Vitrified IVF embryos are stored in liquid nitrogen at minus 196 degrees Celsius, which is the boiling point of liquid nitrogen at standard atmospheric pressure. At this temperature, all thermodynamic activity relevant to biological degradation is effectively halted.
Embryos stored in the vapour space above liquid nitrogen in a dewar are at temperatures somewhat above minus 196 degrees Celsius but still well below the threshold at which any biological activity would resume. Typical vapour-phase storage temperatures range from minus 150 to minus 190 degrees Celsius depending on the position within the dewar.
The critical threshold generally referenced in the cryobiological literature is minus 130 degrees Celsius, which is approximately the glass transition temperature for biological vitrified materials. Below this temperature, the vitrified glass state is maintained. Above this temperature, the material begins to transition back toward a liquid state, and ice crystal formation becomes possible during prolonged exposure.
If a temperature excursion occurs, the required steps are: document the event including the time, duration, and temperatures recorded by the monitoring system; assess whether the excursion was significant enough to potentially affect sample viability; report the incident through the clinic’s serious incident reporting process if it meets the threshold for reporting; inform affected patients if their samples may have been compromised; and implement corrective action to prevent recurrence.
Cryolab supplies continuous monitoring systems for UK IVF clinics that provide early warning before critical temperatures are reached. Visit cryolab.co.uk“>Cryolab
