Abstract â–¡ 172

We have previously reported on the dimensions of the infant upper airways shown by respiration timed radiographs and video recordings.

The air pressure changes in the infant upper airway differ from those of the adult.

In the adult the pharyngeal pressure becomes negative as the diaphragmatic contraction enlarges the thoracic cavity. On expiration the rib cage and diaphragmatic rebound create a positive pharyngeal pressure which assists the return of the pharyngeal tube to its original size.

In contrast, in infants, there is a negative pharyngeal pressure generated on inspiration - but on expiration there is no positive pressure to assist in restoring the pharyngeal lumen. Thus the upper airway dimensions, and compliance, in infants have a much greater effect on their respiratory efficiency than they have in adults.

The pharyngeal pressures in infants and in adults during normal and obstructed respiration are demonstrated.