Data from a recent US study adds further support for the use of nerve stimulation as an alternative to PAP therapy for obstructive sleep apnoea.
If you can’t tolerate CPAP for obstructive sleep apnoea, there’s growing evidence for a somewhat shocking alternative.
Hypoglossal nerve stimulation – where electrodes are placed on one or both hypoglossal nerves – has been approved by the US FDA as an alternative treatment for OSA for more than a decade. However, the evidence base supporting its use is somewhat limited.
Now, the results of a new randomised controlled trial with open label extension suggests that six months of proximal HGNS treatment results in clinically significant improvements for OSA. The findings were published in Annals of Internal Medicine.
“pHGNS is a multicontact electrode array system that stimulates specific sectors of the hypoglossal nerve trunk, in contrast to distal HGNS, which stimulates branches of the hypoglossal nerve,” the researchers wrote. “In theory, pHGNS may enable stimulation of more tongue and airway muscles than distal HGNS, resulting in improved airway tone rather than only protruding the tongue.”
The treating Obstructive Sleep aPnoea using taRgEted hYpoglossal nerve stimulation (OSPREY) trial involved a seven-month RCT phase (where pHGNS was turned on in the active treatment arm one month after surgery) and a six-month open-label phase (where all participants had their pHGNS turned on). Participant recruitment occurred in 23 primary care centres across the US.
Individuals aged 22 years or older were eligible for the trial if they had a BMI of 35kg/m2 or lower and had a diagnosis of moderate-to-severe OSA (defined as an apnoea-hypopnea index of 15-65 events/hour as measured by in-laboratory polysomnography). An inability to tolerate PAP therapy was also a requirement. People with relevant medical conditions (e.g., chronic insomnia, moderate-to-severe respiratory disease or cerebrovascular disease) were excluded.
One hundred and four patients were enrolled in the study, with 67 allocated to the pHGNS group and 37 to the control group. The average age of included patients was 55.6 years while the average BMI was 30.6 kg/m2. Approximately three quarters of participants were male (73.1%), and a similar proportion of participants had previously failed or not tolerated using CPAP to control their OSA (76.0%).
Adherence during the RCT component was reasonably high, with participants using pHGNS for at least four hours on a median of 79.9% of nights over the first six months. The median duration of pHGNS usage during this period was 6.3 hours per night. These figures were maintained when data from the open-label extension period was considered (72.8% and 6.2 hours per night).
A greater proportion of patients in the pHGNS group met the primary outcome and displayed an AHI response – defined as a ≥50% reduction in their AHI from baseline and an AHI below 20 events/hour – at the seven-month mark compared to the control group (58.2% versus 13.5%). The improvement in the active treatment group persisted at the 13-month follow-up (64.6% response rate), and an increased response rate was also observed in patients who switched from control to active treatment after the RCT component (42.9% response rate).
“This reduction in AHI is clinically meaningful given the estimated minimum clinically important difference of five events/hour. A difference of 15 events/hour may indicate a change in severity category based on thresholds defined by the American Academy of Sleep Medicine,” the researchers said.
Related
pHGNS was also associated with improvements in oxygen desaturation index (ODI), Clinical Global Impression of Improvement (CGI-I) scores and daytime sleepiness as measured by the Epworth Sleepiness Scale (ESS):
- 68.7% of patients achieved at least a 25% improvement at ODI between baseline and month seven after receiving pHGNS, compared to 37.8% in the control group
- 56.3% of patients in the active treatment arm had a CGI-I of “much improved” or “very much improved” from baseline to month seven, compared to 8.6% in the control group
- Patients in the active treatment group reported a greater change in median ESS score between baseline and month seven (10.0 to 6.0) compared to patients in the control group (9.0 to 9.0).
No serious adverse device effects were recorded over the course of the trial, but 77.9% of participants experienced a treatment-emergent adverse event and 2.9% experienced a serious TEAE at the seven-month mark. Forty-one percent of TEAEs were related to the implantation procedure. Less than 3% of patients reported tongue discomfort and 6% of patients reported tongue movement disturbances.
“Future pHGNS research should include optimising patient selection and therapy titration, demonstrating long-term clinical outcomes and exploring additional device features that were not yet activated in this clinical trial (including multielectrode stimulation rather than single-electrode stimulation),” the researchers concluded.
“The full capabilities of the pHGNS platform remain unexplored, particularly regarding the potential for increased therapeutic efficacy when activation of lingual musculature is shaped by paired rather than single-electrode stimulation.”
