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medical gases

Calculating amount of gas left in cylinder

  • Assuming the gas is stored in the cylinder in the gaseous state as medical oxygen is:
    • Boyle's law: P1V1 = P2V2
    • Look on the top of the cylinder, it should tell you how many litres when full (V1) and the maximum pressure that should be attained when full (P1) - this is usually ~15,000kPa
    • Look at the pressure gauge when the valve is turned on (P2)
      • thus proportion of gas left in cylinder if volume of cylinder if unknown = P2/P1
    • Maximum volume of gas at atmospheric pressure when cylinder is full will be:
      • = P1V1/101.325
    • Remaining volume when used at atmospheric pressure (101.325kPa) will be:
      • = P2V2/101.325 [NB. V2 will equal V1 as it is still in same volume cylinder]
    • eg. a “C” size cylinder will last ~20min when used at 16-20L/min (eg. on Oxylog ventilator)

medical oxygen

  • Australian standard pin index valve for oxygen equipment
  • black cylinder with white collar
  • the cylinders should be labelled ‘Medical Oxygen’
  • a full cylinder should have a plastic stopper inserted in the valve outlet, or if a smaller cylinder, plastic tape wound around the outlet.
  • the gas is delivered through a valve to a regulating device which reduces the pressure to a safe 390-400 kPa.
  • the oxygen flow is then delivered through a ‘yoke’ device that fits onto the valve stem of the cylinder. The yoke has fittings that match the valve stem, and has a measuring device attached to control the flow of oxygen.
  • flow rates of oxygen are varied by either a fixed flow outlet set between 3-8 litres per minute (lpm), or by an adjustable flow meter that delivers between 1-25 lpm.
  • cylinder sizes available in Australia:
    • “B” size: 200L
    • “C” size: 400-490L
      • there are various “C” size cylinders which are the most common ones used by ambulance services:
        • round bottom without long neck: 290L with brass collar, 320L without
        • round bottom with long neck: 400L
        • flat bottom: 440L
    • “Y” size: 680L
    • “D” size: 1,500-1,650L
    • “E” size: 4,000L
    • “G” size: 7,600L

references and resources

medical_gases.txt · Last modified: 2009/03/18 02:22 by

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