Beyond Voluntary Effort: Reliability and Validity of Magnetic Femoral Nerve Stimulation for Assessing Quadriceps Strength in Critically Ill Patient

NCT07891273 | Not Yet Recruiting

• 1 other identifier: S71944
• Study Type: interventional
• Target: 33
• Locations: 0 countries
• Sites: N/A

Brief Summary

Intensive care unit-acquired weakness (ICU-AW) is a common complication of critical illness and can negatively affect recovery and long-term physical functioning. Early and reliable assessment of muscle strength is essential for detecting muscle weakness and monitoring changes during an intensive care unit (ICU) stay. However, conventional strength assessments, such as manual muscle testing, require voluntary muscle contractions, making them unsuitable for patients who are not yet cooperative and limiting the possibility of assessing muscle strength during the early stages of critical illness. Magnetic femoral nerve stimulation offers an alternative, non-volitional approach to assessing quadriceps muscle strength. Nevertheless, the reliability and validity of this technique in critically ill patients remain insufficiently established. This prospective methodological study aims to investigate the reliability and convergent validity of quadriceps twitch force measurements obtained using magnetic femoral nerve stimulation in critically ill patients. A total of 33 cooperative adult patients admitted to medical or surgical ICUs will be included. Participants will undergo repeated quadriceps twitch force assessments over two consecutive days, performed by two assessors. Measurements will be conducted using a custom-developed frame designed to facilitate standardized quadriceps strength assessment at the bedside. Both single and paired magnetic stimulation techniques will be evaluated. The primary outcome is the intra-rater reliability of paired twitch force measurements. Secondary outcomes include the inter-rater reliability of paired twitch force measurements, the intra-rater and inter-rater reliability of single twitch force measurements, and the convergent validity of twitch force measurements assessed through their association with maximal voluntary contraction force and potentiated twitch force. Reliability and agreement will be evaluated using intraclass correlation coefficients and complementary measurement error analyses. Establishing these measurement properties could support objective, non-volitional muscle strength assessment in critically ill patients, including those unable to participate in conventional strength testing. This could facilitate early baseline strength assessment, longitudinal monitoring of muscle recovery, and the evaluation of interventions aimed at preventing or treating ICU-AW..

Conditions

Critical Illness; ICU-acquired Weakness

Keywords

critical illness; ICU-acquired weakness; femoral nerve magnetic stimulation; quadriceps muscle strength; non-volitional muscle strength assessment

Outcome Measures

Primary Outcomes (1)

• Intra-rater reliability of paired quadriceps twitch force measurements

  Intra-rater reliability of paired quadriceps twitch force measurements will be assessed using the intraclass correlation coefficient (ICC) with 95% confidence intervals, comparing measurements performed by the same assessor on two consecutive days. Measurement error and agreement will additionally be evaluated using the standard error of measurement (SEM), minimal detectable change (MDC95), and Bland-Altman analysis.

  Day 1 and Day 2 (two consecutive days)

Secondary Outcomes (7)

• Inter-rater reliability of paired quadriceps twitch force measurements

  Day 2 (morning and afternoon)

• Intra-rater reliability of single quadriceps twitch force measurements

  Day 1 and Day 2 (two consecutive days)

• Inter-rater reliability of single quadriceps twitch force measurements

  Day 2 (morning and afternoon)

• Convergent validity of single twitch force with maximal voluntary contraction

  Day 1

• Convergent validity of paired twitch force with maximal voluntary contraction

  Day 1

Study Arms (1)

Magnetic Femoral Nerve Stimulation

EXPERIMENTAL

All participants will undergo quadriceps muscle strength assessments over two consecutive days, following the same standardized measurement sequence. On the first day, the first assessor will perform single and paired twitch force measurements using magnetic femoral nerve stimulation, alongside maximal voluntary contraction and potentiated twitch force assessments. On the second day, single and paired twitch force measurements will be repeated by the first assessor in the morning and by a second assessor in the afternoon to evaluate intra-rater and inter-rater reliability.

Diagnostic Test: Magnetic Femoral Nerve Stimulation

Interventions

Magnetic Femoral Nerve Stimulation DIAGNOSTIC_TEST

Participants will be positioned prone in their hospital bed, with the knee flexed at approximately 90° using a dedicated measurement setup. A magnetic stimulation coil will be placed over the femoral nerve to elicit involuntary quadriceps muscle contractions. The resulting twitch force will be measured using a strain gauge dynamometer attached at the ankle. Stimulation intensity will be progressively increased to establish supramaximal stimulation, after which both single and paired magnetic stimuli will be applied to assess quadriceps twitch force.

Magnetic Femoral Nerve Stimulation

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Voluntary written informed consent of the participant has been obtained prior to the initiation of any study-related measurements
• Adults (≥18 years)
• Expected to remain in the ICU for more than an additional 2 days starting from study enrolment
• Fully cooperative, as assessed daily during routine clinical care by ICU physiotherapists using five standardized commands ("open/close your eyes", "look at me", "open your mouth and stick out your tongue", "nod your head", and "raise your eyebrows when I have counted to 5")
• Quadriceps muscle strength of at least 3/5 on the Medical Research Council (MRC) scale for knee extension.

You may not qualify if:

• Medical instability A: Cardiorespiratory instability
• Mean arterial pressure \< 60 mmHg or \> 110 mmHg
• Fraction of inspired oxygen (FiO₂) ≥ 60%
• PaO₂/FiO₂ ratio \< 200
• Respiratory rate \> 30 breaths·min-¹ B: Neurological instability
• Intracranial pressure \> 20 mmHg
• Cerebral perfusion pressure \< 70 mmHg C: Surgery within the past 24h D: Body temperature \> 40
• Contraindications to magnetic stimulation A: Implanted metal or electronic devices, including
• Lower limb prostheses
• Internal and external fixation devices of the lower limb
• Vascular stents
• Cardiac pacemakers or defibrillators
• Implanted nerve stimulators B: Lower limb structural, skin, or soft tissue conditions
• Acute or chronic injuries
• Wounds preventing supine positioning

Sponsors & Collaborators

• Daniel Langer: lead
• Universitaire Ziekenhuizen KU Leuven: collaborator

MeSH Terms

Conditions

Critical Illness

Condition Hierarchy (Ancestors)

Disease Attributes; Pathologic Processes; Pathological Conditions, Signs and Symptoms

Central Study Contacts

Daniel Langer

CONTACT

+32 16 34 71 25; daniel.langer@kuleuven.be

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR INVESTIGATOR
• PI Title: Co-investigator, associate professor

Study Record Dates

• First Submitted: October 16, 2026
• First Posted: October 23, 2026
• Study Start (Estimated): December 1, 2026
• Primary Completion (Estimated): May 1, 2027
• Study Completion (Estimated): May 1, 2027
• Last Updated: October 23, 2026

Record last verified: 2026-10

Data Sharing

• IPD Sharing: Will not share