Experimental evaluation of the effectiveness of respiratory support for the correction of toxic pulmonary edema

Abstract

Background. Pharmacological support and respiratory therapy are considered as approaches to the treatment of toxic pulmonary edema induced by inhalation intoxication of pulmonary toxicants. In severe intoxication, pharmacological tactics are ineffective. Information about the effectiveness of respiratory support for the correction of toxic pulmonary edema is limited in the available literature. Aim. Experimental evaluation of the effectiveness of the mechanical ventilation with maintained positive end-expiratory pressure (PEEP) for the correction of toxic pulmonary edema in rabbits caused by severe intoxication with thermal degradation products of fluoroplast-4. Methods. Rabbits were exposed to inhalation intoxication with thermal degradation products of fluoroplast-4 (2HLC50). The rabbits underwent mechanical ventilation or mechanical ventilation with maintained PEEP. The survival rate, mean life expectancy, arterial blood gas composition and saturation were evaluated, and chest computed tomography and X-rays of the chest organs were performed. Results. The exposure to thermal degradation products of fluoroplast-4 at a concentration of 2HLC50 (toxicity index of pyrolysis products) resulted in extremely severe intoxication of rabbits. In this process, the toxicity of thermal degradation products was due to their pulmonotoxic component, perfluoroisobutylene. Mechanical ventilation did not prevent the development of toxic pulmonary edema. At the same time, mechanical ventilation with PEEP provided an increase in the survival rate and a significant (p=0.024) increase in mean life expectancy compared with animals that did not receive treatment. In rabbits that did not receive treatment and rabbits that received only mechanical ventilation, signs of the alveolar phase of toxic pulmonary edema and pronounced arterial hypoxemia and hypercapnia were detected already in five hours after the exposure. In contrast, rabbits treated with mechanical ventilation with PEEP showed only signs of the interstitial phase of edema without a pronounced impairment of oxygenation. On the 7th day after the exposure, there were no disorders of the respiratory system structure and function in the survived rabbits treated with mechanical ventilation with PEEP. Conclusion. The use of mechanical ventilation with PEEP is effective for the correction of toxic pulmonary edema in rabbits induced by extremely severe intoxication with thermal degradation products of fluoroplast-4 containing perfluoroisobutylene, and the protective effect is due specifically to the creation of positive end-expiratory pressure.