Importance of the PaCO2 from 3 to 6 months after initiation of long-term non-invasive ventilation

SummaryBackgroundThe level at which arterial carbon dioxide tension (PaCO2) a few months after introduction of long-term non-invasive positive pressure ventilation (NPPV) is associated with a favorable prognosis remains uncertain.MethodsData on 184 post-tuberculosis patients with chronic restrictive ventilatory failure who were receiving long-term domiciliary NPPV were examined retrospectively. Average PaCO2 3–6 months after NPPV (3- to 6-mo PaCO2) and potential confounders were analyzed with discontinuation of long-term NPPV as the primary outcome. The effects of 3- to 6-mo PaCO2 on annual hospitalization rates due to respiratory deterioration from 1 year before to 3 years after the initiation of NPPV were examined. The effect of the difference between the PaCO2 value at the start of NPPV (0-mo PaCO2) and the PaCO2 value 3- to 6-mo later (d-PaCO2) on continuation rates for NPPV was also assessed in patients who initiated NPPV while in a chronic state.ResultsPatients with relatively low 3- to 6-mo PaCO2 values maintained a relatively low PaCO2 6–36 months after NPPV (p < 0.0001) and had significantly better continuation rates (p < 0.03) and lower hospitalization rates from the 1st to 3rd year of NPPV (p = 0.008, 0.049, 0.009, respectively) than those with higher levels. The 0-mo PaCO2 (p = 0.26) or d-PaCO2 (p = 0.86) had no predictive value.ConclusionA relatively low 3- to 6-mo PaCO2 value was predictive of long-term use of NPPV. The target values for 3- to 6-mo PaCO2 may, therefore, be less than 60 mmHg in post-tuberculosis patients, although more studies are needed.