Changing either the flow rate or the oxygen content of the delivered gas can alter the amount of supplemental oxygen delivered. In general, when liter flow is less than 1 liter/minute, delivered oxygen is less than 0.7 FiO2, even when the delivered gas is 100 percent oxygen. With flow of than 0.5 liter/minute, the oxygen concentration in the hypopharynx drops to less than 0.4 FiO2. Once below 0.125 liter/minute, the delivered oxygen approaches room air. Hence, effective weaning can be achieved by using unblended oxygen and reducing the liter flow. Alternatively, maintaining the flow but blending in room air at the gas source can reduce oxygen content. This technique permits more controlled weaning (the oxygen blenders generally utilized are more sensitive than flow meters) than does weaning by flow. Once the infant is tolerating room air flow via the nasal cannula, the flow rate can usually be weaned rapidly.