Blood Flow Restriction Training for Mechanically Ventilated Patients With ICU-Acquired Weakness (BFRT-ICU)

Effects of Blood Flow Restriction Training at Different Limb Occlusion Pressures on Muscle Strength, Lower-Limb Muscle Morphology and Serum Inflammatory Factors in Mechanically Ventilated ICU-Acquired Weakness Patients: A Prospective Three-Arm Randomized Controlled Trial

Patients receiving mechanical ventilation in the intensive care unit (ICU) frequently develop ICU-acquired weakness - a condition marked by widespread muscle loss and weakness caused by prolonged bed rest, severe illness, and systemic inflammation. This complication can lengthen time on the ventilator, extend ICU stays, and lead to lasting physical disability. Standard rehabilitation therapies in the ICU have limited ability to slow muscle loss because critically ill patients cannot tolerate high levels of exercise.

Blood flow restriction training (BFRT) is a rehabilitation technique that uses an inflatable cuff on the upper leg to partially restrict blood flow during low-intensity exercise. This approach is known to stimulate muscle growth and preserve strength with much lower physical effort than traditional strength training, making it a promising option for vulnerable ICU patients.

This randomized controlled trial is designed to test the safety and effectiveness of BFRT in mechanically ventilated adults with ICU-acquired weakness. A total of 120 eligible patients will be randomly divided into three groups:

A control group receiving standard ICU medical care and routine rehabilitation A group receiving standard care plus BFRT at 40% of individual limb occlusion pressure A group receiving standard care plus BFRT at 60% of individual limb occlusion pressure All patients will receive 2 weeks of intervention. The research team will measure and compare muscle strength, lower limb muscle size (via ultrasound), blood inflammatory markers, duration of mechanical ventilation, length of ICU stay, and ventilator weaning success rates across the three groups.

This study aims to determine whether adding BFRT to standard rehabilitation can improve muscle function, reduce systemic inflammation, and shorten hospital recovery time for these patients, and which pressure level provides the optimal balance of benefits and safety.

Study Overview

• Status: Not yet recruiting
• Conditions: Intensive Care Unit Acquired Weakness
• Intervention / Treatment: Other: Standard ICU Care and Routine Rehabilitation; Other: Blood flow restriction training

Detailed Description

Intensive care unit-acquired weakness (ICUAW) is a prevalent neuromuscular complication in critically ill patients undergoing invasive mechanical ventilation, with reported incidence ranging from 25% to 60% in high-risk populations. Its pathophysiology is multifactorial, involving immobilization-induced muscle protein turnover imbalance, systemic inflammatory response-mediated myofiber injury, neuromuscular junction dysfunction, and metabolic disturbances. ICUAW not only prolongs mechanical ventilation and ICU length of stay but also increases nosocomial complication risk and leads to persistent long-term functional impairment, imposing substantial burden on patients and healthcare systems.

Current standard rehabilitation for ICUAW relies mainly on passive range-of-motion exercises, bed mobility training, and low-intensity assisted active movements. However, due to limited cardiopulmonary reserve, reduced baseline muscle strength, and hemodynamic instability in critically ill patients, conventional rehabilitation often fails to deliver sufficient mechanical stimulus to counteract rapid muscle atrophy, resulting in only modest clinical benefits. There remains an unmet need for safe, low-load rehabilitation modalities that can effectively mitigate muscle wasting in this vulnerable population.

Blood flow restriction training (BFRT) is an evidence-based rehabilitation modality that applies an inflatable cuff to the proximal limb to partially occlude venous return while preserving arterial inflow, paired with low-intensity resistance exercise. Prior studies in orthopedic, chronic disease, and healthy populations have consistently shown that BFRT produces muscle hypertrophy and strength gains comparable to high-load resistance training, despite using only 20-30% of maximal voluntary contraction intensity. Its mechanisms include local hypoxic stress, metabolic product accumulation, activation of the mTOR anabolic pathway, inhibition of ubiquitin-proteasome catabolic signaling, and increased secretion of myokines with systemic anti-inflammatory effects.

