Evaluation of body position in upper airway stimulation for obstructive sleep apnea-is continuous voltage sufficient enough?

PURPOSE

The definition of positional obstructive sleep apnea (POSA) is widely accepted as a difference of 50% or more in AHI between supine and non-supine position. Upper airway stimulation (UAS) is an effective treatment for OSA but the implant delivers a single voltage over sleep period without consideration of body position. Clinical practice suggests different outcomes for OSA in supine position under UAS treatment.

METHODS

Outcomes of 44 patients were analyzed 12 months after implantation in a two-center, prospective consecutive trial in a university hospital setting. Total night and supine AHI were evaluated and the ratio of time spent in supine was considered. Correlation between the classic and the modified definition of POSA and treatment response were evaluated.

RESULTS

The time ratio spent in supine position did not differ before implantation and after 12 months. Total and supine AHI were reduced with the use of UAS therapy (p < 0.001) but both the baseline and final supine AHI were higher than total night AHI. Considering POSA definition as a ratio of supine to non-supine AHI, there was no clear cutoff for defining responders neither with nor without the additional component of time in supine position.

CONCLUSIONS

The OSA reduction is strong for the total AHI and supine AHI. Nonetheless, here, there is no cutoff for defining POSA as critical for UAS therapy response. Therefore, there is no evidence for excluding POSA patients from UAS in general. Future technology improvement should take body position and adaptive voltage into account.