title: Suction against resistance: a new breathing technique to significantly improve the blood flow ratio of the superior and inferior vena cava.
abstract: OBJECTIVE
  Optimal contrast within the pulmonary artery is achieved by the maximum amount of contrast-enhanced blood flowing through the superior vena cava (SVC), while minimum amounts of non-contrasted blood should originate from the inferior vena cava (IVC). This study aims to clarify whether "suction against resistance" might optimise this ratio.
  
  
  METHODS
  Phase-contrast pulse sequences on a 1.5T MRI magnet were used for flow quantification (mean flow (mL/s), stroke volume (Vol) in the SVC and IVC in volunteers. Different breathing manoeuvers were analysed repeatedly: free breathing; inspiration; expiration; suction against resistance, and Valsalva. To standardise breathing commands, volunteers performed suction and Valsalva manoeuvers with an MR-compatible manometer.
  
  
  RESULTS
  Suction against resistance was associated with a significant drop of the IVC/SVC flow quotient (1.63 [range 1.3-2.0] p < 0.05 at -10 mmHg and 1.48 [1.1-1.9] p < 0.01 at -20 mmHg) corresponding to increased blood flow from SVC and diminished flow originating from the IVC. The remaining breathing commands (free breathing 2.2; inspiration 2.4; expiration 2.4; Valsalva 10 mmHg 2.3; Valsalva 20 mmHg 2.6; and Valsalva 30 mmHg 2.2) showed no differences (p > 0.05).
  
  
  CONCLUSIONS
  Suction against resistance caused a significant drop in the IVC/SVC quotient. Theoretically, this breathing manoeuver might significantly improve the enhancement characteristics of CT angiography.
  
  
  CONCLUSIONS
  Suction provokes reduction in blood flow in the inferior vena cava. Ratio between the inferior and superior vena cava blood flow diminished during suction. Manometer used during breathing standardises MR phase-contrast blood flow measurements.
authors.affiliation: Institute of Radiology and Nuclear Medicine, Clinical Research Unit of St. Anna Hospital Luzern, St. Anna Strasse 32, 6006, Luzern, Switzerland, Andreas.Gutzeit@hirslanden.ch.
authors.forename: Andreas
authors.initials: A
authors.lastname: Gutzeit
authors.forename: Justus E
authors.initials: JE
authors.lastname: Roos
authors.forename: Klaus
authors.initials: K
authors.lastname: Hergan
authors.forename: Constantin
authors.initials: C
authors.lastname: von Weymarn
authors.forename: Stephan
authors.initials: S
authors.lastname: Wälti
authors.forename: Carolin
authors.initials: C
authors.lastname: Reischauer
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Froehlich
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000502:physiology; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000502:physiology; D012119:Respiration; D013318:Stroke Volume / Q000502:physiology; D013396:Suction; D014636:Valsalva Maneuver / Q000502:physiology; D014682:Vena Cava, Inferior / Q000502:physiology*; D014683:Vena Cava, Superior / Q000502:physiology*
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