Reducing Oxygen Consumption in Critical Care

The ventilator modification will be fitted to a ResMed Lumis 150, Breas® Nippy 4+ or Vivo 1, 2 or 3 ventilator. The participants oxygen level will be measured with and without the modification in place at their baseline ventilation, and with 1, 2 and 3 litres oxygen extra to their baseline. the researcher will then leave the modification on and slowly reduce the oxygen going into the ventilator, maintaining the participants SP02 at an acceptable level (\>95%)