Iatrogenic tension pneumothorax resulting from misconnection of the endotracheal tube to the auxiliary oxygen flowmeter of the anaesthetic machine.

A 1-year-old, male entire English Springer Spaniel dog, presented for computed tomography investigation of bilateral pelvic limb gait abnormality. The dog developed tension pneumothorax shortly after intubation because of erroneous connection of the endotracheal tube to the auxiliary oxygen flowmeter instead of the breathing circuit. A prompt diagnosis, based on reduced compliance during manual ventilation, bradycardia and second-degree atrioventricular block, combined with barrel-shaped thoracic distension, led to an emergency needle thoracocentesis, followed by bilateral thoracostomy tube placement. Computed tomography was then performed as scheduled with an added scan sequence for the thorax. General anaesthesia was maintained using total intravenous techniques with propofol and ketamine infusions. Hospital morbidity and mortality rounds identified various active and system failures as contributing factors. The 22 mm connector attached to the auxiliary oxygen flowmeter tubing was recognized as the major contributing factor, as it could be connected to both the endotracheal tube and oxygen mask. Consequently, the decision was made to no longer use the auxiliary oxygen flowmeter for preoxygenation. This report discusses the circumstances leading to this adverse event and highlights the danger of anaesthesia-related errors.