Reliability of the microdialysis pump CMA 107 under hyperbaric conditions

ObjectiveMicrodialysis 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 2.4 bar absolute pressure.MethodsThe CMA 107 with a perfusion rate of 2 μL/min was stored in a decompression chamber. The ambient pressure was increased from 1 to 2.4 bar absolute within 15 min, maintained for 90 min and then decreased to 1 bar within 15 min. The vials were changed every 15 min, 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.ResultsThe 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.ConclusionThe study demonstrated that an absolute ambient pressure up to 2.4 bar 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.