Developmental changes in collapsibility of the passive pharynx during infancy.

The upper airway configuration significantly changes during the first year of life in humans, possibly leading to alteration of collapsibility of the pharyngeal airway. The present study evaluated developmental changes of passive pharyngeal mechanics in nine normal infants ranging in age from 2 to 12 mo. The static pressure-area relationship of the passive pharynx was quantified under general anesthesia with complete paralysis. We found a direct association between age and maximal velopharyngeal area (r = 0.840, p = 0.005). Velopharyngeal closing pressure progressively decreased with increasing age (r = -0.809, p = 0.008) and the closing pressures were below atmospheric pressure in all infants (range: -0.7 to -9.8 cm H(2)O; mean +/- SD: -3.6 +/- 2.7 cm H(2)O). Shape of the pressure-area curves became steeper in slope with maturation, indicating increased pharyngeal wall stiffness during development. Accordingly, we conclude that anatomic properties of the pharynx gain stability in favor of maintaining patent airway during development in normal infants.