Abstract
A subset of obese patients experience persistent nocturnal hypoxia despite continuous positive airway pressure (CPAP) for OSAS. Bi-level ventilation (BIPAP) has been used as second line therapy despite little evidence of its benefits.
Aim: To evaluate the role of additional oxygen therapy in nocturnal hypoxia in obese patients with OSAS on CPAP.
Methods: Retrospective analysis of electronic records, sleep polygraphy, oximetry, blood gases and lung function of OSA patients with nocturnal hypoxia despite CPAP.
Results: Sixty-two patients (male = 35), mean age 62 ± 11, mean Body Mass Index (BMI) 43.8 ± 13 with OSAS (mean Apnoea Hypopnoea Index 42 events/hour) and nocturnal hypoxia (pre-CPAP time spent with saturations <90% = 60.6%, mean daytime pCO2 5.9kPa) were started on fixed CPAP (mean pressure 12.5cmH2O) following a night of Auto-titration and later on nocturnal oxygen therapy when their post-CPAP oximetry showed persistent nocturnal hypoxia (mean time spent with saturations <90% = 46%). After addition of oxygen (mean 1.4 litres/min), the mean time with saturation <90% dropped to 5.3%. Only 17% (11/62) subsequently developed hypercapnia (mean pCO2 7.5 kPa) requiring BIPAP. There was no difference in BMI, AHI, time with hypoxia on CPAP or daytime gases between the patients that went on BIPAP compared to those on CPAP and oxygen. The former group had significantly lower FEV1, but not FEV1/FVC ratio.
Conclusion: In our experience, the majority of obese OSAS patients with persistent nocturnal hypoxia despite CPAP can be managed by additional nocturnal oxygen without causing hypercapnia. Further studies are required to identify this subset of patients.
- © 2014 ERS