Oesophageal and diaphragmatic activity during sucking in lambs

Abstract

SUMMARY1. Buccal, pharyngeal, oesophageal and diaphragmatic movements during swallowing of saliva and sucking from a bottle were studied in lambs by recording electromyograms (e.m.g.s) from the mylohyoid, thyrohyoid and thyroarytenoid muscles, cervical and caudal thoracic oesophagus and vertebral and costal regions of the diaphragm. Buccal and pleural pressure recordings were also made.2. Swallows of saliva characteristically involved contraction of the mylohyoid followed sequentially by contraction of the thyrohyoid, cervical, and finally, caudal thoracic oesophagus.3. Sucking (indicated by the mylohyoid e.m.g.s and buccal pressure) was initially at rates up to 6 sec', sustained at up to 4 sec-' for 30-45 sec and, once established, accompanied by swallows in a 1:1 association with sucking.4. Respiration ceased during the pharyngeal phase of swallowing. At the time the primary contraction (ofswallowing) involved the caudal thoracic oesophagus vertebral fibres of the diaphragm forming the hiatus oesophageus became quiescent, although costal fibres continued to contribute to inspiration. 5. During sucking, respiration was shallow and rapid, with diaphragm contractions sandwiched between swallows.6. Towards the end of an episode ofsucking, contractions of the diaphragm became more intense and occurred in groups with pressure changes corresponding to both individual contractions and the grouped activity.7. Primary oesophageal contractions occurred only after single swallows or at the end of a series of swallows.8. During periods when sucking and swallowing were frequent, short episodes of oesophageal contraction occurred, each being between thyrohyoid contractions. 9. Recording from contiguous sites of the caudal thoracic oesophagus confirmed a caudally progressive character of those short contractions of the oesophagus observed during sucking.10. Factors contributing to these changes in oesophageal activity and consequences of altered diaphragmatic activity in sucking have been discussed.

Oxygen Transport and Utilization during Feeding in the Young Lamb

“…2) demonstrated by our lambs closely resembles the pattern previously reported for the newborn lamb (Harding et al 1978;Harding & Titchen, 1981). An epoch of feeding was composed of periods of sucking separated by pauses during which no sucking was observed.…”

Ingestion in Fetal Sheep and Its Relation to Sleep States and Breathing Movements

“…During each swallow there is a characteristically high amplitude and brief burst of activity in both of these muscles. In the post-natal lamb recordings of similar bursts of activity were obtained when swallowing could be confirmed visually or by palpation of the larynx (Harding & Titchen, 1982). As further evidence of the ability of laryngeal e.m.g.…”

“…Detection of individual swallows has shown that the maximum frequency (2-3 s-') was lower than that found in the post-natal lamb when suckle feeding (4-5 s-1) (Harding & Titchen, 1982). A disadvantage of monitoring ingestion by e.m.g.…”

“…), or the thyrohyoid muscle (t.h.). These muscles have characteristic large amplitude and brief discharges during individual swallowing movements in post-natal lambs (Harding & Titchen, 1982) as well as in other species (Doty, 1968). In addition to laryngeal sites, electrodes were sewn into the cervical oesophagus in five fetuses.…”

Respiratory phase resetting and airflow changes induced by swallowing in humans.

“…1 fulfil our criteria for phase resetting. Other studies in humans (Wilson et al 1981;Selley et al 1989;Nishino & Hiraga, 1991) and in animal models (Miller & Sherrington, 1916;Sumi, 1963;Harding & Titchen, 1981;Dick et al 1993;McFarland & Lund, 1993) concluded that there were shifts in the timing of the first inspiratory cycle after swallowing. It should be pointed out that immediate shifts in firing of medullary respiratory neurones due to deglutition could represent alterations only in bulbospinal output pathways without resetting the respiratory oscillator.…”