University of Calgary

Marc Poulin

  • Professor

Research Interests

Research Interests:

Positions

Professor, Department of Physiology & Pharmacology, Cumming School of medicine

The Brenda Strafford Foundation Chair in Alzheimer Research

Professor, Department of Clinical Neurosciences, Cumming School of Medicine

Professor, Faculty of Kinesiology

Member, Hotchkiss Brain Institute

Associate Member, Libin Cardiovascular Institute of Alberta

Specialty

Dr. Poulin is a Professor in the Cumming School of Medicine (Departments of Physiology & Pharmacology and Clinical Neurosciences) and Faculty of Kinesiology at the University of Calgary. His research focuses on the mechanisms that regulate cerebral blood flow in young healthy humans, how these mechanisms become altered with ageing, and the role of interventions such as exercise on the cerebral circulation.

Current Work

The cerebral circulation is endowed with complex regulatory mechanisms to ensure a continuous and adequate blood (and oxygen) supply to the brain. Under normal circumstances, one of the most potent regulators of cerebral blood flow (CBF) is the partial pressure of carbon dioxide (PCO2), and to a lesser extent, the partial pressure of oxygen (PO2), in the arterial blood. The physiological significance of the effects of changes in the arterial PCO2 (i.e. hypercapnia and hypocapnia) and reductions in arterial PO2 (i.e. hypoxia) on CBF is to increase cerebral perfusion in an attempt to maintain oxygen delivery when the oxygen supply to the brain is compromised or reduced. The regulation of CBF by arterial PCO2 and PO2 is a fundamental regulatory process that can become significantly impaired with many pathophysiological states and environmental conditions, including for example disease processes such as chronic obstructive pulmonary disease, sleep apnea, stroke, ischemia, atherosclerosis, hypertension, and diabetes, by ageing, and upon exposure to the hypoxia of altitude.

Desired Outcomes

Our goal is to better understand the physiological mechanisms that underlie the regulation of CBF by oxygen and carbon dioxide in young healthy humans, and to investigate the age-related alterations in this regulation. Furthermore, physical inactivity is now clearly established as a risk factor for stroke and other age-related disease processes but very little is known about the mechanisms by which exercise exerts its protective effect on the cerebral circulation. Thus, our work also aims to better understand this important relationship between CBF, ageing, and exercise.

Training and Achievements

Education:

D.Phil. (1999), Faculty of Physiological Sciences, University of Oxford (New College), Oxford, United Kingdom.
Ph.D. (1993), Faculty of Kinesiology, University of Western Ontario, London Ontario.
M.A. (1988), Faculty of Kinesiology, University of Western Ontario.
HBPHE (1986), Faculty of Kinesiology, Laurentian University, Sudbury, Ontario.
Certificate of Bilingualism (1986), Laurentian University.

Awards:

New Opportunities Fund, Canada Foundation for Innovation, 2003-2006.
Heritage Senior Medical Scholarship and Research Prize, Alberta Heritage Foundation for Medical Research, 2005-2010.

Research

Dr. Poulin is a Professor in the Cumming School of Medicine (Departments of Physiology & Pharmacology and Clinical Neurosciences) and Faculty of Kinesiology at the University of Calgary. His research focuses on the mechanisms that regulate cerebral blood flow in young healthy humans, how these mechanisms become altered with aging, and the role of interventions such as exercise on the cerebral circulation.

Current Research Interests

General Goal and Significance
The cerebral circulation is endowed with complex regulatory mechanisms to ensure a continuous and adequate blood (and oxygen) supply to the brain. Under normal circumstances, one of the most potent regulators of cerebral blood flow is the partial pressure of carbon dioxide (PCO2), and to a lesser extent, the partial pressure of oxygen (PO2), in the arterial blood. The physiological significance of the effects of changes in the arterial PCO2 (i.e. hypercapnia and hypocapnia) and reductions in arterial PO2 (i.e. hypoxia) on cerebral blood flow is to increase cerebral perfusion in an attempt to maintain oxygen delivery when the oxygen supply to the brain is compromised or reduced. The regulation of cerebral blood flow by arterial PCO2 and PO2 is a fundamental regulatory process that can become significantly impaired with many pathophysiological states and environmental conditions, including for example disease processes such as chronic obstructive pulmonary disease, sleep apnea, stroke, ischemia, atherosclerosis, hypertension, and diabetes, by ageing, and upon exposure to the hypoxia of altitude.

