Loop gain predicts the response to upper airway surgery in patients with obstructive sleep apnoea: Ventilatory control abnormalities predict surgical responsiveness.

Loop gain predicts the response to upper airway surgery in patients with obstructive sleep apnoea: Ventilatory control abnormalities predict surgical responsiveness.

Sleep. 2017 May 22;:

Authors: Joosten SA, Leong P, Landry SA, Sands SA, Terrill PI, Mann D, Turton A, Rangaswamy J, Andara C, Burgess G, Mansfield D, Hamilton GS, Edwards BA

Abstract
Study Objectives: Upper airway surgery is often recommended to treat OSA patients who cannot tolerate continuous positive airways pressure (CPAP). However, the response to surgery is variable, potentially because it does not improve the non-anatomical factors (i.e. loop gain and arousal threshold) causing OSA. Measuring these traits clinically might predict responses to surgery. Our primary objective was to test the value of loop gain and arousal threshold to predict surgical success defined as 50% reduction in apnea-hypopnea index (AHI) and AHI <10 events/hr post-surgery.
Methods: We retrospectively analyzed data from patients who underwent upper airway surgery for OSA (n=46). Clinical estimates of loop gain and arousal threshold were calculated from routine polysomnographic recordings pre- and post-surgery (median of 124 [91 to 170] days follow-up).
Results: Surgery reduced both the AHI (39.1±4.2 vs. 26.5±3.6 events/hr; p<0.005) and estimated arousal threshold (-14.8[-22.9 to -10.2] vs. -9.4[-14.5 to -6.0] cmH2O) but did not alter loop gain (0.45±0.08 vs. 0.45±0.12; p=0.278). Responders to surgery had a lower baseline loop gain (0.38±0.02 vs 0.48±0.01, p<0.05) and were younger (31.0 [27.3-42.5] vs 43.0 [33.0-55.3] years, p<0.05) than non-responders. Lower loop gain remained a significant predictor of surgical success after controlling for covariates (logistic regression p=0.018; R.O.C. area under curve=0.80).
Conclusions: Our study provides proof-of-principle that upper airway surgery most effectively resolves OSA in patients with lower loop gain. Predicting the failure of surgical treatment, consequent to less stable ventilatory control (elevated loop gain), can be achieved in the clinic and may facilitate avoidance of surgical failures.

PMID: 28531336 [PubMed - as supplied by publisher]

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