Metabolic Response to Supine Physiotherapy in Mechanically Ventilated ICU Patients

Metabolic Response to Supine Physiotherapy in Mechanically Ventilated Critically Ill Patients Assessed by Indirect Calorimetry

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.

Study Overview

• Status: Active, not recruiting
• Conditions: Critical Illness; Mechanical Ventilation; Intensive Care Unit-Acquired Weakness; Physical Rehabilitation in the Intensive Care Unit
• Intervention / Treatment: Procedure: Supine Physiotherapy Session

• Study Type: Observational
• Enrollment (Estimated): 40

Contacts and Locations

Study Locations

• Spain
  • Badajoz
    • Badajoz, Badajoz, Spain, 06006
      • Hospital Universitario de Badajoz

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

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.

Description

Inclusion Criteria:

• Adults aged 18 years or older.
• Admission to the intensive care unit.
• Invasive mechanical ventilation via endotracheal tube or tracheostomy.
• Ability to remain in the supine position during the measurement period.
• Clinical indication for supine physiotherapy as part of usual ICU care.
• Richmond Agitation-Sedation Scale (RASS) score between -5 and 0 at the time of the session.
• Hemodynamic stability, defined as mean arterial pressure ≥65 mmHg with or without vasopressor support and no initiation or increase >20% in vasopressor dose within the previous 60 minutes.
• Respiratory stability, defined as no changes in ventilator settings within the previous 30 minutes and oxygen saturation ≥90% with FiO₂ ≤0.60 and PEEP ≤12 cmH₂O.
• Technical conditions allowing valid indirect calorimetry measurement (absence of significant air leaks and no planned circuit disconnections).

Exclusion Criteria:

• Use of extracorporeal membrane oxygenation (ECMO) or other extracorporeal gas exchange systems.
• Continuous renal replacement therapy during the measurement period when it may interfere with metabolic measurements.
• Significant air leaks in the airway or ventilator circuit that invalidate indirect calorimetry measurements.
• Planned procedures or interventions during the measurement period that could interfere with gas exchange (e.g., bronchoscopy, recruitment maneuvers, ventilator setting changes).
• Severe respiratory instability requiring FiO₂ >0.60 or PEEP >12 cmH₂O.
• Ongoing neuromuscular blockade infusion.
• Clinical contraindications to limb mobilization (e.g., unstable fractures, active bleeding, uncontrolled intracranial hypertension).
• Agitation or risk of unplanned device removal (RASS >0).
• Refusal of participation by the patient or legally authorized representative, when applicable.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Passive Supine Physiotherapy; 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 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.
Active-Assisted Supine Physiotherapy; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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.	During a single physiotherapy session (baseline rest and intervention periods).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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.	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.	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.	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.	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.	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.	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.	During a single physiotherapy session (baseline, intervention, and recovery periods).

Collaborators and Investigators

• Sponsor: Universidad de Extremadura

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2026
• Primary Completion (Estimated): May 30, 2026
• Study Completion (Estimated): May 30, 2026

Study Registration Dates

• First Submitted: January 14, 2026
• First Submitted That Met QC Criteria: January 14, 2026
• First Posted (Actual): January 23, 2026

Study Record Updates

• Last Update Posted (Actual): March 19, 2026
• Last Update Submitted That Met QC Criteria: March 18, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Pathologic Processes; Disease Attributes; Pathological Conditions, Signs and Symptoms; Critical Illness
• Other Study ID Numbers: 12 (Israel lung Association)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No