Loop gain in severely obese women with obstructive sleep apnoea

Our objective was to assess whether obstructive sleep apnoea (OSA) patients were characterised by a reduced central CO₂ controller gain (CG) and an enhanced plant gain (PG). We matched three groups of women (n=10 per group) enrolled in a previous study (Essalhi et al., J. Asthma. 50: 565-572, 2013): obese women with a respiratory disturbance index (RDI)≥15/h and with a RDI<15, and lean women without OSA (RDI<5). Tidal ventilation recordings during wakefulness with end-tidal PCO₂ monitoring allowed the assessment of loop gain (LG) and its components (PG and CG). LG were similar for the three groups (p=0.844) while both PG and CG depicted significant differences (p=0.046 and p=0.011, respectively). Obese women with OSA were characterised by an increased PG and a reduced CG as compared to obese women without OSA. A negative relationship between CG and RDI (rho = -0.46, p=0.008) was evidenced. In conclusion, OSA in women is associated with a reduced central CO₂ controller gain and an enhanced plant gain.