Pulmonary contusion in adults

INTRODUCTION — Pulmonary contusion, or "bruising" of the lung parenchyma, is relatively common in the setting of blunt trauma, occurring in 15 to 75 percent of patients [1]. The causes, severity, and resultant morbidity and mortality also vary widely [1]. A high index of suspicion and careful consideration of the impact a pulmonary contusion may have on overall injury care is key to achieving optimal patient outcomes.

The clinical features, diagnosis, and management of pulmonary contusion are reviewed. Additional information on associated injuries, such as rib fractures, is provided in separate topic reviews. (See "Inpatient management of traumatic rib fractures and flail chest in adults" and "Surgical management of severe rib fractures".)

DEFINITION AND MECHANISM OF INJURY — Lung contusion is direct or indirect damage to the lung parenchyma leading to edema or alveolar hematoma and loss of the physiologic function of the affected areas [2]. Injury to the lung parenchyma can result from blunt or penetrating trauma mechanisms.

Causes of pulmonary contusion include motorized vehicle collision (including motorcycles and all-terrain vehicles), falls, and assaults. Gunshot wounds may produce contusion in tissue adjacent to the missile tract. Less common in the civilian setting is contusion from blast injury [3]. While higher energy transfer injury mechanisms, such as falls from a height or motor vehicle collisions, result in more lungs with more contusions, even trivial mechanisms can result in pulmonary contusions. In an analysis of older adult blunt trauma patients, 18.6 percent had evidence of pulmonary contusion despite relatively low-energy mechanisms of injury [4]. Fortunately, these are often clinically insignificant.

ANATOMY AND PATHOPHYSIOLOGY — The fragile nature of lung tissue makes it prone to shear injury when subjected to significant energy or rapid deceleration. There is no literature supporting any particular lobe or segment (figure 1) as more commonly contused. Contusions often occur in the periphery of the lung but can also occur centrally.

Energy imparted on the chest wall results in peripheral contusions and is often associated with rib fractures. Compression waves following blast injury create a similar appearance. The shear effect on tissue adjacent fixed structures such as the pulmonary hilum can result in central lung contusion. Low-velocity gunshot wounds often create a discrete tract-related contusion, whereas higher-velocity wounds can cause contusion to an entire lobe.

The large amount of air-fluid interface within the lung makes the alveolar-capillary membrane prone to injury. Following energy transfer, the injured alveolus may partially or completely fill with blood or fluid. Edematous, thickened septal walls can also develop. As a result, gas exchange and lung compliance decrease while shunting around the injured area increases. An increase in vascular resistance and decreased flow has been postulated as a possible mechanism to minimize the impact of this resultant shunt [5]. This process worsens in the first one to three days following injury, resolving in approximately one week.

Interestingly, the inflammatory response may not be limited to the injured lung. Progression to the contralateral lung and systemic effects are possible, a potential explanation for the clinical worsening of patients sometimes seen in the days immediately after injury. A porcine model of pulmonary contusion showed a progression of similar alveolar dysfunction in the uninjured lung (assuming an initial unilateral injury) potentially mediated by platelet-derived thromboxane and endothelial-derived prostacyclin [6]. Inflammatory cytokines can increase systemically, causing at least a transient period of immunosuppression and theoretically increasing the risk for infection [7]. (See "Acute respiratory distress syndrome: Epidemiology, pathophysiology, pathology, and etiology in adults".)

TRAUMA EVALUATION — The initial resuscitation, diagnostic evaluation, and management of the patient with blunt or penetrating thoracic injury, including suspected pulmonary injury, are based upon protocols from the Advanced Trauma Life Support (ATLS) program, established by the American College of Surgeons Committee on Trauma. Complete details and steps involved in this evaluation are reviewed separately. The aspects relevant to the diagnosis of pulmonary contusion in the context of multisystem trauma are reviewed below. (See "Initial evaluation and management of blunt thoracic trauma in adults" and "Initial evaluation and management of chest wall trauma in adults" and "Initial evaluation and management of penetrating thoracic trauma in adults".)

