Effect of lateral positioning on upper airway size and morphology in sedated children.

BACKGROUND Lateral positioning decreases upper airway obstruction in paralyzed, anesthetized adults and in individuals with sleep apnea during sleep. The authors hypothesized that lateral positioning increases upper airway cross-sectional area and total upper airway volume when compared with the supine position in sedated, spontaneously breathing children. METHODS Children aged 2-12 yr requiring magnetic resonance imaging examination of the head or neck region using deep sedation with propofol were studied. Exclusion criteria included any type of anatomical or neurologic entity that could influence upper airway shape or size. T1 axial scans of the upper airway were obtained in the supine and lateral positions, with the head and neck axes maintained neutral. Using software based on fuzzy connectedness segmentation (3D-VIEWNIX; Medical Imaging Processing Group, University of Pennsylvania, Philadelphia, PA), the magnetic resonance images were processed and segmented to render a three-dimensional reconstruction of the upper airway. Total airway volumes and cross-sectional areas were computed between the nasal vomer and the vocal cords. Two-way paired t tests were used to compare airway sizes between supine and lateral positions. RESULTS Sixteen of 17 children analyzed had increases in upper airway total volume. The total airway volume (mean +/- SD) was 6.0 +/- 2.9 ml in the supine position and 8.7 +/- 2.5 ml in the lateral position (P < 0.001). All noncartilaginous areas of the upper airway increased in area in the lateral compared with the supine position. The region between the tip of the epiglottis and vocal cords demonstrated the greatest relative percent change. CONCLUSIONS The upper airway of a sedated, spontaneously breathing child widens in the lateral position. The region between the tip of the epiglottis and the vocal cords demonstrates the greatest relative percent increase in size.