Our goal is to better understand the physiological mechanisms that underlie the regulation of cerebral blood flow by oxygen and carbon dioxide in young healthy humans, and to investigate the age-related alterations in this regulation. Furthermore, physical inactivity is now clearly established as a risk factor for stroke and other age-related disease processes but very little is known about the mechanisms by which exercise exerts its protective effect on the cerebral circulation. Thus, our work also aims to better understand this important relationship between cerebral blood flow, aging, and exercise

Integrated Approach

The regulation of cerebral blood flow involves the complex integration of multiple systems, including cerebrovascular, cardiovascular and respiratory systems. Oxygen and carbon dioxide sensing structures (chemoreceptors) modulate neural outputs to the respiratory and circulatory systems. These systems work in tandem to optimize the levels of oxygen and carbon dioxide of the blood and the distribution of oxygen to tissues (most importantly, the brain) and the removal of carbon dioxide from the circulation. Physiological and environmental conditions can affect these systems, resulting in acute or chronic problems. As such, it is important to understand the inter-relationships and integrated regulations of these systems under controlled experimental conditions.

Ongoing Research

Presently, research is being conducted in multiple areas. In particular, we are studying the role of nitric oxide as a vasodilator, the effect of acute high fat and high carbohydrate diets on the cerebral circulation, the effects of age on the regulation of cerebral blood flow, and the effects of simulated high altitude exposure on ventilatory and cerebrovascular acclimatization. We hope our research will yield important new knowledge about the basic mechanisms that regulate brain circulation in humans.

With a significant increase in the proportion of Canadians aged 65 and over in the next decade, gaining a better understanding of the cerebrovascular physiology of aging is extremely important. Such studies in our laboratory, whose main research efforts are committed to a systems-approach in human cerebrovascular physiology on the whole person, are especially critical as our understanding of the human genome develops, and may offer unique avenues for translating fundamental knowledge into solving the complexities of debilitating cerebrovascular disorders and aging. We hope that our work will have a major impact in advancing our knowledge of cerebrovascular regulation and that this will help improve the health of Canadians.

Women and Aging

Stroke is the number one cause of major disability in adults and the third leading cause of death in the U.S. and Canada. When all cerebrovascular diseases are considered, the annual cost of stroke in Canada is estimated to be about $3 billion. Compared with men, women over the age of 80 years can expect to live a larger part of their remaining years with moderate and severe dependence because of chronic diseases including stroke. Women are the fastest growing group of the senior population in Canada, and since stroke rates in women double in each successive decade after 55 years of age, the number of strokes will rise substantially over the next 15 years. We are using our techniques and experimental approaches to address a pathophysiological issue central to our understanding of stroke, namely the regulation of cerebral blood flow in the context of gender and age-related physiological modulation.

In a first set of studies, we are studying the effects of age on cerebral blood flow over a woman's life time, starting with changes caused by the menstrual cycle, then after menopause with and without hormone replacement therapy, and finally into old age. We are controlling a potential confounding factor, activity level, by measuring sedentary and physically fit women in the 3 age groups. Hypothesizing that exercise is an important modulator of cerebral blood flow, we predict that those women who are more active will have better outcomes than those who are sedentary. This will enable better assessment of stroke risk and potential life-saving interventions to prevent cerebrovascular accidents, or at least determine if active living may prevent cardiovascular problems in the brain from occurring. Our first studies have started, but our search for volunteers is ongoing. Please contact us if you are interested in participating!


Clinical Studies - Regulation of cerebral blood flow and ventilation in Obstructive Sleep Apnea (OSA) patients

Sleep disordered breathing (SDB) occurs in about 9% of females and 24% of males between the ages of 30-60 years. Although it appears that obstructive SDB patients can be otherwise healthy, it has been suggested that recurrent periods of intermittent hypoxia and hypercapnia, such as those experienced in obstructive sleep apnea (OSA), may impair cerebrovascular reactivity during wakefulness, and increase daytime blood pressure. Furthermore, a strong association has been shown between OSA and cerebrovascular disease (i.e., transient ischemic attacks and stroke).

