Pathophysiologic Responses of Sheep to Brief High-Level Nitrogen Dioxide Exposure

Abstract

AbstractThe cardiopulmonary response to short-duration, high-concentration nitrogen dioxide (NO2) exposure was examined in conscious domestic sheep (Ovis aries). Six intubated animals in each of 3 groups were given a 15-min exposure to either air (control) or approximately 700 or 500 ppm NO2− Pulmonary and systemic hemody-namics, pulmonary mechanics, blood gases, and hematologic variables were measured immediately before and after exposure and at 1, 4, and 24 h after exposure. Minute ventilation was monitored during exposure, and a pulmonary histopathologic examination was performed 24 h postexposure. Negligible effects were observed in the control group. Exposure to 100 ppm NO2 caused a modest increase in minute ventilation during exposure, and an increased number of leukocytes was found within interalveolar capillaries upon histologic examination. Exposure to 500 pprn NO2 induced an immediate and profound lung irritant response characterized by an increase in lung resistance, respiratory rate, and minut...