Anatomical aspects of postintubational subglottic stenosis.

The subglottic regions of 54 human adult male and female larynges were studied with regard to anatomical aspects of postintubational stenosis. Fourteen specimens were impregnated with curable polymers and cut into 600-800 microns sections along different planes. Forty formalin-fixed hemilarynges were dissected. Measurements of the upper cricoid lamina and the thickness of the endocricoid soft tissues were taken for statistical analysis. Immediately beneath the glottis, the upper part of the cricoid lamina consists of two lateral plates with an average angle of 110 degrees. Distally, the cricoid adopts a more and more rounded lumen. At the level of the cricothyroid joint, the definite airway lumen is always laterally narrowed by a prominent thickening of the endocricoid soft tissue. Large amounts of loose connective tissue facilitate the development of edema in case of injury in this region. Dorsally, the submucous stratum is smaller and consists mainly of dense connective tissue. The blood vessels are fixed to the cricoid perichondrium by collagenous fibers. Any pressure applied from the airway lumen will force the vessels against the nonresilient cartilage, resulting in occlusion and ischemia. These pathophysiologic mechanisms are important for the development of early laryngeal damage during endotracheal intubation, possibly resulting in posterior stenosis due to scarring later on.