Effects of respiration on soft palate movement in feeding

Abstract

Cyclic soft palate elevation is temporally associated with masticatory jaw movement. However, the soft palate is normally lowered during nasal breathing to maintain retropalatal airway patency. We tested the hypothesis that the frequency and amplitude of soft palate elevation associated with mastication would be reduced during inspiration. Movements of radiopaque soft palate markers were recorded by videofluorography while 11 healthy volunteers ate solid foods. Breathing was monitored with plethysmography. Masticatory sequences were divided into processing and stage II transport cycles (food transport to the oropharynx before swallowing). In food processing, palatal elevation was less frequent and its displacement was smaller during inspiration than expiration. In stage II transport, the soft palate was elevated less frequently during inspiration than expiration. These findings suggest that masticatory soft palate movement is diminished during inspiration. The control of breathing appears to have a significant effect on soft palate elevation in mastication.

Figure 1.

Locations of the soft palate and jaw markers and those positions in Cartesian coordinates. (A) A small metal pellet (4 mm diameter, 0.2 g) glued to the tip of a thin flexible rubber tube (internal diameter 1.5 mm) was placed on the surface of the center of the soft palate transnasally. The other end of the tube was taped to the face of the participant. Radiopaque lead markers (5 mm diameter) were also cemented to the buccal surfaces of the left upper and lower canines and first molars to measure movement of the jaws. (B) The position of the soft palate and jaw was expressed in Cartesian coordinates (in mm) with the upper canine at the origin. The upper occlusal plane, defined by a line passing through the upper canine and molar markers, was the horizontal axis (X axis). The line perpendicular to the X axis at the upper canine was the vertical axis (Y axis).

Figure 2.

Drawings and videofluorographic images of the three patterns of soft palate elevation occurring during mastication. (A) Pull-up pattern; the soft palate elevated independently of the tongue. Soft palate was drawn upward by contraction of its levator muscles. (B) Push-up pattern; the soft palate was pushed upward by the tongue. (C) Push-pull pattern; soft palate push-up followed by pull-up. The arrows indicate pulling and pushing of the soft palate movement. In B and C, the gray material between the tongue surface and the soft palate represents a bolus of food that is propelled by the tongue during stage II transport.

Figure 3.

Two examples of vertical jaw and soft palate movements over time with concurrent respiratory patterns in processing cycles while participants were eating a cookie. These feeding sequences were in different participants. Upward movement is shown as upward deflection on the graph. The inspiratory and expiratory phases are shown in gray and white, respectively. (A) Cyclical elevation of the soft palate was temporally linked to rhythmic jaw movement during expiration, but soft palate elevation was minimal during inspiration. (B) Soft palate elevation was temporally linked to jaw movement in every cycle. However, the amplitude of soft palate elevation was smaller during inspiration than expiration.

Figure 4.

Interaction of respiration and soft palate motion in (A) the frequency and (B) displacement of soft palate movement. (A) Stacked columns showing the percentage and number of processing and stage II transport cycles of the jaw that occurred during inspiration (gray) and expiration (white). The counts of jaw cycles with no soft palate movement (the no-up pattern) served as the statistical control for cycles with soft palate movement. During processing, jaw cycles with pull-up were significantly less frequent during inspiration (p < 0.001, logistic regression analysis). During stage II transport, cycles with push-up and push-pull were significantly less frequent during inspiration (p < 0.004). Swallow cycles are not shown, since there was no air movement during the swallow. (B) Bar graphs showing the mean (± SD) adjusted amplitude of soft palate displacement for each soft palate movement pattern and each jaw cycle type. The amplitude of pull-up soft palate displacement was significantly smaller during inspiration (dark bar) than during expiration (white bar) in processing cycles (p = 0.04, mixed-model ANOVA). During stage II transport cycles, the amplitude of push-pull displacement was significantly smaller during inspiration than during expiration (p = 0.03). Swallow cycles are not shown, since there was no air movement during the swallow. *P < 0.05 for comparison with control cycles. *P < 0.05 for inspiration vs. expiration.