Severe hypercapnia associated with a chemodectoma causing profound tracheal narrowing in a cat

An 11-year-old, domestic short-haired cat presented out-of-hours with a 1-day history of dyspnoea and open-mouthed breathing. Ninety minutes after arrival, the cat acutely deteriorated. Butorphanol (0.2 mg/kg) was administered intravenously via a preplaced cephalic vein cannula, after which anaesthesia was induced (1.3 mg/kg alfaxalone). The cat’s trachea was intubated with a 3.5 mm internal diameter cuffed endotracheal tube (ETT), but it was not possible to give a manual breath and a capnograph trace was absent; therefore the ETT was replaced with a 4.5 mm internal diameter cuffed ETT. A manual breath was still not possible but a capnograph trace was present (end-tidal carbon dioxide tension of 95 mmHg (12.7 kPa)). Intravenous dexamethasone (0.15 mg/kg) and terbutaline (0.01 mg/kg) were administered. Computed tomography revealed a heart base mass compressing the trachea and decreasing its lumen to 1 mm diameter. The cat was euthanased due to poor prognosis. Histopathology revealed a chemodectoma.