1. intubated and on mechanical ventilation, or requiring immediate intubation as per the treating clinician's assessment 2. heparin allergy or heparin-induced thrombocytopenia 3. aptt \>120 s, not due to anticoagulant therapy and does not correct with the administration of fresh frozen plasma 4. platelet count \<20 × 109 /l 5. pulmonary bleeding or uncontrolled bleeding 6. pregnant or might be pregnant 7. acute brain injury that may result in long-term disability 8. myopathy, spinal cord injury, or nerve injury or disease with a likely prolonged incapacity to breathe independently e.g. guillain-barre syndrome 9. treatment limitations in place (ceiling of care), i.e. not for intubation, not for icu admission 10. death is imminent or inevitable within 24 h 11. clinician objection 12. refusal to consent

1. intubated and on mechanical ventilation, or requiring immediate intubation as per the treating clinician's assessment 2. heparin allergy or heparin-induced thrombocytopenia 3. aptt \>120 s, not due to anticoagulant therapy and does not correct with the administration of fresh frozen plasma 4. platelet count \<20 × 109 /l 5. pulmonary bleeding or uncontrolled bleeding 6. pregnant or might be pregnant 7. acute brain injury that may result in long-term disability 8. myopathy, spinal cord injury, or nerve injury or disease with a likely prolonged incapacity to breathe independently e.g. guillain-barre syndrome 9. treatment limitations in place (ceiling of care), i.e. not for intubation, not for icu admission 10. death is imminent or inevitable within 24 h 11. clinician objection 12. refusal to consent

intubated and on mechanical ventilation, or requiring immediate intubation as per the treating clinician's assessment heparin allergy or heparin-induced thrombocytopenia aptt >120 s, not due to anticoagulant therapy and does not correct with the administration of fresh frozen plasma platelet count <20 × 109 /l pulmonary bleeding or uncontrolled bleeding pregnant or might be pregnant acute brain injury that may result in long-term disability myopathy, spinal cord injury, or nerve injury or disease with a likely prolonged incapacity to breathe independently e.g. guillain-barre syndrome treatment limitations in place (ceiling of care), i.e. not for intubation, not for icu admission death is imminent or inevitable within 24 h clinician objection refusal to consent

intubated and on mechanical ventilation, or requiring immediate intubation as per the treating clinician's assessment heparin allergy or heparin-induced thrombocytopenia aptt >120 s, not due to anticoagulant therapy and does not correct with the administration of fresh frozen plasma platelet count <20 × 109 /l pulmonary bleeding or uncontrolled bleeding pregnant or might be pregnant acute brain injury that may result in long-term disability myopathy, spinal cord injury, or nerve injury or disease with a likely prolonged incapacity to breathe independently e.g. guillain-barre syndrome treatment limitations in place (ceiling of care), i.e. not for intubation, not for icu admission death is imminent or inevitable within 24 h clinician objection refusal to consent