PaCO2 Six months after the Initiation of Long-term Noninvasive Ventilation in Patients with COPD

Background and Objective The appropriate target level for PaCO2 after the introduction of long-term noninvasive positive pressure ventilation (NPPV) in patients with COPD remains uncertain, and therefore must be tested. Methods Data on 54 patients with COPD receiving long-term domiciliary NPPV were examined retrospectively. PaCO2 a few months after NPPV and potential confounders were analyzed with discontinuation of long-term NPPV as the primary outcome. The differences in annual hospitalization rates due to respiratory deterioration between those from 1 year before to 2 years after initiation of NPPV were compared according to the PaCO2 measured at 6 months after NPPV (6-mo PaCO2). Results 6-mo PaCO2 seemed to be most related to continuation of NPPV (p=0.019). Patients with 6-mo PaCO2 of less than 60 mmHg had maintained a significantly lower PaCO2 value 6 to 24 months after NPPV (p=0.04) and had a significantly higher continuation rate of NPPV (p=0.03) than those with a 6-mo PaCO2 of 60 mmHg or more. Annual hospitalization rates due to respiratory deterioration were not associated with the 6-mo PaCO2 level, but fatal hospitalization rates during the first year of NPPV were significantly correlated with relatively high 6-mo PaCO2 (p=0.008). Conclusion A relatively low 6-mo PaCO2 value was predictive of long-term use of NPPV. The target values of 6-mo PaCO2 may, therefore, be less than 60 mmHg in COPD patients with extremely severe hypercapnia, although more prospective studies are needed.