A short-term memory in the respiratory centres: statistical analysis

It has been observed previously that the successive values of depth and duration of respiratory cycles recorded in man are not independent random variable. The present study has been performed in order to test whether a serial dependence of the characteristics of the respiratory cycles results from an inherent property of the central respiratory oscillator. In the "isolated respiratory centre" preparation of the cat (spinalized, bivagotomized, curarized and artificially ventilated) the following respiratory data have been studied: the value of integrated phrenic discharge per breath (S), inspiratory duration (TI), expiratory duration (TE) and total cycle duration (T), at rest and during hypercapnia and hyperthermia. Each recording in a steady-state condition provided a set of four series of data; using statistical analysis of time series the following results were obtained: 1. In each series the successive values are not independent random variables. This suggests that a cycle may be considered as an event whose characteristics condition those of the following cycle. 2. TE is not independent of the preceding TI, and TI is not independent of the immediately preceding TE. However, this last relation cannot be asserted in hypercapnia and hyperthermia. 3. A positive correlation exists between S and TI. This result indicates that a simultaneous adjustment of S and TI, in terms of one another, does exist in absence of the vagal mechanism.