Thoracotomy and sternotomy

Changes in respiratory function occurring after a thoracotomy may last as long as 3 weeks. In addition to loss of functional lung tissue, the chest wall compliance decreases by as much as 75 per cent. Marked increases in the work of breathing occur. Hypoventilation and respiratory acidosis can occur into the first postoperative day. Hypoxemia can last up to 10 days. The intraoperative collapsing of one lung to facilitate surgery is unique to thoracic surgery. Hypoxic vasoconstriction of the collapsed lung minimizes any increase in the shunt. The collapsed lung should be periodically inflated to prevent prolonged postoperative atelectasis.

Sternotomy results in less postoperative pain and discomfort than a thoracotomy. However, there is no appreciable difference in immediate postoperative pulmonary function. There is no difference in the vital capacity and peak flow of patients undergoing sternotomy compared with those undergoing lateral thoracotomy. After 4 to 7 days the sternotomy patient recovers more rapidly towards preoperative pulmonary function than the lateral thoracotomy patient. Sternotomy for a pulmonary resection may be advantageous to patients with severely impaired preoperative pulmonary function but it is technically more challenging.

During a pneumonectomy, the mediastinum will shift and the remaining lung will distend to fill the available space. Gas exchange efficiency decreases. Early attempts at limiting distension with thoracoplasty resulted in unwanted scoliosis on the operated side and worsened long-term breathing capacity. This problem was solved by using plombage or sponges to fill the space and limiting mediastinal shift, until it was realized that the remaining lung can fill the hemithorax with few complications if the mediastinum is kept in place (neutral position) until fibrosis occurs.

Distension of the remaining lung, movement of the diaphragm, and the production of connective tissue to fill the remaining thoracic space result in reduction of the size of the thoracic cavity. On the operated side, the diaphragm is elevated and the interspaces between the ribs are smaller. As the remaining lung distends to fill the space, only compensatory dilatation occurs.

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