Pulmonary contusion
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Pulmonary contusion is injury to the lung parenchyma caused by blunt chest trauma, resulting in edema and bleeding into the alveolar spaces. It is commonly caused by motor vehicle accidents. Clinically, patients may experience respiratory distress, coughing blood, and decreased breath sounds. Chest x-rays often under-estimate the injury, while CT scans can detect contusions immediately and assess severity. Treatment involves supportive care, oxygen supplementation, ventilation if needed, and prevention of complications like ARDS and pneumonia. Most contusions resolve within a week but can occasionally lead to long-term lung issues.
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Pulmonary contusion
- 2. Outline • Introduction • Epidemiology • Etiology • Types • Pathophysiology • Clinical presentation • Investigations • Management • Complications • Prognosis
- 3. Introduction • A pulmonary contusion (or lung contusion) is injury to the lung parenchyma leading to edema and blood accumulating in the alveolar spaces and loss of normal lung structure and function. • A pulmonary contusion is usually caused by blunt trauma but can also result from explosion injuries or a shock wave associated with penetrating trauma. • The forces associated with blunt thoracic trauma can be transmitted to the lung parenchyma. This results in pulmonary contusion, characterized by development of pulmonary infiltrates with hemorrhage into the lung tissue
- 5. Epidemiology • Globally, 10% of all trauma admissions result from chest injuries and 25% of trauma-related deaths are attributable to chest injuries. • In Tanzania, trauma including chest injuries continues to be one of the leading causes of morbidity among the young and old with an estimated mortality of 40%. In Bugando Medical Centre, chest trauma has been commonest cause of surgical admission and contributes significantly to high morbidly and mortality . • In a study done at MNH, out of 119 patients with chest injuries, lung contusion was found in 25 (21%) of the cases. • The causes and pattern of chest injuries have been reported in literature to vary from one part of the world to another partly because of variations in infrastructure, civil violence, wars and crime. Motor traffic accidents are the commonest cause accounting for up to 70% in some cases.
- 6. Etiology • In blunt trauma, pulmonary contusion is usually caused by the rapid deceleration that results when the moving chest strikes a fixed object. About 70% are due to MVAs, other causes include; falls, sport injuries and assaults. • Penetrating trauma can cause pulmonary contusion. It usually surrounds the path along which the projectile traveled through the tissue. The pressure wave forces tissue out of the way, creating a temporary cavity; the tissue readily moves back into place, but it is damaged.
- 8. Pathophysiology Bleeding and edema Consolidation and collapse Ventilation and perfusion mismatch Pulmonary hypoxic vasoconstriction with increased vascular resistance If it is severe enough, the hypoxemia resulting from fluid in the alveoli cannot be corrected just by giving supplemental oxygen; this problem is the cause of a large portion of the fatalities that result from trauma.
- 9. Clinical presentation • Clinical findings in pulmonary contusion depend on the extent of the injury. • Patients present with varying degrees of respiratory difficulty. • Symptoms include: respiratory distress, coughing up blood or bloody sputum, bronchorrhea (production of watery sputum), wheezing • Signs include: dyspnea, tachypnea, tachycardia, hypotension, ecchymosis • Respiratory system examination demonstrates decreased breath sounds over the affected area or crackles may be appreciated and tenderness may be elicited if there is associated chest wall injury.
- 10. Investigations • Chest x – ray – Patch irregular infiltrates to frank consolidation which often does not localize in a lobar or segmental pattern • However it will often under-estimate the size of the contusion and the true extent of injury is not apparent on plain films until 24-48 hours following injury • General imaging differential considerations include: aspiration pneumonia, segmental / focal atelectasis, pulmonary hemorrhage.
