An Australian study of patients with obstructive sleep apnoea (OSA) has been unable to identify reliable clinical predictors of which patients will respond to surgery, even with prior knowledge of the OSA endotypes.

While used as a second-line treatment for patients who are unable to tolerate continuous positive airway pressure (CPAP) and/or oral appliance therapy, responses to surgery are unpredictable and many patients will have residual OSA post-surgery, according to researchers at Monash Lung, Sleep, Allergy & Immunology, Monash Health, Melbourne.

In a bid to help clinicians avoid unsuccessful and unnecessary surgery, the team examined outcomes from upper airway surgery based on anatomical and non-anatomical OSA endotypes such as upper airway collapsibility, airway muscle response/compensation, respiratory arousal threshold and loop gain.

The prospective study involved patients with OSA (apnoea–hypopnoea index [AHI] ≥ 15 events/h) who underwent multilevel upper airway surgery, with a majority receiving palate-based surgery and at least one other type such as nasal surgery, tonsillectomy, and/or tongue-based surgery.

The results showed that using both CPAP dial-down and clinical polysomnographic methods, there was a trend towards overall improvement with surgery in upper airway anatomy/ collapsibility. However the effects were highly variable, with large changes in upper airway collapsibility observed in both positive and negative  directions.

The OSA patients who benefited the most from surgery were those who gained the greatest improvement in upper airway collapsibility, as improvements in AHI and upper airway collapsibility were strongly correlated. However, surgery  had no effect on the non-anatomical endotypes causing OSA, and most of the observed effect sizes for the non-anatomical endotypes were quite small.

Overall, there were no baseline endotypic predictors of surgical response in OSA patients, the researchers reported in Respirology.

The lack of any identifiable physiological predictors of treatment success was in contrast to previous studies, the researchers noted, and the reasons for the discrepancies between studies were unclear, they said.

The consistent findings across methods provide some support for the use of the simpler [polysomnographic] methods to detect group-level changes in OSA endotypes in future research, but the absence of associations between methods means that our results do not provide clear support for the use of non-anatomical [polysomnographic] endotypes as a replacement for CPAP dial-down methods at this time,” they concluded.