A Critical Analysis of Research on Swallow-induced Respiratory Functions in Healthy Individuals as a Function of Head/Body Position

Abstract

Pulmonary functions and respiratory airflow are known to change with the body and head positions. The precise coordination of swallowing with regular respiratory patterns prevents lower airway infiltration during bolus passage. This review was conducted to analyze the influence of head and body positions on the respiratory measures surrounding a swallow in healthy individuals. An all-inclusive search run on the most popular health science databases retrieved 18,588 articles that were screened for a set of inclusionary criteria. Among the 23 articles that satisfied these criteria, 19 were excluded with reasons. Relevant data were extracted and analyzed from the four articles for the level of research evidence, study characteristics, and significant findings. Three out of the four studies provided level II evidence, and only one included randomization and counter-balancing of trials. All findings were reported on young, healthy individuals, and none explored head positioning effect. The duration of respiratory apnea (RA) did not significantly differ across vertical and horizontal positions but the addition of 60° head-down tilt to the reclined body posture prolonged this measure. The number of inspiratory swallows increased in lying as compared to a vertical position. Rudimentary evidence on altered coordination of respiratory arrest with other related pharyngeal physiology was also available.