# Venturi mask

A Venturi mask is an oxygen delivery facemask that uses a jet of oxygen to entrain a fixed proportion of room air, so that the patient breathes a predetermined, constant fraction of inspired oxygen (FiO2) regardless of their breathing pattern. It is also called an air-entrainment mask or a fixed-performance mask, and the technique is known as high airflow with oxygen enrichment (HAFOE).<sup>[1](https://pubmed.ncbi.nlm.nih.gov/21216516/)</sup><sup> • </sup><sup>[2](https://www.sciencedirect.com/topics/medicine-and-dentistry/venturi-mask)</sup><sup> • </sup><sup>[3](https://www.who.int/docs/default-source/medical-devices/tech-specs-o2-therapy-monitoring-final-draft.pdf)</sup>

| Key fact | Detail |
|---|---|
| Principle | Oxygen forced through a narrow jet accelerates and creates negative pressure that entrains room air; the jet size sets the delivered FiO2<sup>[2](https://www.sciencedirect.com/topics/medicine-and-dentistry/venturi-mask)</sup> |
| Entrainment example | A 24% oxygen Venturi mask has an air-to-oxygen entrainment ratio of 25:1<sup>[2](https://www.sciencedirect.com/topics/medicine-and-dentistry/venturi-mask)</sup> |
| Origin | Designed by the British physician E. J. Moran Campbell in 1960, named after the Italian physicist Giovanni Battista Venturi (1746–1822)<sup>[1](https://pubmed.ncbi.nlm.nih.gov/21216516/)</sup><sup> • </sup><sup>[4](https://journals.sagepub.com/doi/10.1177/0310057X20953068)</sup> |
| Accuracy at rest | In a 1984 study, 24–40% masks delivered FiO2 within 1.9% absolute of nominal; the 60% mask read low at 50.3%<sup>[5](https://www.sciencedirect.com/science/article/pii/S0140673684919305)</sup> |
| Main clinical use | Controlled low-concentration oxygen for patients with COPD at risk of carbon dioxide retention, targeting saturation 88–92%<sup>[6](https://doi.org/10.1136/thoraxjnl-2016-209729)</sup> |
| Flow requirement | The device must deliver total flow above the adult peak resting inspiratory flow rate of about 30 L/min; 24–40% devices produce 40–50 L/min at zero back pressure<sup>[7](https://pubmed.ncbi.nlm.nih.gov/15200545/)</sup> |

## How it works

The mask applies the principle described by Giovanni Battista Venturi and formalized in the Bernoulli relation: as a gas flows through a constriction, its velocity and kinetic energy increase and its pressure falls. In the mask, oxygen from the supply passes through a fixed orifice, or jet, into a larger chamber; the resulting negative pressure draws in room air around the jet, and the mixed gas flows to the patient.<sup>[2](https://www.sciencedirect.com/topics/medicine-and-dentistry/venturi-mask)</sup><sup> • </sup><sup>[8](https://history.stjohn.org.au/wp-content/uploads/2020/10/SJH_2014_vol14.pdf)</sup>

The size of the constriction determines the final oxygen concentration for a given oxygen flow. Interchangeable, color-coded Venturi barrels are marked with the recommended oxygen flow rate and the FiO2 they deliver, and calibrated variable devices can be adjusted to a chosen concentration. Because the total gas flow delivered to the patient exceeds the peak inspiratory flow rate, the concentration stays fixed despite the patient's respiratory pattern.<sup>[2](https://www.sciencedirect.com/topics/medicine-and-dentistry/venturi-mask)</sup>

Fixed performance depends on total flow. A fixed-performance venturi should provide its stated concentration at an outflow exceeding an adult's peak resting inspiratory flow rate, approximately 30 L/min. Measured at zero downstream pressure, the outflow of 24–40% oxygen devices ranged from 40 to 50 L/min, but only 2–3 cmH2O (mmH2O) of back pressure was needed to halve this flow and raise the oxygen concentration, so downstream resistance matters.<sup>[7](https://pubmed.ncbi.nlm.nih.gov/15200545/)</sup>

