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.