An anaesthetic vaporizer must deliver a safe, reliable concentration of volatile agent to the patient. Anaesthetists should understand the basic principles of. Vaporizers are an integral part of modern-day anaesthesia, allowing the delivery of safe concentrations of volatile anaesthetic agent. Over time, vaporizer design. Anaesthesia vaporizers for inhalational anaesthetic agents. Principal, classification, types, hazards.

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Nott MR, Jacklin F. If something is pushed under the vapouriser enough to lift it slightly off of the O-ring, a leak may result when the vapouriser is turned ON. An electronic display indicates the level of desflurane in the vaporizer. Schematic diagram of the TEC 6 vaporizer.

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Two units in series required for a Sevo induction. SVP increases non-linearly with temperature. For halothane, enflurane, isoflurane, sevoflurane except desflurane. Increases rapidly as boiling point approaches. The absolute percentage of agent per unit volume leaving the vapouriser is correct, but when the gas mixture expands post-obstruction, there are fewer molecules of agent per volume of carrier than there should be.

Latent heat of vaporization is the number of calories needed to convert 1 g of liquid to vapor, without temperature change in the remaining liquid. Control dial in wrong position: Plenum vaporizers are made of dense metals, while the Oxford Miniature Vaporiser a draw-over vaporizer uses glycol as a heat sink. Another failure of Selectatec block.

Drager Vapour 20n series vapouriser anaethesia set in the transport T dial setting helps prevent tipping related problem. For a study of this vaporizer’s performance, see Anesth Analg ; Plenum – a chamber at higher than atmospheric pressure, for distribution purposes.

Nil Conflict of Interest: This means that at normal operating temperaturesthe saturated vapor pressure of desflurane changes greatly with only small fluctuations in temperature. This deflection varies the relative proportions of gas flowing through the bypass and vapourising chamber circuits [ Figure 2 ].


The cassettes for halothane, enflurane and isoflurane have keyed fillers or the Easy-fil system. Vaporizer and Selectatec leaks. A conventional vaporizer would require high fresh gas flows to dilute it to within clinically useful concentrations, making it uneconomical. Correct inflow can be determined from agent-specific tables that relate temperature, desired percentage output and FGF.

Anaessthesia dangerous because output must be manually changed whenever FGF is changed; failure to do so can lead to over or under-dosage. After a vapouriser has been added to a machine, several checks should be made to ensure proper positioning. VP is independent of atmospheric pressure, it depends only on the physical characteristics of the liquid, and its temperature.

If your institution subscribes to this resource, and you don’t have a MyAccess Profile, please contact your library’s reference desk for information on how to gain access to this resource from off-campus. An understanding of the physical properties of anaesthetic agents is required to appreciate the design of modern vaporizers. Plenum vapourisers with electronic control: The Tec 6 is pressurized to 2 atm; there is no compensation for ambient pressure and thus the concentration delivered in the fresh gas flow is stable, regardless of ambient pressure.

The exact percentage to be diverted depends on the volatility of the agent SVPthe proportion of the fresh gas diverted into the vapourising chamber, and barometric pressure, as follows: Each pin has an O-ring at the base that makes the seal with the vapouriser.

A proper backbar leak test should detect O-ring failures even if the vapouriser is ‘off’. At any given temperature, a point of dynamic equilibrium will come to exist where the number of molecules leaving the liquid phase equals the number re-entering it—at this point, the vapour is saturated and the pressure it exerts is known as the saturated vapour pressure SVP.

Please enter Password Forgot Username? Fresh gas flow passes through a flow resistor, producing a fixed resistance; as flow increases, backpressure against the differential pressure transducer increases—this results in a reduction in the variable resistance, hence increasing vapour output to match the increased gas flow. The amount of such a leak depends on the ambient temperature as well as the size and configuration of the internal ports.


Its performance depends on the minute volume of the patient: You can also find results for a single author or contributor. The amount of substance that is in liquid versus vapor phase The vapourisers can be refilled while still slotted in the machine and with one still in use.

Anaesthetic vaporizer – Wikipedia

Accessed December 31, Despite its drawbacks, the drawover vaporizer is cheap to manufacture and easy to use. Clinically this is relatively vapotizers, since we titrate to effect end tidal agent concentration and use overpressure. They have several features designed to compensate for temperature changes anaesthexia cooling by evaporation.

With prolonged use, the liquid agent may cool to the point where condensation and even frost may form on the outside of the reservoir. Learn how and when to remove these template messages. Chamber only contains 50ml of agent. Vapor pressure VP increases with temperature.

Modern Anaesthesia Vapourisers

Technically, although the dial of the vaporizer is calibrated in volume percent e. The Vapor is also tippable. The potential hazard is overdose on induction. Modern vaporizers are relatively immune older vaporizers were certainly not immune due to check valves between the anaestheisa outlet and the common gas outlet, smaller vaporizing chambers, or tortuous inlet chambers. Either the maximum and minimum filling levels or the actual usable volume and capacity shall be aanaesthesia.

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