title: The response of the vena cava to abdominal breathing.
abstract: BACKGROUND
  Recently, abdominal-breathing or diaphragmatic-breathing methods have increased in popularity. Little is known how abdominal breathing affects the circulatory system. This study was designed to determine the impact of the respiratory pattern on central venous flow using echocardiography.
  
  
  METHODS
  The superior vena cava (SVC) and inferior vena cava (IVC) were observed in people who had practiced abdominal breathing for at least 2 years, while they were breathing in three different techniques: slow respiration, slow respiration with inspiratory pause, or normal respiration. In addition, the observation during normal respiration was compared with that of a control group.
  
  
  RESULTS
  The abdominal-breathing group consisted of 20 people with mean duration of training of 9.6 years. The respiratory collapsibility index of IVC during slow respiration with inspiratory pause was 62±19% compared with 48±19% during normal respiration (p=0.012) in the abdominal-breathing group. The abdominal-breathing group had a higher IVC collapsibility index compared to the control group during normal respiration (48±19% versus 26±12%, p<0.001), assuming a similar respiratory rate of about 10/min. Neither the size nor the minute flow of SVC differed among breathing patterns or between groups.
  
  
  CONCLUSIONS
  The IVC of people who practice abdominal breathing has a greater degree of collapse than those of normal people, suggesting that abdominal-breathing exercise can positively affect venous return via IVC. For those who practice abdominal breathing, the collapsibility of the IVC is the best during slow respiration with inspiratory pause. The SVC did not seem to be affected by abdominal-breathing training.
authors.affiliation: Division of Cardiology, Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Kyeongmin
authors.initials: K
authors.lastname: Byeon
authors.forename: Jin-Oh
authors.initials: JO
authors.lastname: Choi
authors.forename: Jeong Hoon
authors.initials: JH
authors.lastname: Yang
authors.forename: Jidong
authors.initials: J
authors.lastname: Sung
authors.forename: Seung Woo
authors.initials: SW
authors.lastname: Park
authors.forename: Jae K
authors.initials: JK
authors.lastname: Oh
authors.forename: Kyung Pyo
authors.initials: KP
authors.lastname: Hong
mesh_terms: D000005:Abdomen; D000328:Adult; D001783:Blood Flow Velocity; D001945:Breathing Exercises; D003964:Diaphragm; D004452:Echocardiography / Q000379:methods; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D012119:Respiration; D056152:Respiratory Rate; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging / Q000502:physiology*; D014683:Vena Cava, Superior / Q000000981:diagnostic imaging / Q000502:physiology*