Note: With oxygen delivery methods, it’s really about how much FIO2 can be delivered, not really the flow rate in liters.
Related article: Fraction of Inspired Oxygen (FiO2).
| Method | FIO2 and Flow Rates | Indications | Comments |
| First-Line Options | |||
| Standard nasal cannula | The NC can deliver an inspiratory oxygen fraction (FIO2) of 24-40% at supply flows ranging from 1-5 L·min-1 | The formula is FIO2 = 20% + (4 × oxygen liter flow). The FIO2 is influenced by RR, tidal volume and pathophysiology. The slower the inspiratory flow the higher the FIO2. – Flow rates >4 liters per minute irritate nasopharynx |
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| Venturi mask | Typical FIO2 delivery settings are 24, 28, 31, 35 and 40% oxygen. | The Venturi mask is often used when the clinician has a concern about CO2 retention | A Venturi mask mixes oxygen with room air, creating high-flow enriched oxygen of a settable concentration. It provides an accurate and constant FIO2. |
| Second-Line Options | |||
| Face Tent/Shield | Delivers only 40% Oxygen at 10-15 liters per minute | High-flow, soft plastic “bucket” over nose and mouth. Better tolerated than a face mask |
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| Simple face mask | It delivers an FIO2 of 40-60% at 5-10 L·min-1. | The face mask is indicated in patients with nasal irritation or epistaxis. It is also useful for patients who are strictly mouth breathers. | The volume of the face mask is 100-300 mL. The FIO2 is influenced by RR, TV, and pathology.
The face mask is obtrusive, uncomfortable and confining. It muffles communication, obstructs coughing and impedes eating. |
| Nonrebreathing face mask with a reservoir and one-way valve | It may deliver FIO2 up to 90% at high flow settings. Oxygen flows into the reservoir at 8-10 L·min-1, washing the patient with a high concentration of oxygen. | The nonrebreathing face mask is indicated when an FIO2 >40% is required. | Its major drawback is that the mask must be tightly sealed on the face, which is uncomfortable. There is also a risk of CO2 retention. |
| Reservoir cannulas | Liter flows of =8 L·min-1 have been reported to adequately oxygenate patients with a high flow requirement | Reservoir cannulas improve the efficiency of oxygen delivery. Hence, patients may be well oxygenated at lower flows. | |
| High-flow transtracheal catheters | Patients who have been extubated may benefit from an interim of high-flow transtracheal oxygen to better ensure weaning success. | Transtracheal catheters deliver oxygen directly into the trachea. There are wash-out and storage effects that promote gas exchange as well as providing high-flow oxygen. High-flow transtracheal catheters may reduce the work of breathing and augment CO2 removal. | |
| High-flow warmed and humidified nasal oxygen | Nasal oxygen has been administered at lows ranging from 10-40 L / min. | When this oxygen is warmed to body temperature and saturated to full humidity, it is comfortable. | Can give SaCO2 equivalent to or surpassing nonrebreathing face masks at the same supply flow setting. |
Source: American thoracic society article