Timing of respiration and swallowing events during deglutition

Abstract

Background: Dysphagia is a common symptom that can be due to disease, but can also occur without a known cause. Today, we know that the coordination of swallowing and respiration is essential for a safe swallow. Swallowing consists of several subsecond events. To study these events, it’s important to use modalities with high temporal resolution. In the first study in this thesis, we examined young healthy individuals with simultaneous videofluoroscopy, videomanometry and respiratory recordings, all with high temporal resolution. We know that dysphagia is more common in elderly and in patients with gastroesophageal reflux disease, (GERD).Whether this increased incidence of dysphagia in elderly is due to a disease process or is part of normal ageing is somewhat unclear. Furthermore, we believe that the increased incidence of dysphagia in GERD patients is due to reflux of gastro-duodenal content into the pharynx and larynx, which likely alter the sensory nerves of the mucosa which might deteriorate the sensitivity. To evaluate these two groups, we used our young healthy controls as a reference. However, to be able to use this control group, we used the same technique, modalities and protocol as in the study with young healthy volunteers. All of the above described studies were mostly experimental studies. Of this reason we wanted to perform a more clinical study and as swallowing maneuvers are the main treatment for dysphagia, caused by functional (neuromuscular) dysfunction. The aim of this study was to evaluate different swallowing maneuvers by intraluminal pharyngeal manometry in healthy volunteers.

Material and Methods: We examined all volunteers in our first three studies, with simultaneous videofluoroscopy, videomanometry and respiratory recordings, all with high temporal resolution. In the young group, the onset of 13 predetermined swallowing and respiratory events and the surrounding respiratory phase pattern were studied in different body positions and different respiratory drives, which were induced by breathing 5% CO2. In the elderly group we did not induce hypercapnia. However, six of the included 26 volunteers were examined in both the upright and the decubitus position, to evaluate whether posture had any effect on swallowing and respiratory coordination or on the swallowing safety. Our results demonstrated a highly repeatable and fixed temporal coordination of the swallowing and respiratory events despite position and respiratory drive. In our last study we only used simultaneous videofluoroscopy and videomanometry. Ten healthy volunteers without any swallowing complaints were included in the study. They started with three normal swallows without using any swallowing maneuvers and then they performed three swallows using each maneuver - the supraglottic, the super- supraglottic and the Mendelsohns maneuver. The supraglottic and the super-supraglottic swallows were explained during the examination. Subjects were instructed and trained in the Mendelsohns maneuver.

Results: Our results demonstrated a highly repeatable and fixed temporal coordination of the swallowing and respiratory events in the young individuals, despite position and respiratory drive. We could demonstrate that swallowing and respiratory coordination in elderly individuals did not differ significantly comparing the upright and decubitus position. The most significant results were several manometric values that were altered in the elderly individuals compared to the young. Even in the GERD patients, we could demonstrate almost the same results, with several impaired manometric values. In our study of swallowing maneuvers, we could demonstrate a few altered manometric values, preferable with the Mendelsohns maneuver and with the super-supraglottic swallow.

Conclusions: We believe that these differences in the manometric values in the elderly mainly are due to age-related changes with decreased sensitivity in the mucosa of the mouth and pharynx. We speculate that the altered muscle force in the mouth and pharynx are age- related. In the GERD patients, we believe that the impaired manometric values are due to reflux of gastro-duodenal content into the pharynx which ought to result in decreased sensitivity, that might cause an impaired force in the muscles of the mouth and pharynx. The reason why we only could confirm a few statistically significant manometric changes when healthy volunteers performed three different swallowing maneuver, might be explained by the need of more extensive training of the swallowing maneuvers or it could be due to the fixed pattern of the normal swallow.