Disposable reservoir cannula provides more comfortable high-flow oxygen delivery than a mask or high-flow cannula while facilitating equivalent patient oxygenation. Allows patients to eat, drink and talk in an unobstructed manner. Reduces patient anxiety, thereby increasing compliance. Allows high-flow therapy to continue in a home care setting by reducing the liter flow required to achieve adequate saturation, facilitating earlier patient discharge. Effectively oxygenates hard-to-saturate patients, including some with refractory hypoxemia. Accommodates the use of handheld nebulizers, incentive spirometer sand suctioning devices without interruption oxygen therapy. May be used with or without supplemental humidification.