Computerised techniques for detecting gaseous microemboli in blood using pulsed Doppler ultrasound

Pulsed Doppler ultrasound and spectral analysis were used to monitor nonpulsatile blood flow generated in a test rig. Two computerised techniques are described for detecting microemboli in blood by analysis of Doppler blood velocity data (sonagram). The two ultrasound microemboli indices identify different features in the ultrasound signals to detect microembolic phenomena. Both indices showed significant increases ( p < 0.001) for samples of agitated blood (containing gaseous microemboli) as compared to normal blood injected sequentially into the test rig. The linear relationship demonstrated between data obtained by the two methods ( r = 0.91, p < 0.01) indicates that both are providing similar quantitative information regarding the number of microemboli detected. These two computerised techniques may be applied to sonagrams obtained from arterial blood flow and thereby provide information regarding the presence of gaseous microemboli in the circulation during cardiopulmonary bypass surgery.