Non-invasive ventilation (NIV) has already shown to improve survival and quality of life in patients with amyotrophic lateral sclerosis (ALS). Quality of sleep seems already to be impaired in patients with preserved diaphragmatic dysfunction. Until now, only few research has been performed on the quality of sleep in patients with ALS when using NIV, and these data are mainly based on patient reported outcomes.Further on, only very little research has been done on patient-ventilator interaction.