FIG. 12: When looking at the results of the RESCUE trial, it is important to realize that not all patients with acute respiratory failure responded in the same way.[13] The panel in the lower left of the Figure illustrates data from the RESCUE trial showing that both patients randomized to NIV and patients on the control arm had improvements in respiratory failure over the first 3 months of the trial, and the magnitude of improvement was similar on both the NIV and the control arms. This is important because among the patients who were treated for acute decompensated respiratory failure in RESCUE, significant numbers did not in fact have chronic respiratory failure.

We know that the patients with and without acute decompensated respiratory failure have different trajectories over the following years. This is shown in the right panel of the Figure, a study that divided patients with acute exacerbations of COPD attending hospital into patients without evidence of respiratory failure (Type 1), patients who had evidence of respiratory failure in the acute setting that resolved during follow-up (Type 2.1), and patients with acute respiratory failure that persisted into the chronic phase (Type 2.2).[14] Over 5 years of follow-up, patients with both acute and chronic respiratory failure (Type 2.2) had a significantly worse outcome (including high mortality rates) than the patients with transient respiratory failure (Type 2.1), who had outcomes very similar to the patients with no respiratory failure (Type 1).