title: Influence of oxygen ventilation on Doppler microemboli signals in patients with artificial heart valves.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the influence of inhalation of 100% oxygen on microembolic signal (MES) counts 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 conditions. The first 30 patients subsequently underwent transcranial Doppler monitoring for at least 20 minutes under noninvasive positive pressure ventilation with 100% oxygen and for an additional 30 minutes under resting conditions. The same protocol was applied to all following patients with a baseline MES count > or = 10, while the examination was discontinued in the remaining patients.
  
  
  RESULTS
  Baseline 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 > or = 10 were identified. Oxygen application was feasible in 43 patients. An exponential MES decrease was noted in 42 patients during oxygen inhalation (statistically significant in 38 patients), followed by a subsequent increase in 38 of 43 patients (statistically significant in 25 patients) under resting conditions.
  
  
  CONCLUSIONS
  The exponential reduction of MES counts observed in this study corresponds to blood denitrogenation, thus strongly arguing for nitrogen bubbles as underlying embolic material in prosthetic valve carriers.
authors.affiliation: Department of Neurology, University of Halle, Germany. dimitrios.georgiadis@medizin.uni-halle.de
authors.forename: D
authors.initials: D
authors.lastname: Georgiadis
authors.forename: A
authors.initials: A
authors.lastname: Wenzel
authors.forename: D
authors.initials: D
authors.lastname: Lehmann
authors.forename: A
authors.initials: A
authors.lastname: Lindner
authors.forename: H R
authors.initials: HR
authors.lastname: Zerkowski
authors.forename: S
authors.initials: S
authors.lastname: Zierz
authors.forename: M P
authors.initials: MP
authors.lastname: Spencer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003327:Coronary Disease / Q000000981:diagnostic imaging* / Q000209:etiology*; D004617:Embolism / Q000000981:diagnostic imaging* / Q000209:etiology*; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen; D011175:Positive-Pressure Respiration; D012119:Respiration; D014463:Ultrasonography
chemical_list: D010100:Oxygen