Funk and colleagues assessed long-term NIV in COPD patients after acute-on-chronic respiratory failure.^[16]  In this study, once acute respiratory failure had been treated sufficiently, all patients received HMV for 6 months, followed by randomization either to withdraw from NIV or to remain on HMV.  

The left panel in this Figure shows the probability of clinical worsening, which was significantly lower in the group pursuing HMV compared to the group who stopped HMV.  The right panel shows changes in 6-min walk distance; patients pursuing HMV significantly improved their exercise capacity over time, whereas the group who stopped HMV did not improve.