The Preservation Shield from Adventurer's Vault 2 has the following power:
Power (Daily): Minor Action. You and each ally within 5 squares of you gain temporary hit points equal to the number of healing surges you have remaining.
The ritual Soul Pool from the book Azagar's Book of Rituals allows the participants to put all their healing surges into a single pool from which they all draw (along with some other effects, such as all participants using the highest surge value among them).
Once the ritual is complete you and your companions' available healing surges become equal to the total number of all your healing surges combined. Thus, four characters with 7, 9, 12 and 8 healing surges would have a total of 36 available healing surges in their pool. In addition, the healing surge value for the pool becomes equal to the creature with the highest healing surge value, granting all creatures in the pool the same number of hit points whenever they spend a healing surge.
Any time you or one of your companions uses a healing surge during the duration of the ritual, the healing surge is taken from the pool of healing surges rather than their own individual pool, allowing a member of your group to spend more healing surges than he normally could. This does not change the function of the healing surge nor does it alter any ability, power, or magic item that affects healing surges, such as how many times a creature can use second wind or how many hit points you can receive from a potion of vitality.
So my question is: what would you use to determine how many temporary hit points would you receive if you used the Preservation Shield power while under the effects of Soul Pool? The total number of surges in the pool? Zero (since you technically put your surges into the pool)? Something else?