Impact of volume and rate of milk delivery on coordination of respiration and swallowing in infant pigs

Abstract

The coordination of respiration and swallowing is a life-critical function in infants. Varying volume and rate of milk delivery changes swallowing frequency and bolus volume but any impact on swallow-respiration coordination is unknown. Five infant pigs were filmed with simultaneous high speed videofluoroscopy and plethysmography while feeding from an automatic system delivering milk across a range of volumes and frequencies. Swallow inspiration delay, respiratory cycle duration, and distribution of inspiratory and expiratory swallows were calculated. At constant volume, there were more inspiratory phase swallows when frequency increased. At high constant frequency, increasing volume changed swallow-respiration coordination patterns, with increased occurrence of inspiratory phase swallows. Respiratory cycle duration did not change in response to changes in oral milk delivery. These results suggest that the observed pattern of expiratory swallowing in infants is achieved primarily by regulation of milk intake, not modulation of respiratory patterns by oral sensation.

Keywords: coordination; dysphagia; infant; respiration; swallow.

FIGURE 1

Representative trace of respiration measures from a plethysmograph (solid line) obtained during infant pig milk bottle feeding. Increases in voltage represent chest expansion (inspiration), decreases in voltage represent contraction (expiration). Vertical dashed lines indicate occurrence of swallows. Note presence of respiratory cycles without swallows, as well as both inspiratory and expiratory phase swallows.

FIGURE 2

Representative inspiratory and expiratory swallows. Plethysmograph trace is indicated by the solid line. The shaded region is inspiration. The grey dot marks the transition between expiration and inspiration. The vertical dashed line marks occurrence of the swallow. The two headed arrow indicates the swallow respiration delay.

FIGURE 3

Violin plot with median and overlain scatterplot of each swallow inspiration delay (a) and respiration cycle duration measurement (b) for delivery of 0.3 mL aliquots of milk at three different frequencies. Brackets with asterisks indicate significant pairwise differences between groups. Dotted line in (a) indicates time of swallow.

FIGURE 4

Violin plots with median and overlain scatterplot of each swallow-inspiration delay (a, b) and respiration cycle duration (c, d) measurement for delivery of aliquots of milk of varying volumes at 2 Hz (a, c), 4 Hz (d), and 5 Hz (a). Brackets with asterisks indicate significant pairwise differences between groups. Horizontal dashed lines in (a) and (b) indicate time of occurrence of the swallow.