title: Cardiovascular responses to water immersion in humans: impact on cerebral perfusion.
abstract: Episodic increases in cerebrovascular perfusion and shear stress may have beneficial impacts on endothelial function that improve brain health. We hypothesized that water immersion to the level of the right atrium in humans would increase cerebral perfusion. We continuously measured, in 9 young (means ± SD, 24.6 ± 2.0 yr) healthy men, systemic hemodynamic variables along with blood flows in the common carotid and middle and posterior cerebral arteries during controlled filling and emptying of a water tank to the level of the right atrium. Mean arterial pressure (80 ± 9 vs. 91 ± 12 mmHg, P < 0.05), cardiac output (4.8 ± 0.7 vs. 5.1 ± 0.6 l/min, P < 0.05) and end-tidal carbon dioxide (PetCO2, 39.5 ± 2.0 vs. 44.4 ± 3.5 mmHg, P < 0.05) increased with water immersion, along with middle (59 ± 6 vs. 64 ± 6 cm/s, P < 0.05) and posterior cerebral artery blood flow velocities (41 ± 9 vs. 44 ± 10 cm/s, P < 0.05). These changes were reversed when the tank was emptied. Water immersion is associated with hemodynamic and PetCO2 changes, which increase cerebral blood velocities in humans. This study provides an evidence base for future studies to examine the potential additive effect of exercise in water on improving cerebrovascular health.
authors.affiliation: School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia;
authors.forename: Howard H
authors.initials: HH
authors.lastname: Carter
authors.forename: Angela L
authors.initials: AL
authors.lastname: Spence
authors.forename: Christopher J A
authors.initials: CJ
authors.lastname: Pugh
authors.forename: Philip
authors.initials: P
authors.lastname: Ainslie
authors.forename: Louise H
authors.initials: LH
authors.lastname: Naylor
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Green
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D002245:Carbon Dioxide / Q000378:metabolism; D002302:Cardiac Output; D017536:Carotid Artery, Common / Q000502:physiology*; D002560:Cerebrovascular Circulation; D045853:Exhalation; D064368:Healthy Volunteers; D006439:Hemodynamics; D006801:Humans; D006874:Hydrostatic Pressure; D007101:Immersion; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology*; D020769:Posterior Cerebral Artery / Q000502:physiology*; D012039:Regional Blood Flow; D056152:Respiratory Rate; D014867:Water; D055815:Young Adult
chemical_list: D014867:Water; D002245:Carbon Dioxide
keywords: cardiovascular; cerebral blood flow; hemodynamics; water immersion