Endotracheal intubation in horses: a study of two cuff inflation pressures, correlation with liquid aspiration, and tracheal wall damage

Abstract

Nine adult horses were anesthetized for a nonsurvival abdominal adhesion study. Horses were randomly assigned into two groups to receive endotracheal tube cuff pressures of either 80 cm H2O (Group P80) or 120 cm H2O (Group P120). After intubation (Bivona 30 mm ID), anesthesia was maintained with isoflurane. Horses were ventilated 10 times per minute with a suitable inspiratory pressure to maintain Pe’CO2 in the 35-40 mm Hg (4.7-6.0 kPa) range. Cuff pressure was continuously monitored with a pressure transducer (TruWave, Baxter) calibrated to the atmospheric pressure and maintained at a constant pressure. Twenty-five millilitres of methylene blue dye in saline were instilled proximal to the cuff over 5 minutes. The horses were euthanized 123 ± 23 minutes later (mean ± SD). Immediately, the trachea was opened distal to the tip of the endotracheal tube, and the mucosa was observed for evidence of dye leaking past the cuff. The cervical trachea was resected and the lumen exposed by a ventral longitudinal incision. Biopsies (1-2 rings) were obtained at mid-cuff level and distal to the tip of the endotracheal tube, and placed in formalin for later histologic examinations (H&E stain).