Non-invasive ventilation (NIV) is an important therapy for patients with a number of neurological diseases. Specifically, NIV has been shown to be an effective treatment for people with amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease), which is a fatal, non-curable, progressive disease of the motor neurons. However, due to changes in facial structure associated with the disease, many ALS patients find that traditional NIV masks don't fit well. In this study, investigators will perform a feasibility study on NIV mask interfaces which are custom designed for each ALS patient and then manufactured via 3D printing.