The rise of hikikomori research: a bibliometric analysis of an emerging global phenomenon.

Over the past two decades, advances in critical care medicine have markedly improved the survival rate of critically ill patients, yet the incidence of ICU-acquired weakness (ICUAW) among ICU survivors ranges from 50 to 100% (, ), with the condition persisting for months to years (–). ICUAW comprises critical illness myopathy (CIM), critical illness polyneuropathy (CIP), and overlapping syndromes; Persistent ICU-acquired weakness (ICUAW) after ICU discharge further increases mortality risk. A cohort study demonstrated that patients with ICUAW at discharge had a higher 1-year mortality rate than those who recovered (). This indicates that the severity and duration of ICUAW are critical determinants of long-term survival. Beyond mortality, ICUAW impairs patients’ long-term functional status and quality of life. Among COVID-19 survivors, residual ICUAW 6 months after ICU discharge was associated with reduced functional independence and greater functional dependence (). Current approaches for ICUAW assessment carry prominent methodological limitations. Widely used tools, including the Medical Research Council (MRC) score and handgrip strength testing (), as well as electromyography and nerve conduction studies, all require conscious patient cooperation—a condition frequently unmet in ICU patients under sedation, delirium or impaired mental status. Although computed tomography and magnetic resonance imaging (CT/MRI) enable precise muscular morphological evaluation, they cannot be implemented at the bedside (, ). Neuroelectrophysiological tests are vulnerable to interference from tissue edema and environmental artifacts (), while muscle biopsy is invasive and unsuitable for repeated measurements. Bedside muscle ultrasound, with the strengths of non-invasiveness, repeatability and operational simplicity, has been widely adopted to evaluate muscular atrophy (, ). Nevertheless, static morphological measurements alone cannot fully reflect actual muscle contractile function and strength. Drawing on ultrasonic evaluation of myocardial contractile function, the present study integrated electrical stimulation and muscle ultrasound to induce passive rectus femoris contraction and quantify transverse diameter change during contraction. We aimed to establish a cooperation-free strategy for muscular strength measurement. Lower limb muscles are affected earliest in ICUAW progression (); Studies have confirmed that dynamic changes in the cross-sectional area (RFCSA) and thickness (TH) of the rectus femoris are highly correlated with the development of intensive care unit-acquired weakness (ICUAW). Ultrasonic measurement of these two indicators can effectively predict ICUAW. Combined with its superficial anatomical location, few artifacts under electrical stimulation and clear ultrasound images, the above characteristics collectively prove that the rectus femoris is an ideal detection target for predicting the occurrence of ICUAW (). This study aimed to verify the correlation between rectus femoris diameter change (ΔRF-d) and global muscle strength, so as to provide a non-invasive, bedside and cooperation-independent diagnostic tool for ICUAW.