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Boulet LM, Tymko MM, Jamieson AN, Ainslie PN, Skow RJ, Day TA. Influence of prior hyperventilation duration on respiratory chemosensitivity and cerebrovascular reactivity during modified hyperoxic rebreathing. Exp Physiol 2016; 101:821-35. [DOI: 10.1113/ep085706] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 03/16/2016] [Indexed: 12/30/2022]
Affiliation(s)
- Lindsey M. Boulet
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Michael M. Tymko
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Alenna N. Jamieson
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
| | - Philip N. Ainslie
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Rachel J. Skow
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
- Faculty of Physical Education and Recreation; University of Alberta; Edmonton Alberta Canada
| | - Trevor A. Day
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
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Mikhail Kellawan J, Harrell JW, Schrauben EM, Hoffman CA, Roldan-Alzate A, Schrage WG, Wieben O. Quantitative cerebrovascular 4D flow MRI at rest and during hypercapnia challenge. Magn Reson Imaging 2016; 34:422-8. [DOI: 10.1016/j.mri.2015.12.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 12/13/2015] [Indexed: 12/01/2022]
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Hoiland RL, Tymko MM, Bain AR, Wildfong KW, Monteleone B, Ainslie PN. Carbon dioxide-mediated vasomotion of extra-cranial cerebral arteries in humans: a role for prostaglandins? J Physiol 2016; 594:3463-81. [PMID: 26880615 DOI: 10.1113/jp272012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/01/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cerebral blood flow increases during hypercapnia and decreases during hypocapnia; it is unknown if vasomotion of the internal carotid artery is implicated in these responses. Indomethacin, a non-selective cyclooxygenase inhibitor (used to inhibit prostaglandin synthesis), has a unique ability to blunt cerebrovascular carbon dioxide reactivity, while other cyclooxygenase inhibitors have no effect. We show significant dilatation and constriction of the internal carotid artery during hypercapnia and hypocapnia, respectively. Indomethacin, but not ketorolac or naproxen, reduced the dilatatory response of the internal carotid artery to hypercapnia The differential effect of indomethacin compared to ketorolac and naproxen suggests that indomethacin inhibits vasomotion of the internal carotid artery independent of prostaglandin synthesis inhibition. ABSTRACT Extra-cranial cerebral blood vessels are implicated in the regulation of cerebral blood flow during changes in arterial CO2 ; however, the mechanisms governing CO2 -mediated vasomotion of these vessels in humans remain unclear. We determined if cyclooxygenase inhibition with indomethacin (INDO) reduces the vasomotor response of the internal carotid artery (ICA) to changes in end-tidal CO2 (P ETC O2). Using a randomized single-blinded placebo-controlled study, participants (n = 10) were tested on two occasions, before and 90 min following oral INDO (1.2 mg kg(-1) ) or placebo. Concurrent measurements of beat-by-beat velocity, diameter and blood flow of the ICA were made at rest and during steady-state stages (4 min) of iso-oxic hypercapnia (+3, +6, +9 mmHg P ETC O2) and hypocapnia (-3, -6, -9 mmHg P ETC O2). To examine if INDO affects ICA vasomotion independent of cyclooxygenase inhibition, two participant subsets (each n = 5) were tested before and following oral ketorolac (post 45 min, 0.25 mg kg(-1) ) or naproxen (post 90 min, 4.2 mg kg(-1) ). During pre-drug testing in the INDO trial, the ICA dilatated during hypercapnia at +6 mmHg (4.72 ± 0.45 vs. 4.95 ± 0.51 mm; P < 0.001) and +9 mmHg (4.72 ± 0.45 mm vs. 5.12 ± 0.47 mm; P < 0.001), and constricted during hypocapnia at -6 mmHg (4.95 ± 0.33 vs. 4.88 ± 0.27 mm; P < 0.05) and -9 mmHg (4.95 ± 0.33 vs. 4.82 ± 0.27 mm; P < 0.001). Following INDO, vasomotor responsiveness of the ICA to hypercapnia was reduced by 67 ± 28% (0.045 ± 0.015 vs. 0.015 ± 0.012 mm mmHg P ETC O2(-1) ). There was no effect of the drug in the ketorolac and naproxen trials. We conclude that: (1) INDO markedly reduces the vasomotor response of the ICA to changes in P ETC O2; and (2) INDO may be reducing CO2 -mediated vasomotion via a mechanism(s) independent of cyclooxygenase inhibition.
