Loop gain in severely obese women with obstructive sleep apnoea

• The concept of loop gain describes stability and variability of respiratory control.
• An enhanced CO2 plant gain is evidenced in obese women with obstructive sleep apnoea.
• A reduced central CO2 controller gain is evidenced in obese women with OSA.

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.