Flail Chest and Pulmonary Contusion

1 What are the most common injuries in patients sustaining blunt chest trauma?

Rib fractures are the most common injury after chest trauma, and multiple rib fractures leading to flail chest occur in 15% to 25% of patients. Pulmonary contusion is the most common intrathoracic injury, occurring in 40% to 60% of patients with blunt chest trauma. Although isolated pulmonary contusion may occur after an explosion injury, most trauma patients have concurrent injury to the chest wall.

2 What are the risk factors for adverse outcomes after blunt thoracic injury?

Thoracic injury and its complications are responsible for up to 25% of blunt trauma mortality. Increasing age and a larger number of rib fractures are most closely linked with increased complications. The greatest risk factors for mortality in patients with blunt chest trauma are age of 65 years or more, sustaining three or more rib fractures, and the presence of medical comorbidities, especially cardiopulmonary disease. Rib fractures cause intense pain and can lead to splinting of the chest with a rapid, shallow breathing pattern, as well as poor secretion clearance, increasing the risk for development of pneumonia. After injury, the development of pneumonia is a significant risk factor for mortality.

3 What is the sensitivity of chest radiograph for diagnosis of rib fractures?

Compared with a computed tomography (CT) scan, chest radiography misses approximately 50% of rib fractures. For stable patients with mild injury, the diagnosis of rib fracture is often clinical, with findings of significant pain and tenderness on examination. However, for patients with more severe injuries, any rib fracture or pulmonary contusion visible on the initial chest radiograph significantly increases the incidence of pulmonary morbidity or mortality.

4 What is a flail chest, and how is it diagnosed?

Flail chest is defined as fractures of three or more consecutive ribs or costal cartilages fractured in two or more places (Fig. 68-1). These fractured segments give rise to a free-floating portion of the thorax, which moves paradoxically throughout the respiratory cycle, with inward motion with inspiration and outward motion with exhalation. Although rib fractures may be diagnosed radiographically, flail chest is a clinical diagnosis. Patients often present with chest wall pain, tenderness, bruising, and palpable step-offs of the ribs, but flail chest is distinguished from other chest trauma by noting the paradoxical movement of the chest wall during spontaneous respiration. Patients receiving positive pressure ventilation usually do not demonstrate the classic paradoxical movements. Respiratory dysfunction usually does not arise from the paradoxical chest motion but rather is due to underlying contusions and splinting from pain.

Figure 68-1 Diagram illustrating respiratory dysfunction with flail chest.

5 What is a pulmonary contusion?

Pulmonary contusion is a bruise of the lung, with alveolar and interstitial hemorrhage and destruction of the pulmonary parenchyma. The subsequent inflammation leads to asymmetric edema, atelectasis, and poor mucous clearance from the airways. These factors lead to progressive ventilation-perfusion mismatch and loss of pulmonary compliance, which may be manifested clinically as progressive respiratory failure develops over the first 6 to 24 hours after the injury. Contusions tend to worsen over the 24 to 48 hours after injury and then slowly resolve within 7 days.

6 What is the role of radiographs in the diagnosis of pulmonary contusion?

Pulmonary contusions are diagnosed radiographically. Although initial chest radiographs may be unremarkable, a nonsegmental infiltrate typically develops over a 6-hour period. If the contusions are visible on the initial chest radiograph, the injury is likely to be more severe, and enlargement of the contused area on the radiograph over the next 24 hours is a poor prognostic sign. Classic radiograph patterns include irregular consolidations or a diffuse patchy pattern (Fig. 68-2). Even after development of chest radiograph findings, plain radiographs may underestimate the severity of the contusions. CT scan is more sensitive for diagnosis of pulmonary contusions and can quantify the volume of lung involved.

Figure 68-2 Radiograph of a patient with a pulmonary contusion.

7 What is the relationship among rib fractures, flail chest, and pulmonary contusions?

Pulmonary contusions often occur without flail chest and may even be present in the setting of minimal to no rib fractures. Flail chest, however, indicates that the chest wall sustained a large force, and therefore more than 90% of patients with flail chest have associated intrathoracic injuries, often pulmonary contusions. These patients also frequently have a hemothorax, a pneumothorax, or both. Patients with flail chest are likely to have additional traumatic injuries, including head injury and intraabdominal injuries. The pattern of rib fractures on imaging has been shown to be suggestive of other injuries in a recent series of trauma patients. Lower rib fractures were highly predictive of solid organ injury when compared with upper and midzone rib fractures, and scapular and sternal fractures were more common with upper zone fractures.

8 What is the relationship between pulmonary contusions and acute respiratory distress syndrome (ARDS)?

Patients with a pulmonary contusion are at higher risk than other patients for development of pneumonia and ARDS. The volume of lung parenchyma involved as determined by CT scan has been shown to be a risk factor for the development of ARDS, with patients having contusion volumes of greater than 20% being at the highest risk. Of these patients, ARDS has been shown to develop in approximately 80%.

9 What is the mortality rate and cause of death for patients with flail chest and pulmonary contusions?

The overall mortality rate of patients with blunt chest trauma is 16% with either a pulmonary contusion or flail chest to 42% when patients had both. Although these patients have severe thoracic injury, the most common cause of death in patients with flail chest and pulmonary contusions is brain injury.

