Abstract

Chronic wounds and pathological scars reduce the quality of life for millions of people worldwide. Through mathematical modeling and clinical testing, understanding of how these conditions occur continues to increase. These tools have also been employed to investigate the efficacy of treatments that could impact wound healing and scar remodeling. The purpose of this work is to investigate the physiological effects of vibration treatment on wound healing, blood flow, and scar remodeling through mathematical modeling and experimental testing. This work presents and validates a mathematical murine model for whole body vibration enhanced wound healing (VEWH). This VEWH model builds on existing wound healing models by including experimentally derived vibration terms and is validated with experimental data of vibration accelerated closure of mice wounds. The VEWH model consists of 7 biological and chemical components: capillary tips and sprouts, macrophages, oxygen, chemoattractants, fibroblasts, and extracellular matrix (ECM). Model simulations suggest that vibration primarily increases wound closure rate through mechanotransduction of fibroblast cells leading to increased ECM and that the optimal vibration frequencies are between 5 Hz and 25 Hz. Recently, with the increasing popularity of percussion massage devices, localized vibration (LV) has become a common form of vibration treatment. However, this treatment modality has received less scientific investigation compared to whole body vibration. This work presents a study on the efficacy of LV induced popliteal blood flow at various frequencies and durations applied to the calf muscles. Twenty-six healthy, recreationally active university students participated in a total of 8 trials (control (0 Hz), 30 Hz, 38 Hz, and 47 Hz each for 5 minutes and 10 minutes). Blood flow measurements including mean arterial blood velocity and volume flow, arterial diameter, and heart rate were taken using ultrasound techniques. Results found that both 38 Hz and 47 Hz conditions significantly increased blood flow without affecting heart rate. A follow up study was conducted with twenty-one healthy, recreationally active university students. Here participants received two trials of LV to the calf using a percussion massage device. One trial (control) consisted of 47 Hz LV for 10 minutes, the other trial involved consuming antihistamine medication (180 mg Fexofenadine) at least one hour prior to receiving 47 Hz LV for 10 minutes. The results revealed a significant increase in blood flow due to the control trial and a non-significant increase in blood flow after the antihistamine trial. This suggests that a potential primary mechanism of LV induced blood flow is increased histamine concentration by mechanosensing mast cells and that this response is force dependent. Finally, this work presents a continuum hypothesis-based model of hypertrophic scar growth and remodeling with angiogenesis and local vibration therapy. Simulations indicate a potential decrease of scar height up to 50% and a decrease in dermal viscosity as a potential biological mechanism of vibration treatment. Measurements from a case study involving two hypertrophic burn scars that received 47 Hz vibration for 15 minutes, 3 days/week for 6 weeks showed a decrease in scar thickness of 17% and 52%. Two non-burn scars are also tested and presented. Further data is required to fully validate the presented model.

Degree

PhD

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2024-06-05

Document Type

Dissertation

Handle

http://hdl.lib.byu.edu/1877/etd13706

Keywords

vibration treatment, hypertrophic scar, mathematical model, percussion massage

Language

english

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