A pulmonary contusion is one of the most common chest injuries and is frequently associated with flail chest. It is best characterized as a physical
damage to the lung parenchyma as well as other underlying tissues in the respiratory system resulting in hemorrhage and localized edema.
Pulmonary contusion is highly associated with trauma to the thoracic cavity resulting in a rapid compression and decompression to the chest wall such as a blunt forceful trauma to the chest. Pulmonary contusion represents a wide spectrum of lung injury characterized by the progressive development of infiltrates and varying degrees of respiratory dysfunction which if left untreated can lead to pulmonary distress and eventually respiratory failure. Although this condition is a common yet potentially life-threatening chest injury, mortality is often attributed to other closely associated injuries such as those sustained in a motor vehicular accident.
Pathophysiology of pulmonary contusion
The primary pathologic defect in pulmonary contusion is the abnormal and the copious accumulation of inter-alveolar and interstitial fluids in the alveolar spaces which hinders effective gas exchange. The injury is highly attributed to damage of the lung parenchyma and its vascular network which results in the extravasation of blood and serum proteins into the alveolar spaces. The leakage of blood and serum proteins alters the homeostatic oncotic pressure which is mainly responsible for the loss of fluid from the rich vascular network of the pulmonary circulation. Blood, edema and cellular debris (a normal immune response to cellular and tissue injury) enter the lungs which accumulate in the alveolar and bronchial levels where they interfere with the effective gas exchange.
This results in an increase in the pulmonary vascular resistance and pulmonary artery pressure significantly altering the saturation levels of the blood with the imbalance exchange of oxygen and carbon dioxide. The individual typically experiences hypoxemia and carbon dioxide retention resulting in respiratory acidosis. On rare occasions, the contused lungs occur mainly on the adjacent side of the impact of injury which is called as countercoup contusion.
Clinical manifestations of pulmonary contusion
Pulmonary contusion may be mild, moderate or severe. The clinical manifestations greatly vary from decreased breath sounds, increased heart rate and respiration cycles, hypoxemia, chest pains, central cyanosis and respiratory acidosis. Changes in sensorium including increased agitation, anxiety, combative irrational behavior, aggression and feeling of impending doom are a common sign of brain functioning deprived of oxygen. In addition, individuals with moderate contusion may expectorate copious amounts of mucus, serum and blood. It is also common that some individuals may have difficulty expectorating airway secretions despite constant coughing.
Medical management of pulmonary contusion
Treatment priorities normally include maintaining the airway, providing, adequate oxygenation and controlling pain, In mild cases of pulmonary
contusion, adequate hydration must be prioritized through the introduction of intravenous fluids and oral intake in order to liquefy secretions for easier mobilization and expectoration. Volume expansion techniques, postural drainage and chest physiotherapy including breathing and coughing exercises are helpful in clearing the airway and facilitating lung expansion. Antimicrobial medication may be prescribed for the treatment of pulmonary infection as this is a very common complication of pulmonary contusion because the fluid and blood that extravasated into the alveolar and interstitial spaces are considered an excellent medium for bacterial growth.