Assessment of pharyngeal airway stability in normal and micrognathic infants

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Abstract
Whether negative airway pressure during inspiration can collapse the pharyngeal airway and neural control of pharyngeal airway-dilating muscles is important in preventing this collapse was investigated. Nasal mask occlusions were performed to increase negative pharyngeal airway pressures during inspiration in 8 normal and 5 micrognathic infants. Both groups developed midinspiratory pharyngeal obstruction, but obstruction was more frequent in micrognathic infants and varied in some infants with sleep state. The airway usually reopened with the subsequent expiration. The occasional failure to reopen was presumably due to pharyngeal wall adhesion. If airway obstruction occurred in sequential breaths during multiple-breath nasal mask occlusions in normal infants, there was a breath-by breath change in the airway pressure associated with airway closure (airway closing pressure); the airway closing pressure became progressively more negative. Micrognathic infants showed less ability to improve the airway closing pressure, but this ability increased with age. Nasal mask occlusion can test the competence of the neuromuscular mechanisms that maintain pharyngeal airway patency in infants. Micrognathic infants had spontaneous midrespiratory pharyngeal airway obstructions during snoring. Their episodes of obstructive apnea began with midinspiratory pharyngeal obstruction similar to that seen during snoring and nasal mask occlusions. Evidently, there is a similar pathophysiology for snoring, spontaneous airway obstruction and obstruction during snoring.