Patient responses to oxygen therapy (PROT)

This is an observation study measuring physiological responses in patients on oxygen therapy via a ventilator within the ICU. This study will only include participants who are receiving oxygen therapy with non-invasive ventilatory support (such as NHF and CPAP mode). The participants' oxygen saturation (SpO2) responses to changes in the fraction of inspired oxygen (FiO2) will be measured for up to 24 hours. Participants will receive standard care as usual, the only difference is that they will wear an additional pulse oximeter which connects to a data logging machine. This data logging machine will be used to continuously measure the SpO2 and FiO2 during the 24-hour observational period. The assessment of these responses may begin at any time as participants will already be receiving oxygen therapy via a ventilator at the time of screening and enrolment. These responses will be monitored by ICU staff, who may adjust the FiO2 depending on the participants oxygen requirements, in which these FiO2 changes will be recorded by the data logging machine during the study period. Demographics and medical history will be collected at baseline.