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Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Kevin W Wildfong
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Brad Monteleone
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
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Pfoh JR, Tymko MM, Abrosimova M, Boulet LM, Foster GE, Bain AR, Ainslie PN, Steinback CD, Bruce CD, Day TA. Comparing and characterizing transient and steady-state tests of the peripheral chemoreflex in humans. Exp Physiol 2016; 101:432-47. [DOI: 10.1113/ep085498] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 11/30/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Jamie R. Pfoh
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
| | - Michael M. Tymko
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Maria Abrosimova
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
| | - Lindsey M. Boulet
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Glen E. Foster
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Anthony R. Bain
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Philip N. Ainslie
- School of Health and Exercise Sciences, Faculty of Health and Social Development; University of British Columbia Okanagan; Kelowna British Columbia Canada
| | - Craig D. Steinback
- Faculty of Physical Education and Recreation; University of Alberta; Edmonton Alberta Canada
| | - Christina D. Bruce
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
| | - Trevor A. Day
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
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55
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MacKay CM, Skow RJ, Tymko MM, Boulet LM, Davenport MH, Steinback CD, Ainslie PN, Lemieux CCM, Day TA. Central respiratory chemosensitivity and cerebrovascular CO2 reactivity: a rebreathing demonstration illustrating integrative human physiology. ADVANCES IN PHYSIOLOGY EDUCATION 2016; 40:79-92. [PMID: 26873894 DOI: 10.1152/advan.00048.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
One of the most effective ways of engaging students of physiology and medicine is through laboratory demonstrations and case studies that combine 1) the use of equipment, 2) problem solving, 3) visual representations, and 4) manipulation and interpretation of data. Depending on the measurements made and the type of test, laboratory demonstrations have the added benefit of being able to show multiple organ system integration. Many research techniques can also serve as effective demonstrations of integrative human physiology. The "Duffin" hyperoxic rebreathing test is often used in research settings as a test of central respiratory chemosensitivity and cerebrovascular reactivity to CO2. We aimed to demonstrate the utility of the hyperoxic rebreathing test for both respiratory and cerebrovascular responses to increases in CO2 and illustrate the integration of the respiratory and cerebrovascular systems. In the present article, methods such as spirometry, respiratory gas analysis, and transcranial Doppler ultrasound are described, and raw data traces can be adopted for discussion in a tutorial setting. If educators have these instruments available, instructions on how to carry out the test are provided so students can collect their own data. In either case, data analysis and quantification are discussed, including principles of linear regression, calculation of slope, the coefficient of determination (R(2)), and differences between plotting absolute versus normalized data. Using the hyperoxic rebreathing test as a demonstration of the complex interaction and integration between the respiratory and cerebrovascular systems provides senior undergraduate, graduate, and medical students with an advanced understanding of the integrative nature of human physiology.
