title: Blood pooling in extrathoracic veins after glossopharyngeal insufflation.
abstract: OBJECTIVE
  Trained breath-hold divers hyperinflate their lungs by glossopharyngeal insufflation (GPI) to prolong submersion time and withstand lung collapse at depths. Pulmonary hyperinflation leads to profound hemodynamic changes.
  
  
  METHODS
  Thirteen divers performed preparatory breath-holds followed by apnea with GPI. Filling of extrathoracic veins was determined by ultrasound and magnetic resonance imaging and peripheral extravasation of fluid was assessed by electrical impedance. Femoral vein diameter was measured by ultrasound throughout the easy-going and struggle phase of apnea with GPI in eight divers in a sub-study.
  
  
  RESULTS
  After GPI, pulmonary volume increased by 0.8 ± 0.6 L above total lung capacity. The diameter of the superior caval (by 36 ± 17%) and intrathoracic part of the inferior caval vein decreased (by 21 ± 16%), while the diameters of the internal jugular (by 53 ± 34%), hepatic (by 28 ± 40%), abdominal part of the inferior caval (by 28 ± 28%), and femoral veins (by 65 ± 50%) all increased (P < 0.05). Blood volume of the internal jugular, the hepatic, the abdominal part of the inferior caval vein, and the combined common iliac and femoral veins increased by 145 ± 115, 80 ± 88, 61 ± 60, and 183 ± 197%, respectively. In the sub-study, femoral vein diameter increased by 44 ± 33% in the easy-going phase of apnea with GPI, subsequently decreasing by 20 ± 16% during the struggle phase. Electrical impedance remained unchanged over the thigh and forearm, thus excluding peripheral fluid extravasation.
  
  
  CONCLUSIONS
  GPI leads to heart and pulmonary vessel compression, resulting in redistribution of blood to extrathoracic capacitance veins proximal to venous valves. This is partially reversed by the onset of involuntary breathing movements.
authors.affiliation: Department of Integrative Physiology, University of Split School of Medicine, Šoltanska 2, 21000, Split, Croatia.
authors.forename: Tanja
authors.initials: T
authors.lastname: Mijacika
authors.affiliation: Department of Cardiology, Copenhagen University Hospital, Hvidovre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Daria
authors.initials: D
authors.lastname: Frestad
authors.affiliation: The Cardiac MRI Group, Department of Cardiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Kasper
authors.initials: K
authors.lastname: Kyhl
authors.affiliation: Department of Integrative Physiology, University of Split School of Medicine, Šoltanska 2, 21000, Split, Croatia.|Department of Physiology, Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia.
authors.forename: Otto
authors.initials: O
authors.lastname: Barak
authors.affiliation: University of Zagreb School of Kinesiology, Zagreb, Croatia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Drvis
authors.affiliation: Department of Anesthesiology, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.affiliation: Department of Radiology, University Hospital Center, Split, Croatia.
authors.forename: Ante
authors.initials: A
authors.lastname: Buca
authors.affiliation: Department of Integrative Physiology, University of Split School of Medicine, Šoltanska 2, 21000, Split, Croatia.
authors.forename: Ante
authors.initials: A
authors.lastname: Obad
authors.affiliation: Department of Integrative Physiology, University of Split School of Medicine, Šoltanska 2, 21000, Split, Croatia. zeljko.dujic@mefst.hr.
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Dujic
authors.affiliation: Department of Cardiology, Copenhagen University Hospital, Herlev, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Per Lav
authors.initials: PL
authors.lastname: Madsen
mesh_terms: D000328:Adult; D062485:Breath Holding; D004242:Diving / Q000502:physiology; D005260:Female; D005268:Femoral Vein / Q000000981:diagnostic imaging / Q000502:physiology; D006439:Hemodynamics; D006801:Humans; D008168:Lung / Q000098:blood supply / Q000000981:diagnostic imaging / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D011897:Random Allocation; D014684:Venae Cavae / Q000000981:diagnostic imaging / Q000502:physiology
keywords: Blood shift; Breath-hold diving; Magnetic resonance imaging; Pulmonary hyperinflation; Ultrasound