Whilst treatment of sleep apnea with Continuous Positive Airway Pressure (CPAP) has been shown to eliminate apneic events and reduce hypertension, it remains unclear whether CPAP is also effective in reversing the impairment of cerebrovascular reactivity, which has been described previously in sleep apnea. We are studying the daytime sensitivity of cerebral blood flow to acute variations in arterial Po2 and Pco2 in humans with and without OSA, and whether there are changes in this sensitivity after one month of treatment of OSA with CPAP in young, non-morbidly obese, and otherwise healthy patients. A first set of studies is evaluating cerebrovascular parameters during wakefulness. Our purpose-built chamber will permit us to evaluate these same parameters during sleep. This is an exciting and important research program that is poised to expand during the next 5 years to help us better understand diseases such as OSA.

High Altitude Physiology

Athletic populations and those participating in activities at high altitude also stand to benefit from this research. At higher altitudes, the partial pressure of oxygen decreases, making exercise and physical activity more difficult. A better understanding of ventilatory and cerebrovascular acclimatization is an important area of study that will help us better understand altitude-related disorders such as acute mountain sickness, high altitude cerebral edema and high altitude pulmonary edema. This program is part of a new and exciting initiative in Mountain Medicine and High Altitude Physiology at the University of Calgary (www.mmhap.myweb.med.ucalgary.ca).

Publications

Most recent publications are listed at: http://www.ucalgary.ca/poulin/publications/full-papers

Pandit, J.J., R. Mohan, N.D. Paterson, and M.J. Poulin. Cerebral blood flow sensitivities to CO2 measured with steady-state and modified rebreathing methods. Respiratory Physiology & Neurobiology. (accepted 2 May 2007). In Press.


Brugniaux, J.V., A.N.H. Hodges, P.J. Hanly and M.J. Poulin. Cerebrovascular responses to altitude (Invited Review). Respiratory Physiology & Neurobiology. (accepted 19 April 2007). In Press.

Foster, G.E., P.J. Hanly, M. Ostrowski and M.J. Poulin. The sensitivity of the cerebral vasculature to hypoxia is reduced in patients with obstructive sleep apnea and improved with CPAP therapy. American Journal of Respiratory and Critical Care Medicine. 175:720-725, 2007.

Foster, G.E., M.J. Poulin and P.J. Hanly. Intermittent hypoxia and vascular function: implications for obstructive sleep apnea (Invited Review). Experimental Physiology. 92.1:51-65, 2007.

Teppema, L.J., G.M. Balanos, C.D. Steinback, A.D. Brown, G.E. Foster, H.J. Duff, R. Leigh and M.J. Poulin. Effects of acetazolamide on ventilation, cerebral blood flow and pulmonary vascular responses in humans during normoxia and hypoxia. American Journal of Respiratory and Critical Care Medicine. 175:277-281, 2007.

Vantanajal, J.S., J.C. Ashmead, T.J. Anderson, R.T. Hepple and M.J. Poulin. Differential sensitivities of cerebral and brachial blood flow to hypercapnia in humans. Journal of Applied Physiology. 102:87-93, 2007.

Steinback, C.D. and M.J. Poulin. Ventilatory responses to isocapnic and poikilocapnic hypoxia in humans. Respiratory Physiology & Neurobiology. 155:104-113, 2007.

Kurji, A., C.T. Debert, W.W. Whitelaw, J.M. Rawling, R. Frayne and M.J. Poulin. Differences in middle cerebral artery blood velocity waveforms of young and postmenopausal women. Menopause. 13:303-313, 2006.

Harris, A.D., K. Ide, M.J. Poulin, R. Frayne. Control of end-tidal PCO2 reduces middle cerebral artery blood velocity variability: implications for physiological neuroimaging. Neuroimage. 29: 1272-1277, 2006.

Ainslie, P.N., J.C. Kolb, K. Ide and M.J. Poulin. Effect of 5 nights of normobaric hypoxia on cardiovascular responses to acute isocapnic hypoxia in humans: relationship to ventilatory chemosensitivity. Ergonomics. 48:1523-1534, 2005.

Ainslie, P.N., J.C. Ashmead, K. Ide, B.J. Morgan and M.J. Poulin. Differential responses to CO2 and sympathetic stimulation in the cerebral and femoral circulations in humans. Journal of Physiology. 566.2:613-624, 2005.

Reimer, R.A., C.T. Debert, J. House and M.J. Poulin. Changes in dietary intake during the luteal versus follicular phase in young women and in postmenopausal women taking or not taking hormone replacement therapy Physiology & Behavior. 84:303-312, 2005.

Mitsis, G.D., M.J. Poulin, P.A. Robbins and V.Z. Marmarelis. Nonlinear modeling of the dynamic effects of arterial pressure and CO2 variations on cerebral blood flow in healthy humans. IEEE Transactions on Biomedical Engineering. 51:1932-1943, 2004.

