An observational study in Critical Illness, Mechanical Ventilation and Intensive Care Unit-Acquired Weakness, sponsored by Universidad de Extremadura. Active, not recruiting at 1 site in Spain. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-03-19.
Sponsored by Universidad de Extremadura · Observational
Critically ill patients who require mechanical ventilation frequently experience rapid loss of muscle mass and physical function during their stay in the intensive care unit (ICU). As part of standard care, physiotherapy and limb mobilization exercises are commonly provided, even in patients who are sedated and confined to bed in a supine position. However, the actual physiological and metabolic intensity of these routine physiotherapy interventions is poorly understood, and current prescriptions are largely based on clinical judgment rather than objective measures of patient effort or tolerance.
Oxygen consumption (VO₂) is a direct indicator of metabolic demand and physiological workload. In mechanically ventilated patients, indirect calorimetry integrated into the ventilator allows continuous measurement of VO₂ and carbon dioxide production without adding invasive procedures. While indirect calorimetry is routinely used to individualize nutritional support in the ICU, its potential role in quantifying the metabolic cost of physiotherapy interventions has been scarcely explored.
The aim of this prospective observational study is to quantify the acute metabolic response to a standardized session of supine physiotherapy in adult critically ill patients receiving invasive mechanical ventilation. During routine physiotherapy sessions performed as part of usual care, oxygen consumption will be continuously measured using indirect calorimetry integrated into the ventilator circuit. Each session will include a baseline resting period, the physiotherapy intervention itself, and a post-intervention recovery period, allowing patients to act as their own controls.
Physiotherapy sessions will consist of passive limb mobilization in deeply sedated patients and passive or active-assisted mobilization in patients who are awake or lightly sedated and able to cooperate. The primary outcome will be the change in oxygen consumption during physiotherapy compared with baseline rest. Secondary analyses will describe the total metabolic load of the session, peak oxygen consumption, and the time required for oxygen consumption to return toward baseline levels after the intervention. Basic cardiorespiratory variables, such as heart rate, blood pressure, oxygen saturation, and ventilatory parameters, will also be recorded to assess physiological stability and tolerance.
By objectively characterizing the metabolic cost of common supine physiotherapy interventions, this study aims to improve understanding of the physiological demands imposed on mechanically ventilated ICU patients. The results may help inform safer and more individualized physiotherapy prescriptions in critical care, supporting a more objective approach to dosing rehabilitation based on patients' real metabolic responses rather than solely on activity type or sedation level.
1,881 studies on the registry are indexed under Critical Illness; 462 are open to participants now.
This study's planned enrollment of 40 is below the median of 130 across 867 observational studies indexed under Critical Illness.
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Adult critically ill patients admitted to the intensive care unit who require invasive mechanical ventilation and receive routine supine physiotherapy as part of standard care. The study population includes both deeply sedated patients undergoing passive mobilization and awake or lightly sedated patients able to perform active-assisted mobilization, allowing characterization of metabolic responses across different levels of consciousness and participation.
Exclusion Criteria:
Adult critically ill patients receiving invasive mechanical ventilation who undergo standardized passive supine physiotherapy as part of usual ICU care. During the physiotherapy session, oxygen consumption is continuously measured using indirect calorimetry integrated into the ventilator, including baseline rest, intervention, and recovery periods.
Procedure: Supine Physiotherapy Session
Adult critically ill patients receiving invasive mechanical ventilation who undergo active-assisted supine physiotherapy as part of usual intensive care unit care. Physiotherapy consists of active-assisted limb mobilization, in which the patient voluntarily initiates the movement and the physiotherapist provides assistance as needed to complete the range of motion. This intervention is applied in patients who are awake or lightly sedated and able to cooperate.
Procedure: Supine Physiotherapy Session
Adult critically ill patients receiving invasive mechanical ventilation who undergo passive supine physiotherapy as part of usual intensive care unit care. Physiotherapy consists exclusively of passive limb mobilization performed by a physiotherapist, with no voluntary muscle activation by the patient, and is applied in deeply sedated patients.
Change in Oxygen Consumption (ΔVO₂) During Supine Physiotherapy
Oxygen consumption (VO₂) will be continuously measured using indirect calorimetry integrated into the mechanical ventilator during a standardized supine physiotherapy session performed as part of usual ICU care. The primary outcome is the change in VO₂ (ΔVO₂), defined as the difference between mean VO₂ during the physiotherapy intervention and mean VO₂ during a preceding baseline resting period, within the same session. Each participant serves as their own control.
Time frame: During a single physiotherapy session (baseline rest and intervention periods).
Total Metabolic Load of the Physiotherapy Session (VO₂ Area Under the Curve Above Baseline)
Oxygen consumption (VO₂) will be continuously measured by indirect calorimetry during baseline rest, the physiotherapy intervention, and the recovery period. Total metabolic load will be expressed as the area under the VO₂-time curve above baseline (AUC above baseline), integrating the excess VO₂ over time attributable to the session.
Time frame: During a single physiotherapy session (baseline, intervention, and recovery periods)
Peak Oxygen Consumption During Supine Physiotherapy
Peak VO₂ will be defined as the highest VO₂ value observed during the physiotherapy intervention period, measured continuously via indirect calorimetry. The outcome will be reported as the absolute peak VO₂ and may be expressed relative to baseline.
Time frame: During the physiotherapy intervention period of a single session
Relative Change in Oxygen Consumption During Supine Physiotherapy (%ΔVO₂)
The relative change in oxygen consumption will be calculated as the percentage difference between mean VO₂ during the physiotherapy intervention and mean VO₂ during baseline rest within the same session.
Time frame: During a single physiotherapy session (baseline rest and intervention periods).
Time to Recovery of Oxygen Consumption Toward Baseline After Physiotherapy
Recovery time will be defined as the time required after the end of the physiotherapy intervention for VO₂ to return to within ±10% of the baseline mean value and remain within that range for a sustained period (as per protocol). If VO₂ does not return to this range within the maximum monitoring window, recovery will be recorded as not achieved within the session.
Time frame: Immediately after the physiotherapy intervention, up to the end of the recovery monitoring period within a single session.
Cardiorespiratory Stability During Supine Physiotherapy
Physiological stability during the session will be assessed by changes from baseline in heart rate, blood pressure (including mean arterial pressure), peripheral oxygen saturation (SpO₂), and ventilatory parameters recorded during baseline rest, intervention, and recovery. Clinically relevant events leading to interruption of the session (e.g., desaturation, hypotension, arrhythmia) will be documented.
Time frame: During a single physiotherapy session (baseline, intervention, and recovery periods).
Carbon Dioxide Production (VCO₂) and Respiratory Exchange Ratio (RER) During Supine Physiotherapy
Carbon dioxide production (VCO₂) will be continuously measured by indirect calorimetry during baseline rest, intervention, and recovery. Respiratory exchange ratio (RER) will be calculated as VCO₂/VO₂ for the same periods to describe metabolic response patterns.
Time frame: During a single physiotherapy session (baseline, intervention, and recovery periods).
Energy Expenditure During Supine Physiotherapy
Energy expenditure will be estimated from VO₂ and VCO₂ as provided by the indirect calorimetry system. Values will be summarized for baseline rest, the physiotherapy intervention, and the recovery period within the same session.
Time frame: During a single physiotherapy session (baseline, intervention, and recovery periods).
Plan to share: No
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Universidad de Extremadura