RESUMO
Objective To measure the maximum dissolved oxygen concentration of the lithotripter to avoid visible air bubbles during lithotripsy.Methods The present situation of degassing of lithotripter and clinical requirements for water were introduced.Under the following conditions of 7.5 L water capacity,35 L/h water flow,ambient temperature 28 ℃,17 kV,60 shocks per minute,the lithotripter discharged 10 000 shocks continuously without a visible air bubble in the circulating water,then the dissolved oxygens in the water were measured by using AZ8403 dissolved oxygen meter.The maximum value of dissolved oxygen in the water was determined therefore without a visible air bubble.Results The visible tiny air bubble emerged during lithotripsy if the dissolved oxygen in the water was above 3.37 mg/L and ambient temperature was about 28 ℃;the bubble could be avoided if the dissolved oxygen was under 3.34 mg/L and ambient temperature was about 28 ℃.Conclusion The circulating water with dissolved oxygen concentration less [han 3 mig/L and about 28 ℃ ambient temnperature are recommended for the electromagnetic extracorporea] shock wave lithotripter during lithotripsy.