Modification of mastication and respiration during swallowing in the adult
human.
McFarland, David H., James P. Lund.
Ecole d'orthophonie et d'audiologie and Centre de recherche en sciences
neurologiques, Universit[acute]e de Montr[acute]eal, Montr[acute]eal,
Qu[acute]ebec H3C 3J7, Canada, Facult[acute]e de m[acute]edecine dentaire and
Centre de recherche en sciences neurologiques, Universit[acute]e de
Montr[acute]eal, Montr[acute]eal, Qu[acute]ebec H3C 3J7, Canada.
APStracts 2:0160N, 1995.
SUMMARY AND CONCLUSIONS
1. The normal interactions between respiration, mastication, and swallowing
were studied in adult humans while seated. Respiratory movements and movements
of the larynx were recorded with mercury-elastic strain gauges placed around
the rib cage and neck. A rigid body containing infrared-emitting diodes (IRED)
was attached to the forehead, and a single IRED was applied to the chin. Jaw
and head movements were transduced using the OPTOTRAK spatial motion analysis
system. Recordings were made before, during, and after the mastication of
pieces of carrot. 2. Movements of the larynx were used as a marker for
swallowing. Measurements were made of the duration of masticatory and
respiratory cycles, and the phase relationship between the two rhythms was
determined. Deviations in masticatory and respiratory movements during
swallowing were detected; the phases of the masticatory and respiratory cycles
in which the deviations occurred were determined, and the interval between
each deviation and the swallowing marker was calculated. 3. Three
characteristic swallowing patterns were observed: interposed, terminal, and
spontaneous. Interposed swallows occurred within a masticatory sequence,
terminal swallows ended the sequence, and spontaneous swallows occurred
sporadically between masticatory sequences. 4. Results revealed that
mastication could have a profound effect on the respiratory rhythm in some
subjects. One subject, whose data was excluded from further analyses, became
apneic for a long period, followed by short and shallow breaths near the end
of the masticatory sequence. In most subjects, respiratory rate increased
during mastication and then dropped below baseline as soon as mastication
ended. The end-inspiration diameter of the rib cage tended to fall in the pre-
swallow period and increase post-mastication relative to baseline. 5. There
was a weak but significant tendency for inspiration to begin during the jaw
opening phase of mastication, but phase-coupling did not become stronger as
swallowing was approached. 6. Deviations in respiration during swallowing
occurred during the late expiratory phase of the breathing cycle. Swallows
within a masticatory sequence occurred most frequently during the early
opening phase of the masticatory cycle, and terminal swallows occurred after
the end of the sequence with the mandible in the resting, postural position.
Swallowing temporarily reset both the masticatory and respiratory rhythms.
Most swallows prolonged the duration of one or two respiratory cycles,
however; swallows were often repetitive, and in some subjects, two or three
swallows fell within a single respiratory cycle, prolonging it for several
seconds. 6. A tight temporal relationship was observed between deviations in
respiration and the swallowing marker: all deviations occurred before or
coincident to the marker. The time of deviations in mastication relative to
the swallowing marker depended upon swallow type. There was no link between
the start of pauses in the two rhythms, suggesting that the commands from the
swallowing CPG to the other two pattern generators are independent. 7. We
suggest that disordered coordination of mastication and swallowing with
respiration may cause prolonged apnea in susceptible individuals.
Received 22 November 1994; accepted in final form 17 May 1995.
APS Manuscript Number J735-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.