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Effect of Mandibular Position on Upper Airway Collapsibility and Resistance

¹ Nagasaki University Graduate School of Biomedical Sciences, Course of Medical and Dental Sciences, Dept. of Translational Medical Sciences, Division of Clinical Physiology, 1-7-1 Sakamoto, Nagasaki-shi, 852-8588, Japan; and
² The Johns Hopkins University School of Medicine, Division of Pulmonary and Critical Care Medicine, and Johns Hopkins Sleep Disorders Center, Baltimore, MD, USA;

View larger version (27K): [in a new window]   Figure 1. Diagram of experimental techniques.

View larger version (55K): [in a new window]   Figure 2. A representative polysomnographic recording is illustrated, showing the change in upper inspiratory airflow (VI) (top channel) and nasal pressure (Pn) (second channel from top). As shown, progressively sub-atmospheric levels of nasal pressure (Pn) were applied in stepwise manner (left to right) and kept constant at each pressure level for 5 or 6 breaths. At Pn values below 3 cm H2O, inspiratory flow limitation ensued, as indicated by a flattening of the inspiratory airflow contour (see downward arrow from left), while the esophageal pressure (Peso) continued to become increasingly more negative. We obtained maximal inspiratory flow (VImax) by taking the difference between zero inspiratory flow and maximal inspiratory flow, as illustrated by the dotted lines. A period of zero flow was accompanied by similar changes in esophageal pressure (Peso), hypopharyngeal pressure (Phypo), and oropharyngeal pressure (Poro) during inspiratory efforts, together with failure of these pressure changes to be transmitted to the nasopharynx. Similar findings were observed in all subjects.

View larger version (23K): [in a new window]   Figure 3. A representative example of the nasal pressure (Pn) vs. inspiratory flow (VImax) relationship in one subject. Nasal resistance (Rua) was defined as the reciprocal of the slope of the relationship between VImax and Pn, and Pcrit as the x intercept of the regression line, as illustrated. In the neutral position (open circle), Pcrit was –4.2 cm H2O and Rua was 23.3 cm H2O/L/sec. In centric occlusion (filled circle), Pcrit was –8.0 cm H2O, and Rua was 15.0 cm H2O/L/sec, while in the ‘incisor aligned’ position (open square), Pcrit was –9.3 cm H2O and Rua was 14.3 cm H2O/L/sec. In the mandibular advancement position (filled square), Pcrit was –18.5 cm H2O, and Rua was 27.3 cm H2O/L/sec.