The Effects of Nasal and Multi-Level Upper Airway Surgery on Upper Airway Collapsibility and Non-Anatomical Endotypes...

Nasal breathing is the preferred route of breathing during sleep. Indeed, nasal blockage can cause obstructive sleep apnoea (OSA) in otherwise healthy people. Whilst multi-level pharyngeal surgery reduces OSA severity, efficacy varies and changes in OSA pathophysiology post-surgery have not been well characterised. Similarly, whether isolated nasal surgery improves upper airway collapsibility and OSA severity remains unclear. Accordingly, this study aimed to assess changes in upper airway collapsibility and estimated OSA endotypes following nasal and multi-level upper-airway surgery. In-laboratory polysomnography was performed pre- and post-nasal or multi-level upper airway surgery in 10 people with OSA. Brief (250 ms) negative pressure pulses (~-12 cmH₂O) were also applied in early inspiration and early expiration during wakefulness to calculate the upper airway collapsibility index (UACI). Endotype changes were estimated from polysomnography. Multi-level upper-airway surgery reduced OSA severity with a corresponding 76% reduction in the UACI (38% ± 26% vs. 9% ± 19%, p = 0.02) during inspiration with similar improvements during expiration (69% ± 36% vs. 21% ± 31%, p = 0.01). Similarly, upper-airway collapsibility and loop gain endotypes improved following multi-level surgery. For isolated nasal surgery, OSA severity, upper-airway collapsibility and OSA endotypes were not systematically different pre- versus post-surgery. These findings indicate major improvements in upper-airway collapsibility during wakefulness and sleep, and reductions in loop gain following multi-level upper-airway surgery but no systematic changes in key OSA pathophysiology/severity measures following isolated nasal surgery, although the sample size for this comparison was small. Further application of these physiological measures may help explain, at least in part, between patient differences in therapeutic efficacy with different upper airway surgical approaches.