In normal practice oxygen supply can be easily met with existing hospital infrastructure. COVID - 19 however results in lung damage which greatly increases the amount of oxygen patients require - as a consequence some hospitals in the UK and other countries had situations where there was not enough oxygen for their inpatients.

COVID - 19 has caused many more patients to requiring assistance with their breathing using a ventilator. Due to the limited supply of sophisticated ventilators that 're-use' oxygen patients breathe out, some hospitals have used ventilators normally used by patients at home (domiciliary ventilators). Whilst these are inexpensive and commonly available, any oxygen the patient breathes out is simply released into the atmosphere.

The address this problem, and in turn reduce the oxygen demand on hospital infrastructure the biomedical engineering team (BME) at the Royal Brompton Hospital, London devised a simple 3-D printed modification which captures and reuses oxygen on commonly used domiciliary ventilators. Laboratory testing found this modification can increase the oxygen given by the ventilator without increasing the oxygen consumption of the ventilator - effectively reducing oxygen demand on hospital infrastructure.

This study will evaluate this modification in patients admitted to intensive care requiring assistance with their breathing. This will involve measuring oxygen levels on domiciliary ventilators (Breas Nippy 4+, ResMed Lumis 150 or Vivo 1, 2 or 3) with and without the modification and with small increases in oxygen supplied to the patient for a total study period of 2 hours.

Inclusion Criteria:

• Patient in critical care using a ResMed LumisTM 150, Breas® Nippy 4+ or Vivo 1, 2 or 3 ventilator or deemed safe by treating consultant safe to switch to one.
• 28% or more of entrained oxygen (FiO2)
• Judged to be safe to tolerate increased fraction of inspired oxygen for periods of 10 minutes
• Arterial line insitu for clinical reasons

Exclusion Criteria:

• Thought to be clinically unstable during study protocol (2 hours)

Mechanically ventilated patients in critical care