An unusual cause of increasing airway pressure during anesthesia.

The research article discusses abnormal airway pressure in a mare during anesthesia for surgery on a chest wound. Investigating the cause, it was found that a fault in the animal’s ventilator led to this issue.

Overview of the Case

• The subject of the research is a mare (a female horse) who had undergone anesthesia for the purpose of thoracic laceration surgery.
• Post the introduction of controlled ventilation during the process, there was a noted increase in the inspiratory plateau pressure.
• This increased pressure persisted despite lowering the volume of intake during each breath, or the tidal volume.
• Tension pneumothorax, a severe condition where air gets trapped between the chest wall and lung, causing the lung to collapse, was initially suspected as the cause of increased pressure.

Investigation and Findings

• The suspect of tension pneumothorax was eventually ruled out due to normal readings of arterial PCO2 and PO2. These concern measurements of carbon dioxide and oxygen partial pressures in arterial blood respectively, which are essential indicators of respiratory functions.
• The focus was then shifted towards the anesthetic equipment and a significant observation was made. Even with the fresh gas flow being halted, excess gas was observed to continually exit through the bellows pop-off valve, a safety device meant to limit the pressure within the system.
• The exact issue was discovered to be a hole in the bellows (the portion of the ventilator that assists in the process of breathing by sending gas to the breathing system). It was found that the driving gas from the ventilator was entering the breathing circuit through this hole, leading to the increased pressure.

Recommendation and Conclusion

• The research article ends by suggesting that testing the integrity of the bellows prior to its usage can help to avoid a similar complication in the future.
• It emphasized how an equipment malfunction could potentially lead to serious complications, underscoring the importance of thorough pre-procedural checks of all the anesthesia apparatus.