Biomedical Physiology and Kinesiology - Theses, Dissertations, and other Required Graduate Degree Essays

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Serial ultrasonographic evaluation of diaphragm thickness during mechanical ventilation in ICU patients.

Date created: 
2013-08-29
Abstract: 

While mechanical ventilation (MV) is life-saving in patients with acute respiratory failure, prolonged mechanical ventilation is associated with numerous potential complications. Recent studies have suggested that the ventilator is a likely cause of the decreased diaphragm force generating capacity (dFGC) seen in mechanically ventilated patients. Further, mode of ventilation has been associated with diaphragm atrophy, which has been identified as a key factor influencing dFGC. Animal studies suggest that even as little as 18 hours of mandatory modes of ventilation lead to diaphragm-muscle atrophy and weakness. This study utilizes ultrasound to investigate the rate at which diaphragm thickness changes in response to mode of MV in critically ill patients, and validates the reliability of our sonography techniques. We acquired daily ultrasonographic images of the right diaphragm in the zone of apposition in critically ill patients (n=8) in the ICU of the Royal Columbian hospital. As a control for generalized muscle wasting in the critically ill, we acquired daily ultrasonographic images of the quadriceps from each subject. Patients on all modes of ventilation were included. Inter-operator and inter-observer reliability tests were conducted. A mean increase in diaphragm thickness of 8.41±3.88% was detected over a mean of 5.5±4.28 days in all patients on PS ventilation (n=8), a mean increase of 1.53±1.39% per day. Patients ventilated on AC mode (n=4) showed a mean decline in diaphragm thickness of 21.2±10.8% over 4.5±4.4 days, an average decrease of 4.7±5.7% per day. Mean decline in quadriceps thickness for all participants in this study (n=8) was 14.4±13.6% over a mean period of 7.1±4.7 days, an average decline of 2±2.7% per day. Ultrasound provides a reliable non-invasive method of measuring diaphragm thickness and tracking rates of change in thickness in mechanically ventilated critically ill patients. This may be a useful tool in critical care units to identify patients who may be at risk of weaning difficulties secondary to diaphragms that are weakened as a result of atrophy.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Andy Hoffer
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

A Complex Systems Approach to Perceptions of Obesity in Service Users, Health Care Practitioners and Policy Makers

Date created: 
2013-08-14
Abstract: 

Current research supports the complexity of obesity and the need for collaboration between sectors to create change, yet there is still a pervasive perception that individuals are to blame for their weight. The Applied Research Collaborations for Health Research group, Dalhousie University, Halifax, Nova Scotia conducted key informant interviews to examine the beliefs of service users, health practitioners and policy makers regarding obesity. These data were used to conduct a secondary analysis using qualitative analysis methodology to explore perceptions of obesity within a complex systems framework. Three major themes were common among participant groups. There was a desire for immediate results, a focus on individual blame and a resultant tension for change. Exploring these themes using a complex system lens demonstrated the importance of engaging contradictory groups to work together in a collaborative framework. Aligning paradigms across the treatment spectrum is crucial to working towards solutions that embrace complexity.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diane Finegood
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Cerebrovascular and respiratory responses to poikilocapnia and eucapnia in resting normothermic and hyperthermic humans

Date created: 
2012-06-07
Abstract: 

Human cerebrovascular responses in the middle cerebral artery (MCA), posterior cerebral artery (PCA), and basilar artery (BA) were assessed in two studies. In the first study, an index of cerebrovascular conductance (ICVC) in the MCA was decreased (P<0.05) in poikilocapnic, hyperthermic humans, while ICVC was maintained in the PCA and BA. Eucapnia during hyperthermia returned ICVC in the MCA, PCA, and BA to resting ICVC values. In the second study the effects of volitional hyperventilation on cerebral blood velocity (CBV) and ICVC responses in normothermic humans were assessed in the same three cerebral vessels. Results indicated that, unlike in hyperthermia, responses were uniform with CBV and ICVC decreases (P<0.05) in normothermic poikilocapnia in all three cerebral vessels with no differences (P>0.05) from normothermic resting values when PETCO2 was restored to eucapnic partial pressures. In conclusion, evidence suggests there are regional differences of cerebrovascular responses in hyperthermic, but not normothermic humans.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Matthew White
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Association of Clinical and Molecular Features of Previously Treated Tumour Sites with Risk for Second Oral Malignancy

Author: 
Date created: 
2013-08-16
Abstract: 