History and physical — The clinical findings depend on the severity of the lung injury. Patients with mild contusion will likely be asymptomatic. Patients who have an associated chest wall contusion or a few rib fractures, usually from a ground-level fall, may have transient changes in heart rate or mild tachypnea mostly related to pain and not specifically due to the underlying contusion. On initial examination, the lungs are clear or slightly diminished in affected lung regions. Over time, breath sounds may become reduced over the injured area, and breathing difficulties and cough may develop.

For patients with moderate-to-severe contusion, usually following motorized vehicle collision, more obvious clinical signs will be apparent. This is especially true in contusions involving multiple segments, lobes, or bilateral injury. These patients may demonstrate shortness of breath, air hunger, or anxiety. Tachypnea and tachycardia are present. Lung sounds are diminished or absent on auscultation over the involved lobe or segments. Hemoptysis may develop but is usually mild and self-limited.

Associated injuries — Pulmonary contusion rarely occurs in isolation. Other pulmonary injuries of high-impact blunt chest trauma may include parenchymal laceration or tracheobronchial injury. Other associated injuries include:

●Chest wall injury – Not all pulmonary contusions have significant chest wall injury, but nearly all significant chest wall injury has associated pulmonary contusion. Rib fractures and sternal fractures are common; flail segments can also be seen. Apical lung contusion may accompany clavicle fractures or other injuries to the shoulder girdle. Blast injury from low-order explosives or blunt chest injury in young patients with a more compliant chest wall may result in contusion without rib fracture; otherwise, the clinician can expect to identify an associated chest wall injury. (See "Inpatient management of traumatic rib fractures and flail chest in adults".)

●Cardiovascular injury – Blunt cardiac injury may accompany lung contusion [8]. Since the most common arrhythmia associated with blunt cardiac injury is sinus tachycardia, diagnosis can be one of exclusion. Thus, patients with significant tachycardia despite judicious volume resuscitation and adequate analgesia generally undergo electrocardiogram to evaluate for blunt cardiac injury. Echocardiography can be used to evaluate patients who are hemodynamically unstable for structural or valvular abnormalities. (See "Management of cardiac injury in severely injured patients" and "Overview of blunt and penetrating thoracic vascular injury in adults".)

●Extrathoracic injury – Extrathoracic injury may also be present. Moderate-to-severe traumatic brain injury, upper spinal column fractures, blunt solid (eg, spleen, liver) or hollow organ injury, retroperitoneal hematoma, pelvic fracture, and extremity injury are all possible [8-10].

Clinical severity scoring — Scoring systems for pulmonary contusion are helpful from a research perspective but likely add little to clinical care. Efforts to correlate scores with contusion severity, complications, or the need for mechanical ventilation or mortality have proven difficult. The number of lobes involved, laterality, number of associated rib fractures, Glasgow Coma Scale score, and chest abbreviated injury score have all been used in various scales [11-15]. Most contain significant heterogeneity in the values used and are retrospective with poor predictive power. There is no clear superior scale used prospectively to guide clinical care. Two examples of such scoring systems include:

●American Association for the Surgery of Trauma (AAST) Organ Injury Scale (table 1).

●Blunt Pulmonary Contusion – 18 (BPC18) Score.

DIAGNOSIS — The diagnosis of pulmonary contusion relies on the demonstration of the injury on lung imaging studies. The appearance on lung imaging varies over time, and the sensitivity and specificity of the individual imaging modalities varies.

Lung imaging — For patients with suspected pulmonary contusion that is asymptomatic or mildly symptomatic, plain chest radiography or ultrasonography may suffice. For patients with more severe associated injuries at risk for more severe pulmonary contusion or with significant cardiopulmonary symptoms, we obtain computed tomography (CT) of the chest.

Chest radiography — Chest radiography is often performed as an adjunct to the primary survey. In all but the most severe cases, initial imaging is often normal. Pneumothorax or hemothorax may be seen on plain radiographs, which may be related to lung injury or rib or sternal fracture. Moderate-to-severe pulmonary contusion from high energy transfer are more likely to be seen on initial emergency department evaluation. In the author's clinical experience, these patients have a high incidence of severe acute respiratory distress syndrome. The area of contusion is described as a faint, hazy, or partially consolidated-appearing lung tissue, often at the periphery of the lung. (See 'Anatomy and pathophysiology' above.)

