Does in-bed cycling, started within the first 2 days of an admission to ICU, reduce delirium in adults receiving mechanical ventilation?

INTERVENTION: Participants will be stratified to site and randomised 1:1 using permuted block randomisation to receive either early (within =48 hours following invasive mechanical ventilation) in‐bed cycling in addition to usual care vs usual care alone for 5 days per week across 14 days or until out‐of‐bed mobilisation begins (whichever comes first). CONDITION: Delirium in critically ill patients ; Mental and Behavioural Disorders PRIMARY OUTCOME: Feasibility and acceptability of early (within =48 hours following invasive mechanical ventilation) in‐bed cycling to reduce ICU delirium in mechanically ventilated patients. The following measures will be collected to determine trial feasibility: ; 1. Recruitment rate (% of participants enrolled vs participants eligible); 2. Retention rate (% of enrolled participants who completed the intervention protocol in full excluding deaths); 3. Intervention fidelity (% intervention sessions completed); 4. The acceptability of the intervention will be evaluated by the key stakeholders (assessed by qualitative interviews); There will be no interim analysis therefore these measures will be collected up until the end of the study period. The end of the study period is defined as the date of the last follow‐up visit of the last participant undergoing the study (via telephone or in‐person). INCLUSION CRITERIA: 1. Adults (aged 18 years and above) 2. Unplanned ICU admissions 3. MV initiated within =48 hours of ICU admission 4. Expected to remain on MV >72 hours SECONDARY OUTCOME: 1. Occurrence of ICU delirium measured using the Confusion Assessment Method for the Intensive Care Unit (CAM‐ICU) on days 0‐14 and up to day 30; 2. Delirium‐free days (CAM‐ICU) day‐0‐14, and up to day 30; 3. Duration (days) of ICU‐Delirium (CAM‐ICU) days 0‐14, and up to day 30 ; 4. Severity of ICU‐Delirium using the Confusion Assessment Method for the Intensive Care Unit 7 (CAM‐ICU‐7), delirium severity scale on days 0‐14; 5. Physical function measured using the Functional Status Score for the Intensive Care Unit (FSS‐ICU) on day‐14 or out‐of‐bed mobilisation (whichever comes first); 6. Quality of life measured using the EQ‐5D‐5L questionnaire and the SF‐36 questionnaire at day 90. The quality of life of participants will also be measured from the perspective of their relative or carer using the proxy EQ‐5D‐5L questionnaire at day 90. ; 7. Pain measured using the SF‐36 questionnaire at day 90; 8. Cognition after ICU discharge assessed using the Montreal Cognitive Assessment (MoCA) on day 90; 9. Presence of delirium after ICU discharge measured using the Family Confusion Assessment Method (FAM‐CAM) at day 90; 10. Time to delirium resolution (days) measured using time from delirium diagnosis to time delirium resolved in days/ patient health records; 11. ICU and hospital length of stay (days) measured using days of ICU admission to discharge and days of hospital admission to discharge/patient electronic health records; 12. Ventilator‐free days (days) on days 0‐30 measured using days spontaneously breathing i.e., nil invasive ventilator support required between day 0 and day 30 from randomisation/patient electronic health records; 13. Sedation‐free days (days) on days 0‐30 measured using days nil sedation administered between day 0 and day 30 from randomisation/patient electronic health records; 14. [Severity of sedation] measured using the Daily Richmond Agitation Sedation Scale (RASS) at day 0 to day 14 from randomisation or out‐of‐bed mobilisation commences (whichever comes first); 15. Adverse events measured using [adverse events related to the trial procedures and serious adverse events/electronic Case Report Form] at from day 0 to day 90 from randomisation; 16. Deaths measured using eCRF and patient electronic health records at from day 0 to day 90 from randomisation