Equis ISSN 2398-2977

Pneumothorax

Contributor(s): Nicola Menzies-Gow, Graham Munroe

Introduction

  • Pneumothorax is air in the pleural cavity via lung, mediastinal or thoracic wall disease or injury.
  • Can be divided into open, closed or tension pneumothorax.
  • Signs: unilateral condition is quite well tolerated; respiratory distress, change in breathing patterns and arterial oxygen concentrations accompany severe or bilateral disease.
  • Diagnosis: chest auscultation and percussion, thoracic radiography, ultrasonography and thoracocentesis are helpful.
  • Treatment: includes aspiration of air and oxygen insufflation as well as treatment of any underlying cause.
  • Prognosis: guarded, varying with initiating cause.

Pathogenesis

Etiology

  • Trauma:
    • Penetrating wounds to thorax .
    • Puncture or rupture of trachea (intrathoracic)   Trachea: foreign body  .
    • Rupture of esophagus   Esophagus: trauma  , eg following choke, FB.
    • Parturitional trauma in neonates - fractured ribs.
  • Secondary to:
  • Iatrogenic:
    • Thoracotomy - especially standing   Thorax: thoracotomy  .
    • Subsequent to repair of diaphragmatic hernia   Diaphragm: hernia  .
    • Thoracocentesis or thoracic drainage   Thorax: thoracentesis  .
    • Excessive positive pressure ventilation, especially in the neonate   →   ruptured alveoli, bullae and pleural blebs.

Pathophysiology

  • Uncommon.
  • Air escapes into the pleural cavity via the lung, mediastinal space or thoracic wall.
  • May be uni- or bi-lateral.
  • Open, closed or tension pneumothorax.
  • Leads to pulmonary collapse and prevents inspiratory lung expansion.
  • A potentially life-threatening condition.
  • Air can gain access to the pleural space by traversing the lung, mediastinal space and thoracic wall.
  • Open pneumothoraxoccurs when a wound allows air to enter and leave the pleural cavity.
  • Closed pneumothoraxinvolves trapping air within the chest.
  • Tension pneumothoraxoccurs when a flap of tissue acts as a one way valve allowing air to enter but not leave the thorax.
  • Unilateral pneumothorax may be tolerated quite well in the horse but if the thin, fenestrated caudal mediastinum breaks down, bilateral pneumothorax will ensue   →   severe impairment of lung function   →   death.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Joswig A & Hardy J (2013)Axillary wounds in horses and the development of subcutaneous emphysema, pneumomediastinum and pneumothorax.Equine Vet Educ25(3), 139-143 VetMedResource.
  • Epstein K L (2009)Pneumothorax and pneumomediastinum: Causes, diagnosis and treatment.Equine Vet Educ21(12), 642-647 Wiley Online Library.
  • Cornelisse C Jet al(1999)What is your diagnosis? Bilateral pneumothorax.JAVMA214(9), 1323-1324 PubMed.
  • Jorgensen J S (1997)What is your diagnosis? Unilateral pneumothorax with collapse of the left caudal lung lobe.JAVMA210(8), 1109-1110 PubMed.
  • Hance S Ret al(1992)Subcutaneous emphysema from an axillary wound that resulted in pneumomediastinum and bilateral pneumothorax in a horse.JAVMA200(8), 1107-1110 PubMed.
  • Spurlock S Let al(1988)Consolidating pneumonia and pneumothorax in a horse.JAVMA192(8), 1081-1082 PubMed.
  • Rantanen N W (1986)Disease of the thorax.Vet Clin North Am Equine Pract2(1), 49-66 PubMed.
  • Thomson J U (1977)Emergency field treatment of pneumothorax in the horse.Vet Med Small Anim Clin72(2), 250 PubMed.
  • Lowe J E (1967)Pneumothorax in a horse from a puncture wound - A case report.Cornell Vet57(2), 200-204 PubMed.


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