Anesthesia Machine: High, Intermediate & Low Pressure Systems
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What are the 3 parts of the pneumatic part of the anesthesia machine?
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high, intermediate and low pressure systems
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high-pressure system
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receives gases from cylinders at high, variable pressures and reduces those pressures to lower, more constant pressure suitable for use in the machine
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hanger yoke
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orients and supports the cylinder, provided a gas-tight seal and ensures a unidirectional gas flow
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body of the yoke
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threaded into the frame of the machine and provides support for the cylinders
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retaining screw also known as
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also known as the clamping device or retaining bar
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Purpose of retaining screw
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threaded into the distal end of the yoke and when tightened, presses the cylinder valve outlet against the washer and nipple so a gas-tight seal is achieved
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nipple
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part of the yoke through which the gas enters the machine
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why is it important that cylinder valves and yokes not be contaminated
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fire hazard
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pressure regulator
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reduces the high and variable pressure found in a cylinder to a lower, more constant pressure suitable for use in an anesthesia machine. Can be direct or indirect acting
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pressure
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force acting against an area
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intermediate pressure system
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receives gases from the pressure regulator or the pipeline inlet to the anesthesia machine
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what are the pneumatic components of the intermediate pressure system
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pneumatic part of the master switch, pipeline inlet connections, pipeline pressure indicators, piping, the gas power outlet, oxygen pressure failure devices, the oxygen flush, flow control valves
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piping
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used to connect components inside the machine and must be able to withstand 4x the intended service pressure without rupturing
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oxygen failure safety device
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whenever the oxygen supply pressure falls below the minimum, the delivered oxygen concentration will not decrease below 19%
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where is the low pressure system located
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downstream of the flow control devices
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what are the components of the low pressure system
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flowmeters, hypoxia prevention safety devices, unidirectional valves, pressure relief devices, common gas outlet, vaporizers
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flowmeter
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indicate the rate of flow of a gas passing through them
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what principle is measuring gas flow in a mechanical meter based on
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flow past resistance is proportional to pressure
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rate of flow through the tube depends on
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pressure drop against constriction, size of the annular opening, physical properties of the gas
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what does the flowmeter assembly consist of
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the tube through which the gas flows, the indicator, a stop at the top of the tube and the scale that indicates the flow
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where is the greatest accuracy of the flowmeter
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middle half of the tube
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common (fresh) gas outlet
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receives all of the gases and vapors from the machine and delivers the mixture to the breathing system
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pin index safety system
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has specific locations for pins and holes for each gas
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when placing a cylinder in a yoke
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you must fully retract the retaining screw and pin index safety system must be mated
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if a flowmeter tube is broken
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the tube, the indicator and scale must be replaced as a unit
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at low flows, flow is a function of
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the viscosity of the gas
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viscosity of the gas is more important with
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a longer and narrower constriction
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with high flows, flow is a function of
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the density of the gas
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what should the oxygen flowmeter be next to
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the manifold outlet
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a leak in the flowmeter that is farthest from the manifold outlet may result in
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a loss of gas from the middle flowmeter
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why should gas cylinder valves on the anesthesia machine with a pipeline supply by kept closed
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so that pipeline pressure failure will be recognized early, to prevent gas from flowing retrograde into the pipeline system, to prevent pressure alterations in the pipeline from drawing down the cylinder contents