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Affiliation(s)
- Christina M MacKay
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada; Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
| | - Rachel J Skow
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada; Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
| | - Michael M Tymko
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada; School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Lindsey M Boulet
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada; School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Margie H Davenport
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
| | - Craig D Steinback
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; and
| | - Philip N Ainslie
- School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Chantelle C M Lemieux
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada;
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Hartley GL, Watson CL, Ainslie PN, Tokuno CD, Greenway MJ, Gabriel DA, O'Leary DD, Cheung SS. Corticospinal excitability is associated with hypocapnia but not changes in cerebral blood flow. J Physiol 2016; 594:3423-37. [PMID: 26836470 DOI: 10.1113/jp271914] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 01/22/2016] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS Reductions in cerebral blood flow (CBF) may be implicated in the development of neuromuscular fatigue; however, the contribution from hypocapnic-induced reductions (i.e. P ETC O2) in CBF versus reductions in CBF per se has yet to be isolated. We assessed neuromuscular function while using indomethacin to selectively reduce CBF without changes in P ETC O2 and controlled hyperventilation-induced hypocapnia to reduce both CBF and P ETC O2. Increased corticospinal excitability appears to be exclusive to reductions in P ETC O2 but not reductions in CBF, whereas sub-optimal voluntary output from the motor cortex is moderately associated with decreased CBF independent of changes in P ETC O2. These findings suggest that changes in CBF and P ETC O2 have distinct roles in modulating neuromuscular function. ABSTRACT Although reductions in cerebral blood flow (CBF) may be involved in central fatigue, the contribution from hypocapnia-induced reductions in CBF versus reductions in CBF per se has not been isolated. This study examined whether reduced arterial PCO2 (P aC O2), independent of concomitant reductions in CBF, impairs neuromuscular function. Neuromuscular function, as indicated by motor-evoked potentials (MEPs), maximal M-wave (Mmax ) and cortical voluntary activation (cVA) of the flexor carpi radialis muscle during isometric wrist flexion, was assessed in ten males (29 ± 10 years) during three separate conditions: (1) cyclooxygenase inhibition using indomethacin (Indomethacin, 1.2 mg kg(-1) ) to selectively reduce CBF by 28.8 ± 10.3% (estimated using transcranial Doppler ultrasound) without changes in end-tidal PCO2 (P ETC O2); (2) controlled iso-oxic hyperventilation-induced reductions in P aC O2 (Hypocapnia), P ETC O2 = 30.1 ± 4.5 mmHg with related reductions in CBF (21.7 ± 6.3%); and (3) isocapnic hyperventilation (Isocapnia) to examine the potential direct influence of hyperventilation-mediated activation of respiratory control centres on CBF and changes in neuromuscular function. Change in MEP amplitude (%Mmax ) from baseline was greater in Hypocapnia tha in Isocapnia (11.7 ± 9.8%, 95% confidence interval (CI) [2.6, 20.7], P = 0.01) and Indomethacin (13.3 ± 11.3%, 95% CI [2.8, 23.7], P = 0.01) with a large Cohen's effect size (d ≥ 1.17). Although not statistically significant, cVA was reduced with a moderate effect size in Indomethacin (d = 0.7) and Hypocapnia (d = 0.9) compared to Isocapnia. In summary, increased corticospinal excitability - as reflected by larger MEP amplitude - appears to be exclusive to reduced P aC O2, but not reductions in CBF per se. Sub-optimal voluntary output from the motor cortex is moderately associated with decreased CBF, independent of reduced P aC O2.
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Affiliation(s)
- Geoffrey L Hartley
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada.,Centre for Physical and Health Education, Schulich School of Education, Nipissing University, North Bay, Ontario, Canada
| | - Cody L Watson
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada
| | - Craig D Tokuno
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Matthew J Greenway
- Michael G. DeGroote School of Medicine, Niagara Regional Campus, McMaster University, Hamilton, Ontario, Canada
| | - David A Gabriel
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Deborah D O'Leary
- Department of Health Sciences, Brock University, St. Catharines, Ontario, Canada
| | - Stephen S Cheung
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
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Feddersen B, Neupane P, Thanbichler F, Hadolt I, Sattelmeyer V, Pfefferkorn T, Waanders R, Noachtar S, Ausserer H. Regional differences in the cerebral blood flow velocity response to hypobaric hypoxia at high altitudes. J Cereb Blood Flow Metab 2015; 35:1846-51. [PMID: 26082017 PMCID: PMC4635241 DOI: 10.1038/jcbfm.2015.142] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/16/2015] [Accepted: 05/15/2015] [Indexed: 11/09/2022]
Abstract
Symptoms of acute mountain sickness (AMS) may appear above 2,500 m altitude, if the time allowed for acclimatization is insufficient. As the mechanisms underlying brain adaptation to the hypobaric hypoxic environment are not fully understood, a prospective study was performed investigating neurophysiological changes by means of near infrared spectroscopy, electroencephalograpy (EEG), and transcranial doppler sonography at 100, 3,440 and 5,050 m above sea level in the Khumbu Himal, Nepal. Fourteen of the 26 mountaineers reaching 5,050 m altitude developed symptoms of AMS between 3,440 and 5,050 m altitude (Lake-Louise Score ⩾3). Their EEG frontal beta activity and occipital alpha activity increased between 100 and 3,440 m altitude, i.e., before symptoms appeared. Cerebral blood flow velocity (CBFV) in the anterior and middle cerebral arteries (MCAs) increased in all mountaineers between 100 and 3,440 m altitude. During further ascent to 5,050 altitude, mountaineers with AMS developed a further increase in CBFV in the MCA, whereas in all mountaineers CBFV decreased continuously with increasing altitude in the posterior cerebral arteries. These results indicate that hypobaric hypoxia causes different regional changes in CBFV despite similar electrophysiological changes.
