Venturi mask

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The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy. [1] [2] The mask was invented by Moran Campbell at McMaster University Medical School as a replacement for intermittent oxygen treatment. Dr. Campbell was fond of quoting John Scott Haldane's description of intermittent oxygen treatment; "bringing a drowning man to the surface – occasionally". [3] [4] By contrast the venturi mask offered a constant supply of oxygen at a much more precise range of concentrations.

Contents

Use

Venturi masks are used to deliver a specified fraction of inspired oxygen (FIO2). Many masks are color-coded and have a recommended oxygen flow specified on them. [5] When used with this oxygen flow, the mask should provide the specified FIO2. Other brands of mask have a rotating attachment that controls the air entrainment window, affecting the concentration of oxygen. This system is often used with air-entrainment nebulizers to provide humidification and oxygen therapy. The total flow of gas (oxygen plus the entrained air) will be greater than the patient's peak inspiratory flow so the delivered FIO2 is independent of their respiratory pattern. [5]

A controlled FIO2 is particularly important for patients whose ventilation is dependent on hypoxic drive, [5] as may be seen in patients with chronic obstructive pulmonary disease. Administration of too much oxygen may lead to a reduction in their respiratory rate and retention of carbon dioxide, and ultimately to reduced consciousness or even death. [6]

Mechanism

The mechanism of action is variously described with reference to the venturi effect or Bernoulli's principle. [7] However, a fixed performance oxygen delivery system works on the principle of jet mixing. Where the flow of moving oxygen meets the static air, viscous shearing causes a predictable amount of the air to be dragged into the flow. [7] [8]

See also

Related Research Articles

<span class="mw-page-title-main">Hypoxia (medicine)</span> Medical condition of lack of oxygen in the tissues

Hypoxia is a condition in which the body or a region of the body is deprived of adequate oxygen supply at the tissue level. Hypoxia may be classified as either generalized, affecting the whole body, or local, affecting a region of the body. Although hypoxia is often a pathological condition, variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise.

<span class="mw-page-title-main">Respiratory failure</span> Inadequate gas exchange by the respiratory system

Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes increased respiratory rate, abnormal blood gases, and evidence of increased work of breathing. Respiratory failure causes an altered mental status due to ischemia in the brain.

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<span class="mw-page-title-main">Oxygen therapy</span> Use of oxygen as a medical treatment

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<span class="mw-page-title-main">Nasal cannula</span> Medical device to deliver supplemental oxygen

The nasal cannula (NC) is a device used to deliver supplemental oxygen or increased airflow to a patient or person in need of respiratory help. This device consists of a lightweight tube which on one end splits into two prongs which are placed in the nostrils curving toward the sinuses behind the nose, and from which a mixture of air and oxygen flows. The other end of the tube is connected to an oxygen supply such as a portable oxygen generator, or a wall connection in a hospital via a flowmeter. The cannula is generally attached to the patient by way of the tube hooking around the patient's ears or by an elastic headband, and the prongs curve toward the paranasal sinuses. The earliest, and most widely used form of adult nasal cannula carries 1–3 litres of oxygen per minute.

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<span class="mw-page-title-main">Portable oxygen concentrator</span> Device used to provide oxygen therapy

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<span class="mw-page-title-main">Acute exacerbation of chronic obstructive pulmonary disease</span> Medical condition

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References

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  4. Sekhar, KC; Rao, SSC Chakra (2014). "John Scott Haldane: The father of oxygen therapy". Indian Journal of Anaesthesia. 58 (3): 350–352. doi: 10.4103/0019-5049.135087 . ISSN   0019-5049. PMC   4091013 . PMID   25024490.
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  7. 1 2 Kittredge P (1983). "Neither Venturi nor Bernoulli". Lancet. 1 (8317): 182. doi:10.1016/s0140-6736(83)92779-4. PMID   6130219. S2CID   10964089.
  8. Scacci R (1979). "Air entrainment masks: jet mixing is how they work; the Venturi and Bernoulli principles are how they don't". Respir. Care. 24: 928–931.