FIG. 8: There has been a major study that addressed these issues, the RESCUE (REspiratory Support in COPD after acUte Exacerbation) trial, from the large Dutch group who used a randomized controlled trial design to look at patients with severe COPD who had an acute decompensated episode of respiratory failure requiring NIV.[13] They selected patients who remained hypercapnic, using an arterial partial pressure of carbon dioxide (PaCO2) cutoff of 6 kPa (45 mmHg). At the end of the patients’ acute exacerbations, the investigators excluded the type of patients that we would expect them to exclude, with other reasons for respiratory failure such as neuromuscular disease or obstructive sleep apnea with significant chest wall disease. They further minimized the enrollment through a range of important criteria until they finally randomized 201 patients in the study, looking at admission-free survival over the following 12 months.