title: Respiratory sinus arrhythmia: why does the heartbeat synchronize with respiratory rhythm?
abstract: Respiratory sinus arrhythmia (RSA) is heart rate variability in synchrony with respiration, by which the R-R interval on an ECG is shortened during inspiration and prolonged during expiration. Although RSA has been used as an index of cardiac vagal function, it is also a physiologic phenomenon reflecting respiratory-circulatory interactions universally observed among vertebrates. Previous studies have shown that the efficiency of pulmonary gas exchange is improved by RSA, suggesting that RSA may play an active physiologic role. The matched timing of alveolar ventilation and its perfusion with RSA within each respiratory cycle could save energy expenditure by suppressing unnecessary heartbeats during expiration and ineffective ventilation during the ebb of perfusion. Furthermore, evidence has accumulated of a possible dissociation between RSA and vagal control of that heart rate, suggesting differential controls between the respiratory modulation of cardiac vagal outflow and cardiac vagal tone. RSA or heart rate variability in synchrony with respiration is a biological phenomenon, which may have a positive influence on gas exchange at the level of the lung via efficient ventilation/perfusion matching.
authors.affiliation: Department of Internal Medicine, Suzuka National Hospital, 3-2-1 Kasado, Suzuka 513-8501, Japan. f-yasuma@mtb.biglobe.ne.jp
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Yasuma
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Hayano
mesh_terms: D000328:Adult; D000368:Aged; D001146:Arrhythmia, Sinus / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange; D012119:Respiration; D015656:Respiratory Mechanics; D012143:Respiratory Physiological Phenomena; D012680:Sensitivity and Specificity; D014630:Vagus Nerve / Q000502:physiology*