Physiological Flow of Liquids in Healthy Swallowing

Swallowing safety was measured using the Penetration-Aspiration Scale, an 8-point categorical scale which captures the depth to which any material enters the airway and whether or not the material is ejected. Levels 1 and 2 on the scale are considered safe, while levels > 2 are considered unsafe. Actual scale scores (1-8) will be recorded and then converted to binary categorical scores (< 3 vs >/= 3). We will report the frequency (count) of participants showing scores > 2 by bolus consistency.

Residue is material remaining behind in the pharynx after the swallow. We measured residue by tracing the area of barium visible on a lateral view x-ray (in pixels, using ImageJ software) and dividing that area by the squared length C2-C4 cervical spine. This cervical spine scalar provides a common anatomical reference that is a proxy for pharyngeal size, and enables the comparison of residue severity across different people with different neck length and pharynx size. In healthy swallowing, residue is expected to be minimal. We report median values and 97.5% confidence intervals for amount of residue by consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquids).

The number of swallows needed to clear a single bolus will be counted. 1-2 swallows is considered efficient, while > 2 for a single bolus is considered inefficient. We report the frequency (count) of participants displaying > 2 swallows per bolus by consistency.

The time interval between the first frame showing the bolus entering the pharynx (passing the ramus of the mandible) and the first frame showing onset of the hyoid burst movement in swallowing, calculated in milliseconds. We report median values and 97.5% confidence intervals for each bolus consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquid barium). Longer time intervals reflect delays in initiating the pharyngeal swallow.

The time interval between the first frame showing onset of the hyoid burst movement in swallowing and the first frame showing opening of the upper esophageal sphincter, calculated in milliseconds. We report median values and 97.5% confidence intervals for each bolus consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquid barium). Longer time intervals reflect a delay in opening of the upper esophageal sphincter.

The time interval between the first frame showing opening of the upper esophageal sphincter and the first subsequent frame showing closure of the upper esophageal sphincter behind the tail of the bolus, calculated (in milliseconds). We report median values and 97.5% confidence intervals for each bolus consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquid barium). Shorter durations of upper esophageal sphincter opening reflect inadequate durations of opening to allow material to pass through the sphincter from the pharynx into the esophagus.

The time interval between the first frame showing onset of the hyoid burst movement in swallowing and the first frame showing closure of the laryngeal vestibule, calculated in milliseconds. We report median values and 97.5% confidence intervals for each bolus consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquid barium). Longer time intervals reflect delays in achieving airway closure.

The time interval between the first frame showing closure of the entrance to the airway (laryngeal vestibule closure onset) and the first subsequent frame showing opening of the entrance to the airway (laryngeal vestibule closure offset) calculated in milliseconds. We report median values and 97.5% confidence intervals for each bolus consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquid barium). Shorter durations of laryngeal vestibule closure reflect premature termination of airway protection.

During swallowing, the muscles of the pharynx contract to achieve constriction (closure) of the pharynx behind the bolus. The squeezing and pressure generated by this action help to move the bolus downwards through the pharynx. We measured the degree of pharyngeal constriction by identifying the frame of greatest pharyngeal constriction, and tracing the area of any unobliterated pharyngeal space on lateral view x-ray (in pixels, using ImageJ software). The resulting area measure was then divided by the squared length of the C2-C4 cervical spine. This cervical spine scalar provides a common anatomical reference that is a proxy for pharyngeal size, enabling the comparison of constriction across different people with different neck length and pharynx size. In healthy swallowing, constriction is expected to be complete, with larger measures reflecting incomplete or poor constriction. We report median values and 97.5% confidence intervals for pharyngeal constriction by consistency.

During swallowing, the upper esophageal sphincter opens to allow the bolus to move from the pharynx into the esophagus. Narrow opening of the sphincter may obstruct bolus flow. We measured the degree (diameter) of upper esophageal sphincter opening on the frame of maximum distension. Line measurements were made in Image J software. This line measure was then divided by the length of the C2-C4 cervical spine. This cervical spine scalar provides a common anatomical reference that is a proxy for pharyngeal size, enabling the comparison of constriction across different people with different neck length and pharynx size. We report median values and 97.5% confidence intervals for pharyngeal constriction by consistency (thin, slightly thick, mildly thick, moderately thick and extremely thick liquid).

The area of the pharynx was measured, in pixels (using ImageJ software), on a lateral view videofluoroscopic image showing the pharynx at rest. The resulting area measure was then divided by the squared length of the C2-C4 cervical spine. This cervical spine scalar provides a common anatomical reference that is a proxy for pharyngeal size, enabling the comparison of pharyngeal size across different people with different neck length. Larger pharyngeal area measures may reflect atrophy of the pharyngeal muscles while smaller pharyngeal area may reflect narrowing due to edema.We report median values and 97.5% confidence intervals for pharyngeal area.

During swallowing, the tongue rises to contact the hard palate, generating pressure that squeezes the bolus backwards through the mouth towards the pharynx. The amplitude of tongue-palate pressure were measured continuously throughout swallowing using the KayPentax Digital Swallow Workstation Swallowing Signals Lab 3-bulb tongue pressure array, and the highest (peak) pressure was identified for each swallow. We will report mean values and standard error for peak pressure by bolus consistency (thin, slightly thick, mildly thick and moderately thick liquid). Higher amplitudes of pressure represent greater force for bolus propulsion.