Lung ultrasonography — Lung ultrasonography may be the better screening tool compared with plain radiography for identifying pulmonary contusion. Because of the increased interstitial edema, additional artifacts are seen arising from the pleural line when contusion is present. In a meta-analysis that included 1681 chest trauma patients, the pooled sensitivity of ultrasonography for the detection of pulmonary contusion was 92 percent (95% CI 81-96), with a pooled specificity of 89 percent (95% CI 85-93) [16]. For radiography, sensitivity was 44 percent (95% CI 32-58) while specificity was 98 percent (95% CI 88-100).

Computed tomography — Thoracic CT scanning is recommended for a variety of potential thoracic injuries and should also be obtained in any patient with a significant mechanism that suggests pulmonary injury. CT should also be obtained in patients with symptoms of hypoxemia, tachycardia, or metabolic acidosis.

Multidetector thoracic CT scan is sensitive for even the most subtle pulmonary contusions, including clinically insignificant pulmonary contusion [17], showing the injury anatomy in three dimensions. Thoracic CT defines the location and extent of pulmonary contusion and identifies associated injuries.

The following findings suggest pulmonary contusion on thoracic CT [3]:

●Focal crescentic ground glass opacities (interstitium and vasculature remain visible), and affected areas are not necessarily confined to a particular lobe or segment.

●Subpleural sparing often present in smaller contusions, which can distinguish these from pneumonia or other lung pathology.

●Demonstration of rib fracture(s) overlying parenchymal abnormalities.

●Peribronchovascular changes associated with blast injury.

Differential diagnosis — The differential diagnosis of pulmonary contusion includes other pulmonary entities with similar imaging features; however, these are not necessarily related to other associated injuries. With atelectasis, consolidation is confined to the posterior chest in a supine patient. With aspiration, consolidation is often confined to a particular lower lobe. Pulmonary laceration may be from penetrating trauma or displaced rib fracture and may initially appear similar to pulmonary contusion on chest radiography [3]. An infectious etiology such as pneumonia should be considered several days after injury when the initial findings fail to resolve.

MANAGEMENT — Management of pulmonary contusion is predominantly supportive but may include tube thoracostomy for hemothorax/pneumothorax or surgery to stabilize the chest wall in the case of severe rib fractures. For severe injuries that have destroyed the pulmonary architecture, pulmonary resection may be necessary. About 90 percent of thoracic trauma patients can be treated with supportive methods [8].

It is important to control hemorrhage from other sources before focusing on supportive care of pulmonary contusion, though at times damage control surgery may be focused on injuries to the lung itself, which may require lung resection [18,19]. (See "Overview of pulmonary resection", section on 'Traumatic injury'.)

The principles of damage control and resuscitation should be followed with hemorrhage control, timely surgery, early stabilization of long-bone fractures, and appropriate prophylaxis (eg, venous thromboembolism prophylaxis). Respect the possibility that progressive organ dysfunction may play a significant role in subsequent resource utilization and outcome. However, perioperative management can become difficult if a progressing pulmonary contusion impedes oxygenation or ventilation. Less well defined is which aspect contributes most to pulmonary dysfunction and ultimately morbidity and mortality: the contusion or the associated injury [20,21]. (See "Overview of damage control surgery and resuscitation in patients sustaining severe injury" and 'Mortality and complications' below.)

Supportive care — Supportive care for pulmonary contusion includes pain control, pulmonary support, judicious fluid administration, and early mobilization. Repeat imaging is obtained to follow progress, as needed. With appropriate support, mild symptoms often resolve within 24 to 48 hours from injury.

The importance of careful observation and anticipating clinical worsening until consistent improvement is seen cannot be overstated. Mild-to-moderate injury begins to improve within three to five days and is often resolved within one week. More severe injuries may continue to worsen beyond the usual time frame. This severe degree of contusion may take up to three weeks to resolve.

