Trauma to the chest may severely compromise the function of the heart or lungs, leading to cardiogenic shock and hypoxia.
Of the several causes that may alter respiration after trauma, tension pneumothorax, flail chest, and open pneumothorax are immediate threats to the patient's life and therefore require rapid diagnosis and treatment. Hemothorax, closed pneumothorax, pulmonary contusion, diaphragmatic rupture with herniation of abdominal contents into the thorax, and atelectasis from a mucous plug, aspiration, or chest wall splinting can also interfere with breathing and pulmonary gas exchange and deteriorate into life-threatening complications.
A tension pneumothorax develops when air enters the pleural space from the lung or through the chest wall via a one-way valve- like opening, which allows entry of air but no exit. The progressively increasing intrathoracic pressure in the affected hemithorax leads to complete collapse of the affected lung, shifting the mediastinum (the section of the chest between the lungs, where the heart, esophagus and phrenic and vagus nerves are situated) toward the contralateral side, and severely impairing central venous return. In addition to ipsilateral (located on or affecting the same side of the body) lung collapse, compression of the contralateral (located on or affecting the opposite side of the body) lung occurs by the displaced mediastinum, further impairing ventilatory capacity, resulting in hypoventilation and hypoxemia. Decreased venous return by elevated intrathoracic pressure leads to profound hypotension and cardiac arrest if untreated.
Clinically, tension pneumothorax is characterized by chest pain, dyspnea, tachycardia, hypotension, distended neck vein, contra lateral tracheal deviation, and ipsilateral lung hyperresonance to percussion with the absence of breath sounds by auscultation.
Insertion of a 14-gauge cannula (Figure 5.2) 3-6 cm long into the second intercostal space at the midclavicular line (Figure 5.3) will convert a tension pneumothorax to an open pneumothorax. Definitive treatment includes chest tube (Figure 5.3) placement.
A simple pneumothorax is an accumulation of air between the parietal and visceral pleura. The ipsilateral collapse of lung tissue results in a severe ventilation/perfusion abnormality and hypoxia. The overlying chest wall is hyperresonant to percussion, breath sounds are decreased or absent, and a chest film confirms lung collapse. Treatment includes placement of a chest tube in the fourth or fifth intercostal space, anterior to the midaxillary line. A persistent air leak following chest tube placement may indicate injury to a major bronchus.
Open Pneumothorax ("Sucking chest wound"): Open pneumothorax results from a large defect of the chest wall usually caused by a wound that creates a communication between the pleural space and external environment. In an open or "sucking" wound of the chest wall (Figure 5.5), the lung on the affected side is exposed to atmospheric pressure and equilibration between intrathoracic pressure and atmospheric pressure is immediate, resulting in the lung's collapse and a shift of the mediastinum to the unaffected side. The patient's effective oxygenation and ventilation is thereby severely compromised, leading to hypoxia and hypercarbia.
This is an immediately life-threatening condition. In the spontaneously ventilating patient, open pneumothorax is initially treated by application of a sterile occlusive dressing with Vaseline gauze that must be large enough to cover the entire wound and is taped securely on three sides.
Taping all edges of the dressing before a chest tube is placed is contraindicated because accumulation of air in the affected thoracic cavity will lead to the development of tension pneumothorax. In patients with airway or breathing difficulty, early intubation and initiation of positive pressure ventilation should be considered. For large, open chest wall defects, surgical debridement of dead and devitalized tissue closure of the wound (with or without prosthetic patch) is often required under general anesthesia.
Rib, Sternum, and Scapular Fractures
Rib fractures contribute significantly to the morbidity and mortality associated with chest injuries. The elderly and patients with poor respiratory reserve are particularly vulnerable. Fractured ribs cause severe pain, which can be more debilitating and harmful than the injury itself. Because pain characteristically occurs with inspiration, the patient tends to splint the chest wall and therefore hypoventilates. Pain limits one's ability to cough and breathe deeply, resulting in sputum retention, atelectasis, and a reduction in functional residual capacity. These factors, in turn, result in decreased lung compliance, ventilation-perfusion mismatch, and hypoxemia. There may be paradoxical respiration as occurs with flail chest. There may be associated hemopneumothorax and pulmonary contusions. Crushing injuries produce multiple fractures, the sites being dependent on the direction of the compressing forces. Lower rib fractures are associated with injuries to the spleen and liver. Impacting the anterior chest on a steering wheel during motor vehicle accident often fractures the sternum and several ribs anteriorly on both sides.
When rib fractures occur at multiple sites in more than three ribs on the same side (Figure 5.6), the chest wall in the injured area moves paradoxically, that is, it moves inward during inspiration and outward during expiration. This manifests as inefficient ventilation, and this commonly coexists with pulmonary contusion, pneumothorax, or hemothorax. Effective pain relief by itself can improve respiratory function and often avoid the need for mechanical ventilation. Other therapeutic measures include supplemental oxygen, continuous positive airway pressure of by facemask, airway humidification, chest physiotherapy, incentive spirometry, bronchodilators, airway suctioning and nutritional support.
Hemothorax is accumulation of blood in the pleural space. Massive hemothorax is defined as a rapid accumulation of more than 1,500 cc of blood in the pleural space. Such a massive hemorrhage usually indicates large pulmonary lacerations or great vessel or intercostal vessel injury. Hemothorax causes shock and respiratory compromise by lung compression secondary to blood accumulation. The initial management includes the simultaneous resuscitation of blood volume and decompression of the chest cavity with a large (36-40 Fr) chest tube (Figure 5.7) which will attach to drainage bottle (Figure 5.8).