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Hypoglossal nerve stimulation (HGNS) is associated with increases in airflow in patients with sleep apnoea, according to a new study.
Using a neurostimulation device from Apnex Medical, researchers found "progressive increases in respiratory airflow with increasing stimulation intensity," Dr Alan R. Schwartz, of the Johns Hopkins Sleep Disorders Centre in Baltimore, told Reuters Health by email.
"Stimulation increased airflow markedly and abolished respiratory flow limitation in the majority of patients," said Dr Schwartz, whose findings appeared online in the American Journal of Respiratory and Critical Care Medicine.
Hypoglossal nerve stimulation better
Continuous positive airway pressure is the standard treatment for obstructive sleep apnoea, but hypoglossal nerve stimulation has also been shown to reduce pharyngeal collapsibility and the severity of the condition.
However, the researchers point out, "airflow responses to graded increases in HGNS have not been described; nor has the magnitude of these responses been well characterised."
To help do so, the team studied 30 patients with obstructive sleep apnoea who had had the HGNS system implanted. They first underwent a standard overnight sleep study and then were examined with the HGNS system activated.
Flow change a result of stimulation
With increasing current, there were linear increases in maximal aspiratory airflow and respiratory airflow limitation (IFL) was abolished in 57% of the patients.
In those who continued to have IFL, the flow response slope was significantly greater and the stimulation amplitude at peak flow was lower without differences in peak flow.
Both groups "attained normal or near normal levels of maximal respiratory airflow during sleep of about 400 mL/s or greater," the researchers note.
Dr Schwartz added that "flow changed instantaneously with stimulation and increased progressively with stimulus intensity, suggesting that increases in flow are a direct effect of stimulation rather than a result of arousals from sleep."
Airflow returns with baseline levels stimulated breath
In addition, aspiratory airflow returned to baseline levels during and immediately following the stimulated breath.
"Further studies in additional patients, sleep stages and body positions will be required to determine the clinical and physiologic predictors of this response," the researchers write.
"The FDA has authorised the conduct of one or two clinical trials for HGNS devices. FDA approval for clinical use will depend on these trial results," Dr Schwartz added.
This study was supported in part by Apnex Medical and Dr Schwartz and other authors received compensation from the company as medical advisers.
(David Douglas, Reuters Health, January 2012)
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