Background: Supplemental nocturnal oxygen is widely used for hypoxaemic respiratory failure in adults with CF.
Methods: In order to determine the factors that predict the development of progressive hypercapnia on oxygen ("failure of oxygen therapy") and the subsequent role of bi-level pressure support ventilation (BVS), we reviewed the outcomes of 39 adults with CF who were treated for hypoxaemic respiratory failure between 1991 and 2002 using strict physiological criteria for the commencement of oxygen and the subsequent commencement of BVS.
Results: Twenty of the 39 failed oxygen therapy, 13 of these within 12 months. Baseline PaCO2, rather than age, BMI or FEV1, predicted failure of oxygen therapy within 12 months. A PaCO2>6.5 kPa (49 mm Hg) was significantly associated with failure within 12 months (p=0.04). Twenty patients with mean PaCO2 7.9+/-1.3 kPa (59+/-10 mm Hg) and mean pH 7.38+/-0.05 had a significant reduction in their mean PaCO2 after 1 month of BVS (p=0.007).
Conclusions: Both oxygen and BVS can successfully stabilise patients to transplant. In patients commencing oxygen, baseline PaCO2 is predictive of the development of progressive hypercapnia within 12 months. BVS can successfully attenuate the rise in PaCO2 in the short term.