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Cats subjected to common carotid artery occlusion and hemorrhage developed a waxing and waning of respiratory amplitude recurring with a period of 24 s (range 10-60). Occasionally the waning phase terminated with apnea. This respiratory pattern, reminiscent of "periodic" breathing, was usually associated with an oscillation of sympathetic neural activity, and of systemic arterial pressure, of the same period. A similar pattern of modulation of phrenic nerve activity was observed during neuromuscular block and artificial ventilation and when, at the same time, the associated systemic arterial pressure oscillation was eliminated. These findings suggest that this breathing pattern is not the result of an analogous pattern in the discharge of gas tension-sensitive and/or blood flow- and pressure-sensitive receptors that is fed back to the central nervous system (CNS). Hence the pattern must be generated within the CNS with no need of rhythmic sensory information. The pattern can be accounted for by the assumption that the central respiratory drive potentials are riding on top of a slow oscillation of phrenic motoneuron membrane potential with a 24-s period.
Preiss et al. (Sat,) studied this question.