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Affiliation(s)
- Berend Feddersen
- Department of Neurology, Klinikum Grosshadern, University of Munich, Munich, Germany.,Department of Palliative Medicine, Specialized Palliative Home Care Team, University of Munich, Munich, Germany
| | - Pritam Neupane
- Department of Internal Medicine, Sinai Hospital, Johns Hopkins University, Baltimore, Maryland, USA
| | - Florian Thanbichler
- Department of Neurology, Klinikum Grosshadern, University of Munich, Munich, Germany
| | - Irmgard Hadolt
- Research Unit of Biomedical Engineering in Anesthesia and Intensive Care Medicine, Medical University of Graz, Graz, Austria
| | - Vera Sattelmeyer
- Klinik für Neurochirurgie, Dr Horst Schmidt Klinik, Wiesbaden, Germany
| | - Thomas Pfefferkorn
- Department of Neurology, Klinikum Grosshadern, University of Munich, Munich, Germany
| | - Robb Waanders
- Department of Neuropsychology, Landeskrankenhaus Rankweil, Rankweil, Austria
| | - Soheyl Noachtar
- Department of Neurology, Klinikum Grosshadern, University of Munich, Munich, Germany
| | - Harald Ausserer
- Department of Neurology, Klinikum Grosshadern, University of Munich, Munich, Germany.,Department of Neurology, Franz-Tappeiner Krankenhaus, Meran, Italy
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58
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Nuding SC, Segers LS, Iceman KE, O'Connor R, Dean JB, Bolser DC, Baekey DM, Dick TE, Shannon R, Morris KF, Lindsey BG. Functional connectivity in raphé-pontomedullary circuits supports active suppression of breathing during hypocapnic apnea. J Neurophysiol 2015; 114:2162-86. [PMID: 26203111 PMCID: PMC4600964 DOI: 10.1152/jn.00608.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 07/18/2015] [Indexed: 01/17/2023] Open
Abstract
Hyperventilation is a common feature of disordered breathing. Apnea ensues if CO2 drive is sufficiently reduced. We tested the hypothesis that medullary raphé, ventral respiratory column (VRC), and pontine neurons have functional connectivity and persistent or evoked activities appropriate for roles in the suppression of drive and rhythm during hyperventilation and apnea. Phrenic nerve activity, arterial blood pressure, end-tidal CO2, and other parameters were monitored in 10 decerebrate, vagotomized, neuromuscularly-blocked, and artificially ventilated cats. Multielectrode arrays recorded spiking activity of 649 neurons. Loss and return of rhythmic activity during passive hyperventilation to apnea were identified with the S-transform. Diverse fluctuating activity patterns were recorded in the raphé-pontomedullary respiratory network during the transition to hypocapnic apnea. The firing rates of 160 neurons increased during apnea; the rates of 241 others decreased or stopped. VRC inspiratory neurons were usually the last to cease firing or lose rhythmic activity during the transition to apnea. Mayer wave-related oscillations (0.04-0.1 Hz) in firing rate were also disrupted during apnea. Four-hundred neurons (62%) were elements of pairs with at least one hyperventilation-responsive neuron and a correlational signature of interaction identified by cross-correlation or gravitational clustering. Our results support a model with distinct groups of chemoresponsive raphé neurons contributing to hypocapnic apnea through parallel processes that incorporate disfacilitation and active inhibition of inspiratory motor drive by expiratory neurons. During apnea, carotid chemoreceptors can evoke rhythm reemergence and an inspiratory shift in the balance of reciprocal inhibition via suppression of ongoing tonic expiratory neuron activity.
