Experimentally Induced Open Pneumothorax in Horses.

The study is an examination of how horses react to a unilateral open pneumothorax scenario, a condition where air builds up in the chest cavity. Different measurements such as pleural pressure, left ventricular function, and intra-abdominal pressure were taken to understand how open pneumothorax impacts the horse’s physiology. The study found that horses can endure open pneumothorax with little impact on their cardiovascular workings, even if no air is drawn from the chest cavity to restore thoracic wall integrity.

Methodology

• The study focused on seven healthy adult horses – four females and three males.
• A surgical procedure called a left hemithorax thoracotomy was performed on each horse to induce a unilateral open pneumothorax.
• This open pneumothorax condition was maintained for 60 minutes during each procedure.
• The researchers measured several parameters at varying times before, during, and after the procedure. These measurements included pleural pressure, esophageal pressure, arterial blood gas analysis, left ventricular function, and ultrasonographic assessment to evaluate pneumothorax extent/resolution.
• Intra-abdominal pressure was measured only when the pneumothorax was present.

Findings

• A moderate correlation was found between pleural and esophageal pressure.
• Esophageal pressure increased after the open pneumothorax procedure and this rise persisted until the fifth postoperative day.
• The oxygen levels in the arterial blood decreased and remained low until the third postoperative day when they returned to normal.
• However, no significant changes were found in the carbon dioxide levels, the pH in arterial blood, and in left ventricular function.
• The extent and resolution of pneumothorax were tracked using thoracic ultrasonography.

Implications

• The research revealed that esophageal pressure, along with arterial blood gas analysis and thoracic ultrasonography, could be effective diagnostic tools for pneumothorax in horses.
• The study also concluded that horses can survive open pneumothorax with minimal cardiovascular impairment, even when free air is not aspirated from the pleural space to repair the integrity of the thoracic wall.