Now that non-invasive ventilation (NIV) is well established in clinical practice, particularly for chronic obstructive pulmonary disease (COPD),^1,2 it is likely that more patients will survive an acute exacerbation, especially in countries such as the UK where comparatively few patients with COPD are ventilated invasively. However, it is possible that some patients are now just being saved for a future life of poor quality at home, punctuated by recurrent admissions to hospital because their respiratory reserve is so marginal that even trivial exacerbations are sufficient to provoke life threatening ventilatory failure.

Before NIV was widely available, Connors et al³ showed that hypercapnia during an admission with an acute exacerbation of COPD was a poor prognostic indicator. In a prospective study of a cohort of 1016 patients who were admitted with an exacerbation of COPD and a Paco₂ of 50 mm Hg (6.6 kPa) or more, they found that 11% of the patients died during the index hospital stay. The 60 day (20%), 180 day (33%), 1 year (43%), and 2 year (49%) mortality rates were all high; 446 patients (44%) were readmitted 754 times in the following 6 months. At 6 months only 26% of the cohort were both alive and able to report a “good”, “very good”, or “excellent” quality of life. Survival time was independently related to severity of illness, body mass index (BMI), age, prior functional status, Pao₂/Fio₂, congestive heart failure, serum albumin, and the presence of cor pulmonale. Given that current recommendations state that patients with an acute respiratory acidosis (pH <7.35) after initial treatment and a Paco₂ above 6 kPa should be offered NIV,⁴ all patients who have received NIV acutely fall …