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Affiliation(s)
- Sarah C Nuding
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Lauren S Segers
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Kimberly E Iceman
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Russell O'Connor
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Donald C Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida; and
| | - David M Baekey
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida; and
| | - Thomas E Dick
- Departments of Medicine and Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Roger Shannon
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Bruce G Lindsey
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida;
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60
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Tymko MM, Skow RJ, MacKay CM, Day TA. Steady-state tilt has no effect on cerebrovascular CO2reactivity in anterior and posterior cerebral circulations. Exp Physiol 2015; 100:839-51. [DOI: 10.1113/ep085084] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 05/11/2015] [Indexed: 01/13/2023]
Affiliation(s)
- Michael M. Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science; University of British Columbia; Kelowna British Columbia Canada
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
| | - Rachel J. Skow
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
- Faculty of Physical Education and Recreation; University of Alberta; Edmonton Alberta Canada
| | - Christina M. MacKay
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
- Faculty of Physical Education and Recreation; University of Alberta; Edmonton Alberta Canada
| | - Trevor A. Day
- Department of Biology, Faculty of Science and Technology; Mount Royal University; Calgary Alberta Canada
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61
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Lucas SJE, Cotter JD, Brassard P, Bailey DM. High-intensity interval exercise and cerebrovascular health: curiosity, cause, and consequence. J Cereb Blood Flow Metab 2015; 35:902-11. [PMID: 25833341 PMCID: PMC4640257 DOI: 10.1038/jcbfm.2015.49] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 01/25/2015] [Accepted: 03/01/2015] [Indexed: 12/14/2022]
Abstract
Exercise is a uniquely effective and pluripotent medicine against several noncommunicable diseases of westernised lifestyles, including protection against neurodegenerative disorders. High-intensity interval exercise training (HIT) is emerging as an effective alternative to current health-related exercise guidelines. Compared with traditional moderate-intensity continuous exercise training, HIT confers equivalent if not indeed superior metabolic, cardiac, and systemic vascular adaptation. Consequently, HIT is being promoted as a more time-efficient and practical approach to optimize health thereby reducing the burden of disease associated with physical inactivity. However, no studies to date have examined the impact of HIT on the cerebrovasculature and corresponding implications for cognitive function. This review critiques the implications of HIT for cerebrovascular function, with a focus on the mechanisms and translational impact for patient health and well-being. It also introduces similarly novel interventions currently under investigation as alternative means of accelerating exercise-induced cerebrovascular adaptation. We highlight a need for studies of the mechanisms and thereby also the optimal dose-response strategies to guide exercise prescription, and for studies to explore alternative approaches to optimize exercise outcomes in brain-related health and disease prevention. From a clinical perspective, interventions that selectively target the aging brain have the potential to prevent stroke and associated neurovascular diseases.
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Affiliation(s)
- Samuel J E Lucas
- 1] School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK [2] Department of Physiology, University of Otago, Dunedin, New Zealand
| | - James D Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Patrice Brassard
- 1] Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada [2] Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Damian M Bailey
- 1] Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, South Wales, UK [2] Université de Provence Marseille, Sondes Moléculaires en Biologie, Laboratoire Chimie Provence UMR 6264 CNRS, Marseille, France
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62
