Synchronization between cardiac and respiratory rhythms in healthy subjects and patients.

Synchronization between cardiac and respiratory rhythms may be important for oxygen transport to tissues. The aim of this study was to investigate the synchronization between cardiac and respiratory rhythms. We evaluated the rhythms in 12 healthy males and 24 patients. The incidence rates of heart beats were obtained in each time interval relative to the initiation time point of inspiration. A simple index of timing variability of heart beats was defined. When the variability is large, the link between cardiac and respiratory rhythms was considered to be strong. The variability value of patients with disorder in the autonomic nervous system was larger than that of healthy subjects (p < 0.05). The variability of patients on controlled ventilation was lower than that of healthy subjects (p < 0.01), whereas the value on cardiac pacemaker did not differ from healthy subjects. In conclusion, the synchronization between cardiac and respiratory rhythms was confirmed, and it is suggested that the synchronization is enhanced when feed-back signals from respiratory movement to respiratory center were decreased.