A COMPARISON OF THE PULMONARY RESPONSE TO THE ENDOTRACHEAL INSTILLATION OF 0.1 N HYDROCHLORIC ACID AND HARTMANN'S SOLUTION IN THE RABBIT

Abstract

Lung function and structure were studied in anaesthetized rabbits subjected to endotracheal instillation of Hartmann's solution (Group I) or 0.1 N HCl (pH 1.0) (Group II) in order to differentiate mechanical effects from those caused by the chemical burn. In both groups a marked and similar decrease in static lung compliance and Pao2 was observed 10 minutes after the instillation. During the subsequent hour the measurements changed towards recovery in Group I, while in Group II they fell to approximately 50% of baseline, and profound metabolic acidosis developed. The lungs showed histological changes similar to those of the clinical acid aspiration syndrome with the possible presence of a localized consumption coagulopathy. The data suggest a biphasic response to acid aspiration. The early disturbance, independent of the pH of the aspirate, is attributed to airway closure and alveolar collapse following contact between the fluid and airway receptors, and to alveolar instability resulting from an alteration in alveolar surface forces. Subsequent deterioration resulted from the acid burn.