INFLUENCE OF OXYGEN VENTILATION ON DOPPLER MICROEMBOLI SIGNALS IN PATIENTS WITH ARTIFICIAL-HEART VALVES

Background and Purpose The purpose of this study was to evaluate the i nfluence of inhalation of 100% oxygen on microembolic signal (MES) cou nts in patients with artificial cardiac valves. Methods A total of 134 outpatients were examined. Transcranial Doppler baseline monitoring ( 45-minute duration) was performed in all patients under resting condit ions. The first 30 patients subsequently underwent transcranial Dopple r monitoring for at least 20 minutes under noninvasive positive pressu re ventilation with 100% oxygen and for an additional 30 minutes under resting conditions. The same protocol was applied to all following pa tients with a baseline MES count greater than or equal to 10, while th e examination was discontinued in the remaining patients. Results Base line MES counts <10, which remained unchanged during oxygen inhalation and the subsequent resting period, were observed in 26 of 30 initial patients. A total of 46 patients with MES counts greater than or equal to 10 were identified. Oxygen application was feasible in 43 patients . An exponential MES decrease was noted in 42 patients during oxygen i nhalation (statistically significant in 38 patients), followed by a su bsequent increase in 38 of 43 patients (statistically significant in 2 5 patients) under resting conditions. Conclusions The exponential redu ction of MES counts observed in this study corresponds to blood denitr ogenation, thus strongly arguing for nitrogen bubbles as underlying em bolic material in prosthetic valve carriers. (Stroke.