Quantitative assessment of pulmonary aspiration: A novel porcine model

Pulmonary aspiration is a common cause of ventilator-associated pneumonia in the intensive care setting. Current bench and animal models of aspiration are based on the qualitative assessments. The purpose of the present study was to develop a porcine model for the real-time quantitative assessment of aspiration.

Five sus scrofa piglets were anaesthetized and underwent placement of a pH probe through the endotracheal tube so that the distal tip of the probe resided at the carina. The pH probe was sutured to the posterior tracheal wall via an open approach and the position of the probe tip was verified by flexible endoscopy. 10 mL of acidic solution (pH = 2.7) was delivered through a catheter attached to the outside of the endotracheal tube so that the solution remained between the endotracheal tube and trachea proximal to the inflated endotracheal tube cuff. The pH probe was connected to a pH metre, a multifunctional data acquisition device with an analogue output signal measuring the voltage generated, and a computer for analysis. Leakage of fluid past the endotracheal tube cuff (aspiration) was therefore continuously assessed quantitatively by detecting voltage changes over a period of time.

The mean voltage of the tracheal mucosa at the beginning of the experiment (maximum voltage) was 916.6 mV ± 24.5 mV (range 891.0-945.7 mV). There was a slight drop in voltage at the end of the 2 h period to 840.8 ± 22.6 mV (range = 812.3-867.3 mV). After deflation of the endotracheal tube cuff, the mean voltage dropped to 497.3 mV ± 24.8 mV (range 435.7-567.1 mV) with a mean drop in voltage of 419.3 mV ± 32.6 mV (range 368.9-455.3 mV).

This porcine model allows for the continuous quantitative assessment of aspiration over time. Such a model may be of value for the evaluation of techniques for reducing aspiration.