Mechanism of cell injury
The mechanism of cell injury from freezing is both chemical and mechanical, and a main effect is directly related to the formation of ice crystals within the cells. Rapid freezing does not allow sufficient time for intracellular water to leave the cell and, consequently, it leads to intracellular ice crystallization and mechanical rupture of the cell membrane. During slow thawing, recrystallization takes place – i.e. small ice crystals aggregate to form larger crystals – leading to further mechanical damage of the cell membranes.
- Apply a quick freeze/slow thaw technique.
- Repeated freeze/thaw cycles may improve efficacy.
- Extend the ice ball beyond the target margins to ensure freezing of the entire target.
Using open spray tip technique
Select a spray aperture appropriate for the lesion to be treated. To obtain in-depth freezing it is essential to place the spray aperture close to the lesion (5 - 10 mm distance), as the liquid content of the spray is higher close to the aperture.
When possible, raised warts should be approached tangentially from at least two sides. This allows the ice ball to move down through the wart while sparing the surrounding tissue. Spraying directly at the lesion (perpendicular to the surface) will cause more lateral spread with less penetration. To avoid this, apply the spray intermittently or use a smaller spray aperture.
Superficial desquamation is obtained using the larger apertures (“A” or “B”) at approx. 5 cm distance (higher vapor content) and slowly “painting” the surface with vaporized nitrogen.