In addition to the pulmonary injury and associated injuries, management of the patient's pre-existing medical comorbidities should be incorporated into the care plan. Home medications should be resumed early, particularly any heart rate control agents, statins, and diuretics. The patient can be transitioned from the intensive care unit (ICU) to a monitored or other setting once oxygen and ventilation are normalizing and exercise tolerance is consistently improving. A balanced but conservative approach will mitigate risk of unplanned ICU return or readmission.

Pain control — Pain is a natural consequence of the disease process and because pulmonary contusion is commonly associated with rib fractures and other painful associated injuries, successful analgesia is an important intervention to ensure favorable outcomes [22]. (See "Pain control in the critically ill adult patient".)

Pain management in patients with traumatic rib fractures and flail chest are reviewed separately. (See "Inpatient management of traumatic rib fractures and flail chest in adults", section on 'Pain control'.)

Pulmonary support — Supportive pulmonary measures aim to reduce the need for intubation and include measures to improve pulmonary volume expansion and management of secretions.

●Support oxygenation – Hypoxemia requires supplemental oxygen administered using an appropriate delivery device for the situation (eg, nasal cannula, high-flow, mask). For patients with pulmonary contusion and significant hypoxemia, a high-flow nasal cannula is likely preferred to noninvasive positive-pressure ventilation [23,24]. High-flow cannulas may match patient needs better while avoiding complications, such as gastrointestinal distention, pressure injury to the face, and worsened anxiety/delirium. Mild-to-moderate contusions likely require short-duration supplemental oxygen therapy from a standard delivery device. It is important to titrate oxygen therapy to the patient's symptoms, rather than simply based on spot saturation values obtained perhaps during routine vital signs checks. Symptom evaluation should also occur during mobility exercises or ambulation, not only at rest. This provides a more accurate assessment of the patient's need and readiness for discontinuation.

●Support ventilation – It is also important to institute measures to prevent atelectasis or poor chest wall mechanics that lead to respiratory failure, unplanned intubation, and prolonged ICU stay. We use a standardized approach to respiratory care based on age, incentive spirometry volume, and presence of and number of associated rib fractures. Depending on the clinical scenario, treatment may include one or a combination of simple cough assist, positive expiratory pressure (PEP), intrapulmonary percussive ventilation, or high-frequency chest wall oscillation (shake vest) every four or six hours. Documentation of progress leads to de-escalation of therapy, but any changes require consultation with the management team. Simpler hand-held devices such as incentive spirometry or vibratory PEP can be administered more frequently by the patient or by nonrespiratory therapy providers [25].

●Intubate only when necessary – Elevated end-tidal carbon dioxide values from noninvasive monitoring may identify worsening gas exchange that requires mechanical ventilation. The decision to intubate and initiate mechanical ventilatory support has evolved greatly [26]. Obligatory mechanical ventilation in the absence of respiratory failure with the idea of decreasing progression of pulmonary contusion or with a goal of stabilizing the chest wall should be avoided [1]. In the past, early intubation was encouraged, but this practice led to prolonged lengths of stay and an increased rate of complications [27,28]. Patients should only be intubated for appropriate clinical indications of progressive or refractory hypoxemia or hypoventilation. Using this strategy, later studies demonstrated decreased ventilator days and improved mortality [28].

●Extubate as soon as possible – Patients requiring mechanical ventilation should be supported in a manner based on institutional and physician preference and separated from the ventilator at the earliest possible time [1]. No mode of mechanical ventilation has been shown to be superior to another for the management of pulmonary contusion and is there no evidence to definitively support alternative modes (eg, airway pressure release ventilation, high-frequency oscillatory ventilation, or independent lung ventilation). For patients who require ventilation, we follow a lung-protective strategy. (See "Acute respiratory distress syndrome: Ventilator management strategies for adults", section on 'Low tidal volume ventilation: Initial settings'.)

Patients with prolonged ICU and overall length of stay often require tracheostomy; this should be done within 10 days of admission to lessen the impact of potential subglottic stenosis. (See "Tracheostomy: Rationale, indications, and contraindications".)