Limb occlusion pressure (LOP) - the minimum cuff pressure required to fully occlude distal arterial blood flow - is the gold standard for individualizing BFRT pressure prescription. Prescribing pressure as a percentage of individual LOP minimizes variability caused by differences in limb circumference, vascular tone, and body composition, which is particularly critical for the heterogeneous critically ill population. Available evidence suggests pressures below 30% LOP provide insufficient hypoxic stimulus to activate muscle anabolic pathways, while pressures above 70% LOP carry elevated risk of arterial occlusion and adverse events. The 40% LOP and 60% LOP levels selected for this trial represent low and moderate-low pressure ranges, hypothesized to match the poor physical tolerance of ICUAW patients while delivering graded therapeutic effects.

To date, most BFRT research has been conducted in outpatient or post-surgical populations. High-quality randomized controlled trials evaluating BFRT efficacy and safety in mechanically ventilated patients with ICUAW remain scarce. Furthermore, few studies have simultaneously examined effects on muscle morphology, systemic inflammation, and hard clinical endpoints, leaving the optimal pressure parameter and comprehensive clinical value of BFRT in critical care unclear.

This is a single-center, prospective, three-arm parallel-group randomized controlled trial conducted in a tertiary teaching hospital intensive care unit. The protocol has been approved by the hospital ethics committee. A total of 120 eligible mechanically ventilated adults with ICUAW will be enrolled and randomly assigned 1:1:1 to a usual care control group, a 40% LOP BFRT group, and a 60% LOP BFRT group. All participants will receive standard ICU medical management and routine rehabilitation for 2 weeks. The two intervention groups will receive additional daily BFRT sessions on bilateral lower extremities at their respective pressure levels.

Randomization will use a computer-generated random number sequence, with allocation concealment maintained via sequentially numbered, sealed opaque envelopes. Outcome assessors and ultrasound technicians will be blinded to group assignment to reduce measurement bias. Analyses will be performed on both intention-to-treat and per-protocol populations, with multiple imputation used to handle missing data.

The BFRT protocol follows standardized operational procedures. Prior to the first session, each patient's LOP will be measured in supine resting position using an automated pneumatic cuff system with built-in pressure sensors. Each session includes three lower-extremity exercises - straight leg raise, isometric quadriceps contraction, and glute bridge - performed for 3 sets of 10 repetitions, with 30-second rest between sets and 3-minute rest between limbs. Training intensity is monitored via the Borg Rating of Perceived Exertion scale, targeted at 9-11 to maintain low exertion. BFRT sessions are scheduled at least 6 hours apart from routine rehabilitation to avoid cumulative fatigue.

Comprehensive safety monitoring is implemented throughout the intervention. Continuous bedside cardiac monitoring tracks heart rate, invasive blood pressure, respiratory rate, and peripheral oxygen saturation. Predefined stopping criteria for hemodynamic instability, respiratory compromise, and limb intolerance are applied to ensure patient safety. All adverse events are documented and reviewed by an independent safety monitoring team.

Outcome assessments occur at baseline and after 2 weeks of intervention. The primary outcome is change in muscle strength measured by the Medical Research Council sum score. Secondary outcomes include changes in lower limb muscle architecture (rectus femoris and medial gastrocnemius cross-sectional area and thickness) via standardized musculoskeletal ultrasound, changes in serum pro-inflammatory cytokines (TNF-α, IL-6, IL-8) measured by enzyme-linked immunosorbent assay, and clinical prognosis indicators including mechanical ventilation duration, ICU length of stay, and ventilator weaning success rate.

This study aims to provide high-level clinical evidence on the efficacy, optimal pressure parameter, and safety profile of BFRT in mechanically ventilated ICUAW patients. It is hypothesized that BFRT will attenuate muscle atrophy, improve strength, reduce systemic inflammation, and accelerate clinical recovery in a pressure-dependent manner without increasing adverse events. Findings are expected to inform clinical practice and establish standardized BFRT protocols for early critical care rehabilitation.

