The influence of low, normal and high Pa(O2) on the respiratory effects of Pa(CO2) oscillations in anaesthetised cats.

The present study examines the influence of oxygen tension on the recurrent tidal volume changes caused by oscillations in arterial P(CO2). The oscillations have a period equal to two respiratory cycles, and are produced by giving alternately CO2 -enriched and CO2 -free gas mixtures. The results show alternation of the tidal volume with the same incidence (is greater than 50%) at low, normal and high oxygen tensions. However, the magnitudes of the breath-by-breath changes are significantly greater at low oxygen tension than at normal oxygen tension. Under high oxygen tension breath-by-breath tidal volume changes are indistinguishable from those at normal oxygen tension.