A 34 year old woman presented to the Emergency Department with a two day history of progressively worsening double vision, followed by ataxia and slurred speech. She reports a diarrhoeal illness eight days ago, though this has now resolved. She is normally fit and well and takes no regular medication.
Today she has noticed difficulty swallowing and feels breathless. Her respiratory rate is 28/min and SpO2 is 94% on 2L/min oxygen. Her GCS is 15/15. A CT head is performed, which is normal. A peak expiratory flow is measured, which is 300L/min.