Ward-level oxygen delivery devices

With thanks to Dr Horsley, Infectious Diseases registrar at North Manchester General Hospital

Nasal cannulae:

  • 1-6 L/min
  • Deliver ~22-44%
  • Higher flow rates (>4 L/min) generally intolerable

Simple face mask:

  • 2-10 L/min
  • Deliver ~35-60% (between 5 and 10 L/min)
  • Uncontrolled and variable oxygen concentration
  • Ideally >  ~6 L/min to prevent CO2 accumulation

Reservoir mask:

  • Ideally ~12-15 L – reservoir must be inflated and doesn’t fully collapse during inspiration
  • Deliver ~85-90% at 15 L/min
  • Uncontrolled and variable concentration

Venturi mask: *reserve only for patients at risk of Type II respiratory failure*

  • Fixed flow rates of 24-60% depending on valve used (colour coded)
  • Based on the Bernoulli principle
    • Gas flow through narrowed section increases in velocity but decreases in pressure, drawing in air in a predictable ratio
  • “Fixed” oxygen concentrations

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