Trial Summary: CYCLE – Critical Care Cycling to Improve Lower Extremity Strength

Survivors of critical illness may face physical disability up to 5 years following their discharge from the intensive care unit (ICU).1 Muscle mass decreases within the first 72 hours of a patient’s ICU stay.2 Leg muscles account for 75% of total skeletal muscle mass3 and are most vulnerable to weakness from immobility.4 Therefore, addressing immobility while patients are in the ICU is an important opportunity to optimize physical function.4 The Society of Critical Care Medicine guidelines recommend rehabilitation or mobilization in the ICU for critically ill adults, as the benefits likely outweigh the risks.5 However, the guidelines did not recommend specific types or timing of rehabilitation activities due to heterogeneous evidence. Further, two recent prominent randomized controlled trials (RCTs)6,7 and a systematic review8 raised concerns for an increased risk of safety events in patients randomized to early rehabilitation interventions, prompting discussion within the critical care and rehabilitation communities. Data from high-quality, rigorous clinical trials, performed in the Canadian context are urgently needed.

CYCLE (Critical Care Cycling to Improve Lower Extremity Strength) is a Canadian, physiotherapist-led, CIHR-funded research program started in 2013. In-bed cycling is an underused, promising intervention aimed at minimizing immobility and improving physical function post-ICU discharge. The CYCLE research program has culminated in an international RCT with the following objectives: 1) to determine if early in-bed cycling and usual care physiotherapy (PT) compared to usual care PT alone in critically ill, mechanically ventilated adults improves the primary outcome of physical function, and 2) to conduct an economic evaluation of the CYCLE RCT.

Characteristics of CYCLE RCT:

Study design: 360-patient, 17 site (14 Canada, 1 Australia, 2 United States), concealed, open-label, parallel-group.

Population: Adults (³18 years old) within the first 7 days of ICU admission, first 4 days of mechanical ventilation, and who could ambulate independently before their critical illness (with or without a gait aid). Intervention: 30 minutes per day of cycling, 5 days per week in addition to usual care PT activities. A specialized in-bed cycle ergometer provides passive (no patient induced muscular contribution), active-assisted (partial patient), or active cycling (full patient). Starting at enrollment, individual participants receive in-bed cycling for the duration of their index ICU admission, or until the patient can march on the spot for two consecutive days, or to a maximum of 28 days, whichever occurs first. ICU physiotherapists deliver the intervention as part of their usual clinical role.

Comparison: Patients allocated to the control arm receive usual care PT activities per current institutional practice.

OutcomesPrimary: Physical Function ICU Test-Scored,9 a reliable and valid measure in critically ill patients, 3-days post ICU discharge completed by assessors blinded to treatment allocation. Secondary: Safety, muscle strength, physical function, frailty, psychological distress, quality of life (EQ-5D),10-12 mortality, and healthcare utilization (ICU and hospital length of stay). Follow-up: 90-days post-randomization.

Meaningful impact: CYCLE is the largest study of critical care in-bed cycling rehabilitation in the world. Results of the CYCLE RCT will provide Canadian efficacy and safety evidence to determine whether inbed cycling during critical illness improves short-term physical and functional outcomes and accelerates recovery in ICU survivors.

Given recent concerns raised regarding the safety of ICU rehabilitation, additional data are urgently needed to inform contemporary clinical practice.