P160

CHVÁLOVÁ, M., M. KUNCOVÁ, J. HAVRÁNKOVÁ, F. PALEČEK (Dept. Pathol. Physiol., Fac. Paediat., Charles Univ., Prague, Reg. Hyg. Centre, Ostrava). Regulation of Respiration in Experimental Silicosis. Physiol. bohemoslov., 23(6]: 539-547, 1974.

Experimental silicosis was produced in rats by the intratracheal injection of 50 mg quartz dust. Functional tests of ventilation mechanics were carried out in silicotic and control animals and the ventilation response to CO2 was determined. Pao2 was lower in the group of silicotic rats (44.7 torr]; the PaCO2 difference between the silicotic and control rats was non-significant. Higher respiration frequency and minute ventilation values and greater lung resistance and functional residual capacity were measured in silicotic rats, while lung compliance was lower. The ventilation response curve of silicotic rats was parallel with the curve for the control group, but displayed a shift to higher ventilation values. A detailed analysis showed animals with a flattened CO2 ventilation response curve in both groups. The study draws attention to certain regulatory factors which play a role in experimental silicosis: 1. greater functional residual capacity, 2. a change in the relationship between tidal volume and respiration frequency and 3. a change in the CO2 ventilation response curve. The possible causes of flattening of the CO2 ventilation response curve are discussed.