In a recent study published in JAMA Otolaryngology, a team of researchers performed additional data analysis on patients from the STAR trial. This was the pivotal trial that led to the FDA approval of Inspire here in the US. In this analysis, they looked at oxygen levels in patients using the Inspire hypoglossal nerve stimulator.
The main goal was to see if the Inspire device improved patients’ oxygen levels using a sophisticated new metric called hypoxic burden. Hypoxia means the body is deprived of oxygen. Hypoxic burden looks at how severe, frequent, and prolonged the drops in oxygen are. A higher hypoxic burden is strongly linked to long-term health risks like heart disease, stroke, and dementia.
Key Results After 12 Months of Treatment:
- Significant Oxygen Improvement: Inspire dramatically improved oxygen levels, with an average reduction of 76.6% in the hypoxic burden.
- Daytime Energy Boost: For those who started with severe hypoxia, reductions in hypoxic burden were strongly linked to feeling less sleepy during the day. This improvement in daytime sleepiness was not linked to changes in the traditional measure of sleep apnea severity, the Apnea-Hypopnea Index (AHI) (which counts how often breathing stops).
- Rethinking “Failure”: Crucially, 50% of patients who were labeled as “nonresponders” (meaning the treatment failed according to the AHI standard) still moved from having dangerous, high levels of oxygen deprivation to low levels of deprivation.
Conclusions:
These findings suggest that relying solely on the old AHI score might lead doctors to wrongly classify a successful treatment as a “failure”.
One of the reasons the AHI doesn’t tell the whole story is that apneas (total stoppage of breathing) and hypopneas (reduced airflow but not total obstruction) are counted equally. However, hypopneas don’t cause the more severe and prolonged reductions in oxygen levels that occur with apneas. With treatment, a patient’s AHI may not go down as much as we’d like, but many of their apneas are now just hypopneas. This explains why a “non-reponder” might still have significant improvements in oxygen levels, feel less sleepy, AND have significantly reduced risk of heart and brain complications in the future.
Hypoxic burden provides essential, complementary information about sleep apnea severity and associated health risks. In this analysis, meaningful reductions in hypoxic burden occurred in both responders and “non-responders” implanted with the Inspire hypoglossal nerve stimulator.