Effect of the "cough technique" on cryotherapy freezing temperature.

OBJECTIVE: To assess the impact of the cough technique on the tip temperature reached in a cryotherapy device commonly used to treat precancerous cervical lesions. METHODS: During February to March 2009, bench testing was conducted in Peru on 3 Wallach LL100 cryotherapy units using locally obtained carbon dioxide as the refrigerant. The temperature at the cryo tip was measured continuously with a thermocouple. Mean temperatures recorded with and without the cough technique were compared across the 3 cryotherapy devices. RESULTS: Higher mean temperatures were observed with the cough technique (-21.7 degrees C [95% CI, -23.0 to -20.4]; -22.0 degrees C [95% CI, -24.2 to -19.7]; -29.4 degrees C [95% CI, -30.3 to -28.6]) compared with mean temperatures observed with the standard procedure (-38.6 degrees C [95% CI, -44.8 to -32.4]; -36.0 degrees C [95% CI, -43.5 to -28.5]; -41.4 degrees C [95% CI, -49.8 to -33.0]). No test performed with the cough technique reached a temperature below -33 degrees C. CONCLUSION: Higher temperatures were observed when the cough technique was used. Caution should be exercised by practitioners who use this procedure when performing cryotherapy because the temperatures obtained may not be sufficient to destroy precancerous tissue.

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 (N2O) and carbon dioxide (CO2), and two methods using a standard and extended version of the cough technique with CO2. RESULTS: Uninterrupted freezing with both N2O and CO2 produced tissue temperatures less than -20 degrees C (-40 degrees C and -30 degrees C respectively). CO2 cryotherapy procedures using the two cough techniques produced temperatures greater than -20 degrees C in the model tissue. CONCLUSION: CO2 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.