- 12. Computed tomography (CT) • More sensitive • Unlike X-ray, CT scanning can detect the contusion almost immediately after the injury. • Helps determine the size of the contusion which often tend to correlated with the overall prognosis • Wagner and Miller have determined that the pulmonary contusion can be divided into mild, moderate and severe based on the size of the contused portion of the lung. • Mild (<18%), Moderate (18 – 28%) and severe (>28%)
- 13. A CT scan showing a pulmonary contusion (red arrow) accompanied by a rib fracture (blue arrow)
- 14. Management • The primary treatment is supportive and efforts should be directed in diagnosing critical concordant chest injuries and providing supplemental oxygen to treat hypoxia. • The ATLS course manual states: “Patients with significant hypoxia i.e. paO2< 65mmHg SpO2< 90% should be intubated and ventilated within the first hour of injury” • Intubation should be provided with the goal of reducing the edema, improving the functional residual capacity and decreasing hypoxemia. • Positive end expiratory pressure via mechanical ventilation (PEEP) or non – invasive positive pressure ventilation remains controversial as the optimal treatment and therefore should be use with caution on case by case basis.
- 15. Fluid resuscitation • Controversy – hypervolemia vs. hypovolemia • Current standard of care – maintenance of euvolemia
- 16. Other Supportive care: • Pain control • Pulmonary toilet – suctioning, deep breathing, coughing • Chest physiotherapy – breathing exercises, percussion • Optimal positioning – placing the good lung in a dependent position
- 17. Complications • Adult respiratory distress syndrome – in up to 38% of patients • Pneumonia – inability to clear bacteria and secretions; intubation and mechanical ventilation further increases the risk. Up to 50% of patients tend to develop a bacterial respiratory infection.
- 18. Prognosis • Most resolve 5 to 7 days after injury • Signs detectable by radiography are usually gone within 10 days after injury • Lung fibrosis with decreased functional residual capacity can occur up to 6 years after injury • Contusion can also permanently reduce the compliance of the lungs • A larger contusion is associated with an increased risk.
- 19. References 1. East and Central African Journal of Surgery, Vol. 15, No. 1, Mar-Apr, 2010, pp. 124-129 The Pattern and Management of Chest Trauma at Muhimbili National Hospital, Dar es Salaam. F.A. Massaga, M. Mchembe 2. http://www.cardiothoracicsurgery.org/content/6/1/7 3. http://en.wikipedia.org/wiki/Pulmonary_contusion 4. Pattern and outcome of chest injuries at Bugando Medical Centre in Northwestern Tanzania. Monafisha K Lema, Phillipo L Chalya, Joseph B Mabula and William Mahalu
Editor's Notes
- Bleeding and edema[edit] In contusions, torn capillaries leak fluid into the tissues around them.[33] The membrane between alveoli and capillaries is torn; damage to this capillary–alveolar membrane and small blood vessels causes blood and fluids to leak into the alveoli and the interstitial space (the space surrounding cells) of the lung.[11] With more severe trauma, there is a greater amount of edema, bleeding, and tearing of the alveoli.[17] Pulmonary contusion is characterized by microhemorrhages (tiny bleeds) that occur when the alveoli are traumatically separated from airway structures and blood vessels.[24] Blood initially collects in the interstitial space, and then edema occurs by an hour or two after injury.[30] An area of bleeding in the contused lung is commonly surrounded by an area of edema.[24] In normal gas exchange, carbon dioxide diffuses across the endothelium of the capillaries, the interstitial space, and across the alveolar epithelium; oxygen diffuses in the other direction. Fluid accumulation interferes with gas exchange,[34] and can cause the alveoli to fill with proteins and collapse due to edema and bleeding.[24] The larger the area of the injury, the more severe respiratory compromise will be.[17] Consolidation and collapse[edit] Pulmonary contusion can cause parts of the lung to consolidate, alveoli to collapse, and atelectasis (partial or total lung collapse) to occur.[35] Consolidation occurs when the parts of the lung that are normally filled with air fill with material from the pathological condition, such as blood.[36] Over a period of hours after the injury, the alveoli in the injured area thicken and may become consolidated.[24] A decrease in the amount of surfactant produced also contributes to the collapse and consolidation of alveoli;[16] inactivation of surfactant increases their surface tension.[31] Reduced production of surfactant can also occur in surrounding tissue that was not originally injured.