Is it permissible to pay zakat on money for the treatment of a wife suffering from a chronic and expensive illness, given that the salary is insufficient for both treatment and living expenses?

A husband is obligated to provide for his wife's medical treatment. It is not permissible for him to give her zakat, because her maintenance is his obligation. Giving her zakat would preserve his own money. Scholars have unanimously agreed that a man should not give zakat to his wife, because she is not in need of zakat due to the obligation of his expenditure upon her.