENESIS — Pulmonary contusion results when kinetic energy is transmitted to the pulmonary parenchyma. The lungs are damaged in the following ways:

●Hemorrhage occurs when deceleration at different rates, such as occurs in a motor vehicle crash, causes shearing of lighter alveolar tissue from heavier bronchial structures.

●Energy transmitted to the liquid-gas interface of the alveolar membrane and the intraalveolar air disrupts the lipid bilayer, resulting in increased cell membrane permeability and extravasation of fluid [2,6].

●Rebound or overexpansion of intrapulmonary air, after a pressure wave passes, overstretches and damages lung parenchyma.

Damage to lung tissue, including extravasation of fluid into the interstitium and inactivation of surfactant, results in alveolar collapse, ventilation-perfusion mismatch, and hypoxemia.

The clinical features of pulmonary contusion in children are also influenced by mechanical differences in the chest wall, which is more compliant and elastic than that of an adult. As a result, more kinetic energy can be transmitted to the intrathoracic structures without bony injury. For this reason, pulmonary contusion without rib fracture occurs more often in children than adults [4].

INITIAL ASSESSMENT AND STABILIZATION — As with any significantly injured child, priority is given to the maintenance of oxygenation, ventilation, and cardiovascular support and the management of immediately life-threatening injuries that frequently coexist with pulmonary contusions such as pneumothorax, hemothorax, or hemorrhagic shock (table 1). Whenever possible, trauma resuscitation for the unstable child should be performed in a pediatric trauma center and ongoing care directed by a trauma surgeon with pediatric expertise. (See "Trauma management: Approach to the unstable child", section on 'Primary survey' and "Thoracic trauma in children: Initial stabilization and evaluation".)

Careful physical examination should note signs of respiratory distress (ie, increased respiratory rate or retractions), abnormal breath sounds, or signs of chest wall injury (ie, focal tenderness, swelling, abrasions, or paradoxical movement). Pulse oximetry should be monitored for all patients. (See "Trauma management: Approach to the unstable child", section on 'Secondary survey'.)

Initial laboratory testing in patients with pulmonary contusion is the same as for any seriously injured child and is described separately. (See "Trauma management: Approach to the unstable child", section on 'Laboratory studies'.)

Chest radiography should be performed for all children with suspected pulmonary contusion and all significantly injured children. (See "Trauma management: Approach to the unstable child", section on 'Screening radiographs'.)

The approach to the unstable injured child is discussed in greater detail separately. (See "Trauma management: Approach to the unstable child", section on 'Primary survey'.)

CLINICAL FEATURES — The initial presentation of children with pulmonary contusion is often dominated by clinical features associated with extrathoracic injuries. Nevertheless, pulmonary contusion should be suspected in any child with significant blunt force to the thorax, whether or not there are signs of respiratory distress or chest wall injury.

Although the majority of children with pulmonary contusion have some degree of tachypnea, hypoxemia, or respiratory distress at initial presentation, these features may be subtle [7]. As an example, among children with pulmonary contusion in one series, mild tachypnea (respiratory rate between 20 and 30 breaths per minute) was noted in 16 percent, while another 16 percent had respiratory rates over 30 breaths per minute [5].

Decreased breath sounds, rales, or rhonchi may be noted on physical examination. Limited evidence suggests that these abnormal findings may be absent in more than half of patients [5]. Similarly, the majority of children may not have signs of chest wall injury, such as rib or soft tissue tenderness [4,5].

DIAGNOSIS — Pulmonary contusion is primarily a clinical diagnosis and should be suspected in any child with a history of chest trauma and any one of the following:

●Tachypnea

●Hypoxemia (eg, pulse oximetry <95 percent in room air or high alveolar to arterial oxygen gradient based upon arterial blood gas measurement (calculator 1))

●Abnormal lung examination (eg, rales, rhonchi, decreased breath sounds, or increased work of breathing)

Imaging studies — Chest radiography should be performed for all children with suspected pulmonary contusion and all children with significant thoracic or multisystem trauma. It is initially abnormal in 65 to 97 percent of patients with pulmonary contusion. The primary finding consists of nonanatomic areas of consolidation that are located in the region of impact (image 1) [3-5,8]. Associated injuries such as pneumothorax, hemothorax, or, less commonly, rib fractures may also be apparent.

