Abstract 2053: End-Tidal Carbon Dioxide Predicts the Individual Effectiveness of Nocturnal Oxygen Therapy in Patients with Chronic Heart Failure Associated with Central Sleep Apnea
Background: Central sleep apnea (CSA) is often seen in patients with chronic heart failure (CHF) and has been reported to be an independent risk factor for death and cardiac transplantation in CHF. Nocturnal oxygen therapy is emerging as a new therapeutic option for patients with CHF associated with CSA. However, the problem with this oxygen therapy is that there are some non-responders to the therapy. In this study, we thus aimed to elucidate a determinant of the individual responsiveness of the oxygen therapy.
Methods: Sleep study was performed in 12 consecutive patients with CHF associated with CSA (male/female, 11/1; mean±SD, age, 68±12; body-mass index, 23±3 kg/mm2; LV ejection fraction, 34±12 %; brain-natriuretic peptide, 409±421 pg/ml; apnea-hypopnea index, 31±1 n/h) at 2 consecutive nights. Patients nasally inhaled oxygen at either the first or second night in a randomized order. To predict the percentage reduction in apnea-hypopnea index (%ΔAHI) after the oxygen therapy, multiple regression analysis with a stepwise method was performed with variables of age, brain-natriuretic peptide, circulation time, baseline apnea-hypopnea index, central chemosensitivity and diurnal steady-state end-tidal CO2.
Results: Nocturnal oxygen therapy significantly decreased apnea-hypopnea index (from 32±13 to 12±10 n/h, P<0.0001). Among the 6 variables studied, only end-tidal CO2 significantly predicted %ΔAHI (%ΔAHI = −26.3 × end-tidal CO2 + 53.1, r = 0.76, P<0.005). The cut-off value of end-tidal CO2 for predicting the responders (more than 50% reduction of AHI) was 4 %.
Conclusions: These results indicate that low set points of PaCO2 may determine the individual responsiveness to the oxygen therapy in patients with CHF associated with CSA, suggesting that end-tidal CO2 (more than 4 %) is a useful guide to select the responders to the oxygen therapy.