Qualitative and quantitative methods for investigating gas emboli in blood.

Methods for investigating gas emboli in blood include timed collection of a sample of blood, with subsequent gravitational separation of bubbles or, for more rapid assessment, measurement of bulk compressibility; examination of small samples (usually taken as slipstreams) by optical or electrical impedance devices; and ultrasonography. No method is overwhelmingly superior to the others, as all have deficiencies. The representativeness of the samples examined is a problem that has frequently been overlooked. Developments in the ultrasonic method, including newer transducer materials and signal processing, promise interesting developments in the next few years.