Fluid replacement may be required to ensure adequate blood volume, but fluids are given carefully since fluid overload can worsen pulmonary edema, which may be lethal. The severity ranges from mild to severe: small contusions may have little or no impact on health, yet pulmonary contusion is the most common type of potentially lethal chest trauma. It occurs in 30–75% of severe chest injuries. The risk of death following a pulmonary contusion is between 14 and 40%. Pulmonary contusion is usually accompanied by other injuries. Although associated injuries are often the cause of death, pulmonary contusion is thought to cause death directly in a quarter to half of cases. Children are at especially high risk for the injury because the relative flexibility of their bones prevents the chest wall from absorbing force from an impact, causing it to be transmitted instead to the lung. Pulmonary contusion is associated with complications including pneumonia and acute respiratory distress syndrome, and it can cause long-term respiratory disability. Classification
Pulmonary contusion and laceration are injuries to the lung tissue. Pulmonary laceration, in which lung tissue is torn or cut, differs from pulmonary contusion in that the former involves disruption of the macroscopic architecture of the lung, while the latter does not. When lacerations fill with blood, the result is pulmonary hematoma, a collection of blood within the lung tissue. Contusion involves hemorrhage in the alveoli (tiny air-filled sacs responsible for absorbing oxygen), but a hematoma is a discrete clot of blood not interspersed with lung tissue.
Other indications of thoracic trauma may be associated, including fracture of the sternum and bruising of the chest wall. Over half of fractures of the scapula are associated with pulmonary contusion. The contusion is frequently found underlying fracture sites. When accompanied by a fracture, it is usually concentrated into a specific location—the contusion is more diffuse when there is no fracture. Pulmonary lacerations may result from the same blunt or penetrating forces that cause contusion. Lacerations can result in pulmonary hematomas; these are reported to develop in 4–11% of pulmonary contusions. Epidemiology
Pulmonary contusion is found in 30–75% of severe cases of chest injury, making it the most common serious injury to occur in association with thoracic trauma. Of people who have multiple injuries with an injury severity score of over 15, pulmonary contusion occurs in about 17%. It is difficult to determine the death rate (mortality) because pulmonary contusion rarely occurs by itself. Usually, deaths of people with pulmonary contusion result from other injuries, commonly traumatic brain injury. It is controversial whether pulmonary contusion with flail chest is a major factor in mortality on its own or whether it merely contributes to mortality in people with multiple injuries. The estimated mortality rate of pulmonary contusion ranges from 14 to 40%, depending on the severity of the contusion itself and on associated injuries. When the contusions are small, they do not normally increase the chance of death or poor outcome for people with blunt chest trauma; however, these chances increase with the size of the contusion.