MMA: The Fight Against Sleep Apnea

Introduction Affecting approximately one billion people worldwide, obstructive sleep apnea (OSA) occurs when an individual’s airway self‐obstructs during sleep. Persons suffering OSA are generally less healthy and are more likely to develop a myriad of conditions known collectively as Metabolic Syndrome. One OSA solution is maxillomandibular advancement surgery (MMA), involving maxillomandibular complex (MMC) repositioning. While the surgery reports an 87‐100% success rate, the mechanisms of how MMA reduces OSA is not as clear. Further, a proportion of patients are dissatisfied with their appearance after the procedure. This project aims to simulate ventilation in cadavers who have undergone MMA surgery using an incremental MMA approach to measure airway resistances and relate these changes to resulting facial alteration. Surgery The MMA procedures were performed by the same dental surgeon. The oral distraction devices (KLS Martin, Florida) were left intact for the entirety of the experiment for manual jaw advancements. For each dependent variable, the MMC was advanced from 0mm to 14mm in 2mm increments. Ventilation A patient ventilator (LTV 1000 Pulmonetics, Minnesota) simulated ventilation at each MMA increment. Tidal volumes (TV) were calculated for each cadaver at 6ml/kg of body mass, over the same breathing frequency (12 breaths/minute), resulting in constant air flow rates. At each advancement of the MMC, airway resistance (R) is calculated using breath‐by‐breath analysis of peak inspiratory pressure and plateau pressure at each flow rate. A minimum of 10 breaths were used to calculate R at each MMA increment. Facial Scans After every ventilation condition, topographical scans measured 3D changes in the face (Space Spider Scanner, Artec, California). Scan areas of interest extended from hyoid to infraorbital foramen and to the tragi, laterally. The 3D meshes enable calculation of discreet skin surface alterations at each MMA increment and comparisons to baseline topography. Comparing incremental changes to baselines as percentages, a facial alteration index (∆F%) allows comparisons across individuals. Discussion Determination of cadaveric breath‐by‐breath airway forces during MMA is novel and ongoing. Preliminary results (n=1, F, 27yrs, 46kg) demonstrate inverse relationships between incremental MMA and R. With each 2mm MMA, R decreased an average of 4.3 cmH2O/L/s (r = ‐0.82). The foundation of the change in R is supported by an average decrease in peak inspiratory pressure of 3.67 cmH2O (r = ‐0.95) and an average decrease in plateau pressure of 2.81 cmH2O (r = ‐0.97) with each 2mm MMA. Use of ∆F% analysis enables demonstration of the relationship between MMA, airway resistance, and resultant facial alteration. The combined approaches are hypothesized to predict relationships between airway resistance and facial alteration at each level of MMA. Determination of this relationship will be a powerful tool, enabling surgeon and patient to be involved in informed decision‐making.

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