Respiratory sinus arrhythmia: A phenomenon improving pulmonary gas exchange and circulatory efficiency

Junichiro Hayano, Fumihiko Yasuma, Akiyoshi Okada, Seiji Mukai, Takao Fujinami

Research output: Contribution to journalArticlepeer-review

253 Citations (Scopus)


Background: The primary mechanisms of respiratory sinus arrhythmia (RSA) are understood to be the modulation of cardiac vagal efferent activity by the central respiratory drive and the lung inflation reflex, and the degree of RSA increases with cardiac vagal activity. However, it is unclear whether RSA serves an active physiological role or merely reflects a passive cardiovascular response to respiratory input. We hypothesized that RSA benefits pulmonary gas exchange by matching perfusion to ventilation within each respiratory cycle. Methods and Results: In seven anesthetized dogs, a model simulating RSA was made. After elimination of endogenous autonomic activities, respiration-linked heartbeat fluctuations were generated by electrical stimulation of the right cervical vagus during negative pressure ventilation produced by phrenic nerve stimulation (diaphragm pacing). The vagal stimulation was performed in three conditions phasic stimulation expiration (artificial RSA) and during inspiration (inverse RSA) and constant stimulation (control) causing the same number of heartbeats per minute as the phasic stimulation. Although trial volume, cardiac output, and arterial blood pressure were unchanged, artificial RSA decreased the ratio of physiological dead space to tidal volume (VD/VT) and the fraction of intrapulmonary shunt (Q(sp)/Q(t)) by 10% and 51%, respectively, and increasing O2 consumption by 4% compared with control. Conversely, reverse RSA increased VD/VT and Q(sp)/Q(t) by 14% and 64%, respectively, and decreased O2 consumption by 14%. Conclusions: These results support our hypothesis that RSA benefits the pulmonary gas exchange and may improve the energy efficiency of pulmonary circulation by 'saving heartbeats'.

Original languageEnglish
Pages (from-to)842-847
Number of pages6
Issue number4
Publication statusPublished - 1996
Externally publishedYes


  • heart rate
  • nervous system, autonomic
  • oxygen
  • respiration
  • vagus nerve

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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