P002 Targeted non-CPAP combination therapy resolves obstructive sleep apnoea

Introduction Mandibular advancement splint (MAS) therapy is an effective alternative to CPAP for many people with obstructive sleep apnoea (OSA) but ~50% have residual OSA. This study aimed to resolve OSA in these individuals by combining MAS with other targeted therapies based on OSA endotype characterisation. Methods Eleven people with OSA (apnoea-hypopnoea index (AHI): 35±13 events/h), not fully resolved with MAS alone (AHI>10 events/h) were recruited. Initially, OSA endotypes were assessed via a detailed physiology night. Step one of combination therapy focused on anatomical interventions including MAS plus an oral expiratory positive airway pressure valve (EPAP) and a supine-avoidance device. Participants with residual OSA (AHI>10 events/h) following the anatomical combination therapy night, were then given one or more targeted non-anatomical therapies according to endotype characterisation. This included oxygen (4L/min) to reduce unstable respiratory control (high loop gain), 10mg zolpidem to increase arousal threshold, or 80/5mg atomoxetine-oxybutynin (ato-oxy) for poor pharyngeal muscle responsiveness. Results OSA was successfully treated (AHI<10 events/h) in all participants with combination therapy. MAS combined with EPAP and supine-avoidance therapy resolved OSA in ~65% of participants (MAS alone vs. combination therapy: 17±4 vs. 5±3, events/h, n=7). For the remaining participants, OSA resolved with the addition of oxygen (n=2), one with 80/5mg ato-oxy and another required both oxygen and 80/5mg ato-oxy. Discussion Targeted combination therapy may be a viable treatment alternative for people with OSA who cannot tolerate CPAP or for those who have an incomplete therapeutic response with monotherapy.

P080 An embedded pathway to mandibular advancement splint (MAS) construction in a tertiary hospital reduces barriers to care for low-income individuals

Introduction The aim of this study was to report the outcomes of patients referred within and to a tertiary hospital dental unit for subsidised construction of a MAS over a 5-year period. Methods Medical records of patients referred from 2015–2020 were examined for reason for referral, details of diagnosis, pathway to diagnosis, treatment, compliance, clinician-reported and lab-based outcomes and follow-up reviews. Results One hundred patients referred from: The Hospital Sleep Unit 40, other Tertiary Hospitals 27, Private Sleep Clinics 13, Medical GPs 10. 76 patients were confirmed health care card holders. 30 patients did not proceed for reasons of cost or poor oral health. 59 patients were newly fitted with a MAS (27F,32M), 17 severe, 21 moderate, 17 mild OSA, mean age 52.9(+13.9) years, BMI 30.2(+6.3) kg/m2, ESS 11.4(+5.3). 22 of 36 patients with serial ESS scores had excessive daytime sleepiness upon initial presentation. 15/22(68%)(p<0.005) of patients had resolution of their excessive daytime sleepiness following MAS wear. 8/15(53%) of patients had a subsequent AHI <50%. 33 patients (56%) continued MAS wear, mean follow-up time 13.8(±14.6) months with an average of 5.8(+3.0) visits. 6 were lost to follow up, 20 patients (33%) ceased MAS wear with 10(50%) of these stopping because routine dental treatment affected the device fit or discomfort later developed. Conclusion Subsidised expert construction of MAS embedded in a tertiary hospital is a well-utilised and effective service which reduces barriers for patients. The referrals to this service appear to be appropriate, with most patients proceeding to MAS construction.

