Effect of cough technique and cryogen gas on temperatures achieved during simulated cryotherapy

BACKGROUND: Cryotherapy is often used to treat cervical precancer in developing countries. There are different methods and cryogen gases used for cryotherapy, including the freeze-flush-freeze (cough) technique employed to minimize gas blockage. However, there is limited information to compare their effectiveness. METHODS: Using a tissue model, we compared temperature-time curves for four cryotherapy methods: uninterrupted freezing with nitrous oxide (N(2)O) and carbon dioxide (CO(2)), and two methods using a standard and extended version of the cough technique with CO(2). RESULTS: Uninterrupted freezing with both N(2)O and CO(2 )produced tissue temperatures less than -20°C (-40°C and -30°C respectively). CO(2 )cryotherapy procedures using the two cough techniques produced temperatures greater than -20°C in the model tissue. CONCLUSION: CO(2 )cryotherapy using the cough technique may not achieve sufficiently low temperatures to produce the desired therapeutic effect. Other alternatives to the prevention of gas blockage should be developed.