A patient previously diagnosed with motor neurone disease (MND) and gastrostomy-fed was under surveillance for ventilatory decline via our respiratory centre. At a planned review she was found to be hypercapnic, which would usually prompt an offer of non-invasive ventilation for home use. However, she was alkalotic and not acidotic as we might expect. Her serum potassium was checked urgently and confirmed as low. It was established that the community team had prescribed a feeding regime with insufficient potassium. Correction of hypokalaemia resolved her ventilatory failure. This case demonstrates the importance of co-ordinated care in the management of patients with MND.