Objective In subjects with chronic obstructive pulmonary disease (COPD), the effect of partial pressure of CO₂ (PaCO₂) alterations during long-term non-invasive ventilation (NIV) on continuance remains uncertain. We herein investigated the utility of PaCO₂ stability during long-term NIV as a prognostic outcome.
Methods We retrospectively assessed data from 54 subjects with COPD who received long-term NIV. The annual alteration in PaCO₂ during NIV was determined using a simple linear regression method for each subject who had at least two 6-month intervals of PaCO₂ data. Annual alterations in PaCO₂ during long-term NIV and probable confounders were examined, and long-term NIV discontinuation was the major outcome.
Results Data from 37 subjects who met the criteria were analyzed. PaCO₂ during long-term NIV increased slightly in 19 subjects (group 1, <2 mm Hg/y), and increased greatly in 18 subjects (group 2, >2 mmHg/y). In the multivariate modality model, smaller annual alterations in PaCO₂ (p=0.009) and lower PaCO₂ 6 months after the start of long-term NIV (6 m-PaCO₂) (p=0.03) were associated with a significantly higher probability of continuing NIV. The 2- and 5-year probabilities of continuing NIV were 89% and 66% for group 1 and 78% and 32% for group 2, respectively.
Conclusion A lower 6 m-PaCO₂ and a lower annual alteration of PaCO₂ during long-term NIV are significant predictive variables for patients with COPD.