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Published byCharla Daniel Modified over 9 years ago
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The annular space. The clearance between the head of the float and the flow tube is known as the annular space.
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upper portion › orificial › Density is dominant lower portion: › tubular › Viscosity is dominant
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The oxygen flow control knob is physically distinguishable: › distinctively fluted › projects beyond the other knobs › larger in diameter All knobs: › color-coded › chemical formula or name marked on each › protected with a shield or barrier
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FLOW TUBES: › tapered glass tubes › double flow tubes better visual discrimination at low flow rates 200ml to 1 L/min and 1 to 10 to 12 L/min connected in series total gas flow is that shown on the higher flow meter INDICATOR FLOATS AND FLOAT STOPS: floats: plumb-bob, rotating skirted, ball float stops: visible SCALE: › marked directly on the flow tube or to the right of the tube › Rib guides are used in some flow tubes SAFETY FEATURES: › individually hand-calibrated › The tube, float, and scale make an inseparable unit ( The entire set must be replaced if any component is damaged)
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An oxygen leak from the flow tube can produce a hypoxic mixture regardless of the arrangement of the flow tubes
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Sticking of the indicator float damaged float can cause inaccurate readings Backpressure from the breathing circuit not aligned properly in the vertical ambiguous scales
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The output represented in L/minute: graphically numerically or both Even when electrical power is totally interrupted, oxygen should continue to flow (flow control valves are non electronic) Small conventional pneumatic “fresh gas” or “total flow” indicator
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prevent the creation and delivery of a hypoxic mixture minimum oxygen concentration at the common gas outlet is between 23% and 25% Limitations: Wrong Supply Gas Defective Pneumatics or Mechanics Leaks Downstream Inert Gas Administration Dilution of Inspired Oxygen by Volatile Anesthetics
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Ohmeda Link-25 Proportion-Limiting Control system
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North American Dräger Oxygen Ratio Monitor Controller
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Allows direct communication between the oxygen high-pressure circuit and the low-pressure circuit Actuation of the valve delivers 100% oxygen at 35 to 75 L/min to the breathing circuit Provide a high-pressure oxygen source suitable for jet ventilation in ?? Hazards: › Barotrauma (if the anesthesia machine does not incorporate fresh gas decoupling or an appropriately adjusted inspiratory pressure limiter) › Patient awareness
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“old” copper kettle–like technology “new” computerized control technology Physics: Vapor Pressure (boiling point: desflurane 22.8°C, isoflurane 48.5°C, halothane 50.2°C, enflurane 56.5°C, and sevoflurane 58.5°C) Latent Heat of Vaporization (number of calories required to change 1 g of liquid into vapor without a change in temperature) Specific Heat ( the number of calories required to increase the temperature of 1 g of a substance by 1°C) Thermal Conductivity (the speed at which heat flows through a substance)
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Flow Rate Output is less than the dial setting at very low and very high flow rates (<250 mL/min and 15 L/min) Backpressure (pumping effect, is more pronounced at low flow rates, low dial settings, and low levels of liquid anesthetic) Temperature (Automatic temperature-compensating mechanisms) Carrier Gas Composition (sudden transient decrease in vaporizer output)
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Simplified schematic of the Ohmeda Tec–type vaporizer
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Simplified schematic of the North American Dräger Vapor 19.n and 20.n vaporizers
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