Date of Award

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Biomedical Sciences

Track

Neuroscience

Research Advisor

Phyllis Richey, PhD

Committee

Kunal Signal, PhD; R Dale, PhD; Richard Kasser, PhD; William Mihalko, MD, PhD

Keywords

Computed Tomography, Critical Illness, Musculoskeletal Ultrasound, Physical Therapy, Psoas, Rehabilitation

Abstract

Annually, around 5 million people in the U.S. are admitted to Intensive Care Units (ICU) due to critical conditions, with pediatric patients comprising 21% of these admissions. Approximately 40% of pediatric ICU (PICU) patients require mechanical ventilation and extended stays, and about 6% result in death. Survivors often face long-term disabilities, including loss of skeletal muscle mass (SMM), a risk factor for morbidity and mortality. Abdominal computed tomography (CT) scans, often performed during PICU admissions, can assess muscle mass but pose risks of increased cost and radiation exposure. While CT and Magnetic Resonance Imaging (MRI) are gold standards for muscle quantification, alternatives like ultrasound (US) offer non-invasive, cost-effective benefits without radiation. US, commonly used by physical therapists for Rehabilitative Ultrasound Imaging (RUSI), could assess muscle structure and function, aiding therapeutic interventions. However, evidence-based research supporting US as a valid and reliable modality for measuring SMM in pediatric patients is extremely lacking in the literature, as are reliability studies comparing US measured SMM characteristics to gold standards like CT. Accurate SMM assessment is a critical clinical outcome to document as muscle loss during prolonged hospital stays can lead to long-term functional impairments, impacting overall health. Establishing US as a reliable tool for SMM assessment could revolutionize rehabilitation practices and inform Clinical Practice Guidelines for therapeutic interventions in pediatric ICU settings. This research study was comprised of a sequence of three studies which included a retrospective CT rater-reliability, a prospective US rater-reliability and a prospective modality- (US versus CT), reliability. Taken together, the purpose of the overall research project was to determine the reliability of US compared to CT and provide the preliminary evidence-based results to inform a future validation study of US as a dependable tool for evaluating muscle quality and quantity in pediatric patients. The first aim of the current study examined the inter-rater reliability of CT measured cross-sectional area (CSA) and muscle thickness, (mT) of the psoas major and rectus abdominis (RA), two key trunk stabilizing muscles, obtained by a radiologist compared to a physical therapist (PT) (Aim1a) and the intra-rater reliability of the same measurements obtained at multiple timepoints by the PT (Aim1b). The second aim examined inter-reliability of US measurements, obtained by a Registered Diagnostic Medical Sonographer (RDMS) compared to a PT, of the CSA, mT and echo intensity (EI) of the psoas major and RA muscles. The third aim examined the inter-modality reliability of US- compared to CT-obtained CSA and mT measurements of the psoas and RA muscles. The results of this study showed inter- and intra-rater reliability between a radiologist and PT, ICC: 0.951-0.994 (Aim1a) and PT intra-rater reliability ICC: 0.943-0.98 (Aim 1b). Aim 2 inter-rater reliability results between the RDMS and PT showed outstanding ICCs: 0.978-0.999, across all quantitative parameters. Aim 3 inter-modality reliability between CT and US similarly demonstrated outstanding ICCs: 0.985 to 0.999 for all muscle parameters. Additionally, exploratory analyses showed no influence of the subject populations’ demographic or anthropometric variables including sex, race, height, weight, or Body Mass Index (BMI). This study provides robust evidence supporting 1) the reliability of ultrasound as an effective modality for assessing muscle quality and quantity in pediatric patients compared to CT and 2) the proficiency of a PT compared to an RDMS in performing such ultrasound measurements as well as interpreting CT values of the afore mentioned muscle parameters compared to a radiologist. Moreover, the results of this study contribute to the significant gap in the literature on evidence-based results of muscle assessment tools applicable in the pediatric population as well as informing future physical therapy practice guidelines, particularly for the critically ill pediatric population.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.

ORCID

0000-0003-3112-8739

DOI

10.21007/etd.cghs.2024.0671

Additional Files
2024-010-Seewer-DOA.pdf (288 kB)
Declaration of Authorship
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