Oxygen FAQ

Up to date, expert answers to frequently asked questions (FAQ) about oxygen supply systems, respiratory care and pulse oximetry written by OCC & collaborators.

What is the maximum oxygen concentration that can be delivered by a ventilator if I don’t have a high pressure oxygen source?

  • The short answer is that it depends on many factors and varies by ventilator model (so check the manufacturers’ specifications)
  • Some ventilators like the LTV 1200/2200, PB560 and Zoll 731 can run off of a low pressure oxygen supply. They utilize 21% ambient air from the room via a built in compressor or turbine and mix that with the low pressure oxygen input.
  • When utilizing low flow oxygen, ventilators usually will not allow you to use the blender – i.e. you can’t set the FiO2
  • Concentration of oxygen delivered to the patient (FiO2) is determined by: minute ventilation, flow of oxygen supply into the vent, concentration of oxygen supply into the vent, and potentially other factors.
  • For example:
    • LTV 1200/2200 – If input flow is set to minute ventilation, then the LTV1200/2200 can deliver ~100% FiO2 up to ~20LPM minute ventilation. For a patient with 10 LPM minute ventilation and 5 or 10LPM input low pressure oxygen, max FiO2 delivered to the patient is approximately 50 and 75% respectively. (See Figure below left)
    • Zoll 731 – If input flow is set to minute ventilation, and an external reservoir (e.g. ZOLL 731) is used on the compressor intake, then FiO2 of ~100% is possible on the Zoll 731 for minute ventilation up to ~20 LPM. (See Figure below, bottom) For more information on using the ZOLL 731 with low pressure O2 sources see the users manual and this quick reference.
    • PB560 – Some ventilators like the PB560 that only accept low flow oxygen may be limited in the amount that can be delivered into the device at low pressure and thus be limited in FiO2 delivery to the patient (e.g. the PB 560 is designed to deliver a percentage of oxygen equal or lower than 50%. Exceeding this value may cause the ventilator to malfunction and put the patient at risk). (See Figure below right)
  • When using low pressure oxygen supply for devices with bias flow (flow during the expiratory time) and/or during NIV modes with leak compensation, the FiO2 can be diluted significantly.
  • When using low pressure oxygen supply, you likely will need to change the ventilator setting to indicate such a source is being used (e.g. ‘reservoir mode’ or ‘low pressure input’)
  • Due to slight difference in the densities of air and O2, tidal volume may decrease slightly as FiO2 increases via low pressure entrainment. See manufacturer’s specifications, though generally this would be expected to be less than 10% change in tidal volumes.

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