Second oral malignancy (SOM) is a common occurrence for patients with oral cancers, contributing to low 5-year survival rates for this disease (~60%). Oral mucosal changes at previously treated cancer sites are common and can be defined clinically by white-light examination and toluidine blue staining, and molecularly by loss of heterozygosity (LOH) analysis. To determine the role of such changes in predicting SOM, this study analyzed data collected from 194 oral squamous cell carcinoma patients in follow-up after treatment of which 31 (16%) developed SOM. Two features were shown to be associated with elevated risk of SOM: the clinical presence of an oral premalignant lesion (OPL) (P <0.001), and LOH at 9p21 (P = 0.045). The results support the need for biopsy of OPLs observed during follow-up, especially when persistent, and suggest that LOH analysis of such biopsies might differentiate those at-risk for SOM, allowing for early intervention.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Miriam Rosin
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

The interaction between cardiovascular and posture controls and the effects of ageing

Author: 
Date created: 
2010-11-12
Abstract: 

Fainting during quiet standing is a serious problem in syncopal youth and prominent in elderly individuals. This thesis examined the possible interaction of the cardiovascular and posture control systems during quiet stance and the effect of ageing. We hypothesized that there exists a bidirectional interaction between blood pressure (BP) and posture changes through the activation of skeletal muscle pump via the calf muscles. In study one, the analysis methods for non-stationary signals were explored and the wavelet transform coherence method was validated for its applicability. In study two, cardiovascular variables, stabilogram data and posture muscle electromyography (EMG) data were compared to each other. The EMG and BP signals showed discrete regions of high coherence during quiet stance. In a third study, the effect of ageing on the relationship between these two systems was investigated. Age was found to have a statistically significant affect on the relationship between these two systems

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. Andrew P. Blaber
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Cardiovascular disease risk after spinal cord injury: The role of autonomic dysfunction

Date created: 
2013-08-07
Abstract: 

Cardiovascular disease (CVD) is the leading cause for mortality and morbidity after spinal cord injury (SCI) with an earlier onset and more rapid progression compared to the general population. Lifestyle changes after injury have been suggested to be the main contributor to CVD risk, but I proposed that the issue is more complicated. Although less well-known, autonomic function is affected by SCI, in addition to motor and sensory dysfunction. Cardiovascular autonomic dysfunction is a particular concern in individuals with high lesions (above T5) due to the possible disruption of descending spinal sympathetic pathways to the heart and main vascular resistance bed. In this thesis, I propose that cardiovascular autonomic impairment plays a role in the elevated CVD risk. The thesis starts with an evaluation of the prevalence and progression of cardiovascular dysfunction after SCI. Then, the contribution of autonomic dysfunction on CVD risk is investigated. In addition, markers for obesity-related CVD risk specific to individuals with SCI and ECG markers for cardiac arrhythmias in relation to autonomic impairments are explored. Prevalence of cardiovascular dysfunction was found not to improve over time after injury and it was highest in those with lesions above T5. The second study showed that autonomic dysfunction contributes to overall CVD risk and specifically to glucose intolerance, either directly or through an interaction with physical activity levels. The data showed that waist circumference is the best marker for obesity considering ability to detect adiposity and CVD risk, and practicality of use. A specific cut-off for waist circumference was found to be lower compared to the general recommendations. The final study showed increased values for the ECG markers Tpeak-Tend variability, P-wave variability and QTVI, only in those with impairments to descending cardiac sympathetic pathways. The ECG characteristics may be indicative of susceptibility to cardiac arrhythmia related to autonomic dysfunction. Implications of these findings are that management of cardiovascular autonomic dysfunction should remain a priority into the chronic phase of injury, not merely due the direct impact on quality of life, but also due to its contribution to the elevated cardiovascular disease risk after SCI.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Victoria Claydon
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Dissertation) Ph.D.

