Low-flow oxygen and bilevel ventilatory support - Effects on ventilation during sleep in cystic fibrosis

We measured ventilation in all sleep stages in patients with cystic fibrosi s (CF) and moderate to severe lung disease, and compared the effects of low -flow oxygen (LFO2) and bilevel ventilatory support (BVS) on ventilation an d gas exchange during sleep. Thirteen subjects, age 26 +/- 5.9 yr (mean a 1 SD), body mass index (BMI) 20 +/- 3 kg/m(2), FEV1 32 +/- 11% predicted, un derwent three sleep studies breathing, in random order, room air (RA), LFO2 , and BVS +/- O-2 with recording of oxyhemoglobin saturation (Spo(2)) (%) a nd transcutaneous carbon dioxide (TcCO2) (mm Hg). During RA and LFO2 studie s, patients wore a nasal mask with a baseline continuous positive airway pr essure (CPAP) of 4 to 5 cm H2O. Minute ventilation ((V)over dot (I)) was me asured using a pneumotachograph in the circuit and was not different betwee n wake and non-rapid eye movement (NREM) sleep on any night. However, (V)ov er dot (I) was reduced on the RA and LFO2 nights from awake to rapid eye mo vement (REM) (p < 0.01) and from NREM to REM (p < 0.01). On the BVS night t here was no significant difference in VI between NREM and REM sleep. Both B VS and LFO2 improved nocturnal Sp(o2), especially during REM sleep (p < 0.0 5). The rise in TcCO2 seen with REM sleep with both RA and LFO2 was attenua ted with BVS (p < 0.05). We conclude that BVS leads to improvements in alve olar ventilation during sleep in this patient group.