Avoid fluid overload — Contemporary injury resuscitation advocates for the use of good clinical judgment, or "judicious" volume administration that maintains signs of adequate tissue perfusion. While it seems reasonable to presume that excessive volume will exacerbate the progressive alveolar edema seen in pulmonary contusion, trials have provided mixed outcomes [29,30]. Outcomes appear to be more related to severity of initial pulmonary dysfunction or associated chest wall injury. As a result, the management of pulmonary contusion is within the context of other injuries. Seriously injured patients are appropriately monitored for signs of hypovolemia and treated using appropriate endpoints of resuscitation to ensure adequate oxygen delivery while avoiding overload. (See "Ongoing assessment, monitoring, and resuscitation of the severely injured patient", section on 'Fluid therapy'.)

Monitoring and repeat imaging — Patients are monitored with clinical examination and serial radiographic imaging studies. For mild-to-moderate contusion, we plan on follow-up plain radiographic imaging, at least once, to ensure improvement or resolution of the contusion(s). The timing is best determined clinically based on the patient's progress. For severe injury likely requiring more intensive supportive care, radiographs are needed more frequently. Daily initially, then less frequently as the patient's condition improves. Repeat CT imaging can be reserved for patients with delayed bleeding, persistent air leak, or other findings that require more complicated medical decision making.

While there is some disagreement, we suggest aggressive surveillance and initiation of empiric antimicrobial agents when pulmonary contusion fails to resolve and pneumonia is suspected, and quantitative cultures confirm the diagnosis. (See "Treatment of hospital-acquired and ventilator-associated pneumonia in adults", section on 'Empiric therapy'.)

Surgery

Chest wall stabilization — Surgical chest wall stabilization is an option for patients in whom pain control remains suboptimal. Some studies demonstrate the effectiveness of fracture fixation, but only one study has directly addressed this issue in the setting of pulmonary contusion [31]. In our practice, we reserve surgery for chest volume loss, intractable pain, failure to separate from mechanical ventilation, or thoracotomy for another indication (algorithm 1). It is important to differentiate failure to wean due to the pulmonary contusion from failure to wean because of pain associated with rib fractures. The latter will improve with rib fracture fixation, whereas the former will not. However, the decision to operate should be made early; fixation beyond approximately 10 days can become technically challenging. (See "Surgical management of severe rib fractures".)

Pulmonary surgery — Lung intervention of pulmonary resection may be beneficial in a select few cases where the contusion is so severe that a segment or lobe has become nonfunctional or has become a site of significant infection [32-34]. Unfortunately, sufficient literature does not exist to guide those decisions. (See "Overview of pulmonary resection".)

MORTALITY AND COMPLICATIONS — Mortality related to pulmonary contusion depends on the presence of associated severe thoracic injuries (particularly associated flail chest injury or thoracic spinal injury), injury severity score, presence of shock, and mechanism of injury (eg, falls from a height) [20]. In a review of 144 patients with pulmonary contusion or flail chest, mortality was 16 percent for isolated pulmonary contusion but 42 percent when there was a combined injury [20]. In another review of 84 patients with pulmonary contusion with or without either flail chest or upper thoracic spinal cord injury, overall mortality was higher when all three injuries were present (41 percent) compared with the combination of pulmonary contusion and flail chest (6 percent) or pulmonary contusion and upper spinal cord injury (4.3 percent) [9]. Mortality at six months when all three injuries were present was 71 percent.

The main complications following thoracic trauma depend on the mechanism, with pneumonia more common following blunt injury and retained hemothorax for penetrating injury [35]. The risk for health care-associated or ventilator-associated pneumonia is increased in patients with pulmonary contusion and associated injuries. In one review, 321 of 1448 patients (22 percent) with rib fractures had pulmonary contusion [36]. The incidence of pneumonia or empyema was significantly increased for those with moderate or severe pulmonary contusion compared with those without pulmonary contusion. By contrast, in a review 160 patients, 91 with pulmonary contusion and 72 without, who required at least 24 hours of mechanical ventilation, the incidence of pneumonia was similar (47 versus 44 percent) [37].

