Managing disorders of the pleura, thoracic wall and diaphragm

Thoracic wall injuries can result in a wide variety of life threatening sequelae as indicated in the table below.

• Superficial soft tissue injury
• Subcutaneous emphysema
• Fractures of the ribs, sternum and vertebrae (Ultrasonography is more sensitive than radiography for detection of rib fractures)
• Pneumothorax (Right pleural sac is vulnerable to deep puncture wounds because it extends up the neck, to 2-3 cm beyond the first rib)
• Pneumomediastinum
• Pleural effusion
• Haemothorax (causes haemorrhagic shock rather than respiratory failure)
• Infections (pleural infection, pleuropneumonia, pulmonary abscess)
• ARDS
• Pulmonary contusion or laceration (predisposes to bacterial pneumonia)
• Diaphragmatic herniation or laceration
• Involvement of other systems (pericardial puncture, intestinal perforation/rupture, vertebral fractures, splenic or hepatic rupture)

Open external wounds should be closed, ideally by primary closure following local intercostal nerve blocks and aseptic preparation. In emergency situations, further ingress of air may be prevented by manual compression with a gloved hand or application of a non-porous pressure pad such as cling film. Large and complex thoracic defects may require surgical repair under general anaesthesia. Penetrations into the pleural cavity may warrant pleural lavage and drainage.

Pneumothorax and pneumomediastinum causes are listed below

• Penetration of thoracic wall, trachea, oesophagus or stomach
• Fractured ribs
• Blunt external trauma causing tearing of visceral pleura
• Bronchopleural fistula following pleuropneumonia and pneumonia
• Wounds of axilla and ventral neck
• Leaking thoracic drains
• Complication of tracheostomy, percutaneous trans-tracheal aspiration, lung biopsy, thoracostomy
• Excessive positive pressure ventilation in foals (barotrauma)
• Idiopathic

Simple uncomplicated closed pneumothorax without dyspnoea may be treated conservatively, with stall rest and close observation. Air is absorbed from the pleural space, albeit slowly, because the venous blood within the pleural vessels contains a lower total pressure of dissolved gases than does the alveolar air or atmospheric air. If there is dyspnoea, air is aspirated from the pleural cavity via a 10cm blunt teat cannula or 8-10 French catheter inserted in the dorsal lung field at the level of thirteenth intercostal space, using a suction apparatus or a large syringe utilizing a 3-way stopcock. Drainage may be performed intermittently, or employing a continuous aspiration system with a Heimlich valve or an underwater seal device, with or without suction. Bilateral pneumothorax is usually resolved by aspiration from only one hemithorax. However, in severe bilateral pneumothorax, and tension pneumothorax, bilateral tube thoracostomy should be performed. Ultrasonography can be used to assess restoration of lung inflation. Failure of thoracostomy to alleviate the respiratory distress should prompt examination for concomitant injuries such as fractured ribs or diaphragmatic hernia, or continued leakage of air into the pleural cavity. The latter may result from (a) tension pneumothorax, (b) iatrogenic lung puncture during insertion of chest drain, which is rare, (c) leakage around the thoracostomy tube or one way valve, or (d) failure to adequately close external thoracic wounds. Supplemental intranasal oxygen, analgesia to reduce pleurodynia and to minimise chest splinting and its detrimental sequelae, and antimicrobial treatment are warranted. Pleural lavage may be indicated in horse with penetrating thoracic wounds to minimize secondary bacterial pleuritis.

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