Performance of cryotherapy devices using nitrous oxide and carbon dioxide

To compare temperatures reached by 4 different cryotherapy devices commonly used to treat precancerous cervical lesions in low-resource countries using nitrous oxide (N(2)O) and carbon dioxide (CO(2)) as well as with and without a gas conditioner.

Bench testing was conducted using 4 different cryotherapy devices and locally obtained N(2)O and medical- and industrial-grade CO(2) refrigerant with and without a gas conditioner. A thermocouple was used to continuously measure the temperature of the cryotherapy tip. Comparison across the cryotherapy devices was based on the mean and lowest temperatures.

Without the gas conditioner, all of the devices tested reached mean temperatures colder than -50°C with N(2)O, although 2 devices reached warmer temperatures in a proportion of N(2)O tests. Only 2 of the devices reached mean temperatures colder than -50°C with CO(2). One-way analysis of variance identified the device as the dominant factor for the temperature differences, while the gas was not a determinant of temperature variation. The gas conditioner hindered the performance of 2 of the devices, and only improved the performance of 1 device.

Both N(2)O and CO(2) reach appropriate freezing temperatures with some cryotherapy devices. Performance of some cryotherapy devices is suboptimal.