Coupling between Blood Pressure and Subarachnoid Space Width Oscillations during Slow Breathing Author: Agnieszka Gruszecka1, Magdalena K Nuckowska2, Monika Waskow3, Jacek Kot4, Pawel J Winklewski2, Wojciech Guminski5, Andrzej F Frydrychowski6, Jerzy Wtorek7, Adam Bujnowski7, Piotr Lass8,9, Tomislav Stankovski10,11, Marcin Gruszecki1,7 Affiliation: <sup>1</sup> Department of Radiology Informatics and Statistics, Medical University of Gdansk, 80-210 Gdansk, Poland. <sup>2</sup> Department of Human Physiology, Medical University of Gdansk, 80-210 Gdansk, Poland. <sup>3</sup> Institut of Health Sciences, Pomeranian University of Slupsk, 76-200 Slupsk, Poland. <sup>4</sup> National Centre for Hyperbaric Medicine, Institute of Maritime and Tropical Medicine, Medical University of Gdansk, 81-347 Gdynia, Poland. <sup>5</sup> Department of Computer Communications, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 80-233 Gdansk, Poland. <sup>6</sup> NIRTI SA, 53-676 Wroclaw, Poland. <sup>7</sup> Department of Biomedical Engineering, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 80-233 Gdansk, Poland. <sup>8</sup> Department of Nuclear Medicine, Medical University of Gdansk, 80-210 Gdansk, Poland. <sup>9</sup> Department of Molecular Spectroscopy, Faculty of Mathematics, Physics and Informatics, University of Gdansk, 80-309 Gdansk, Poland;. <sup>10</sup> Faculty of Medicine, Ss. Cyril and Methodius University in Skopje, 1000 Skopje, North Macedonia. <sup>11</sup> Department of Physics, Lancaster University, Lancaster LA1 4YW, UK. Conference/Journal: Entropy (Basel) Date published: 2021 Jan 15 Other: Volume ID: 23 , Issue ID: 1 , Pages: E113 , Special Notes: doi: 10.3390/e23010113. , Word Count: 219 The precise mechanisms connecting the cardiovascular system and the cerebrospinal fluid (CSF) are not well understood in detail. This paper investigates the couplings between the cardiac and respiratory components, as extracted from blood pressure (BP) signals and oscillations of the subarachnoid space width (SAS), collected during slow ventilation and ventilation against inspiration resistance. The experiment was performed on a group of 20 healthy volunteers (12 females and 8 males; BMI=22.1±3.2 kg/m2; age 25.3±7.9 years). We analysed the recorded signals with a wavelet transform. For the first time, a method based on dynamical Bayesian inference was used to detect the effective phase connectivity and the underlying coupling functions between the SAS and BP signals. There are several new findings. Slow breathing with or without resistance increases the strength of the coupling between the respiratory and cardiac components of both measured signals. We also observed increases in the strength of the coupling between the respiratory component of the BP and the cardiac component of the SAS and vice versa. Slow breathing synchronises the SAS oscillations, between the brain hemispheres. It also diminishes the similarity of the coupling between all analysed pairs of oscillators, while inspiratory resistance partially reverses this phenomenon. BP-SAS and SAS-BP interactions may reflect changes in the overall biomechanical characteristics of the brain. Keywords: coupling; nonlinear dynamics; time series. PMID: 33467769 DOI: 10.3390/e23010113