Kaps M, Hansen J, Weiher M, Tiffert K, Kayser I, Droste D W
Neurologische Klinik der Medizinischen Klinik zu Luebeck, Germany.
Stroke. 1997 Feb;28(2):322-5. doi: 10.1161/01.str.28.2.322.
Microembolic signals (MES) are frequently observed by transcranial Doppler ultrasound after prosthetic heart valve implantation. Whether these MES are due to solid or gaseous particles is uncertain. We hypothesized that MES are gaseous and that if they are due to cavitation effects, their occurrence should respond to changes of dissolved oxygen concentration in the blood.
Transcranial monitoring of MES was performed in five patients with prosthetic aortic valves, who inspired 100% oxygen through a facial mask. In one patient 100% oxygen was administered under hyperbaric (2.5 kPa) conditions in a hyperbaric chamber.
Inspiration of 100% oxygen reduced the total number of MES from 96/30 min to 2/30 min. Increasing the concentration of dissolved oxygen in the hyperbaric chamber led to an increase from 0.3 MES per minute (1.0 kPa) to 0.9 MES per minute (2.5 kPa).
The dependence of occurrence of MES in patients with prosthetic cardiac valves on the oxygen partial pressure in blood provides strong evidence that these microemboli are gaseous.
人工心脏瓣膜植入术后经颅多普勒超声常可观察到微栓子信号（MES）。这些MES是由固体颗粒还是气体颗粒引起尚不确定。我们推测MES是气态的，并且如果它们是由空化效应引起的，那么它们的出现应该会对血液中溶解氧浓度的变化产生反应。
对5例人工主动脉瓣患者进行经颅MES监测，患者通过面罩吸入100%氧气。其中1例患者在高压舱内（2.5 kPa）接受100%氧气治疗。
吸入100%氧气使MES总数从96/30分钟降至2/30分钟。高压舱内溶解氧浓度增加导致MES从每分钟0.3个（1.0 kPa）增加至每分钟0.9个（2.5 kPa）。
人工心脏瓣膜患者中MES的出现对血液中氧分压的依赖性提供了有力证据，表明这些微栓子是气态的。
