Quantitative Assessment of Aspiration: A Novel Porcine Model

Abstract

Objective: Develop a porcine model for quantitative assessment of pulmonary aspiration.

Method: The porcine model consists of an endotracheally inserted pH probe with the distal end of the probe at the carina. The pH probe is sutured to the posterior tracheal wall, and the position is verified by a flexible endoscope. An acidic solution of known pH (2.5) is delivered through a catheter attached to the endotracheal tube, with the distal end on the cuff of the tube. The pH probe is connected to a multifunctional data acquisition device (NI USB 6009. National Instruments, USA) with an analogue output signal measuring the voltage generated, which is analyzed on software (Lab View 2011, National Instruments). This continuously provides a quantitative assessment of aspiration by detecting any voltage changes over a period of time indicating leakage of fluid around the endotracheal cuff.

Results: The mean voltage measured with the cuff fully inflated and a column of 10 mL of a solution of known pH on the cuff over a period of 2 hours was 885.74 ± 7.8 mvolts. With deflation of the endotracheal tube cuff a significant drop in voltage (mean voltage drop = 363.24 mvolts, P = .001) was measured, indicating leakage of the acidic solution across the endotracheal tube cuff.

Conclusion: The model provides a reliable method of quantifying the amount of aspiration. The model can be run for a long period of time and serves as an effective way of analyzing various techniques and devices for reducing aspiration.