Shear Wave Elastography of Peripheral Nerves for Early Diagnosis of ICU-acquired Weakness

This study aims to determine whether shear wave elastography (SWE), a non-invasive ultrasound technique that measures nerve stiffness, can help detect ICU-acquired weakness (ICU-AW) early in critically ill patients. Adults receiving mechanical ventilation in the ICU will undergo ultrasound examinations of the median and tibial nerves on Days 1, 4, and 7. The study will evaluate whether early changes in nerve elasticity can predict ICU-AW, which is usually diagnosed later using a muscle strength score that requires patient cooperation.

Inclusion Criteria: 1. Age ≥ 18 years; 2. Newly admitted to ICU with an expected ICU stay \> 7 days; 3. Initiated on mechanical ventilation within 24 hours of admission, with an expected ventilation duration \> 48 hours; 4. Patient or legally authorized representative provides written informed consent. Exclusion Criteria: 1. Known pre-existing neuromuscular diseases (e.g., myasthenia gravis, Guillain-Barré syndrome, amyotrophic lateral sclerosis); 2. Pre-existing limb dysfunction that would interfere with muscle strength assessment (e.g., hemiplegia, paraplegia, severe arthritis); 3. Presence of acute trauma, surgery, skin breakdown, infection, or severe edema at the measurement sites (wrist, elbow, ankle) that would interfere with ultrasound probe placement; 4. Pregnant or lactating women; 5. Any other condition that the investigator believes would make the patient unsuitable for the study.