Bone Marrow-Derived Cell Accumulation in the Brain in a Murine Model of Alzheimer’s Disease

Date created: 
2013-08-09
Abstract: 

One difficulty in treating some neurological disorders is that many pharmaceuticals cannot cross the blood brain barrier to reach affected areas. Human and animal studies have shown that bone marrow transplantation can result in the engraftment of donor-derived cells in the central nervous system (CNS) under certain conditions. Understanding these conditions will allow us to optimize recruitment of bone marrow-derived cells (BMDCs) to the CNS and, in the future, use these cells as vehicles for gene delivery. Using a triple transgenic mouse model of Alzheimer’s Disease (AD), I studied accumulation of amyloid-β, a pathological characteristic of AD, and association of BMDCs with amyloid-β. There were difficulties in maintaining chimerism after bone marrow transplantation in these mice. Reconstitution was achieved by depleting natural killer cell activity in the host, suggesting that hybrid resistance may be present.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Charles Krieger
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

Design, implementation and evaluation of a reduced cardiac rehabilitation program

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2013-02-28
Abstract: 

Background: Cardiac rehabilitation remains under-utilized and novel modes of cardiac rehabilitation delivery are needed to address this concern. Purpose: To compare a reduced cardiac rehabilitation program (rCRP) with the standard program (sCRP) in regards to change in exercise capacity and ischemic heart disease risk factors, at program completion and at one-year follow-up. Methods: This was a randomized controlled non-inferiority trial. Secondary prevention patients at low and moderate risk were randomized to either the sCRP (n=60) or to the rCRP (n=61). While the sCRP entailed 32 on-site exercise sessions, the rCRP consisted of 10 sessions throughout the four-month program duration. Mixed model analyses of variance were used to test for non-inferiority of the rCRP and repeated measured ANOVA to assess within-group comparisons. Results: Baseline data were similar between groups. The rCRP was non-inferior to the sCRP group in regards to exercise capacity at four and 16 months (group estimate=5.25, 95% CI 15.51-26.00 seconds, p=0.62). Exercise capacity improved at program completion for the sCRP and rCRP groups; 524 ± 168 to 630 ± 150 seconds and 565 ± 183 to 655 ± 196 seconds, p< 0.01, respectively, and remained higher than baseline at 16 months; 524 ± 168 to 604 ± 172 seconds and 565 ± 183 to 640 ± 192 seconds, p< 0.01, respectively. The rCRP was non-inferior in regards to HDL-C, triglycerides, TC/HDL-C ratio, fasting glucose, blood pressure, body mass index, waist circumference and waist to hip ratio changes. The rCRP had a higher attendance rate than the sCRP group (97.3 ± 62.6 % vs 70.5 ± 22.0 %, p=0.002) and was non-inferior in terms of self-reported physical activity (group estimate=1.02, 95% CI 0.86-1.21, p=0.8105). These improvements were maintained at one-year follow-up. Conclusion: While it utilized less hospital resources, rCRP was “not worse” than the sCRP in terms of exercise capacity and ischemic heart disease risk factor changes as well as program adherence for low and moderate risk patients. Further research is needed to assess if the rCRP helps overcome current CRP utilization barriers.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Scott Lear
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Dissertation) Ph.D.

Design and fabrication of a positioning system for an intravascular electrode system

Author: 
Date created: 
2012-03-06
Abstract: 

Precise placement of intravascular leads is a vital requirement for transvascular neurostimulation as it determines the nerve selectivity and efficiency of stimulation. With the previous positioning method relying on ruler measurements, an electronic position sensor system was designed to minimize placement time, increase accuracy, reproducibility and allow for integration into a control unit system. To keep track of each electrode array, the developed sensor uses one linear membrane potentiometer for each lead. A plastic bead is fitted on each lead and as the bead is lightly squeezed into the membrane potentiometer, the potentiometer resistance changes proportionally to a bead position. The electrode position can therefore be inferred from this measurement. This system is simple, inexpensive and provides an absolute position measurement. This concept is also expected to be easily made into commercial product because of its compact and intuitive nature.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Andy Hoffer
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

The effects of ambient lighting on mobility deficits in older adults with age-related macular degeneration

Date created: 
2013-06-11
Abstract: 

Age-related macular degeneration (AMD) is characterized by loss of central vision. This eye disease restricts mobility and increases the risk for falls. We sought to determine how changes in ambient light affect performance on essential mobility tasks in this population. Subjects had to step to stationary and moving targets and negotiate a sidewalk curb. In each task, lighting simulated an office environment, a moonlit night, and a sudden light reduction. Older adults with AMD were less accurate and more variable in their ability to step to targets compared to controls. A similar result was evident with curb negotiation. Importantly, both groups had greater difficulty with poor lighting. This was most evident when lighting was suddenly reduced and was exacerbated with AMD. Understanding AMD-specific mobility deficits and the influence of lighting will help design rehabilitation programs and better environments to reduce falls, improve mobility, and enhance these individual’s quality of life.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. Dan Marigold
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.