P013 A pilot study for ultrasound examination of the pterygomandibular raphe to predict efficacy of mandibular advancement splint therapy in obstructive sleep apnoea

Background A lack of predictive indicators for mandibular advancement splint (MAS) efficacy limits their use in the treatment of obstructive sleep apnoea (OSA). The absence of a tendinous pterygomandibular raphe (PMR) in the lateral nasopharynx on MRI may predict MAS efficacy, however MRI is time and resource intensive. We aimed to assess the feasibility of ultrasound in determining PMR absence compared to MRI. Methods 10 healthy participants were recruited to undergo both MRI and ultrasound of the lateral airway. Surrounding anatomical landmarks were examined to establish the presence or absence of the PMR. These results will be compared to MRI to determine parameters on ultrasound which correlate to an absent PMR. Progress to date 8 of the 10 participants have undergone both MRI and ultrasound, of which half were women, mean age 53 years, mean BMI 28 and mean AHI 3. In all 8 participants so far parameters for assessment of the PMR were identified and described, including presence of anatomical landmarks, localisation and width of the PMR space, and presence of a hyperechoic structure within the space. Comparison of these parameters with MRI to determine predictors of PMR presence or absence is currently underway. Intended outcome and impact Validation of ultrasound in the assessment for presence or absence of a tendinous PMR will enable further study of this structure as a predictive marker for MAS efficacy in OSA. This could assist clinicians in identifying suitable patients for MAS therapy.

P081 Assessment of Change in Palatoglossus Length with Mandibular Advancement and Relationship to Response to Mandibular Advancement Splint Therapy in Obstructive Sleep Apnoea

Background The palatoglossus is a muscle of the soft palate extending from the palatine aponeurosis inferolaterally along the pharyngeal wall inserting at the posterolateral surface of the tongue. Palatoglossal stimulation dilates the retropalatal space in subjects with obstructive sleep apnoea (OSA). Whether there is alteration in palatoglossus length during mandibular advancement and how this relates to Mandibular Advancement Splint (MAS) outcomes is unknown. Methods Participants with OSA referred for MAS underwent upper airway MRI with and without mandibular advancement. The linear distance between the origin of the palatoglossus muscle at the palatine aponeurosis and its insertion at the tongue was measured to approximate palatoglossus length. The difference in measured lengths with and without mandibular advancement was calculated. Change in palatoglossus with advancement was compared to treatment outcomes. Progress to date 71 participants with mean±SD AHI 26.0±16.1 events/hr were included in our study. Mean±SD palatoglossus length was 49.58±5.74mm. With mandibular advancement, mean±SD palatoglossus length was 51.21±5.46mm this was a significant change in length of mean±SD 1.63±4.3mm. This was a mean±SD 4.79±9.08% alteration in length with mandibular advancement. Treatment response was not significantly related to change in palatoglossus length (p> 0.05). Intended outcome and Impact Our intention was to demonstrate significant length alteration in palatoglossus with mandibular advancement and correlate this to treatment outcome. This may highlight palatoglossus as a target for MAS or other OSA therapies for future clinicians.

Mandibular advancement splint response is associated with the pterygomandibular raphe

Study Objectives To investigate whether the presence of tendinous PMR could predict treatment outcome and how it affects lateral wall mechanical properties. Mandibular advancement increases the lateral dimensions of the nasopharyngeal airway via a direct connection from the airway to the ramus of the mandible. The anatomical structure in this region is the pterygomandibular raphe (PMR), but a tendinous component is not always present. Whether tendon presence influences treatment outcome is unknown. Methods In total, 105 participants with obstructive sleep apnea completed detailed anatomical magnetic resonance imaging with and without mandibular advancement. The study design was case–control. Variables were compared between participants with and without the tendon present. Results The amount of maximum mandibular advancement decreased when pterygomandibular tendon was present (4.0 ± 1.2 mm present versus 4.6 ± 1.4 mm absent, p = 0.04). PMR tendon-absent participants had a lower posttreatment apnea hypopnea index (16 ± 12 events/hour tendon present versus 9 ± 9 events/hour absent, p = 0.007) and were more likely to have complete response (63% versus 36%, p = 0.02). However, tendon-absent participants were more likely to not complete the study (χ 2 (3) = 10.578, p = 0.014). Tendon-absent participants had a greater increase in midline anteroposterior airway diameter (1.6 ± 1.7 mm versus 0.6 ± 2.3 mm, p = 0.04). Conclusion When PMR tendon is absent, treatment response and amount of maximum advancement improve, possibly at the expense of reduced splint tolerability. Tendon presence may help predict a group less likely to respond to mandibular advancement splint therapy.