Pneumothorax — MRCS Part B Surgical pathology

A chest radiograph after trauma, used to cover pneumothorax in all its forms, then the flail chest and the pulmonary contusion beneath it.

Recognising it before the film

Chest pain and breathlessness after the injury, reduced expansion on one side, a hyper-resonant percussion note and absent breath sounds. Tension adds the signs of obstructed venous return: tachycardia, hypotension, distended neck veins, tracheal deviation away from the affected side, and a patient who is deteriorating in front of you. Tension is diagnosed clinically and treated before any radiograph.

Types

Spontaneous, either primary in a tall thin young smoker from a ruptured apical bleb, or secondary to lung disease such as emphysema, cystic fibrosis or pneumocystis pneumonia; traumatic, from a fractured rib, a stab or a needle; iatrogenic, after a central line, a pleural aspiration or a ventilator; open, when a chest wall wound larger than the trachea lets air in and out of the pleural space with every breath so the lung cannot inflate; and tension, when a flap of tissue acts as a valve so air enters the pleural space on inspiration and cannot leave. The pressure rises, the lung collapses, the mediastinum shifts, the great veins kink and cardiac output falls: it kills by obstructing venous return, not by loss of one lung.

Management

A tension pneumothorax is decompressed at once with a wide-bore cannula in the fourth or fifth intercostal space just in front of the mid-axillary line (or the second space in the mid-clavicular line, above the third rib, if the chest wall is thin), followed by a chest drain in the safe triangle. An open pneumothorax is covered with an occlusive dressing taped on three sides, so that air can escape but not enter, and a drain is placed away from the wound before the wound itself is closed. A traumatic pneumothorax is drained, and always before positive-pressure ventilation. A small primary spontaneous pneumothorax without breathlessness can be observed; a larger or symptomatic one is aspirated, and a drain is placed if that fails or the patient has lung disease. For recurrence, or a first episode in someone whose job or sport makes another dangerous, the options are video-assisted thoracoscopic bullectomy with pleurodesis (by abrasion, pleurectomy or talc) or, in the unfit, chemical pleurodesis through the drain.

Flail chest

Paradoxical movement of a segment of the chest wall, drawn in on inspiration and pushed out on expiration, means that two or more adjacent ribs are broken in two or more places so that the segment is no longer attached to the rest of the cage and follows the pressure in the pleural space rather than the movement of the wall. The radiograph shows the rib fractures, often with a haemothorax or pneumothorax, and the patchy shadowing of the contusion beneath. The segment itself matters less than the contused lung under it, which stiffens, shunts and fills with fluid over the next two days, so hypoxia worsens after admission; its consequences are pneumonia, ARDS and respiratory failure, and the risk is greatest in the elderly and in anyone with lung disease. Management is oxygen, good analgesia (an epidural or a paravertebral block, so the patient can breathe deeply and cough), careful fluids, physiotherapy, drainage of any air or blood, and ventilation with positive pressure if the patient tires. Operative fixation of the ribs shortens ventilation in selected patients.