小野木 啓子

OBJECTIVE: The "chin-down" posture involves tucking the chin to the neck. However, clinicians and researchers have their own forms of the chin-down posture: some consider it to be head and neck flexion, whereas others consider it to be head flexion alone. The purpose of this study was to evaluate the effects of head, neck and combined head-and-neck flexion postures separately. METHODS: Ten healthy volunteers participated in the study. The head and neck were set in neutral (N), head flexion (HF), neck flexion (NF) or combined head-and-neck flexion (HFNF) positions. Participants were instructed to swallow 4 ml of thick barium liquid in an upright sitting position. Head and neck angles at rest, distances in the pharynx and larynx at rest, and duration of swallowing were measured. Statistical analysis was performed with a paired t-test with Bonferroni correction. RESULTS: Head angles in HF, NF and HFNF positions were significantly greater than in the N position. Neck angles were significantly greater in the NF position than in the N position. The distance between the tongue base and the posterior pharyngeal wall, the vallecular space and the airway entrance were smaller in the HF position than in the N position. The tongue base was in contact with the posterior pharyngeal wall longer in the HF position than in the N position. CONCLUSION: Because HF, NF and HFNF positions have different effects, we recommend the use of these terms instead of "chin-down position."

This study used 320-row area detector computed tomography (320-ADCT) to determine whether kinematic swallowing events and bolus movement through the oropharynx are affected by bolus consistency and angle of recline. Fourteen healthy adults (4 men, 10 women; age, 22-90 years) underwent 320-ADCT assessment during three 10-mL barium swallow tests, with honey-thick liquid at 60° recline (60°thick), thin liquid at 60° recline (60°thin), and thin liquid at 45° recline (45°thin). The times of swallowing events were measured and compared among the different tests. Bolus propulsion, onset time of true vocal cord (TVC) closure, and upper esophageal sphincter opening were significantly earlier for 60°thin than for 60°thick. Onset time did not significantly differ between 60°thin and 45°thin; however, greater variability was noted for onset of TVC closure with 45°thin, as the TVC started to close before onset of swallowing in 30% of participants. Modulation of TVC closure depends on bolus transport in different reclining positions. The 45° reclining position elicited pre-swallow TVC closure in some participants, which suggests that excessive recline can increase perceived risk of airway invasion during swallowing.