[26] Inflammation of the lungs, which can result when components of blood enter the tissue due to contusion, can also cause parts of the lung to collapse. Macrophages, neutrophils, and other inflammatory cells and blood components can enter the lung tissue and release factors that lead to inflammation, increasing the likelihood of respiratory failure.[37] In response to inflammation, excess mucus is produced, potentially plugging parts of the lung and leading to their collapse.[24] Even when only one side of the chest is injured, inflammation may also affect the other lung.[37] Uninjured lung tissue may develop edema, thickening of the septa of the alveoli, and other changes.[38] If this inflammation is severe enough, it can lead to dysfunction of the lungs like that seen in acute respiratory distress syndrome.[39] Ventilation/perfusion mismatch[edit] Normally, the ratio of ventilation to perfusion is about one-to-one; the volume of air entering the alveoli (ventilation) is about equal to that of blood in the capillaries around them (perfusion).[40] This ratio is reduced in pulmonary contusion; fluid-filled alveoli cannot fill with air, oxygen does not fully saturate the hemoglobin, and the blood leaves the lung without being fully oxygenated.[41] Insufficient inflation of the lungs, which can result from inadequate mechanical ventilation or an associated injury such as flail chest, can also contribute to the ventilation/perfusion mismatch.[31] As the mismatch between ventilation and perfusion grows, blood oxygen saturation is reduced.[41] Pulmonary hypoxic vasoconstriction, in which blood vessels near the hypoxic alveoli constrict (narrow their diameter) in response to the lowered oxygen levels, can occur in pulmonary contusion.[27] The vascular resistance increases in the contused part of the lung, leading to a decrease in the amount of blood that flows into it,[38] directing blood to better-ventilated areas.[27] Although reducing blood flow to the unventilated alveoli is a way to compensate for the fact that blood passing unventilated alveoli is not oxygenated,[27] the oxygenation of the blood remains lower than normal.[40] If it is severe enough, the hypoxemia resulting from fluid in the alveoli cannot be corrected just by giving supplemental oxygen; this problem is the cause of a large portion of the fatalities that result from trauma.[41]
- The administration of fluid therapy in individuals with pulmonary contusion is controversial.[41] Excessive fluid in the circulatory system (hypervolemia) can worsenhypoxia because it can cause fluid leakage from injured capillaries (pulmonary edema), which are more permeable than normal.[31][43] However, low blood volume (hypovolemia) resulting from insufficient fluid has an even worse impact, potentially causing hypovolemic shock; for people who have lost large amounts of blood, fluid resuscitation is necessary
- Supportive care[edit] Retaining secretions in the airways can worsen hypoxia[60] and lead to infections.[4] Thus, an important part of treatment is pulmonary toilet, the use of suction, deep breathing, coughing, and other methods to remove material such as mucus and blood from the airways.[7] Chest physical therapy makes use of techniques such as breathing exercises, stimulation of coughing, suctioning, percussion, movement, vibration, and drainage to rid the lungs of secretions, increase oxygenation, and expand collapsed parts of the lungs.[61] People with pulmonary contusion, especially those who do not respond well to other treatments, may be positioned with the uninjured lung lower than the injured one to improve oxygenation.[43] Inadequate pulmonary toilet can result in pneumonia.[40] People who do develop infections are given antibiotics.[17] No studies have yet shown a benefit of using antibiotics as a preventative measure before infection occurs, although some doctors do recommend prophylactic antibiotic use even without scientific evidence of its benefit.[13] However, this can cause the development of antibiotic resistant strains of bacteria, so giving antibiotics without a clear need is normally discouraged.[20] For people who are at especially high risk of developing infections, the sputum can becultured to test for the presence of infection-causing bacteria; when they are present, antibiotics are used.[27] Pain control is another means to facilitate the elimination of secretions. A chest wall injury can make coughing painful, increasing the likelihood that secretions will accumulate in the airways.[62] Chest injuries also contribute to hypoventilation (inadequate breathing) because the chest wall movement involved in breathing adequately is painful.[62][63] Insufficient expansion of the chest may lead to atelectasis, further reducing oxygenation of the blood.[35] Analgesics (pain medications) can be given to reduce pain.[12] Injection of anesthetics into nerves in the chest wall, called nerve blockade, is another approach to pain management; this does not depress respiration the way some pain medications can.[31]