intubated and on mechanical ventilation, or requiring immediate intubation as per the treating clinician's assessment heparin allergy or heparin-induced thrombocytopaenia activated partial thromboplastin time (aptt) > 120 seconds, not due to anticoagulant therapy and does not correct with administration of fresh frozen plasma platelet count < 20 x 109 per 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, i.e. not for intubation, not for icu admission death is imminent or inevitable within 24 hours clinician objection refusal of participant consent

intubated and on mechanical ventilation, or requiring immediate intubation as per the treating clinician's assessment heparin allergy or heparin-induced thrombocytopaenia activated partial thromboplastin time (aptt) > 120 seconds, not due to anticoagulant therapy and does not correct with administration of fresh frozen plasma platelet count < 20 x 109 per 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, i.e. not for intubation, not for icu admission death is imminent or inevitable within 24 hours clinician objection refusal of participant consent