Introduction
Snoring is a cardinal symptom in patients suffering from Obstructive Sleep Apnea Syndrome (OSAS), contributing to excessive daytime sleepiness (EDS), arterial hypertension and cardiovascular disease. The collapsibility of the upper airways is one of the major underlying physiopathological characteristics of OSAS.
Mandibular Advancement Devices (MADs), that advance the lower jaw, have gained popularity as the first choice alternative treatment for CPAP (Continuous Positive Airway Pressure). MADs are assumed to enlarge the retroglossal space by anterior displacement of the tongue and to widen the cross-sectional dimension of the upper airway at the palatal level.
Problem description
The optimal positioning of the mandible is of primary importance during MAD therapy. However, the determination of this positioning remains a result of “trial and error” procedure at present in clinical practice. Both the reduction in pharyngeal collapsibility as well as the widening of cross-sectional area of the upper airway, induced by mandibular advancement, have been reported to be dose-dependent, although a higher protrusion will not always yield to higher efficiency. Furthermore, it is not clear to what extent patients can effectively be screened for successful MAD therapy.
Scientific objectives
The present research intends to focus clinically on selecting the right type of patient for MAD therapy. This is done using advanced imaging and computational fluid dynamics methods based on low-dose CT-Scan images of the upper airway while simulating in a reproducible way mandibular advancement. Drug-induced sleep nasendoscopy (SNE) techniques will be used for the direct evaluation of the effect of mandibular advancement on upper airway dimensions and location of the collapse using both imaging techniques for the calculation of the cross-sectional area as well as objective measurements such as the determination of the critical closing pressure (Pcrit) of the pharyngeal airway for the determination of the collapsibility.
Once the patient is selected for MAD therapy, impressions of the dental arches are made and a custom-made MAD is fabricated in the dental laboratory. The MAD is of the duobloc type where the upper and lower parts are interconnected using a flexible and adjustable joint. The effect of progressive mandibular advancement will be studied once the patient has been teached to optimize the mandibular protrusive position during the so-called titrating process.
The efficacy of the MAD therapy will be studied using a full-scale polysomnography for the evaluation of the outcome in terms of treatment success, once the fitted MAD is fully adjusted and titrated. Intermediary check-up will be done using home-based, automated detection of respiratory events with a nasal pressure monitoring device.
Utilisation objectives
The morbidity and mortality of OSAS-related pathology is well-described. There is increasing evidence that snoring, even without OSAS but with a prevalence of up to 32% in men and 14% in women, is not only bothersome to the bed partner but may also be harmful to the patient itself: lack of concentration – driving accidents – accidents during work – impaired social life are a few of the major symptoms illustrating both the economical as well as the social implications.
The availability of an adequate adjustable MAD may well contribute to a significant improvement of health status of many patients suffering from OSAS with CPAP-intolerance and/or CPAP-reluctance or suffering from mild OSAS as an alternative for invasive and surgical procedures with associated morbidity and mortality.
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