The risk for respiratory failure, acute respiratory distress syndrome, and late sequelae including reduced pulmonary function increases with increasing severity of pulmonary contusion and the occurrence of other severe chest wall injuries, particularly flail chest [38-40].

Another late complication that has been described is pulmonary fibrosis at the site of injury. There is insufficient evidence to make a comment about the clinical relevance, and prior work with steroids showed no benefit and is not recommended.

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: Thoracic trauma" and "Society guideline links: General fracture and stress fracture management in adults" and "Society guideline links: General issues of trauma management in adults".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Rib fractures in adults (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Pulmonary contusion – Pulmonary contusion, or "bruising" of the lung parenchyma, is the consequence of forces impacting the chest and is most commonly due to blunt injuries (eg, motorized vehicle collision, falls, assault), but penetrating injuries (eg, gunshot) can also cause pulmonary contusion. (See 'Definition and mechanism of injury' above.)

●History and physical – The trauma history provides important information about the potential severity of pulmonary contusion and likely associated injuries. (See 'History and physical' above.)

Clinical findings depend on the severity of the lung injury.

•Mild contusion – Patients with mild contusion will likely be asymptomatic. Pain from underlying rib fractures may cause tachycardia or mild tachypnea. Lungs are clear or slightly diminished in affected lung regions. Over time, breath sounds may become reduced over the injured area, and breathing difficulties and cough may develop.

•Moderate-to-severe contusion – Patients with moderate-to-severe contusion have more obvious clinical signs, particularly if multiple segments or lobes are involved. Patients may have shortness of breath, air hunger, or anxiety. Tachypnea and tachycardia are present. Lung sounds are diminished or absent on auscultation over the involved lobe or segments. Hemoptysis may develop but is usually mild and self-limited.

●Associated injuries – Pulmonary contusion rarely occurs in isolation. Associated injuries may include chest wall injury (eg, rib fracture, sternal fracture, clavicle fracture), cardiovascular injury (blunt cardiac injury), and extrathoracic injury (spine fracture, solid organ injury, hollow viscus injury). (See 'Associated injuries' above.)

●Diagnosis – The diagnosis of pulmonary contusion relies on the demonstration of the injury on lung imaging studies. For patients with suspected pulmonary contusion that is asymptomatic or mildly symptomatic, plain chest radiography or lung ultrasonography may suffice. For patients with associated injuries at risk for more severe pulmonary contusion or with significant cardiopulmonary symptoms (hypoxemia, tachycardia, or metabolic acidosis), we obtain CT of the chest. CT of the chest is highly accurate for showing the location and extent of pulmonary contusion. (See 'Diagnosis' above.)

●Management – Management of pulmonary contusion is primarily supportive and includes aggressive pain control, supportive pulmonary care, thoracostomy drainage for pneumothorax/hemothorax (when present), and judicious fluid resuscitation to reduce edema in the contused lung. (See 'Management' above.)

•Pain control – Adequate pain control is fundamental for tolerating deep breathing and coughing, particularly in patients with chest wall injuries. Pain control can generally be achieved with an escalating multimodal regimen (algorithm 1). (See 'Pain control' above.)

•Supportive pulmonary care – Supportive pulmonary measures aim to reduce the need for intubation and include volume expansion and managing secretions. Patient who are not intubated need to be closely monitored for respiratory distress. (See 'Pulmonary support' above.)

●Surgical management – For patients with associated rib fractures experiencing uncontrolled pain or worsening pulmonary function, surgical rib stabilization is an option (picture 1). Pulmonary resection may be needed to manage severe injuries in which the pulmonary architecture has been destroyed. (See 'Surgery' above.)

●Mortality and complications – Mortality from pulmonary contusion is directly related to the severity of contusion, injury severity (ie, associated injuries), and age. Complications include pneumonia (most common), retained hemothorax or empyema, and respiratory failure requiring intubation. The risk of pneumonia is related to the severity of contusion; pneumonia is also a risk factor for developing empyema or respiratory failure. (See 'Mortality and complications' above.)