Detection of air embolism by a re-usable doppler probe integrated in a central venous line

Problem. Air embolisms frequently occur during neurosurgical operations. Fo r detection of air embolisms, a re-usable doppler probe, integrated in a ce ntral venous line, is described. In an in-vitro test series the measuring s ector as well as the function of a 8 MHz doppler probe are presented. Method. The 8 MHz doppler probe is a 1.1 mm diameter cable, into the distal end of which a cylindrical doppler crystal from lead-circonate-titanate (P ZT5) of 2x1.7 mm is integrated and connected with a doppler unit. The detec tion of micro bubbles with a volume of 0.4-5 mul was effected in still liqu id for simple measuring of the spatial characteristics of the probe as well as in flowing liquid for simulation of a blood circulation system. Results. The doppler probe detected qualitatively and reproducibly all gas bubbles offered up to 4 cm around the tip of the probe. Conclusion. A relia ble detection of microbubbles in this test model is possible by means of a 8 Mhz doppler probe. Further animal and clinical studies are planned.