## History

The mask is named after the Italian physicist Giovanni Battista Venturi (1746–1822), who described the principle that increased velocity of a gas results in lower pressure. The device itself was created by the British physician Earl James Moran Campbell, who incorporated this principle into an oxygen delivery facemask; such masks have been used worldwide for over 50 years.<sup>[1](https://pubmed.ncbi.nlm.nih.gov/21216516/)</sup><sup> • </sup><sup>[8](https://history.stjohn.org.au/wp-content/uploads/2020/10/SJH_2014_vol14.pdf)</sup>

**Campbell's design goal.** Writing in 1960, E. J. Moran Campbell made the case that people suffering respiratory failure ought to be given oxygen at concentrations between 24% and 35%, regulated to within ±1%. He designed the Venturi mask to deliver a predetermined and fixed concentration of oxygen, reducing the risk of carbon dioxide retention in patients who depend on hypoxic respiratory drive (COPD patients' breathing triggered by low oxygen, not CO2).<sup>[4](https://journals.sagepub.com/doi/10.1177/0310057X20953068)</sup>

## Clinical use

Venturi masks are chosen when a known, stable oxygen concentration matters more than a high one. According to [British Thoracic Society](https://www.edgepedia.org/british-thoracic-society) guidance, patients with known significant COPD should be given oxygen through a 24% or 28% Venturi mask, or at 1–2 L/min via nasal cannulae, with a target saturation of 88–92%, whereas most other patients should use medium-concentration devices with a target of 94–98%.<sup>[6](https://doi.org/10.1136/thoraxjnl-2016-209729)</sup> For suspected COPD without a known history of hypercapnic respiratory failure, initial management with a 28% Venturi mask appears safe, with downward adjustment to a 24% mask in hospital if saturation rises above 92%.<sup>[9](https://thorax.bmj.com/content/thoraxjnl/72/Suppl_1/ii1.full.pdf)</sup> If saturation remains below 88% in prehospital care despite a 28% mask, the guidance advises switching to nasal cannulae at 2–6 L/min or a simple face mask at 5 L/min, keeping the 88–92% target and alerting the emergency department.<sup>[9](https://thorax.bmj.com/content/thoraxjnl/72/Suppl_1/ii1.full.pdf)</sup>

The World Health Organization classifies the Venturi mask, also known as an air-entrainment mask, as a device able to provide total inspiratory flow at a specified FiO2, and lists it among standard oxygen delivery devices for procurement.<sup>[3](https://www.who.int/docs/default-source/medical-devices/tech-specs-o2-therapy-monitoring-final-draft.pdf)</sup>

## Measured performance

A 1984 Lancet study assessed large-reservoir Venturi masks ('Ventimask') with nominal concentrations from 24% to 60% in a face model, six normal subjects, and ten patients with severe chronic airflow obstruction. In people breathing at rest, the delivered FiO2 from the 24, 28, 35, and 40% masks was within 1.9% absolute of nominal (range −1.2 to +1.9%), but the 60% mask read low at 50.3%. Rebreathing of dead space from the mask, measured as inspired CO2 of 0.2–0.4% in normal subjects and 0.6 ± 0.4% in patients, mattered more than hyperventilation in lowering delivered concentration. In tachypnoeic patients with a respiratory frequency above 30 breaths per minute, the study recommended increasing the oxygen flow to 50% above the rate stated by the manufacturer.<sup>[5](https://www.sciencedirect.com/science/article/pii/S0140673684919305)</sup>

**Flow tolerance.** A study reported in CHEST found no variation in delivered FiO2 when the manufacturer-recommended oxygen flow was reduced or increased by 50%, consistent with the fixed-performance design.<sup>[10](https://journal.chestnet.org/article/S0012-3692%2816%2946187-8/fulltext)</sup>