• Study Type: Interventional
• Enrollment (Estimated): 120
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Rangrang Wang; Phone Number: +86 155-8877-6876; Email: chinawrr1124@163.com
• Study Contact Backup: Name: Fang Xu; Phone Number: +86 130-1261-5163

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

1. Age ≥ 18 years;
2. Received invasive mechanical ventilation for ≥ 48 hours;
3. Meets the clinical diagnosis criteria for ICUAW: The patient has reached a level of consciousness that allows for reliable assessment of voluntary muscle strength, is able to execute standardized motor commands, has an MRC-SS < 48 points, and has no other clearly identifiable cause that explains the muscle weakness;
4. RASS score of -1 to 0, and is able to cooperate with the prescribed muscle strength assessment and rehabilitation training;
5. Current vital signs and respiratory and circulatory status are stable, meeting the safety conditions for rehabilitation training, as assessed by clinical physicians and rehabilitation therapists;
6. The patient or their legal representative has signed the informed consent form, voluntarily participating in the study.

Exclusion Criteria:

1. The presence of pre-existing central or peripheral nervous system diseases, neuromuscular diseases, or severe motor function disorders that significantly affect limb strength or motor function prior to ICU admission;
2. The presence of active deep vein thrombosis, pulmonary embolism, significant peripheral arterial disease, limb ischemia, or other severe lower limb vascular diseases;
3. Severe coagulation function abnormalities, active bleeding, or a clinically judged unacceptable risk of thrombosis/hemorrhage;
4. The presence of fractures, open wounds, local infections, significant skin damage, or other conditions in the target lower limb that are unsuitable for cuff compression and exercise training;
5. Recent acute coronary syndrome, decompensated heart failure, uncontrolled severe arrhythmias, or other active cardiovascular diseases that are unsuitable for BFRT;
6. Instability in respiratory or circulatory status at the time of screening, or the need for new or significantly increased use of vasoactive drugs, failing to meet the safety criteria for rehabilitation training; such individuals may be rescreened after their condition stabilizes;
7. Anticipation of imminent death, or a decision to limit or withdraw life support treatment;
8. Allergy to the cuff material, or the circumference of the target limb is not compatible with the cuff being used;
9. Inability to reliably complete specified assessments such as MRC-SS after adequate arousal.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Conventional Rehabilitation Training; Participants in this arm will receive standard ICU medical care and routine rehabilitation therapy only, without additional blood flow restriction training. Standard medical care includes anti-infective treatment, mechanical ventilation support, enteral nutrition support, electrolyte and acid-base balance maintenance, and evidence-based bundle care. Routine rehabilitation is delivered by trained therapists 6 days per week for 2 weeks (40 minutes per session), covering passive range-of-motion exercises, progressive bed sitting training, diaphragmatic breathing training, and assisted active muscle strength training for all extremities. Training intensity is titrated to patient tolerance with continuous bedside hemodynamic and respiratory monitoring.	Other: Standard ICU Care and Routine Rehabilitation; This arm serves as the control reference, delivering the standard-of-care clinical pathway for critically ill mechanically ventilated patients. It includes comprehensive ICU medical management (anti-infective treatment, ventilatory support, enteral nutrition, hemodynamic maintenance, electrolyte balance correction, and evidence-based nursing bundles) plus standardized early rehabilitation administered by certified therapists per institutional ICU rehabilitation protocols. No investigational blood flow restriction intervention is applied in this group; all care follows routine clinical practice without additional study-specific exercise modifications.