10 What are the basic treatment strategies for flail chest or pulmonary contusions?

All trauma patients should be assessed with use of the principles of advanced trauma life support, directed at diagnosing and intervening in life-threatening injuries immediately. Using a primary survey, verifying the ABCs (airway, breathing, and circulation) is paramount. Prompt endotracheal intubation, tube thoracostomy for suspected hemopneumothorax, and mechanical ventilation are warranted in the unstable patient with chest trauma. For the stable patient with chest trauma, management centers around close monitoring of the respiratory status, pain control, aggressive lung physiotherapy, early mobilization, and adequate nutrition.

11 What are the pitfalls in pain management of patients with blunt chest trauma without an endotracheal tube in place?

Pain control is fundamental to the management of rib fractures to decrease chest wall splinting and alveolar collapse. Patients with pain due to rib fractures seek to minimize their chest wall motion by reducing their tidal volume and coughing effort. Delayed and inadequate pain control are common pitfalls in management of these patients. Effective pain control is a vital adjunct that permits patient mobilization, deep breathing, and secretion clearance, thereby decreasing the risk for pneumonia. Traditionally, intravenous narcotics were used in an attempt to control pain. Narcotic medications can be effective in relieving pain but can result in oversedation with resulting hypoventilation and can depress respiratory efforts and the cough reflex and increase the risk for aspiration. These drawbacks have prompted investigations into alternative therapies for pain control including intrapleural blocks, intercostal blocks, and paravertebral blocks. Several studies suggest that epidural analgesia provides optimal pain relief and may improve outcome in patients with blunt chest trauma. Unfortunately many trauma patients have spinal fractures or coagulopathy that precludes the use of epidural catheters.

12 Does the type of pain control influence the rate of pneumonia in patients with multiple rib fractures?

Pain is recognized as a contributing factor in the morbidity associated with rib fractures and pulmonary contusion. Multiple analgesia modalities have been used to manage pain in patients with rib fractures including oral analgesia, intermittent parenteral opioids, patient-controlled opioid analgesia, interpleural blocks, intercostal blocks, paravertebral blocks, and epidural analgesia. Retrospective studies of trauma patients with rib fractures have shown inconsistent benefits of epidural analgesia compared with other analgesic modalities. In one small (46 patients) prospective randomized trial, Bulger et al. found that the incidence of nosocomial pneumonia was reduced (18% vs. 38%) by epidural analgesia compared with parenteral opioids. However, a recent meta-analysis of epidural analgesia in patients with traumatic rib fractures failed to find a benefit in mortality, intensive care unit (ICU) length of stay, hospital length of stay, or duration of mechanical ventilation. Additional controlled studies comparing analgesic modalities are clearly needed.

13 What is the optimal fluid management strategy in patients with blunt chest trauma?

Judicious fluid resuscitation is required during the initial resuscitation of the patient with blunt chest trauma as the injured lung is prone to fluid overload while at the same time significant secondary injury can result from undertransfusion of fluids. Increased permeability of pulmonary capillaries that occurs early after a pulmonary contusion predisposes the patient to the development of tissue edema and worsening gas exchange. The use of colloid solutions for patients with pulmonary contusion has been advocated by some with the aim of maintaining plasma oncotic pressure and possibly withdrawing water from the contused lung, although no randomized trials exist that demonstrate a clear benefit from colloid administration in this setting. Current opinion on fluid replacement is in favor of ensuring adequate resuscitation to ensure end-organ perfusion followed by avoidance of further unnecessary fluid administration. This may be best achieved with early use of invasive monitoring or echocardiography to guide fluid replacement.

14 Which respiratory therapy procedure(s) should be used for patients with significant blunt chest trauma?

For patients with blunt chest trauma without an endotracheal tube in place, lung expansion therapy using incentive spirometry (IS), deep breathing, and coughing are critical to reduce secretions, prevent atelectasis, and avoid the need for intubation. All patients should have pain assessed and received maximal lung expansion therapy on an hourly basis. Underlying reactive lung disease should be optimized as well. In patients not meeting predicted goals with IS, either intermittent or continuous positive airway pressure (CPAP) therapy should be initiated. These modalities are often limited by the requirement of an awake, cooperative patient. Chest physical therapy consists of postural drainage, enhanced coughing maneuvers, chest vibration, and percussion. Prospective studies are lacking for efficacy, and chest percussion is obviously not well tolerated in patients with thoracic trauma. Nasotracheal suctioning is reserved for patients not able to effectively mobilize their secretions. Vigorous ambulation, when possible, remains the best method of restoring normal respiratory physiology.

