In one of the articles that I read late at night, of which I understand very little and retain even less, it mentioned prolactin levels in chickens and it's relationship with broodiness.
High prolactin = broody.
Lower prolactin = egg laying.
Lowest prolactin = rearing chicks.
If you can safely lower prolactin levels you may be able to pull them out of broodiness. Deficient levels of B6 and/or zinc can raise prolactin levels so supplementing with them *might* help. Several of the other suggestions frequently used by BYCers were also mentioned, increase ventilation, etc. I'll have to look for the article after I see why some chicken is calling me.