Predicting survival after acute exacerbation chronic obstructive pulmonary disease (ACOPD): is long-term application of noninvasive ventilation the last life guard?

Dear editor Patients with acute chronic obstructive pulmonary disease (ACOPD) admitted to an intensive care unit (ICU) still show substantial high hospital mortality (24%).1 After ICU discharge, long-term application noninvasive ventilation (NIV) may be a reasonable and effective indication.2 However, hospital mortality shows higher mortality rates for patients with COPD surviving their first episode after 2 and 5 years.2,3 Some patients with ventilatory failure at hospital discharge have increased arterial carbon dioxide tension (PaCO2), dyspnea, and reduced inspiratory muscle strength, compared with those of a normal patient. This is especially interesting for severe stable hypercapnic COPD, which can benefit substantially from using NIV, particularly showing improvements in gas change, dyspnea, and sleep quality. Currently, describing long-term survival in COPD patients receiving long-term NIV is a difficult issue. Titlestad et al analyzed the long-term survival rate in COPD patients receiving NIV for acute respiratory failure.3 We have read with interest this original and important epidemiological study that reports a 5-year mortality rate of 23.7%, and highlights the effects of NIV, with a trend toward more female mortality than male. However, we consider that it could be useful to add some aspects that are currently lacking, which could be analyzed and remarked on separately to understand this high mortality. First, there is a lack of relevant information on initial hospital admission that may influence higher mortality and could be interesting to take into account, such as: (a) rate of development of non-respiratory organ system dysfunction;1 (b) if there are some correlations with inspiratory pressure levels and adherence with NIV that have shown strength implications for long-term survival;4 (c) previous history of mechanical ventilation (MV); and (d) nutritional status and body mass index.5 Secondly, after hospital discharge, some aspects could be relevant to take into account. One study suggests that home NIV allows a lasting physiological stabilization in selected COPD patients, particularly those with an advanced disease, by reducing hypercapnia and improving inspiratory capacity.9 Further, in Titlestad et al’s article parameters of efficacy of home non invasive mechanical ventilation in non-survivors of COPD are unknown and may explain higher mortality;3 it could be interesting to know if there were some subgroups of COPD patients who remained at a hypercapnic high level after hospital discharge. In addition, for previous studies, prior domiciliary oxygen was a key predictor of 5-year mortality.5 Thirdly, it is very important to know the rate of readmission during this time, as after a severe ACOPD exacerbation, health conditions rapidly deteriorate.10 In this scenario of higher mortality, we need more solid scores after ACOPD to predict mortality and assess the protective role of long-term NIV application. Further large international surveys should be encouraged in order to consolidate new mortality prediction models, and discover whether the long-term application of NIV is the last life guard.