In some children with clinical findings of pulmonary contusion, chest radiographs can initially appear normal, particularly with relatively minor injuries. However, repeat radiographs are not warranted unless the patient's respiratory status deteriorates. If the patient remains clinically stable, it is unlikely that emerging radiographic findings would have an impact on management.

Chest computed tomography (CT) is not recommended solely for diagnosing a pulmonary contusion because, although it is more sensitive for detecting pulmonary contusions than chest radiography, it does not alter clinical management in an otherwise stable patient with normal oxygenation [9,10]. CT of the chest is only useful during primary evaluation when identification of a pulmonary contusion would affect management (ie, in anesthetic management for patients requiring emergency surgery) or when there is suspicion for associated thoracic injury that warrants CT. (See "Thoracic trauma in children: Initial stabilization and evaluation", section on 'Major trauma'.)

Later on in the care of children with pulmonary contusion, chest CT may be helpful to distinguish contusion from other causes of consolidation seen on plain radiography, such as aspiration, atelectasis, or infection [11].

In the acute setting, bedside ultrasound by an experienced practitioner may facilitate rapid identification of pulmonary contusion. Findings of B-lines and dynamic air bronchograms in the affected lung may indicate the presence of contusion [12,13].

MANAGEMENT — Following initial stabilization of the traumatized child, hypoxic patients suspected of pulmonary contusion should be treated as follows:

●Supplemental oxygen to maintain pulse oximetry >95 to 99 percent [7].

●Assess ventilation using blood gases (arterial or venous) or end-tidal carbon dioxide (CO₂).

●Airway support should be provided as needed to maintain oxygenation and ventilation. For children with pulmonary contusion, intubation is typically required for management of extrathoracic injuries, rather than for respiratory insufficiency as the result of the pulmonary injury [4]. As an example, in a small case-series of 26 children with pulmonary contusion, none required intubation for pulmonary contusion alone [14].

●In the absence of shock, fluids should be administered carefully to avoid increasing edema in the contused lung.

The ongoing management of pulmonary contusion is supportive. Patients must be carefully monitored for respiratory deterioration, although the extent of lung injury is often apparent at the initial evaluation [5]. Good pulmonary care, careful fluid management, and adequate analgesia reduce complications and the need for intubation [15-17]. Specific interventions may include the following:

●Intercostal nerve blocks and continuous epidural opiates to provide additional pain relief.

●Placing the child in a position where the injured portion of the lung is dependent to improve perfusion to the normal lung [7].

●For children requiring mechanical ventilation, positive end expiratory pressure (PEEP) to improve alveolar recruitment and oxygenation [15].

COMPLICATIONS — The following complications are associated with pulmonary contusion:

●Pneumonia is the most frequent complication of pulmonary contusion, occurring in 20 to 50 percent of patients [16,18]. The radiographic findings of pulmonary contusion may be difficult to distinguish from those of pneumonia. Therefore, children who develop fever with worsening respiratory function should receive appropriate antibiotic coverage. (See "Pneumonia in children: Inpatient treatment".)

●Acute respiratory distress syndrome (ARDS) may develop in patients who survive the initial injury. While the rate of ARDS among children with pulmonary contusion was 30 percent in one single-center study, limited evidence suggests that ARDS is an infrequent complication of pulmonary contusion alone in children and usually occurs in the presence of other significant stigmata of polytrauma such as a high Injury Severity Score and decreased Glasgow Coma Score [19]. (See "Acute respiratory distress syndrome: Clinical features, diagnosis, and complications in adults" and "Acute respiratory distress syndrome: Epidemiology, pathophysiology, pathology, and etiology in adults".)

●Small pneumatoceles (<4 cm), primarily seen on CT of the chest, may occur in association with pulmonary contusion (over 10 percent in one retrospective, single-center study) [20]. While the presence of these cavitary air-filled lesions in the pulmonary parenchyma may not alter management for most children and typically resolve spontaneously, they present some risk of infection, hemorrhage, or rupture with secondary pneumothorax.

