Upper Airway Size During Inhalation Following Mandibular Advancement with a Stepped Mouthpiece: Evaluation with Acoustic Pharygometry

The size of the upper airway is critical during oral inhalation of drugs. Mandibular advancement
through oral appliances has been introduced in the treatment of subjects with obstructive sleep
apnoea (OSA) as a method to increase the size of the upper airway but has not been extended to
subjects using inhalers.
The main objectives of the 4 studies were to correlate upper airway cross-sectional areas (CSA) and volumes measured with acoustic pharyngometry with oropharyngeal and lung depositions, to evaluate the impact of mandibular advancement and incisor opening achieved with stepped mouthpieces on the upper airways, and to investigate in vitro the impact of an open velum on the acoustic pharyngogram.
Statistically significant correlations between oropharyngeal and lung depositions, and upper
airway CSA at glottis and volume between epiglottis and glottis, were shown in 9 healthy subjects. Four healthy subjects were included in a proof-of-concept study of a new stepped mouthpiece (without tongue depressor) with which different mandibular advancements (-3 to +6 mm) and incisal openings (10, 15 and 20 mm) were achieved. The upper airway CSA and volume was shown to increase in all 4 subjects.
Sixty subjects (30 healthy and 30 with OSA) were included in a study of the impact of mandibular
advancement (0 to 5 mm) and incisal opening (18 mm) achieved with a stepped mouthpiece (with
tongue depressor) on the size of the upper airways. Statistically significant effects were shown following both incisal opening and mandibular advancement, and the effects were larger for the healthy subjects. In the in vitro study the effect of an open velum on the acoustic pharyngogram was investigated through a cast of a human upper airway. The results showed that during acoustic pharyngometry an open velum would pass acoustic impulses into the nasal airways which would create an overestimation of the volume of the upper airways from the pharynx to the glottis.
The thesis highlights the possibility to increase the size of the upper airways during inhalation of drugs.