Production of standardized air bubbles: Application to embolism studies

Gaseous emboli may arise and enter into the circulation system during various clinical procedures. In order to better understand their immediate and long-term consequences, clinical investigations following the insertion of air bubbles into the body as well as new detection techniques need to be carried on. To this end, a device has been developed to generate a uniform stream of microbubbles with diameters ranging between 20 and 300 mum. This device comprises a glass micropipette connected to an air pressure source. The micropipette tip crosses a variable liquid flow and the bubbles produced are carried away by the flow. These bubbles have a very narrow size and density distribution: 90% of the bubbles lie within +/-6% of the mean radius and the number of bubbles does not vary more than 10%. The size and density of the produced bubbles can be controlled by adjusting three independent parameters: the liquid flow, the gas pressure level, and the micropipette shape. For a given micropipette, increasing the liquid flow or decreasing the gas pressure level leads to a reduction of bubble size while the number of bubbles produced increases. As an example, doubling of the liquid flow results in a variation in bubble size up to 40%. This technique offers the advantage of generating uniform bubbles of known size and number depending on the settings selected. It appears to be a valuable tool for embolism studies such as the development of ultrasonic methods for detection of gaseous emboli. (C) 2003 American Institute of Physics.