P033 Assessment of Upper Airway Dilator Muscle Function and Collapsibility in People with Multiple Sclerosis with Versus without Sleep Apnea

INTRODUCTION: Upper airway reflex responses to negative pressure are important to prevent upper airway narrowing and closure. Recent evidence indicates ~30% of people with multiple sclerosis (MS) have an impaired upper airway dilator reflex response. Thus, the aims of this study were to compare genioglossus muscle reflex responses and upper airway collapsibility in non-obese people with MS, with and without OSA. METHODS: Non-obese adults with MS and OSA vs MS without OSA were instrumented with pressure sensors at the choanae and epiglottis. Bipolar fine wires were inserted into the genioglossus. A nasal mask and pneumotachograph were attached to a breathing circuit to deliver brief (~250ms) suction pressure (~-12cmH2O) during early inspiration every 2-10 breaths while awake. Genioglossus reflex onset latency, peak latency and peak amplitude were quantified. The upper airway collapsibility index was the percent difference between choanal and epiglottic airway pressures during negative pressure. RESULTS: 15 people with MS (6 males), aged 48±13years, BMI=25±3kg/m-2 and AHI=13±17events/h (mean±SD) were studied. 47% had OSA (AHI>10events/h). Genioglossus reflex excitation onset latency (22±2 vs. 24±19ms), peak excitation latency (37±11 vs. 38±23ms) and peak amplitude (258±125 vs. 205±95%) were not different between OSA vs. non-OSA. The upper airway was more collapsible in people with OSA (49±32 vs. 17±16%, p=0.04). CONCLUSIONS: There is a high prevalence of OSA among non-obese people with MS. There was no systematic difference in upper airway dilator muscle function. However, the upper airway is ~65% more collapsible in people with MS and OSA despite absence of obesity.