Clinical exam findings
Patients with a flail chest will have considerable pain with movement and respiration, and will often have obvious soft tissue injury (abrasions, contusions, etc.) over the injured site. Paradoxical chest wall motion is the classic sign of flail chest, but may not initially be present if muscular splinting of the chest wall stabilizes the segment in place. If the patient is intubated and receiving PPV during your clinical examination, paradoxical chest wall movement may not be observable, as PPV “splints” the segment internally. Palpation of the injured area will most likely elicit tenderness or pain. In addition, crepitus and obvious loss of chest wall integrity may be palpated.
Patients with mild to moderate flail chest injury and no signs of respiratory failure can be managed with the administration of high-flow supplemental oxygen, cardiac monitoring and IV initiation with analgesia for pain control. Reducing the pain that accompanies respiration can encourage deeper breaths and increase tidal volume, decreasing the work of breathing and correcting hypoxia. Accordingly, the reduction of pain is of paramount importance in the treatment of flail chest in the conscious patient.
Patients with a flail chest and respiratory distress will likely require PPV with a bag-valve mask, and those with respiratory failure may require endotracheal intubation. PPV will serve to splint the flail segment internally and increase tidal volume, reversing developing hypoxia.
In addition to an intact chest wall, an intact and functioning pulmonary system and intrathoracic environment are required to ensure adequate ventilation. Hypoxia can develop secondary to injuries to the tracheobronchial tree, the visceral or parietal pleura, or the lung itself. Common pulmonary injuries include pulmonary contusion, simple and open pneumothorax, tension pneumothorax, hemothorax and traumatic asphyxia.
A pulmonary contusion is a bruise on the lung parenchyma. Pulmonary contusion is reported to be present in 23% of patients with significant blunt chest trauma, and occurs most often from automobile collisions with rapid deceleration.3 Pulmonary contusions can also occur from the cavitational forces generated when a high-velocity projectile such as a bullet travels through the lung, or secondary to shock waves traveling through water or air, as with an explosion.
Regardless of the mechanism, injury to the lung results in injury to capillaries and the leaking of blood into the lung tissue and alveoli. This collection of fluid in the alveoli interferes with normal alveolar-capillary gas exchange. As the patient attempts to compensate, tachypnea and respiratory alkalosis can occur. Lung sounds may be coarse with rhonchi or even diminished or absent. Tachycardia and eventually shock will ensue if things are not corrected, along with respiratory failure.
A pneumothorax occurs when air collects in the pleural space between the lung and the inside of the chest wall. It is a common complication of blunt and penetrating chest trauma and is present by default in every patient with penetrating injuries that pass through the parietal and visceral pleura. Pneumothoraces are classified as simple, open or tension.
A simple pneumothorax occurs when a hole in the visceral pleura allows air to escape the lung and collect in the pleural space. A simple pneumothorax is most often caused when a fractured rib lacerates the pleura. It may also occur without a fracture when blunt trauma is delivered at full inspiration with the glottis closed (holding your breath), resulting in a dramatic spike in intra-alveolar pressure and alveolar rupture. This mechanism is known as the paper bag syndrome.
An open pneumothorax occurs when a hole in the chest wall and pleura allows air to collect in the pleural space. The violation of the pleural space eliminates the normally negative intrapleural pressure that exists between the lung and chest wall, causing the affected lung to collapse. Air may move in and out of the hole in the chest wall with inspiration, resulting in a sucking chest wound.