[Detection of air embolism by a re-usable Doppler probe integrated in a central venous line--application in-vivo]. / Wiederverwendbare, in einen Zentralvenenkatheter integrierbare Dopplersonde zur Detektion von Luftembolien Anwendung in-vivo.

PROBLEM: Air embolism frequently occurs under neurosurgical operations performed in the sitting position. Recently we reported the idea of inserting a re-usable doppler probe into a blind-ending lumen of a central venous catheter (Schregel-Volk-Catheter, SVC). In vitro testing in a circulation model showed a high sensitivity: air bubbles as small as 0.5 microliter were reliably detected at a distance up to 4 cm from the tip of the SVC. METHOD: After approval by the local ethics committee pigs were anaesthetised and a cardiopulmonary bypass was connected. During the bypass period a 12 F SVC (Medex Medical, Germany) with one blind-ending lumen was positioned into the proximal vena cava cranialis or vena cava caudalis. An 8 MHz doppler probe (MTB Basler, Suisse) was introduced into the SVC and connected with the doppler device Multi-Dop T (DWL, Germany). Well defined air bubbles (3-6 microliter) were generated by a bubble generator and injected into the right femoral vein or the left vena jugularis interna. RESULTS: All bubbles were reliably detected by the re-usable doppler probe. Embolic events can be documented, counted and quantified by the Multi-Dop T. CONCLUSION: Using SVC's with a blind-ending lumen could improve and simplify the detection of air embolism. We see several advantages (e.g. sensitivity, costs) compared with established methods (precordial doppler, TEE) for detection of air embolism.

[Detection of air embolism by a re-usable doppler probe integrated in a central venous line]. / Wiederverwendbare, in einen Zentralvenenkatheter integrierbare Dopplersonde zur Detektion von Luftembolien.

PROBLEM: Air embolisms frequently occur during neurosurgical operations. For detection of air embolisms, a re-usable doppler probe, integrated in a central venous line, is described. In an in-vitro test series the measuring sector 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 (PZT5) of 2 x 1.7 mm is integrated and connected with a doppler unit. The detection of micro bubbles with a volume of 0.4-5 microliters was effected in still liquid 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 reliable detection of micro-bubbles in this test model is possible by means of a 8 Mhz doppler probe. Further animal and clinical studies are planned.