E-mail: ni. This article has been cited by other articles in PMC. Abstract Inhalational anaesthetic agents are usually liquids at room temperature and barometric pressure and need to be converted to vapour before being used and this conversion is effected using a vapouriser. Vapourisers have evolved from very basic devices to more complicated ones. Anaesthetists should understand the basic principles of anaesthetic vapouriser, including the principles that affect vapouriser output and how they influence vapouriser design.
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E-mail: ni. This article has been cited by other articles in PMC. Abstract Inhalational anaesthetic agents are usually liquids at room temperature and barometric pressure and need to be converted to vapour before being used and this conversion is effected using a vapouriser.
Vapourisers have evolved from very basic devices to more complicated ones. Anaesthetists should understand the basic principles of anaesthetic vapouriser, including the principles that affect vapouriser output and how they influence vapouriser design.
Most of the modern vapourisers in use are designed to be used between the flow meter and the common gas outlet on the anaesthesia machine. Modern vapourisers are flow and temperature compensated, concentration calibrated, direct reading, dial controlled and are unaffected by positive-pressure ventilation.
Safety features include an anti-spill and a select-a-tec mechanism and a specific vapouriser filling device. Desflurane has unique physical properties requiring the use of a specific desflurane vapouriser. The most recently designed vapourisers are controlled by a central processing unit in the anaesthetic machine. The concentration of vapour is continuously monitored and adjusted by altering fresh gas flow through the vapouriser. This article looks at the basic design and functioning of the modern vapourisers.
Keywords: Aladin cassettes, desflurane vapouriser, direct injection of volatile anesthetic, measured flow vapouriser, plenum vapouriser INTRODUCTION Anaesthetic vapourisers, used for the administration of volatile anaesthetics, have evolved from the simple masks used for open ether anaesthesia to the present day modern electronically controlled vapourisers designed to deliver potent modern inhalation aesthetic agents.
An anaesthetic vapouriser must deliver a safe, reliable concentration of volatile agent to the patient. The safe delivery of volatile anaesthesia today is due in part to the development of increasingly advanced vapourisers. The characteristics of the modern vapourisers with their special construction and operation are discussed below.
The American society for testing and materials anaesthesia workstation standard[ 1 ] contains the following provisions regarding vapourisers: The effects of variations in ambient temperature and pressure, tilting, back pressure and input flow rate and gas mixture composition on vapouriser performance must be stated in the accompanying documents. A system that prevents gas from passing through the vapourising chamber or reservoir of one vapouriser and then through that of another must be provided.
The output of the vapouriser shall be less than 0. All vapouriser control knobs must open counter clockwise. Either the maximum and minimum filling levels or the actual usable volume and capacity shall be displayed. The vapouriser must be designed so that it cannot be overfilled when in the normal operating position. Vapourisers unsuitable for use in the breathing system must have non-interchangeable proprietary or mm fittings.
Conical fittings of 15 mm and 22 mm cannot be used. When mm fittings are used, the inlet of the vapouriser must be male and the outlet female. The direction of gas flow must be marked. Vapourisers suitable for use in the breathing system must have standard mm fittings or screw-threaded, weight-bearing fittings with the inlet female and the outlet male.
In order to give clinically useful concentrations of the agent, the anaesthetic vapour has to be diluted with fresh gas in one of the two ways:[ 2 , 3 ] By splitting the fresh gas flow so that only a portion passes through the vapourising chamber and the rest bypasses it — variable bypass vapourisers. By injecting the vapour directly to the total fresh gas flow without any split — measured flow vapourisers.
Variable bypass vapourisers: Can be classified into Plenum vapourisers: For halothane, enflurane, isoflurane, sevoflurane except desflurane. Plenum vapourisers with electronic control: For halothane, enflurane, isoflurane, sevoflurane and desflurane.
Measured flow vapourisers: Can be classified into Desflurane Vapouriser: Only for desflurane. Direct injection of volatile anaesthetic vapouriser: For halothane, enflurane, isoflurane, sevoflurane and desflurane. The working principle of all these vapourisers is similar.
Modern Anaesthesia Vapourisers
Modern vaporizers[ edit ] There are generally two types of vaporizers: plenum and drawover. Both have distinct advantages and disadvantages. The dual-circuit gas-vapor blender is a third type of vaporizer used exclusively for the agent desflurane. Plenum vaporizers[ edit ] The plenum vaporizer is driven by positive pressure from the anesthetic machine , and is usually mounted on the machine. The performance of the vaporizer does not change regardless of whether the patient is breathing spontaneously or is mechanically ventilated. The internal resistance of the vaporizer is usually high, but because the supply pressure is constant the vaporizer can be accurately calibrated to deliver a precise concentration of volatile anesthetic vapor over a wide range of fresh gas flows. The plenum vaporizer is an elegant device which works reliably, without external power, for many hundreds of hours of continuous use, and requires very little maintenance.
How anaesthesia vaporisers work explained simply.
Available in a wide range of fittings and agents, the Pisces vaporizer offers maximum reliability with the minimum of fuss. The Pisces vaporizer has been uniquely designed to be easily maintained. Each agent specific vaporizer signifies performance, convenience and ergonomic benefits with improved safety features to help improve agent delivery. Clinical Performance: Due to design improvements in the gas pathways, the Pisces vaporizer excels in output stability over a wide range of variables and can work in the most extreme conditions. Gives superb performance over a wide range of vapor concentration, temperature, particularly at low flows. Accuracy and Stability: All Pisces vaporizers are calibrated on a laser refractometer and are fully flow and temperature compensated to ensure output stability.