Inflammatory Effects of Thickened Water on the Lungs in a Murine Model of Recurrent Aspiration

Objective: Liquid thickeners are commonly recommended in individuals with dysphagia and recurrent aspiration as a strategy for pneumonia prevention. The goal of this study was to examine the effects of small amounts of aspirated liquid thickener on the lungs. Study design: Animal model. Prospective small animal clinical trial. Methods: Adult Sprague Dawley rats (n = 19) were divided into two groups and underwent three intratracheal instillations of either xanthan gum-based nectar-thick water (0.1–0.25 mL/kg) or water-only control over the course of 8 days. Blood was collected from a peripheral vein on days 1 and 8 and submitted for complete blood count (CBC) analysis. Rats were euthanized 10 days after the last instillation, and the lungs were harvested. Histopathology was conducted on lung specimens by a blinded licensed veterinary pathologist and scored for evidence of lung injury and pneumonia. Results: Fifteen animals (8 nectar-thickener group, 7 control group) survived until the endpoint of the study (day 18). Serum CBC did not show abnormalities at any timepoint in either group. Histological evidence of lung inflammation and edema were significantly greater in the nectar-thick group compared to controls (P <.05). Signs of inflammation included aggregates of foamy macrophages, expansion of bronchiolar lymphoid tissue, and large numbers of eosinophilic intraalveolar crystals. Histiocytic and neutrophilic pneumonia was noted in one animal that received thickened liquids. Conclusion: Recurrent aspiration of small amounts of thickened water resulted in significant pulmonary inflammation in a murine model of aspiration. Results of this study support the need for further investigation of liquid thickener safety and its efficacy in reducing the pulmonary complications of swallowing disorders. Level of Evidence: NA Laryngoscope, 131:1223–1228, 2021.