Event Abstract Back to Event Chemoreflexes characterization by steady state and rebreathing method: application to ventilation and cerebral blood flow (CBF) Anne Battisti1*, Joe A. Fisher1 and Jim Duffin1 1 University of Toronto, Department of Physiology, Canada Objectives: This study examines the effect of hypoxia by the 2-level isoxic modified rebreathing method (Duffin 2007) and two levels of isoxia at 3 isocapnic levels (PCO2 = 4, 7 & 10 mmHg above resting) on ventilation and cerebral blood flow (CBF). Method: Custom designed software controlling a specialized gas blending device and sequential rebreathing circuit (RespirAct™; Thornhill Research) was used to implement the steady state protocols. Subjects performed 3 tests where their exhaled PO2 (PETO2) was reduced in a single step from resting (100 ± 12 mmHg) to 50 ± 5 mmHg for 10 min. Each test was performed at an end-tidal PCO2 (PETCO2) of 4, 7, or 10 mmHg above resting values, in randomized order. We measured minute ventilation (VE), PetCO2 and PetO2, middle cerebral artery velocity (MCAv), and blood pressure (BP). Thirty minutes was allowed between tests in order to allow time for the chemo and baroreceptors to reset. The modified rebreathing procedure consists of prior hyperventilation, equilibration to a PCO2 below the apneic threshold, and continuous rebreathing. FIO2 is kept iso-oxic at PO2 of 50 or 150 mmHg. Results: 9 subjects completed the tests (6 male). Each realized the 2 rebreathing tests as well as the three isocapnic steady state. The two methods give the sensitivity of VE and MCAv to both hypercapnia and hypoxia. The ventilation response slopes will differ between the two methods, because the SS method includes the cerebrovascular response to CO2, which will reduce the contribution of the central chemoreflex response. Moreover, the SS ventilation responses will be left-shifted by the arterio-venous difference in PCO2, because the rebreathing PCO2 measures are referenced to venous tensions while the SS PCO2 measures are referenced to arterial tensions. By contrast, the TCD responses, which reflect the PCO2 of arterial blood should be similar between the two methods. Conclusion: The two methods give the same trend. However, the interindividual variability regarding the MCAv is larger than expected; and some subjects might have limitations of the MCAv increase. Further analysis still need to be done. Acknowledgement: This work was supported by Thornhill Research Inc. fig2 Conference: B.R.A.I.N. platform in Physiology poster day 2009, Toronto, ON, Canada, 16 Dec - 16 Dec, 2009. Presentation Type: Poster Presentation Topic: Poster presentations Citation: Battisti A, Fisher JA and Duffin J (2009). Chemoreflexes characterization by steady state and rebreathing method: application to ventilation and cerebral blood flow (CBF). Front. Neurosci. Conference Abstract: B.R.A.I.N. platform in Physiology poster day 2009. doi: 10.3389/conf.neuro.03.2009.17.003 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 16 Dec 2009; Published Online: 16 Dec 2009. * Correspondence: Anne Battisti, University of Toronto, Department of Physiology, Toronto, Canada, battistianais@yahoo.fr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Anne Battisti Joe A Fisher Jim Duffin Google Anne Battisti Joe A Fisher Jim Duffin Google Scholar Anne Battisti Joe A Fisher Jim Duffin PubMed Anne Battisti Joe A Fisher Jim Duffin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.