Take a deep breath: Respiratory variations in systemic and cerebral hemodynamics during reduced venous return
Abstract
This thesis within cardiovascular physiology aimed to explore respiration-related variations in systemic and cerebral hemodynamics in the context of reduced venous return. Steady-state and oscillatory lower body negative pressure (LBNP) induced abrupt, gradual, and respiration-synchronous variations in venous return in healthy humans. Hemodynamic data were collected by non-invasive methods. Frequency-domain and frequency-time domain analyses were employed to analyze hemodynamic fluctuations. This thesis has illuminated different aspects of lung-heart-brain interactions. Reduced venous return induced by LBNP affected the respiratory variability in systemic and cerebral hemodynamics. However, changes in systemic hemodynamic variability at the respiratory frequency depended on when the LBNP was induced and released in relation to the respiratory cycle. Although dynamic cerebral autoregulation was functioning during respiration-synchronous oscillatory LBNP, it did not buffer the respiratory frequency variations in arterial blood pressure. This led to a small decrease in internal carotid artery blood flow, supporting the theory that dynamic cerebral autoregulation is frequency-dependent.List of papers
Paper I. Holme N.L.A., Rein E.B., and Elstad M. Cardiac stroke volume variability measured non-invasively by three methods for detection of central hypovolemia in healthy humans. European Journal of Applied Physiology 2016. DOI: 10.1007/s00421-016-3471-2. The article is included in the thesis. Also available at: https://doi.org/10.1007/s00421-016-3471-2 |
Paper II. Skytioti M., Holme N.L.A., and Elstad M. Cardiorespiratory interactions preserve cardiac output during respiration-synchronous lower body negative pressure oscillations in healthy humans. Manuscript. To be published. The paper is not available in DUO awaiting publishing. |
Paper III. Holme N.L.A., Skytioti M., Søvik S., and Elstad M. Cerebral blood flow in healthy humans is decreased by respiration-related oscillations in arterial blood pressure and cardiac output. Manuscript. To be published. The paper is not available in DUO awaiting publishing. |
Paper IV. Holme N.L.A., Zilakos I., Elstad M., and Skytioti M. Cerebral blood flow response to cardiorespiratory oscillations in healthy humans. Autonomic Neuroscience: Basic and Clinical 2023. DOI: 10.1016/j.autneu.2022.103069. The article is included in the thesis. Also available at: https://doi.org/10.1016/j.autneu.2022.103069 |