ICU Combined Assessment of Cardio-Respiratory Exercise

Exercise Testing in ICU Survivors to Evaluate ICU-acquired Weakness

This study aims to investigate how sepsis and critical illness can impair the cardiovascular system and microcirculation in intensive care unit (ICU) patients, which can lead to long-lasting muscle weakness/dysfunction or ICU-Acquired Weakness (ICU-AW) and exercise limitations.

This longitudinal study will assess cardiovascular fitness and microvascular function through two (2) follow-ups after ICU discharge: at (i) 6 months, and (ii) 12 months. The first timepoint will be at 6 months will be required, and the second timepoint at 12 months will be optional based on participant availability. The goal is to understand how microvascular dysfunction contributes to ICU-AW and long-term exercise limitation in ICU survivors.

Specific goals are:

1. Determine the feasibility of study enrollment and protocol completion.
2. Evaluate peak oxygen uptake and oxygen on/off kinetics in ICU survivors using a standardized cardiopulmonary exercise test (CPET) protocol. This protocol has been adapted from Santana et. al. (2025) for the ICU population.
3. Characterize skeletal muscle microvascular function in ICU survivors using high-resolution NIRS during CPET protocol.
4. Determine the association between impairments in skeletal muscle microvascular oxygen delivery and cardiovascular blood flow regulation in ICU survivors.

Inclusion Criteria:

• Patients who have received mechanical ventilation for at least 7 days in the intensive care unit (ICU) and have subsequently been discharged from hospital.

Exclusion Criteria:

• Unable to provide consent
• Trajectory of health expected to be significantly limited in the upcoming 12 months
• those who self-report that they cannot climb at least one flight of stairs due to limited exercise capacity
• have significant orthopedic or musculoskeletal impairment affecting mobility
• have a medical history of neuromuscular disease
• ongoing respiratory limitations (i.e., supplemental oxygen)
• significant heart disease (i.e. ejection fraction less than 30%, unstable ischemic heart disease, severe valvular heart disease)
• a body mass index (BMI) of ≥ 40 kg/m2 (impacting NIRS signal due to adipose tissue thickness)
• if participant's primary residence is a significant distance from the participating study site