Cerebrovascular responses to submaximal exercise in women with COPD

BMC Pulmonary Medicine, Jun 2014

Background COPD patients have decreased physical fitness, and have an increased risk of vascular disease. In the general population, fitness is positively associated with resting cerebral blood flow velocity, however, little is known about the cerebrovascular response during exercise particularly in COPD patients. We hypothesized that COPD patients would have lower cerebral blood flow during exercise secondary to decreased physical fitness and underlying vascular disease. Methods Cardiopulmonary exercise testing was conducted in 11 women with GOLD stage I-II COPD, and 11 healthy controls to assess fitness. Cerebro- and cardio-vascular responses were compared between groups during two steady-state exercise tests (50% peak O2 consumption and 30 W). The main outcome variable was peak middle cerebral artery blood flow velocity ( V ¯ P ) during exercise using transcranial Doppler ultrasonography. Results Physical fitness was decreased in COPD patients. V ¯ P was comparable between COPD and controls (25 ± 22% versus 15 ± 13%, respectively; P > 0.05) when exercising at the same relative intensity, despite patients having higher blood pressure and greater arterial desaturation. However, V ¯ P was elevated in COPD (31 ± 26% versus 13 ± 10%; P ≤ 0.05) when exercising at the same workload as controls. Conclusions Our results are contradictory to our a-priori hypothesis, suggesting that during matched intensity exercise, cerebral blood flow velocity is similar between COPD and controls. However, exercise at a modestly greater workload imposes a large physical demand to COPD patients, resulting in increased CBF compared to controls. Normal activities of daily living may therefore impose a large cerebrovascular demand in COPD patients, consequently reducing their cerebrovascular reserve capacity.

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Cerebrovascular responses to submaximal exercise in women with COPD

BMC Pulmonary Medicine Cerebrovascular responses to submaximal exercise in women with COPD Sara E Hartmann 0 1 Richard Leigh 1 2 6 Marc J Poulin 0 1 3 4 5 0 Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary , Calgary, AB , Canada 1 Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary , Calgary, AB , Canada 2 Department of Medicine, University of Calgary , Calgary, AB , Canada 3 Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary , Calgary, AB , Canada 4 Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary , Calgary, AB , Canada 5 Faculty of Kinesiology, University of Calgary , Calgary, AB , Canada 6 Snyder Institute of Infection , Immunity, and Inflammation , University of Calgary , Calgary, AB , Canada Background: COPD patients have decreased physical fitness, and have an increased risk of vascular disease. In the general population, fitness is positively associated with resting cerebral blood flow velocity, however, little is known about the cerebrovascular response during exercise particularly in COPD patients. We hypothesized that COPD patients would have lower cerebral blood flow during exercise secondary to decreased physical fitness and underlying vascular disease. Methods: Cardiopulmonary exercise testing was conducted in 11 women with GOLD stage I-II COPD, and 11 healthy controls to assess fitness. Cerebro- and cardio-vascular responses were compared between groups during two steady-state exercise tests (50% peak O2 consumption and 30 W). The main outcome variable was peak middle cerebral artery blood flow velocity (VP) during exercise using transcranial Doppler ultrasonography. Results: Physical fitness was decreased in COPD patients. VP was comparable between COPD and controls (25 22% versus 15 13%, respectively; P > 0.05) when exercising at the same relative intensity, despite patients having higher blood pressure and greater arterial desaturation. However, VP was elevated in COPD (31 26% versus 13 10%; P 0.05) when exercising at the same workload as controls. Conclusions: Our results are contradictory to our a-priori hypothesis, suggesting that during matched intensity exercise, cerebral blood flow velocity is similar between COPD and controls. However, exercise at a modestly greater workload imposes a large physical demand to COPD patients, resulting in increased CBF compared to controls. Normal activities of daily living may therefore impose a large cerebrovascular demand in COPD patients, consequently reducing their cerebrovascular reserve capacity. COPD; Exercise; Transcranial Doppler ultrasound; Cerebral blood flow; Women - Background The regulation of cerebral blood flow (CBF) is imperative for adequate delivery of O2 and energy supply to the brain. During cerebral activation and increased metabolism, cerebral arterioles dilate, thereby increasing CBF, and ultimately O2 delivery. This process of neurovascular coupling (i.e., neural activation coupled with an adequate increase in blood flow) is challenged during dynamic exercise. Factors such as age and physical fitness have been suggested to play an important role in this regulatory process both at rest [1], and during exercise [2]. The reduction of physical activity levels and exercise capacity in COPD patients [3-5] may pose a risk to patients cerebrovascular health. Even in the early stages of COPD, patients with mild and moderate obstruction are reported to have reduced exercise capacity [6]. Evidence suggests that patients with moderate COPD are already at an increased risk of cardiovascular disease and stroke, thereby suggesting an underlying vascular pathology. We have previously reported decreased CBF responsiveness to CO2 in women with COPD, suggesting reduced cerebral dilatory function [7]. Cycle ergometry testing offers a functional and translational tool to test integrated responses during exercise. COPD patients may exhibit arterial hypercapnia [8] and hypoxemia, exaggerated vasopressor response [9], and ventilatory limitations [10] during exercise which all have implications on the regulation of CBF. Furthermore, greater distribution of cardiac output to respiratory or peripheral muscles could impact the blood flow delivery to the brain. Presently, few studies have focused on the cerebrovascular response of COPD patients during exercise [11,12], and of these studies, focus has been on exercise limitations. It is currently unknown if the cerebrovascular response to exercise in COPD patients differs from that of a healthy control group. We therefore tested the hypothesis that women with mild-moderate COPD would have reduced cerebral blood flow during exercise, secondary to reduced physical fitness. Women were of particular interest in this study due to a shift in the disease burden from men to women [13], and comparatively, women report worse symptoms for a similar severity of disease to men, and f (...truncated)


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Sara E Hartmann, Richard Leigh, Marc J Poulin. Cerebrovascular responses to submaximal exercise in women with COPD, BMC Pulmonary Medicine, 2014, pp. 99, 14, DOI: 10.1186/1471-2466-14-99