ICU · Respiratory / oxygen therapy
Oxygen Therapy Devices — Escalating FiO2
Also known as Oxygen therapy · Oxygen delivery devices · Nasal cannula · Simple face mask · Non-rebreather mask · Venturi mask · High-flow nasal cannula · HFNC · Escalating FiO2 · Oxygen target
Oxygen delivery devices escalate from low-flow variable-performance devices (nasal cannula, simple mask, non-rebreather reservoir mask) whose delivered FiO2 falls as the patient's inspiratory flow rises, through fixed-performance Venturi masks (bench-validated 24-40 and 60 per cent valves) to high-flow nasal cannula (up to 60 L/min, humidified, with low-level PEEP) and then non-invasive or invasive ventilation. The British Thoracic Society targets a SpO2 of 94-98 per cent for most acutely ill adults (88-92 per cent in COPD or hypercapnia risk). The FLORALI trial (NEJM 2015) found similar intubation rates but better 90-day survival with high-flow nasal cannula in acute hypoxaemic respiratory failure. Oxygen is a drug — give the lowest FiO2 that meets the target.
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Meet the patient
A 64-year-old smoker with chronic bronchitis arrives at 3 a.m. with two days of worsening breathlessness. He is tripoding, pursed-lip breathing, SpO2 84 per cent on room air, RR 32, using every accessory muscle. The ED SHO hands you a non-rebreather mask at 15 L/min and asks whether to add a reservoir bag. You ask a different question first: what is the patient's baseline carbon dioxide? — because the answer (he has none documented, but his cough and barrel chest tell the story) decides whether you reach for the non-rebreather or the fixed-performance 24 per cent Venturi valve.[1]
The two questions that decide his next hour: what FiO2 does he need, and which device delivers it predictably? Below the surface sits the bigger principle — oxygen is a drug with a dose, an indication, a target, and harms. Hold those, and the device ladder slots into place.[1]
References12ShowHide
- [1]O'Driscoll BR, Howard LS, Earis J, Mak V; British Thoracic Society Emergency Oxygen Guideline Group. BTS guideline for oxygen use in adults in healthcare and emergency settings Thorax, 2017.PMID 28507176
- [2]Frat JP, Thille AW, Mercat A, et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure N Engl J Med, 2015.PMID 25981908
- [3]Mackle D, Bellomo R, Bailey M, et al. Conservative Oxygen Therapy during Mechanical Ventilation in the ICU N Engl J Med, 2020.PMID 31613432
- [4]Nielsen FM, Klitgaard TL, Siegemund M, et al. Lower vs Higher Oxygenation Target and Days Alive Without Life Support in COVID-19: The HOT-COVID Randomized Clinical Trial JAMA, 2024.PMID 38501214
- [5]Roca O, Caralt B, Messika J, et al. An Index Combining Respiratory Rate and Oxygenation to Predict Outcome of Nasal High-Flow Therapy Am J Respir Crit Care Med, 2019.PMID 30576221
- [6]Miguel-Montanes R, Hajage D, Messika J, et al. Use of high-flow nasal cannula oxygen therapy to prevent desaturation during tracheal intubation of intensive care patients with mild-to-moderate hypoxemia Crit Care Med, 2015.PMID 25479117
- [7]Guitton C, Ehrmann S, Volteau C, et al. Nasal high-flow preoxygenation for endotracheal intubation in the critically ill patient: a randomized clinical trial Intensive Care Med, 2019.PMID 30666367
- [8]Frat JP, Coudroy R, Quenot JP, et al. Effect of high-flow nasal cannula oxygen versus standard oxygen on mortality in patients with acute hypoxaemic respiratory failure: protocol for a multicentre, randomised controlled trial (SOHO) BMJ Open, 2024.PMID 39448217
- [9]Wagstaff TA, Soni N Performance of six types of oxygen delivery devices at varying respiratory rates Anaesthesia, 2007.PMID 17448063
- [10]Li CJ, et al. Impact of Using a Non-Rebreathing Mask in Patients With Respiratory Failure Am J Med Sci, 2021.PMID 33622528
- [11]Horn DB, et al. Ambient Oxygen Concentration Enrichment When Using a Face Mask Connected to the Breathing Circuit Versus a Venturi Device: A Simulation Study Cureus, 2025.PMID 41018383
- [12]Nishimura M High-Flow Nasal Cannula Oxygen Therapy in Adults: Physiological Benefits, Indication, Clinical Benefits, and Adverse Effects Respir Care, 2016.PMID 27016353