The determination of cardioventilatory coupling from heart rate and ventilatory time series

Abstract

In 35 anaesthetised human subjects, we examined the effect of cardioventilatory coupling on R-R interval and ventilatory period time series. We observed that, in the presence of coupling: (a) ventilatory period fluctuated in a quantal manner, each quantal step corresponding to a multiple (or a little less) of the heart period; (b) heart period fluctuations, associated with respiratory sinus arrythmia, were identical for consecutive ventilatory periods. The regularity of heart period variation lead to geometric patterning of raw R-R time series, R-R consecutive difference time series, the phase portrait (R-R_n vs R-R_n+1) and the map of R-R interval variation (ΔR-R_n vs ΔR-R_n+1). These geometric features may be useful for the determination of cardioventilatory coupling from heart rate time series.