EFFECT OF POSTURE ON UPPER AIRWAY DIMENSIONS IN NORMAL HUMAN

Posture has a major effect on breathing during sleep. Snoring, hypopne as, and apneas are all more common lying than sitting and more common supine than in a lateral lying position. Because the effect of the lat eral lying position on upper airway caliber has not previously been st udied, we examined this in 20 normal awake subjects and also determine d the effect of neck position. The acoustic reflection technique was u sed. Pharyngeal cross-sectional areas (CSA) fell significantly from th e sitting to supine position (oropharyngeal junction, from 1.65 +/- [S EM] 0.6 cm to 1.31 +/- 0.07 cm), but there was no difference in CSA be tween the supine and lateral positions for oropharyngeal junction (1.3 6 +/- 0.06 cm), mean pharyngeal area, maximal pharyngeal area, or phar yngeal volume. Neck hyper-extension significantly increased pharyngeal CSA (e.g., oropharyngeal junction null position 1.51 +/- 0.08, hyper- extension 1.94 +/- 0.11 cm), but there was no significant effect of ne ck flexion on airway CSA. These results confirm that in normal awake s ubjects, pharyngeal areas are smaller lying than sitting but also show ed no significant difference between CSA in the supine and lateral lyi ng positions. The study also demonstrates that the upper airway calibe r increases with neck extension in conscious adults.