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Hoiland RL, Ainslie PN, Wildfong KW, Smith KJ, Bain AR, Willie CK, Foster G, Monteleone B, Day TA. Indomethacin-induced impairment of regional cerebrovascular reactivity: implications for respiratory control. J Physiol 2015; 593:1291-306. [PMID: 25641262 PMCID: PMC4358685 DOI: 10.1113/jphysiol.2014.284521] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 12/03/2014] [Indexed: 01/20/2023] Open
Abstract
Cerebrovascular reactivity impacts CO₂-[H(+)] washout at the central chemoreceptors and hence has marked influence on the control of ventilation. To date, the integration of cerebral blood flow (CBF) and ventilation has been investigated exclusively with measures of anterior CBF, which has a differential reactivity from the vertebrobasilar system and perfuses the brainstem. We hypothesized that: (1) posterior versus anterior CBF would have a stronger relationship to central chemoreflex magnitude during hypercapnia, and (2) that higher posterior reactivity would lead to a greater hypoxic ventilatory decline (HVD). End-tidal forcing was used to induce steady-state hyperoxic (300 mmHg P ET ,O₂) hypercapnia (+3, +6 and +9 mmHg P ET ,CO₂) and isocapnic hypoxia (45 mmHg P ET ,O₂) before and following pharmacological blunting (indomethacin; INDO; 1.45 ± 0.17 mg kg(-1)) of resting CBF and reactivity. In 22 young healthy volunteers, ventilation, intra-cranial arterial blood velocities and extra-cranial blood flows were measured during these challenges. INDO-induced blunting of cerebrovascular flow responsiveness (CVR) to CO₂ was unrelated to variability in ventilatory sensitivity during hyperoxic hypercapnia. Further results in a sub-group of volunteers (n = 9) revealed that elevations of P ET,CO₂ via end-tidal forcing reduce arterial-jugular venous gradients, attenuating the effect of CBF on chemoreflex responses. During isocapnic hypoxia, vertebral artery CVR was related to the magnitude of HVD (R(2) = 0.27; P < 0.04; n = 16), suggesting that CO₂-[H(+)] washout from central chemoreceptors modulates hypoxic ventilatory dynamics. No relationships were apparent with anterior CVR. As higher posterior, but not anterior, CVR was linked to HVD, our study highlights the importance of measuring flow in posterior vessels to investigate CBF and ventilatory integration.
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Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Kevin W Wildfong
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Kurt J Smith
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Chris K Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Glen Foster
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Brad Monteleone
- Faculty of Medicine, University of British Columbia OkanaganKelowna, British Columbia, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal UniversityCalgary, Alberta, Canada
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Hyun SH, Im JW, Jung WS, Cho KH, Kim YS, Ko CN, Park JM, Park SU, Cho SY, Moon SK. Effect of ST36 Acupuncture on Hyperventilation-Induced CO 2 Reactivity of the Basilar and Middle Cerebral Arteries and Heart Rate Variability in Normal Subjects. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE : ECAM 2014; 2014:574986. [PMID: 25132861 PMCID: PMC4123599 DOI: 10.1155/2014/574986] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 06/25/2014] [Indexed: 11/18/2022]
Abstract
This study was conducted to verify the effect of acupuncture on cerebral haemodynamics to provide evidence for the use of acupuncture treatment as a complementary therapy for the high-risk stroke population. The effect of ST36 acupuncture treatment on the hyperventilation-induced CO2 reactivity of the basilar and middle cerebral arteries was studied in 10 healthy male volunteers (mean age, 25.2 ± 1.5 years) using a transcranial Doppler sonography with an interval of 1 week between measurements, and a portable ECG monitoring system was used to obtain ECG data simultaneously. The CO2 reactivity of the basilar and middle cerebral arteries increased significantly after ST36 acupuncture treatment, whereas the mean arterial blood pressure and pulse rate did not change significantly. The high-frequency power significantly increased after ST36 acupuncture treatment, and the percentage increase of high-frequency power correlated significantly with the percentage increase in the CO2 reactivity of the contralateral middle cerebral artery. These data suggest that ST36 acupuncture treatment increases CO2 reactivity, indicating improvement of vasodilatory potential of the cerebral vasculature to compensate for fluctuations caused by changes in external conditions. The increase in parasympathetic tone by ST36 acupuncture treatment is responsible for this therapeutic effect.
