Positional effects of head and/or neck flexion as chin-down posture in normal subjects.

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."