OUTCOMES — Children with pulmonary contusion who survive their initial injuries appear to have an excellent outcome. This was demonstrated in one retrospective series in which children with pulmonary contusion/laceration were evaluated several years after the initial injury [21]. All of the subjects had normal chest radiographs and pulmonary function, with the exception of one child who had asthma. This is in contrast to adult populations, in whom long-term respiratory dysfunction frequently occurs [22].

The effect of pulmonary contusion on the outcome of children with other injuries is uncertain. As an example, evidence regarding the outcome of children with severe head injury who also had a pulmonary contusion, compared with those with no lung injury, is limited and conflicting [23,24].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pediatric trauma".)

SUMMARY AND RECOMMENDATIONS

●Definition – Pulmonary contusion is defined as pulmonary parenchymal damage with edema and hemorrhage in the absence of an associated pulmonary laceration. Because the chest wall in children is more elastic and compliant, associated fractures to the bony thorax are uncommon in children with pulmonary contusions. (See 'Definition' above and 'Pathogenesis' above.)

●Stabilization – As with any significantly injured child, priority is given to the maintenance of oxygenation, ventilation, and cardiovascular support and the management of immediately life-threatening injuries that frequently coexist with pulmonary contusions such as pneumothorax, hemothorax, or hemorrhagic shock (table 1). (See "Trauma management: Approach to the unstable child", section on 'Primary survey' and "Thoracic trauma in children: Initial stabilization and evaluation".)

●Clinical features – Once life-threatening conditions have been identified and treated, a careful physical examination should note signs of respiratory distress (ie, increased respiratory rate or retractions), hypoxemia, abnormal breath sounds, or signs of chest wall injury (ie, focal tenderness, swelling, or abrasions). Pulse oximetry should be monitored for all patients. Clinical features may be subtle, although most children will have some respiratory symptoms. Signs of chest wall injury are frequently absent. (See 'Initial assessment and stabilization' above and 'Clinical features' above.)

●Diagnosis – Pulmonary contusion is primarily a clinical diagnosis and should be suspected in any child with a history of chest trauma and any one of the following (see 'Diagnosis' above):

•Tachypnea

•Hypoxemia (eg, pulse oximetry <95 percent in room air or high alveolar to arterial oxygen gradient based upon arterial blood gas measurement (calculator 1))

•Abnormal lung examination (eg, rales, rhonchi, decreased breath sounds, or increased work of breathing)

●Imaging – Children with suspected pulmonary contusions should undergo chest radiography. The primary findings consist of nonanatomic areas of consolidation that are located in the region of impact (image 1). Associated injuries, such as pneumothorax, hemothorax, or, less commonly, chest wall injuries, such as rib fractures, may also be apparent. In some children with clinical findings of pulmonary contusion, chest radiographs can initially appear normal, particularly with relatively minor injuries. However, repeat radiographs are not warranted unless the patient's respiratory status deteriorates. (See 'Imaging studies' above.)

CT of the chest is only useful during the primary evaluation when identification of a pulmonary contusion would affect management (ie, in anesthetic management for patients requiring emergent surgery) or when there is suspicion for associated thoracic injury that warrants CT such as aortic or other great vessel injury or tracheobronchial injury. Otherwise, chest CT is not recommended solely for diagnosing a pulmonary contusion because it does not alter clinical management in an otherwise stable patient with normal oxygenation. (See 'Imaging studies' above.)

●Management – Initial management is directed toward identifying and stabilizing life-threatening injuries, as well as maintaining oxygenation, ventilation, and cardiovascular support. (See 'Initial assessment and stabilization' above.)

Following initial stabilization of the traumatized child, hypoxic patients suspected of pulmonary contusion should be treated as follows (see 'Management' above):

•Supplemental oxygen to maintain pulse oximetry >95 to 99 percent.

•Assess ventilation using blood gases (arterial or venous) or end-tidal carbon dioxide (CO₂).

•Airway support should be provided as needed to maintain oxygenation and ventilation. For children with pulmonary contusion, intubation is typically required for management of extrathoracic injuries, rather than for respiratory insufficiency as the result of the pulmonary injury.

•In the absence of shock, fluids should be administered carefully to avoid increasing edema in the contused lung.

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Allison Chantal Caviness, MD, who contributed to an earlier version of this topic review.