A quantitative comparison of the early histopathological changes from tracheotomy and endotracheal intubation on the distal trachea in fetal lambs.

Twenty-four premature fetal lambs underwent tracheotomy (n = 11) or endotracheal intubation (n = 13) for 3-9 h for an unrelated experiment. All were maintained with 100% oxygen on a pressure cycled ventilator. No suctioning was performed. At sacrifice, sections of the distal trachea were studied for histopathological changes in epithelium, submucosa and mucous glands. All changes were confined to the epithelium and were reported as either partial or total epithelial erosion in regards to preservation of the basal cell layer. In tracheotomized and intubated animals, both partial and total erosion were seen as early as 3 and 3.5 h, respectively. In the intubated animals, 13.5% of the cumulative tracheal circumference showed total erosion; 19.8% showed partial erosion. In animals undergoing tracheotomy, 9.6% of the cumulative tracheal circumference had total erosion; 19.1% had partial erosion. Possible etiological factors include oxygen toxicity, lack of humidification, effects of mechanical ventilation and indirect trauma from surgery or intubation. The clinical significance for premature infants is discussed.