Intensive Care Unit-acquired weakness (ICU-AW) is a well-recognized, important and preventable sequelae of critical illness, affecting up to 60% of adult ICU patient. ICU-AW is associated with increased mortality and length of stay, and negatively impacts long-term functional outcomes and quality of life in affected patients and their caregivers. While delayed mobilization adversely affects clinical outcomes, early rehabilitation in the critically ill adult population is safe, feasible, cost effective, results in more ventilator free-days and better functional outcomes at hospital discharge. In contrast, there is a paucity of this research in pediatrics. Our research suggests that immobilization is common in critically ill children, and rehabilitation is delayed particularly in the sickest children who are arguably at highest risk of morbidity. It is unclear however, whether delayed rehabilitation leads to adverse outcomes in critically ill children, as has been demonstrated in adults. Our objectives of this study are to evaluate if immobilization and delayed rehabilitation negatively impacts short-term clinical outcomes and the time to functional recovery in critically ill children. The investigators hypothesize that the following factors may influence functional recovery and morbidity in critically ill children:

• Pre-morbid condition
• Age
• Time-to-initiation of acute rehabilitation
• Critical illness disease severity

Overall Study objectives:

1. To describe the functional recovery following prolonged immobility and delayed rehabilitation in critically ill children.
2. To explore the predictors of impaired functional recovery following immobilization in critically ill children.

Prior to conducting a definitive multi-centre study to answer our research questions and achieve our study objectives above, we will conduct a pilot study in order to demonstrate feasibility.

Inclusion Criteria:

• Age over 12 months to 17 years
• PCCU stay of ≥ 48 hours
• Patient is limited to bed-rest and has not been mobilized during the first 48 hours of PCCU admission
• Equal to or greater than one organ dysfunction on PCCU admission (as measured by PELOD)
• Informed consent of patient/substitute decision maker.

Exclusion Criteria:

• Age: < 12 months or ≥18 years
• Patients admitted to step-down/intermediate care
• Patients transferred from Neonatal intensive care unit and never discharge home.

iv) Patients who are already mobilizing well, or are at baseline functional status at time of screening v) Admission diagnosis of a neuromuscular disorder: e.g. Acute Guillain-Barré Syndrome, Botulism, Myasthenia Gravis), or acute spinal cord injury/transverse myelitis vi) Not expected to survive PCCU/hospital stay vii) Previously enrolled into study less than 6 months ago and/or still undergoing study procedures at time of screening

Critically Ill Children