Co‐ordination of spontaneous swallowing with respiratory airflow and diaphragmatic and abdominal muscle activity in healthy adult humans

Abstract

Co-ordination of breathing and swallowing is essential for normal pharyngeal function and to protect the airway. To allow for safe passage of a bolus through the pharynx, respiration is interrupted (swallowing apnoea); however, the control of airflow and diaphragmatic activity during swallowing and swallowing apnoea are not fully understood. Here, we validated a new airflow discriminator for detection of respiratory airflow and used it together with diaphragmatic and abdominal electromyography (EMG), spirometry and pharyngeal and oesophageal manometry. Co-ordination of breathing and spontaneous swallowing was examined in six healthy volunteers at rest, during hypercapnia and when breathing at 30 breaths min -1 . The airflow discriminator proved highly reliable and enabled us to determine timing of respiratory airflow unambiguously in relation to pharyngeal and diaphragmatic activity. During swallowing apnoea, the passive expiration of the diaphragm was interrupted by static activity, i.e. an 'active breath holding', which preserved respiratory volume for expiration after swallowing. Abdominal EMG increased throughout pre-and post-swallowing expiration, more so during hyper-than normocapnia, possibly to assist expiratory airflow. In these six volunteers, swallowing was always preceded by expiration, and 93 and 85% of swallows were also followed by expiration in normo-and hypercapnia, respectively, indicating that, in man, swallowing during the expiratory phase of breathing may be even more predominant than previously believed. This co-ordinated pattern of breathing and swallowing potentially reduces the risk for aspiration. Insights from these measurements in healthy volunteers and the airflow discriminator will be used for future studies on airway protection and effects of disease, drugs and ageing.

Effect of a tracheostomy speaking valve on breathing–swallowing interaction

“…A study in healthy volunteers showed the occurrence of diaphragmatic activity consistent with active breathholding that preserved the expiratory volume just before swallowing, thereby allowing expiration at the end of the swallowing apnoea [20]. However, this activity was not sufficient to induce breath-holding during swallowing in tracheostomised patients with open tracheostomy tubes, as indicated by the finding in our study and an earlier study [6] of significant and continuous expiratory leakage through the tracheostomy tube during swallowing bracketed by expiration.…”

Longitudinal Changes of the Swallowing Process in Subacute Stroke Patients with Aspiration

“…Further analysis should incorporate these important features of aspiration, which can be checked by VFSS. In addition, previous studies have suggested other mechanisms related to airway protection, such as pharyngeal constriction [23], coordination between breathing and swallowing [24], and the sensory regulation of swallowing [25]. In the present study, persistent aspiration after the recovery of swallowing initiation in the nonrecovered group could have resulted from impairments of these mechanisms.…”

Eating on Noninvasive Ventilation*

“…In healthy subjects, experimentally-induced hypercapnia and elastic loading increase respiratory frequency and disrupt the normal breathing-swallowing coordination (11,12). This pattern is similar to what was observed by Terzi et al (5).…”