## Practical limitations

**Oxygen sources.** Venturi barrels assume a supply of near-pure oxygen at the stated flow. When tested with a home oxygen concentrator, most barrels delivered a lower FiO2 than intended; the concentrator output itself fell from 95.8% to 84.7% oxygen as flow increased, and the 24% barrels caused significant back pressure that reduced delivered FiO2 and triggered the concentrator alarm. The authors concluded that a concentrator and Venturi combination should be tested together so the flow rate can be set accordingly.<sup>[11](https://thorax.bmj.com/content/66/Suppl_4/A123.2)</sup>

**Downstream resistance and humidification.** Because modest back pressure can halve the entrained flow and raise the oxygen concentration, kinked tubing or added humidification circuits can change the delivered concentration; a study of a modified Venturi oxygen therapy humidification system found a difference between measured and theoretical FiO2 at the inhalation end that clinicians should account for.<sup>[7](https://pubmed.ncbi.nlm.nih.gov/15200545/)</sup><sup> • </sup><sup>[12](https://pubmed.ncbi.nlm.nih.gov/30045797/)</sup>

**Patient tolerance.** Some patients cannot tolerate wearing the mask; in such cases oxygen can be given by nasal cannula at low flows, but flow rates and arterial blood gases must then be checked more frequently.<sup>[13](https://stacks.cdc.gov/view/cdc/184412/cdc_184412_DS1.pdf)</sup>

## References

1. [Soto-Ruiz KM, Peacock WF, Varon J. The men and history behind the Venturi mask. Resuscitation 2011;82(3):244–246.](https://pubmed.ncbi.nlm.nih.gov/21216516/)
2. [Venturi mask, ScienceDirect Topics overview](https://www.sciencedirect.com/topics/medicine-and-dentistry/venturi-mask)
3. [WHO. COVID-19 Technical specifications for procurement of oxygen therapy and monitoring devices (2020)](https://www.who.int/docs/default-source/medical-devices/tech-specs-o2-therapy-monitoring-final-draft.pdf)
4. [Featherstone PJ, Ball CM. Masks for the delivery of high fractions of inspired oxygen. Anaesth Intensive Care 2020;48(5):336–338.](https://journals.sagepub.com/doi/10.1177/0310057X20953068)
5. [Performance of the large-reservoir oxygen mask (Ventimask). The Lancet 1984;323(8392):1427–1431.](https://www.sciencedirect.com/science/article/pii/S0140673684919305)
6. [O'Driscoll BR, et al. BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax 2017;72(Suppl 1).](https://doi.org/10.1136/thoraxjnl-2016-209729)
7. [The 'fixed performance' venturi: effect of downstream pressure on outflow and FIO2.](https://pubmed.ncbi.nlm.nih.gov/15200545/)
8. [St John History Volume 14 (2014)](https://history.stjohn.org.au/wp-content/uploads/2020/10/SJH_2014_vol14.pdf)
9. [BTS guideline for oxygen use in adults (full text, Thorax)](https://thorax.bmj.com/content/thoraxjnl/72/Suppl_1/ii1.full.pdf)
10. [Controlled Oxygen Therapy in Clinical Practice: Fixed or Variable Venturi Mask? CHEST](https://journal.chestnet.org/article/S0012-3692%2816%2946187-8/fulltext)
11. [P139: The use of venturi masks with oxygen concentrators. Thorax 2011;66(Suppl 4):A123.](https://thorax.bmj.com/content/66/Suppl_4/A123.2)
12. [Study on the accuracy of oxygen concentration of modified oxygen treatment with Venturi and humidity system.](https://pubmed.ncbi.nlm.nih.gov/30045797/)
13. [Oxygen therapy in respiratory failure (CDC stacks document)](https://stacks.cdc.gov/view/cdc/184412/cdc_184412_DS1.pdf)

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*Topic: Encyclopedia › Life and health › Human health and medicine › Diseases and injuries › Respiratory conditions › Respiratory diagnosis, testing, and management*

*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*

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