Effects of Bolus Volume and Temperature on Coordination of Swallowing and Respiration

Abstract

This is a study to investigate the effects of bolus volume and temperature on the respiration pattern and the duration of deglutition apnea during swallowing． The subjects included 4 men and 11 women who understood the purpose of the present study and expressed their consent (mean age 20.4 years，SD 3.1)． The subjects swallowed water bolus 60 times in total： 10ml water at 5℃， 20ml water at 5℃， 10ml water at 25℃，20ml water at 25℃，10ml water at 50℃，and 20ml water at 50℃，respectively，ten times．The respirograms and surface electromyograms（EMGs）of the suprahyoid muscles were simultaneously recorded during swallowing．

The respiration patterns during swallowing were classified．The frequency of the single type（respiration pattern indicating complete deglutition with one swallowing movement）and EAE subtype（respiration pattern consisting of expiration，apnea and expiration） and the duration of deglutition apnea observed in EAE subtype under various bolus conditions were evaluated． Two-way analyses of variance（ANOVA）were employed to assess the data obtained，and the effects of bolus volume and temperature were evaluated． A test was conducted to clarify the difference in population ratio， and the results obtained were used to determine the effects of bolus volume on the frequency of resptration patterns．

In terms of the frequency of the single type，tests performed to evaluate the interactions between bolus volume and temperature showed no significant difference．Regarding the frequency of the single type，a significant difference was recognized only in the bolus volume and a significant decrease was observed in the experiment conducted with a bolus volume of 20ml when compared with 10ml (P＜0.01)．With the frequency of EAE subtype，similar results were obtained (P＜0.05)．The frequency of IAI subtype （respiration pattern consisting of inspiration，apnea and inspiration）increased significantly in the experiment conducted under the condition of bolus volume of 20ml， against 10ml (P＜0.05)．As for the duration of deglutition apnea in EAE subtype，there were no significant interactions between bolus volume and temperature，and there was a significant difference only in bolus volume．The duration of deglutition apnea in EAE subtype increased significantly in the experiment conducted with a bolus volume of 20ml when compared with 10ml (P＜0.05)．

The respiration pattern and the duration of deglutition apnea during swallowing were thus influenced by bolus volume， but not temperature． lt was suggested that， by increasing the bolus volume of swallowing，the respiration-type recognition rate was changed and there was coordination of the prolonged deglutition apnea with respiration．