Experimental: 40% Limb Occlusion Pressure Training Group; Participants in this arm will receive standard ICU medical care and routine rehabilitation identical to the control group, with additional daily blood flow restriction training (BFRT) set at 40% of each patient's individual limb occlusion pressure (LOP). LOP is measured at baseline using an automated inflatable cuff system applied to the proximal thigh, with the patient in supine resting position. BFRT sessions are administered once daily, at least 6 hours apart from routine rehabilitation, for 2 consecutive weeks (≈20 minutes per session). Each session includes 3 lower-limb exercises: straight leg raise, isometric quadriceps contraction, and glute bridge, performed for 3 sets of 10 repetitions per exercise, with 30-second rest between sets and 3-minute rest between the two legs. Training intensity is controlled at Borg RPE 9-11, with continuous bedside monitoring of vital signs to ensure patient safety.	Other: Standard ICU Care and Routine Rehabilitation; This arm serves as the control reference, delivering the standard-of-care clinical pathway for critically ill mechanically ventilated patients. It includes comprehensive ICU medical management (anti-infective treatment, ventilatory support, enteral nutrition, hemodynamic maintenance, electrolyte balance correction, and evidence-based nursing bundles) plus standardized early rehabilitation administered by certified therapists per institutional ICU rehabilitation protocols. No investigational blood flow restriction intervention is applied in this group; all care follows routine clinical practice without additional study-specific exercise modifications.; Other: Blood flow restriction training; Blood flow restriction training (BFRT) is administered using a wireless automated pneumatic cuff system (BFR Cuffs 2.0) placed on the proximal thigh. Training pressure is individually calibrated as a percentage of each patient's resting limb occlusion pressure (LOP), measured via the device's built-in pressure sensor and algorithm to accommodate differences in limb circumference and vascular tone. The intervention partially restricts venous return while preserving arterial inflow, combining low-intensity lower-extremity resistance movements with localized hypoxic and metabolic stress to stimulate muscle anabolic pathways. It is delivered at very low perceived exertion (Borg RPE 9-11) with continuous bedside vital sign monitoring, specifically adapted for hemodynamically stable critically ill patients with ICU-acquired weakness.
Experimental: 60% Limb Occlusion Pressure Training Group; Participants in this arm will receive standard ICU medical care and routine rehabilitation identical to the control group, with additional daily blood flow restriction training (BFRT) set at 60% of each patient's individual limb occlusion pressure (LOP). LOP is measured at baseline using an automated inflatable cuff system applied to the proximal thigh, with the patient in supine resting position. BFRT sessions are administered once daily, at least 6 hours apart from routine rehabilitation, for 2 consecutive weeks (≈20 minutes per session). Each session includes 3 lower-limb exercises: straight leg raise, isometric quadriceps contraction, and glute bridge, performed for 3 sets of 10 repetitions per exercise, with 30-second rest between sets and 3-minute rest between the two legs. Training intensity is controlled at Borg RPE 9-11, with continuous bedside monitoring of vital signs to ensure patient safety.	Other: Standard ICU Care and Routine Rehabilitation; This arm serves as the control reference, delivering the standard-of-care clinical pathway for critically ill mechanically ventilated patients. It includes comprehensive ICU medical management (anti-infective treatment, ventilatory support, enteral nutrition, hemodynamic maintenance, electrolyte balance correction, and evidence-based nursing bundles) plus standardized early rehabilitation administered by certified therapists per institutional ICU rehabilitation protocols. No investigational blood flow restriction intervention is applied in this group; all care follows routine clinical practice without additional study-specific exercise modifications.; Other: Blood flow restriction training; Blood flow restriction training (BFRT) is administered using a wireless automated pneumatic cuff system (BFR Cuffs 2.0) placed on the proximal thigh. Training pressure is individually calibrated as a percentage of each patient's resting limb occlusion pressure (LOP), measured via the device's built-in pressure sensor and algorithm to accommodate differences in limb circumference and vascular tone. The intervention partially restricts venous return while preserving arterial inflow, combining low-intensity lower-extremity resistance movements with localized hypoxic and metabolic stress to stimulate muscle anabolic pathways. It is delivered at very low perceived exertion (Borg RPE 9-11) with continuous bedside vital sign monitoring, specifically adapted for hemodynamically stable critically ill patients with ICU-acquired weakness.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
medical research council sum score	The Medical Research Council sum score (MRC-SS) is a validated clinical scale for evaluating global limb muscle strength in critically ill patients. It assesses 6 bilateral muscle actions: shoulder abduction, elbow flexion, wrist extension, hip flexion, knee extension, and ankle dorsiflexion. Each item is scored from 0 (no visible muscle contraction) to 5 (full strength against maximum resistance), yielding a total score ranging from 0 to 60. A lower score indicates more severe generalized muscle weakness. All assessments are performed by trained evaluators blinded to patient group assignment.	Measured at baseline (prior to randomization) and within 24 hours after completion of the 2-week intervention period.
