Extracorporeal shock waves act by shock wave-gas bubble interaction

The effect of extracorporeal shock waves on hemoglobin release from red blood cells was recently found to be minimized under minute static excess pressure. It was proposed that this can be explained by shock wave-gas bubble interaction. We substantiated this further by two experiments by applying shock waves to suspended human RBC in a lithotripter at a lower frequency (1 pulse every 5 s) and by administering just a single or 2 strong shock waves at 30 kV. Compared to the usual application rate of 1 discharge per s, the lower frequency reduced the hemoglobin release under minimal static excess pressure in the range from 0-100 kPa. A single strong shock wave released a small amount of hemoglobin at ambient pressure and a similar amount at 200 kPa excess pressure. Two strong shock waves increased the hemoglobin release considerably at ambient pressure when there was a 1- or a 10-s pause between them. Under 200 kPa excess pressure, the hemoglobin release was minimal. A similar low hemoglobin release was also found with 1 shock at ambient and the other at excess pressure. The results are interpreted as clear evidence of shock wave-gas bubble interaction as a dominant mechanism of shock wave action.