Changes in pharyngeal dimensions effected by chin tuck.

This study measured the pharyngeal dimensions of 30 subjects when their heads were in an upright neutral position and in the chin-tucked position. Two videoprints of lateral radiographic views of the oral cavity and pharynx were made for each subject: one with the head in neutral position and one with the chin tucked. A 1-cm metal ruler was taped at midline on the front of each patient's neck to account for radiographic magnification of the image. Three angles and three distance measures were made on each videoprint. With the chin tucked, a posterior shift of anterior pharyngeal structures occurred, narrowing the laryngeal entrance and the distance from epiglottis to the pharyngeal wall and the laryngeal entrance, while widening the angle of the epiglottis to the anterior tracheal wall. This posterior shift with the chin tucked improves airway protection. Other clinical implications of these changes in pharyngeal dimensions are discussed.