15 Do all patients with flail chest require mechanical ventilation?

Recent studies have shown that a significant number of patients with flail chest and/or pulmonary contusion can be safely and effectively managed with aggressive pulmonary care including face mask oxygen, CPAP, and chest physiotherapy. CPAP restores functional residual capacity, improves compliance, and stabilizes the flail segment until the underlying pulmonary contusion resolves. CPAP, compared with intermittent positive pressure ventilation, has also been shown to lower mortality and nosocomial infections in patients who required mechanical ventilation. Noninvasive ventilation is particularly attractive for the patient who initially does not require emergent intubation and may decrease the need for subsequent intubation. Patients with frank shock or head injury do not make good candidates for noninvasive ventilation and are at high risk for aspiration. If noninvasive ventilation is attempted then close follow-up is essential as patients may fail and require endotracheal intubation. Early intubation and mechanical ventilation are essential in patients with refractory respiratory failure, shock, or other serious traumatic injuries.

16 What is the optimal mode of ventilation for patients with flail chest or pulmonary contusion?

The optimal mode of ventilation for patients with flail chest or pulmonary contusion continues to be debated. When required, mechanical ventilation strategies should be tailored to optimize oxygenation while minimizing the potential for secondary lung injury. In patients with ARDS, lung protective ventilation strategies using a volume- and pressure-limited approach have resulted in reductions in mortality. This strategy, although not clearly proved in the setting of pulmonary contusion, is aimed at reducing further ventilator trauma. Many of the newer modes of ventilation are consistent with a lung protective strategy and have shown promising results, but data are lacking showing superiority.

17 What is the role of positive end-expiratory pressure (PEEP) in the management of blunt chest trauma?

Providing a constant pressure throughout the respiratory cycle (PEEP) may recruit atelectatic lung regions and prevent the cyclic opening and closing of the airways, thereby reducing additional lung injury. Identifying optimal PEEP is complex, but in general the goal is to select a PEEP level that prevents derecruitment and allows for FiO₂ reduction. PEEP can have significant physiologic effects relevant to the trauma patient. Most notably, PEEP can significantly reduce venous return in the patient with hypovolemia. This can worsen hemodynamics in the setting of hemorrhagic shock. PEEP may also exacerbate ventilation-perfusion mismatch in patients with asymmetric pulmonary injury.

18 What are the indications for surgical stabilization of flail chest injuries?

Surgical stabilization of rib fractures and flail chest remains a controversial issue. Rib fixation can theoretically aid in a patient’s recovery by allowing the patient to mobilize and ventilate comfortably. Studies comparing surgical stabilization and conservative management are few and difficult to conduct because of the heterogeneity of thoracic trauma and other associated injuries.

The proponents of surgical stabilization claim a reduction in ventilator days, pulmonary complications, pain, and chest wall deformity. Proposed indications for rib fracture repair include flail chest; painful, movable rib fractures refractory to conventional pain management; chest wall deformity or defect; rib fracture nonunion; and during thoracotomy for other traumatic indication. A variety of fixation methods have been proposed, including pins, plates, wires, and struts. A prospective study by Tanaka et al. randomly assigned patients to either surgical fixation within 7 days of injury or mechanical ventilation alone. They demonstrated a reduction in pneumonia and ventilator and ICU days in those patients undergoing surgery. These results have not been duplicated in larger trials. Despite these reported benefits, stabilizations are seldom performed.

19 What is the long-term morbidity in flail chest injuries?

Few long-term follow-up studies regarding disability after flail chest injury are available. Outcome in patients with flail chest injuries with or without pulmonary contusion is difficult to delineate without accounting for the presence of other injuries. Flail chest appears to be associated with a worse outcome when compared with multiple rib fractures despite similar rates of lung contusion and extrathoracic injuries. A significant increase in mortality is related to increasing age in patients with a flail chest injury.

Patients with flail chest express fairly consistent symptoms in the few studies completed. Most complaints are subjective, such as chest tightness, pain, and decreased activity level. In a prospective study in 28 patients surviving severe chest injury, Livingston and Richardson found severe pulmonary dysfunction with pulmonary function tests (PFTs) at 40% to 50% of predicted within 2 weeks of hospital discharge but a trend of marked improvement that continued out to at least 18 months after discharge, with PFTs 65% to 90% of predicted. Only 5% of patients met criteria for pulmonary disability. In another study, Kishikawa et al. prospectively followed 18 patients with severe blunt chest trauma. They found that pulmonary function recovered within 6 months in patients without pulmonary contusion, even in the presence of severe residual chest wall deformity. However, patients with pulmonary contusion had decreased functional residual capacity and decreased supine PaO₂ for years afterward. Additional studies are clearly needed.

20 Are prophylactic antibiotics indicated in patients requiring a tube thoracostomy after chest trauma?

Use of antibiotics in patients with isolated chest trauma is controversial. Available studies offer conflicting results because of methodological limitations including small sample sizes, suboptimal antibiotic regimens, prolonged dosing, or variation in the patient populations involved. A recent meta-analysis suggests that prophylactic antibiotics in patients requiring tube thoracostomy can reduce the incidence of empyema and pneumonia. A level III recommendation by the Eastern Association for the Surgery of Trauma guidelines supports administration of a first-generation cephalosporin before tube thoracostomy placement and continued no longer than 24 hours. Although the question of prophylactic antibiotics is not settled, it appears that adequate drainage of a hemothorax and the use of appropriate sterile techniques are the key factors in reducing the risk for infection.