Lower Limb Muscle Morphology Assessed by Ultrasound	Standardized musculoskeletal ultrasound is used to quantitatively evaluate lower limb muscle morphology. Four parameters are measured at fixed anatomical landmarks: cross-sectional area (CSA) and muscle thickness (MT) of the rectus femoris (15 cm above the superior patellar border), and CSA and MT of the medial gastrocnemius (10 cm above the medial malleolus). All scans are performed by sonographers blinded to group allocation, with the mean value of three independent measurements used for statistical analysis. Changes in these parameters reflect the degree of muscle atrophy or preservation over the intervention period.	Measured at baseline (prior to randomization) and within 24 hours following completion of the 2-week intervention.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Serum Inflammatory Cytokine Levels	Fasting venous blood samples are collected in the early morning (6:00-8:00) at each time point. Serum concentrations of three pro-inflammatory cytokines - tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) - are measured using enzyme-linked immunosorbent assay (ELISA) kits following standardized laboratory protocols. All assays are performed by laboratory technicians blinded to group assignment. These biomarkers reflect the magnitude of systemic inflammatory response, a core pathophysiological driver of ICU-acquired weakness.	Measured at baseline (prior to randomization) and within 24 hours following completion of the 2-week intervention.
Duration of Invasive Mechanical Ventilation	Total duration of invasive mechanical ventilation is defined as the number of consecutive days from study enrollment to successful ventilator weaning. Successful weaning is confirmed as sustained liberation from invasive mechanical ventilation for at least 48 hours without requiring re-intubation. Data are extracted from standardized electronic medical records and adjudicated in accordance with institutional critical care ventilator weaning protocols.	Recorded continuously from study enrollment through ICU discharge, with weaning success status verified at 48 hours after extubation.
ICU Length of Stay	ICU length of stay is defined as the total number of consecutive days from the date of study enrollment to the date of ICU discharge. Discharge endpoints include transfer to a general medical ward, step-down care unit, or direct hospital discharge. All data are extracted from standardized electronic medical records and verified by study coordinators in accordance with institutional admission and discharge protocols.	From date of study enrollment until the date of ICU discharge, assessed up to 28 days after enrollment
Ventilator Weaning Success Rate	Ventilator weaning success rate is defined as the proportion of patients who achieve successful liberation from invasive mechanical ventilation without re-intubation within 48 hours, relative to the total number of enrolled patients in each study group. Successful weaning is confirmed as sustained spontaneous breathing without invasive ventilatory support for at least 48 consecutive hours. All outcomes are adjudicated in accordance with institutional standardized critical care weaning protocols, with data extracted from verified electronic medical records.	Assessed from study enrollment through ICU discharge, with weaning success status definitively confirmed at 48 hours after extubation.

Collaborators and Investigators

• Sponsor: Affiliated Hospital of Jining Medical University
• Investigators: Study Director: Xiang Li, Affiliated Hospital of Jining Medical University

Study record dates

Study Major Dates

• Study Start (Estimated): September 15, 2026
• Primary Completion (Estimated): May 1, 2027
• Study Completion (Estimated): September 1, 2027

Study Registration Dates

• First Submitted: August 26, 2026
• First Submitted That Met QC Criteria: September 1, 2026
• First Posted (Actual): September 3, 2026

Study Record Updates

• Last Update Posted (Actual): September 3, 2026
• Last Update Submitted That Met QC Criteria: September 1, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Keywords: Blood flow restriction training
• Additional Relevant MeSH Terms: Therapeutics; Physical Therapy Modalities; Patient Care; Exercise Therapy; Rehabilitation; Aftercare; Continuity of Patient Care; Blood Flow Restriction Therapy
• Other Study ID Numbers: 2025-11-C024; MP-MS-2022-010 (Other Grant/Funding Number: AHJiningMU); 2024YXNS081 (Other Grant/Funding Number: Jining Key Project)

Drug and device information, study documents

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