Coordination of respiration and swallowing: functional pattern and relevance of vocal folds closure

CONTEXT: Breathing and swallowing coordination, despite the expressive number of study, remain as theme deserving further research. OBJECTIVE: To identify a coordination pattern between swallowing and the natural breathing pause that occur in association with it (swallowing apnea) and also the relevance of the vocal folds closure in this process. METHODS: Sixty-six adults, male and female, including normal health people, post-laryngectomy individuals and patients with digestive complaints without dysphagia were analyzed. The respiratory air flux interruptions produced by wet requested swallows and dry, requested and spontaneous swallows, were registered using thermo and piezoelectric receptors coupled to synectics medical manometry equipment, using Polygram upper 4.21 software. The results were analyzed with the Chi-square (3×2) and (2×2) nonparametric independency test with P = 0.05. RESULTS: Swallowing apnea is a preventive breathing stop that start just before and stay present during all deglutition pharyngeal phase. It is a well coordinated phenomena that occur as pattern in association with low elastic resistance of the lung, on the expiratory final phase until inspiration initial phase. This breathing stoppage it is usually followed by a short expiraton preceding a new breathing cycle. The swallow apnea and vocal folds closure are both independents mechanisms. CONCLUSION: It is possible to suppose that in the subconscious condition, swallowing apnea is integrated under coordination of the same control mechanism that also involves the elastic resistance of the lung.

Swallow Pattern Generator Reconfiguration of the Respiratory Neural Network

When the nasal and oral passages converge and a bolus enters the pharynx, it is critical that breathing and swallow motor patterns become integrated to allow safe passage of the bolus through the pharynx. Breathing patterns must be reconfigured to inhibit inspiration, and upper airway muscle activity must be recruited and reconfigured to close the glottis and laryngeal vestibule, invert the epiglottis, and ultimately protect the lower airways. Failure to close and protect the glottal opening to the lower airways, or loss of the integration and coordination of swallow and breathing, increases the risk of penetration or aspiration. A neural swallow central pattern generator (CPG) controls the pharyngeal swallow phase and is located in the medulla. We propose that this swallow CPG is functionally organized in a holarchical behavioral control assembly (BCA) and is recruited with pharyngeal swallow. The swallow BCA holon reconfigures the respiratory CPG to produce the stereotypical swallow breathing pattern, consisting of swallow apnea during swallowing followed by prolongation of expiration following swallow. The timing of swallow apnea and the duration of expiration is a function of the presence of the bolus in the pharynx, size of the bolus, bolus consistency, breath cycle, ventilatory state and disease.

Coordination of breathing and swallowing: effects of bolus consistency and presentation in normal adults

Preiksaitis, Harold G., and Catherine A. Mills.Coordination of breathing and swallowing: effects of bolus consistency and presentation in normal adults. J. Appl. Physiol. 81(4): 1707–1714, 1996.—Respiration and swallowing were recorded simultaneously by inductance plethysmography, submental electromyography, and a throat microphone in 10 normal subjects during eating and drinking tasks that included single boluses of varying volume (5–20 ml) and consistency presented with a syringe and cup, a 200-ml drink taken with and without the use of a straw, and a sandwich meal. Swallows were associated with a brief swallow apnea (SA) lasting ∼1 s. Swallow effects on the duration or tidal volume of the preswallow, postswallow and swallow-associated breathing cycles varied depending on bolus characteristics and presentation. Expiration before and after the SA was the preferred pattern with all drinking and eating tasks. Inspiration followed SA in <5% of single-bolus swallows, but this pattern increased significantly with a 200-ml drink administered by cup or by straw and during a sandwich meal (23.8 ± 5.2, 27.0 ± 2.6, and 16.3 ± 2.7%, respectively). Hence, the swallow-associated breathing pattern seen with single-bolus swallows may not reflect that associated with regular eating and drinking behavior. This finding implies that the risk of aspiration may be reduced by teaching patients prone to aspiration to simplify the complex behavior of eating and drinking to a series of single-bolus swallows.

Coordination of respiration and swallowing: effect of bolus volume in normal adults

The coordination of swallowing and respiration, as measured by nasal airflow, and the effect of changes in the volume of the swallow bolus (0-20 ml) were investigated in 12 normal subjects. Both nonbolus and bolus swallows were usually preceded and followed by expiratory airflow. Swallows followed by inspiratory airflow accounted for 20% of nonbolus swallows but decreased further in frequency in the presence of a bolus. Swallowing was associated with an apneic period lasting 1.90 +/- 0.26 s for nonbolus swallows. Based on the apneic period response to bolus volume, the subjects were divided into two groups. The apneic period decreased by 60% in seven of the subjects regardless of bolus volume. The remaining five subjects gradually increased swallow apnea as bolus volume was increased. At larger bolus volumes, the latter group also exhibited an earlier onset of the swallow apnea and an increase in the number of swallows preceded by inspiration. The duration of the swallow-associated respiratory cycle was similarly prolonged by an increase in bolus volume in both groups. The results indicate that the respiratory pattern associated with swallowing is modulated by the volume of the swallow bolus. Within the normal population, at least two different patterns of response to bolus volume are identified.