Cardioventilatory coupling in the anaesthetised rabbit, rat and guinea-pig

Cardioventilatory coupling is a temporal coherence of respiratory and cardi ac rhythms, seen in humans at rest, and during sleep and anaesthesia. In th is study we compared the cardioventilatory coupling of anaesthetised rabbit s, rats and guinea-pigs. Breathing two successive anaesthetic concentration s (1 or 2% isoflurane) we compared the effect of anaesthetic depth and spec ies on (1) heart rate, (3) heart rate variability, (3) ventilatory rate (f) , (4) ventilatory variability, (5) ratio HR/f, (6) degree of coupling (Shan non entropy of the distribution of intervals between inspiration and the pr eceding electrocardiographic R wave - the RI interval) and (7) coupling pat tern, classified into four sub-patterns (I-IV) based upon inspection of the RI interval time series. Rabbits exhibited significantly less ventilatory variability and coupling than rats or guinea-pigs. The sub-pattern of coupl ing also differed between the three species. Rabbits showed coupling only w hen HR and f were close to integer ratios whereas other species coupled at non-integer ratios. Ventilatory variability in the rat and guinea-pig diffe red according to the pattern of coupling observed. Of the three species stu died, the rat and guinea-pig demonstrated coupling most similar to that of anaesthetised human subjects. Anaesthetic concentration did not influence t he pattern or degree of coupling.