held和viable理解的对吗？

Optimal gas-exchange: PEEP certainly does not require venous admixture to be held < 15%, but it should provide viable gas-exchange (PaO2 60/80 mmHg and PaCO2< 50/55 mmHg) without excessive dead space generation or potentially toxic levels of FiO2.

最佳气体交换：设定PEEP当然不需要将混合静脉血氧饱和度保持<15%，但应提供可行的气体交换（PaO₂ 60/80 mmHg和PaCO₂< 50/55 mmHg），不会产生过多死腔或无需将FiO₂提高到潜在的毒性水平。

held和viable理解的对吗？

without potentially toxic levels of FiO2.无需将FiO2提高到潜在的毒性水平？

谢谢