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Affiliation(s)
- Sang-Ho Hyun
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Jin-Wook Im
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Woo-Sang Jung
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Ki-Ho Cho
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Young-Suk Kim
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Chang-Nam Ko
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Jung-Mi Park
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Seong-Uk Park
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Seung-Yeon Cho
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
| | - Sang-Kwan Moon
- Department of Cardiology and Neurology of Korean Medicine, College of Korean Medicine, Kyung Hee University, No. 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-872, Republic of Korea
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64
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Strohm J, Duffin J, Fisher J. Circadian cerebrovascular reactivity to CO2. Respir Physiol Neurobiol 2014; 197:15-8. [DOI: 10.1016/j.resp.2014.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 03/07/2014] [Accepted: 03/10/2014] [Indexed: 11/29/2022]
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Willie CK, Tzeng YC, Fisher JA, Ainslie PN. Integrative regulation of human brain blood flow. J Physiol 2014; 592:841-59. [PMID: 24396059 PMCID: PMC3948549 DOI: 10.1113/jphysiol.2013.268953] [Citation(s) in RCA: 564] [Impact Index Per Article: 56.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 12/24/2013] [Indexed: 02/06/2023] Open
Abstract
Herein, we review mechanisms regulating cerebral blood flow (CBF), with specific focus on humans. We revisit important concepts from the older literature and describe the interaction of various mechanisms of cerebrovascular control. We amalgamate this broad scope of information into a brief review, rather than detailing any one mechanism or area of research. The relationship between regulatory mechanisms is emphasized, but the following three broad categories of control are explicated: (1) the effect of blood gases and neuronal metabolism on CBF; (2) buffering of CBF with changes in blood pressure, termed cerebral autoregulation; and (3) the role of the autonomic nervous system in CBF regulation. With respect to these control mechanisms, we provide evidence against several canonized paradigms of CBF control. Specifically, we corroborate the following four key theses: (1) that cerebral autoregulation does not maintain constant perfusion through a mean arterial pressure range of 60-150 mmHg; (2) that there is important stimulatory synergism and regulatory interdependence of arterial blood gases and blood pressure on CBF regulation; (3) that cerebral autoregulation and cerebrovascular sensitivity to changes in arterial blood gases are not modulated solely at the pial arterioles; and (4) that neurogenic control of the cerebral vasculature is an important player in autoregulatory function and, crucially, acts to buffer surges in perfusion pressure. Finally, we summarize the state of our knowledge with respect to these areas, outline important gaps in the literature and suggest avenues for future research.
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Affiliation(s)
- Christopher K Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada V1V 1V7.
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Ryan CM, Battisti-Charbonney A, Sobczyk O, Duffin J, Fisher J. Normal hypercapnic cerebrovascular conductance in obstructive sleep apnea. Respir Physiol Neurobiol 2014; 190:47-53. [DOI: 10.1016/j.resp.2013.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Revised: 08/19/2013] [Accepted: 09/10/2013] [Indexed: 10/26/2022]
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Skow RJ, Tymko MM, MacKay CM, Steinback CD, Day TA. The effects of head-up and head-down tilt on central respiratory chemoreflex loop gain tested by hyperoxic rebreathing. PROGRESS IN BRAIN RESEARCH 2014; 212:149-72. [DOI: 10.1016/b978-0-444-63488-7.00009-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Fierstra J, Sobczyk O, Battisti-Charbonney A, Mandell DM, Poublanc J, Crawley AP, Mikulis DJ, Duffin J, Fisher JA. Measuring cerebrovascular reactivity: what stimulus to use? J Physiol 2013; 591:5809-21. [PMID: 24081155 DOI: 10.1113/jphysiol.2013.259150] [Citation(s) in RCA: 201] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cerebrovascular reactivity is the change in cerebral blood flow in response to a vasodilatory or vasoconstrictive stimulus. Measuring variations of cerebrovascular reactivity between different regions of the brain has the potential to not only advance understanding of how the cerebral vasculature controls the distribution of blood flow but also to detect cerebrovascular pathophysiology. While there are standardized and repeatable methods for estimating the changes in cerebral blood flow in response to a vasoactive stimulus, the same cannot be said for the stimulus itself. Indeed, the wide variety of vasoactive challenges currently employed in these studies impedes comparisons between them. This review therefore critically examines the vasoactive stimuli in current use for their ability to provide a standard repeatable challenge and for the practicality of their implementation. Such challenges include induced reductions in systemic blood pressure, and the administration of vasoactive substances such as acetazolamide and carbon dioxide. We conclude that many of the stimuli in current use do not provide a standard stimulus comparable between individuals and in the same individual over time. We suggest that carbon dioxide is the most suitable vasoactive stimulus. We describe recently developed computer-controlled MRI compatible gas delivery systems which are capable of administering reliable and repeatable vasoactive CO2 stimuli.
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Affiliation(s)
- J Fierstra
- J. Duffin: Department of Physiology, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, Ontario, Canada, M5S 1A8.
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