title: Reliability of the microdialysis pump CMA 107 under hyperbaric conditions.
abstract: OBJECTIVE
  Microdialysis measurements of extracellular substances under hyperbaric conditions were manifold used in several investigations. However, to our knowledge there is no analysis, which verified the applicability of microdialysis pumps under hyperbaric conditions. Thus, a goal of this study was to investigate the reliability of the microdialysis pump (MDP) CMA 107 in a hyperbaric environment up to 2.4bar absolute pressure.
  
  
  METHODS
  The CMA 107 with a perfusion rate of 2microL/min was stored in a decompression chamber. The ambient pressure was increased from 1 to 2.4bar absolute within 15min, maintained for 90min and then decreased to 1bar within 15min. The vials were changed every 15min, weighed before as well as after collecting the sample volume and the absolute recovery of glutamate, pyruvate, lactate, glucose and glycerol was determined. The same setup was performed under normobaric conditions.
  
  
  RESULTS
  The pumping capacity was 1.7% greater than expected under normobaric conditions, 36.5% less than expected in the compression phase, 10.5% less than expected in the isopression phase and 26.3% greater than expected in the decompression phase under hyperbaric conditions. The absolute recoveries under hyperbaric conditions were affected during the isopression phase with a deviation from -6 to +20% compared to normobaric environments.
  
  
  CONCLUSIONS
  The study demonstrated that an absolute ambient pressure up to 2.4bar did influence the pumping capacity and the reliability of the absolute recovery. These results need to be taken into consideration when interpreting microdialysis studies performed under hyperbaric conditions.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Martin-Luther-University Halle-Wittenberg, Dryanderstr. 4-7, 06108 Halle (Saale), Germany. dirk.henze@medizin.uni-halle.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Henze
authors.forename: Lars
authors.initials: L
authors.lastname: Köthe
authors.forename: Alexander
authors.initials: A
authors.lastname: Scharf
authors.forename: Tobias
authors.initials: T
authors.lastname: Clausen
mesh_terms: D000399:Air Pressure; D015374:Biosensing Techniques / Q000379:methods*; D006931:Hyperbaric Oxygenation; D007260:Infusion Pumps; D017551:Microdialysis / Q000295:instrumentation*; D015203:Reproducibility of Results; D013997:Time Factors