Atlas of Colposcopy: Principles and Practice

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Treatment by cryotherapy – Cryosurgical unit  

Cryotherapy equipment (a cryosurgical unit) consists of a handle grip (cryogun) with a trigger mechanism that is attached to the cryoprobe on one side and the connecting hose on the other side to transmit gas from the gas cylinder. The hose is connected to the cylinder with a connector and a pressure gauge. In some equipment, the cryogun is replaced by a cryoshaft. The cryoprobe or the cryoshaft has a cryotip made of highly conductive metal. The protrusion of the nipple of the cryotip should not exceed 5 mm.

The gas from the cylinder passes through the hose, the cryogun, and the probe (or shaft) to the cryo tip. The tip is applied to the cervix, and the cervix is frozen as the gas is released to the atmosphere.

Setting up the cryotherapy machine:
  • Check the washer before attaching the cryoprobe to the handle grip (cryogun). Replace the washer if it is broken.
  • Select the appropriately sized cryoprobe, depending on the size of the transformation zone, and attach it to the handle grip (avoid using the probes with endocervical extension).

  • Connect the cryotherapy machine to the gas cylinder and tighten the valve.
  • Open the gas cylinder so that the gas can flow into the handle grip through the hose. Check the gas pressure indicated on the pressure gauge.
  • The ideal gas pressure required to perform the cryotherapy procedure is 40–70 kg/cm2.
  • On opening the cylinder and during the cryotherapy procedure, the indicator of the pressure gauge should be in the green zone. A needle positioned in the yellow zone indicates low gas pressure, and in the red zone indicates high gas pressure. In either case, cryotherapy should not be started or should be discontinued.
  • Large gas tanks (> 15 litre capacity) should be used for the procedure if possible.

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