* invasive mechanical ventilation, or non-invasive ventilation (niv) with cpap or bipap or imminent need for these * contraindications to prone position (see appendix 5) * pregnancy * severe obesity (bmi \>35), * altered level of consciousness (gcs \<13) * attending doctor judged prone position to be unsuitable for the patient for any reason * patients in whom there is a decision that care will not be escalated * failure to have informed consent

* invasive mechanical ventilation, or non-invasive ventilation (niv) with cpap or bipap or imminent need for these * contraindications to prone position (see appendix 5) * pregnancy * severe obesity (bmi \>35), * altered level of consciousness (gcs \<13) * attending doctor judged prone position to be unsuitable for the patient for any reason * patients in whom there is a decision that care will not be escalated * failure to have informed consent

- invasive mechanical ventilation, or non-invasive ventilation (niv) with cpap or bipap or imminent need for these - contraindications to prone position (see appendix 5) - pregnancy - severe obesity (bmi >35), - altered level of consciousness (gcs <13) - attending doctor judged prone position to be unsuitable for the patient for any reason - patients in whom there is a decision that care will not be escalated - failure to have informed consent

- invasive mechanical ventilation, or non-invasive ventilation (niv) with cpap or bipap or imminent need for these - contraindications to prone position (see appendix 5) - pregnancy - severe obesity (bmi >35), - altered level of consciousness (gcs <13) - attending doctor judged prone position to be unsuitable for the patient for any reason - patients in whom there is a decision that care will not be escalated - failure to have informed consent