Quantitative assessment of pulmonary aspiration: A novel porcine model

Immediate Prone Positioning After Massive Gastric Aspiration Reduces Lung Injury Possibly by Attenuating Interleukin-6-Mediated Lung-Tissue Inflammation in Pigs

Gastric aspiration, which can cause acute, diffuse, inflammatory lung injury, is of particular concern in critically ill patients. This study aimed to determine the effects of immediate prone positioning on the degree of lung injury and inflammatory response induced by gastric aspiration. Following induction of gastric aspiration by injection of gastric fluid, 16 healthy pigs were randomized to one of two groups: supine position (SP) or prone position (PP). After ventilation and monitoring for 6 hr, all pigs were euthanized. The ratio of the partial pressure of arterial oxygen/fraction of inspired oxygen (P_aO2/F_IO2) and the partial pressure of arterial carbon dioxide (P_aCO2) were recorded during the 6-hr study period. Serum levels of interleukin (IL)-6 were measured every 2 hr, and the mean optical density (MOD) of IL-6 in lung tissues and lung-injury scores were measured at the end of the experiment. The PP group showed a significantly higher P_aO2/F_IO2 ratio, lower serum IL-6 concentration (p = .015), lower lung-injury scores (p = .012), and lower IL-6 concentration and MOD of IL-6 in lung tissue, especially in dorsal (p = .001, p = .021, respectively) and nondependent regions (p = .005, p = .035, respectively) than the SP group. There were no statistically significant differences in P_aCO2 between the groups. Lung-injury severity was positively correlated with the IL-6 concentration and MOD of IL-6 in lung tissues (p < .05). These results suggest that immediate prone positioning alleviated the degree of aspiration-induced lung injury, possibly through mitigating IL-6-mediated lung inflammation.

Assessment of aspiration risk from dynamic modulation of endotracheal tube cuff pressure

OBJECTIVES/HYPOTHESIS

To assess the risk of aspiration using a novel valve circuit that dynamically modulates endotracheal tube cuff pressure during the ventilatory cycle using bench and live animal models.

STUDY DESIGN

Animal model.

METHODS

The bench model consisted of a cuffed endotracheal tube inserted into an artificial trachea. Leakage of liquid around the cuff was measured after 4 hours of constant or dynamic modulation of cuff pressure at variable peak end expiratory pressures. In the porcine model, eight animals were ventilated with the modulating valve circuit and compared to eight controls ventilated with a constant cuff pressure (25 cm of water). Aspiration was monitored quantitatively using a pH probe (measured as voltage) and visually using fluoroscopy.

RESULTS

There was no difference in the amount of fluid leakage around the endotracheal tube cuff in the constant or dynamically modulated pressure-cuff groups in the bench or animal models.

CONCLUSION

Dynamically modulating endotracheal tube-cuff pressures to minimize tracheal mucosal damage does not increase the tendency to leak around the cuff compared to endotracheal tube cuffs inflated to a constant pressure.

LEVEL OF EVIDENCE

N/A.