EFFECTS OF SUSTAINED CONSTANT ARTIFICIAL VENTILATION ON RAPIDLY ADAPTING PULMONARY STRETCH RECEPTORS AND LUNG MECHANICS IN RABBITS

Abstract

After hyperinflation to produce maximal dynamic lung compliance (Cdyn), the effects of artificial ventilation at constant frequency (f) and tidal volume (V T) for over a 2-hour period on rapidly adapting pulmonary stretch receptor (RAR) activity and lung mechanics were investigated in anesthetized rabbits. At a 20 min from maximal Cdyn the RARs began to significantly increase their activity, and this increase coincided with the increase in tracheal pressure (P T). Afterward, the increases in RAR activity and P T developed more slowly. Throughout the sustained constant artificial ventilation, the values of V T and respiratory airflow were not significantly different from controls. At 2 hours after maximal Cdyn, atropine (2 mg/kg) did not significantly alter either the increases in RAR activity and total lung resistance (R L) or the decrease in Cdyn, but hyperinflation reverted those responses to the control levels. These results suggest that the sustained artificial ventilation increases lung stiffness to invariably stimulate RARs, but that the response is not involved in vagally mediated bronchoconstriction.