Physiotherapy and optimised enteral nutrition in the post-acute phase of critical illness (PHOENIX): a randomised controlled feasibility trial

Background: Survivors of critical illness commonly experience prolonged physical and functional impairment related to muscle wasting, catabolism, and malnutrition. Rehabilitation and nutritional support beyond the intensive care unit (ICU) are frequently inconsistent, and deficits persist following ICU discharge. Although combined rehabilitation and nutritional interventions may support recovery, their feasibility in the post-ICU hospital setting is uncertain. Methods: PHOENIX was a mixed-methods, parallel group, open-label randomised controlled feasibility trial conducted in two United Kingdom university hospitals. Adult ICU survivors who had received four or more days of advanced respiratory support and with ongoing physiotherapy and dietetic rehabilitation needs at ICU discharge were recruited. Participants were randomly allocated to either an ICU-initiated, enhanced physiotherapy and optimised nutrition intervention or usual care. Primary feasibility outcomes were recruitment rate, retention at 30 days, and intervention fidelity. Secondary outcomes, collected to inform a future definitive trial, included days alive and out of hospital at 30 days (DAOH30), physical function, nutritional status, and quality of life. The trial was prospectively registered (ClinicalTrials.gov NCT06159868). Findings: Between May 2024 and January 2025, 172 patients were screened, of whom 60 met eligibility criteria and all consented to participate. Recruitment targets were achieved within eight months, and retention at 30 days was 100%. Enhanced physiotherapy was delivered on 81% of available days, exceeding the predefined feasibility threshold of 70%. Delivery of prescribed nutritional targets was feasible, with intake fidelity exceeding progression criteria for both calories (75.2%) and protein (83.7%). Interpretation: A combined enhanced physiotherapy and optimised nutrition intervention following ICU discharge is feasible, with high recruitment, retention, and intervention fidelity. A definitive multicentre randomised controlled trial is now warranted to evaluate clinical and cost-effectiveness. Funding: This project is funded by the National Institute for Health and Care Research (NIHR) under its Research for Patient Benefit (RfPB) Programme (Grant Reference Number NIHR205370).