Obesity is an escalating issue, with an accompanying increase in referrals of patients with obesity-related respiratory failure. Currently, these patients are electively admitted to hospital for initiation of non-invasive ventilation (NIV), but it is unknown whether outpatient initiation is as effective as inpatient set-up. The investigators hypothesise that outpatient set up using an auto-titrating NIV device will be more cost effective than nurse-led inpatient titration and set-up.