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.