Inclusion Criteria:  All patients with chronic obstructive pulmonary disease (COPD) who meet these criteria for domiciliary NIV:  - Diagnosis of COPD based on spirometry; The ration of the forced expiratory volume in the first one second (FEV1) to the forced vital capacity (FVC) of the lungs (FEV1/FVC ratio), of ⩽ 0.70  And either of:  i) Recent inpatient admission with acute hypercapnic respiratory failure with persistent hypercapnia (pH ≥ 7.35 and PaCO2 ≥ 6 kilopascal (kPa)) 2-4 weeks after the acute episode or ii) COPD with evidence nocturnal hypoventilation (sleep study demonstrating time under 90% saturations for 30% of the sleep time) or iii) Stable CHRF (paO2 ⩽ 8 kPa and paCO2 ≥ 6 kPa)  OR  All patients with OHS who meet these criteria for domiciliary NIV i) Diagnosis of OHS based on Body Mass Index > 30 kg/m2, daytime hypercapnia (PaCO2 ≥ 6kPa) and significant nocturnal hypoventilation (saturations ⩽ 90% for 30% of the total sleep time) or ii) Inpatient admission with acute hypercapnic respiratory failure requiring NIV referred for consideration of domiciliary treatment  who have been offered treatment with NIV and have:  3)  discontinued or demonstrated poor compliance with domiciliary NIV (defined as ⩽ 4 hours usage for 70% of the nights at 4 months with all reasonable measures taken to address barriers to treatment use) evidence of sleep disordered breathing on a sleep study over or equal to 18 years of age able to provide informed consent able to participate for the duration of the study have an expected survival for greater than three months  All patients must meet inclusion criteria for 1 or 2 and all of 3  Exclusion Criteria:  Unstable psychiatric disease Unable to return for review appointments e.g due to move home or lives a long distance from the study site Pregnancy Receiving home NIV treatment at time of inclusion to study Receiving home NIV treatment for other medical illnesses, for example neuromuscular disease Unable to read English