Kolb, J.C., P.N. Ainslie, K. Ide and M.J. Poulin. Protocol for determining the acute cerebrovascular and ventilatory responses to isocapnic hypoxia in humans. Respiratory Physiology & Neurobiology. 141:191-199, 2004.

Ainslie, P.N. and M.J. Poulin. Ventilatory, cerebrovascular and cardiovascular interactions in acute hypoxia: regulation by carbon dioxide. J. Appl. Physiol. 97: 149-159, 2004.

Kolb, J.C., P.N. Ainslie, K. Ide, and M.J. Poulin. Effects of 5 consecutive nocturnal hypoxic exposures on the cerebrovascular responses to acute hypoxia and hypercapnia in humans. Journal of Applied Physiology. 96: 1745-1754, 2004.

Wise, R.G., K. Ide, M.J. Poulin. and I. Tracey. Resting fluctuations in arterial carbon dioxide induce significant low frequency variations in BOLD signal. Neuroimage. 21:1652-1664, 2004.

Ainslie P.N., J.C. Kolb, K. Ide and M.J. Poulin. Effects of 5 nights of normobaric hypoxia on the ventilatory responses to acute hypoxia and hypercapnia. Respiratory Physiology & Neurobiology. 138:193-204, 2003.

Ide, K., M. Eliasziw and M.J. Poulin. The relationship between middle cerebral artery blood velocity and end-tidal PCO2 in the hypocapnic-hypercapnic range in humans. Journal of Applied Physiology, 95:129-137, 2003.

M. Fatemian, D. Kim, M.J. Poulin and P.A. Robbins. Long-haul flights may induce changes similar to ventilatory acclimatisation to altitude. Pflügers Archives. 441:840-843, 2001.

Pandit, J.J., R. Mohan, N.D. Paterson and M.J. Poulin. The cerebral blood flow sensitivities to CO2 determined by Read's rebreathing technique and the steady-state method are not equal. In: Frontiers in Modeling and Control of Breathing: Integration at Molecular, Cellular and Systems Levels (Advances in Experimental Medicine and Biology Series, Volume 499). Eds: C.-S. Poon and H. Kazemi. Kluwer Academic/Plenum Publishers, New York. pp. 279-284, 2001.

Smith, W.D.F., M.J. Poulin, D.H. Paterson and D.A. Cunningham. Dynamic Ventilatory Response to Acute Isocapnic Hypoxia in Septuagenarians. Experimental Physiology. 86.1:117-126, 2001.

Poulin, M.J., R.J. Syed and P.A. Robbins. Indexes of flow and cross-sectional area of the middle cerebral artery using Doppler ultrasound during submaximal dynamic exercise in humans. Journal of Applied Physiology. 86:1632-1637, 1999.

Tansley, J.G., M. Fatemian, L.S.G.E. Howard, M.J. Poulin, and P.A. Robbins. Changes in respiratory control during and after 48 h of isocapnic and poikilocapnic hypoxia in humans. Journal of Applied Physiology. 85:2125-2134, 1998.

Poulin, M.J., P.-J. Liang and P.A. Robbins. Fast and slow components of cerebral blood flow response to step decreases in end-tidal PCO2 in humans. Journal of Applied Physiology. 85:388-397, 1998.

Poulin, M.J. and P.A. Robbins. Influence of cerebral blood flow on the ventilatory response to hypoxia in humans. Experimental Physiology. 83:95-106, 1998.

Personnel

Ms. Heidi Rubba - Administrative Assistant.
Dr. Daniela Cretu, Brain in Motion Study Coordinator

Please see our website for a full list ( www.ucalgary.ca/poulin )

Positions Available

If you are interested in obtaining more information, if you have questions about graduate work, or if you would like more information on postdoctoral positions, please send a curriculum vitae or contact Dr. Marc Poulin directly at:

Dr. Marc J. Poulin
Department of Physiology & Pharmacology
Cumming School of Medicine, University of Calary
Heritage Medical Research Building, Room 210
3330 Hospital Drive NW
Calgary, Alberta
T2N 4N1
Canada
Tel: ++ 403-220-8372
Fax: ++ 403-210-8420
Email: poulin@ucalgary.ca
Web: www.ucalgary.ca/poulin

Twitter: @marcjpoulin   @braininmotion

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