What is the maximum FiO2 that can be delivered by a nasal cannula?

0.45-the fio2 delivered to patients from low-flow systems (e.g., nasal cannula) is determined by the size of the o2 reservoir, the o2 flow, and the patients breathing pattern. As a rule of thumb, assuming a normal breathing pattern, the fio2 delivered by nasal prongs increases by approximately 0.04 for each l/min increase in o2 flow up to maximum fio2 of approximately 0.45 (at an o2 flow of 6 l/min). In general, the larger the patients vt or faster the inspiratory rate, the lower fio2 for given o2 flow.