Rabie Fadil

Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Biomedical Engineering

First Advisor

Kouhyar K. Tavakolian


Upon standing, 500–1000 mL of blood shifts from the central body compartments to the lower extremities and splanchnic circulation, leading to a decreased venous return to the heart, reduced cardiac output, and a consequent decline in blood pressure. In healthy individuals, the drop in blood pressure is quickly compensated via regulatory mechanisms. On the other hand, people with Parkinson’s disease may experience impaired reflex responses and a persistent drop in blood pressure (orthostatic hypotension, OH), leading to visual disturbances, loss of consciousness, postural instability, and fainting. Parkinson’s disease patients have impaired balance and gait control as a symptom of the disease, and the drop of blood pressure upon standing may further predispose patients to falls. A severe drop in blood pressure could also result from blood loss leading to inadequate cerebral blood perfusion and presyncope. This dissertation investigated blood pressure and postural control mechanisms in Parkinson’s disease and healthy elderly individuals during orthostatic challenge with two major applications 1) prevent falls in Parkinson’s disease patients and healthy elderly people by assessing the mechanisms involved in maintaining blood pressure and postural control during an orthostatic challenge and 2) design a robust automated system to track the progression of hypovolemia as well as identifying individuals with low tolerance to blood loss.

In chapter 3 & 4, the interaction and bidirectional causalities between the cardiovascular, musculoskeletal, and postural signals were studied using wavelet transform coherence and convergent cross mapping techniques, respectively. The results showed that the cardio-postural coupling between cardiovascular, musculoskeletal, and postural variables to maintain blood pressure and postural balance is affected by Parkinson’s disease. In chapter 5, the effect of respiration on blood pressure and postural balance was investigated. The causal relationship between respiration and blood pressure as well as between respiration and postural sway in the frequency domain was studied via convergent cross mapping and empirical mode decomposition. Further, in chapter 6, mild, moderate, and severe intensity hemorrhage was simulated via lower body negative pressure (LBNP) to investigate the potential of cardio-respiratory interactions to track the progression of blood loss and identify individuals with low tolerance from those with high tolerance to central hypovolemia.