A NEW GUINEA-PIG MODEL FOR ACUTE INHALATION STUDIES ON COMBINED EFFECTS OF COLD-AIR AND POLLUTANTS

We have developed a new small animal model for acute inhalation studie s on combined effects of cold air and gaseous urban air pollutants. Th e anaesthetised, tracheostomised and paralysed guinea-pig was placed i nside a small, sealed whole-body-box, in which it was ventilated mecha nically by using cyclic negative pressure (P-box) for active expansion of the chest. During a 2-h normal ventilation with warm humid air (n = 6), there was a need for increasing P-box with time to maintain the fixed tidal volume (V-T) of 11 ml/kg. No such need was seen in the exp eriments with 15-min periods of isocapnic hyperventilation at 80 and 1 20 breaths/min (n = 13). During the 2-h normal ventilation and in expe riments with hyperventilation, there was a gradual increase in heart r ate and small gradual decreases in Pa-CO2 and pH with time. Cold air SO2 2.5 ppm produced a significantly stronger bronchoconstriction (De lta V-T = - 30.3 +/- 7.2%, n = 6, P < 0.05) than clean cold dry air (D elta V-T = - 10.6 +/- 1.3%, n = 6) and cold air + NO2 2.5 ppm (Delta V -T = - 13.2 +/- 3.3%, n = 6), although these three exposure conditions produced similar decreases in tracheal air and retrotracheal tissue t emperatures. With the present guinea-pig model, the combined respirato ry effects of cold air and gaseous urban air pollutants can be investi gated in a highly controlled manner. (C) 1998 Elsevier Science B.V. Al l rights reserved.