A method to rapidly evaluate the acute pulmonary effects of aerosols in unanesthetized guinea pigs

A method was developed to rapidly evaluate the acute effects of aerosols on the respiratory tract in unanesthetized but slightly restrained guinea pigs. Each animal was placed in a whole body plethysmograph and was fitted with a head chamber. From the head chamber, inspiratory volume (VI) was measured by integration with time of airflow rate obtained via a pneumotachograph. From the whole body plethysmograph a pressure (delta P) proportional to inspiratory volume was measured. Both VI and delta P were measured while the animal breathed a mixture of 10% CO2, 18% O2, and 72% N2. This procedure resulted in a stable and sustained increase in both VI and delta P. With the animals still breathing 10% CO2, the aerosols to be tested were then introduced. Both sulfuric acid and histamine aerosols produced a significant decrease in VI and delta P. The method is simple and does not necessitate anesthesia or invasive techniques. It should be useful to rapidly evaluate the possible acute effects of airborne contaminants. Furthermore, measurement of delta P alone with the animal in the whole body plethysmograph, obviating the need for the head chamber and the restraint imposed by it, was found to indicate an effect similar to the measurement of VI. This step further simplifies the method to evaluate an acute effect of aerosols on the respiratory tract.