Fig. 4.

Simulations of the effect of phase-dependent barostimulation on the phrenic (PN) and sympathetic (SN) nerve outputs. Stimulus was applied during inspiration (A1), post-inspiration (A2) and late expiration (A3). In A1, the stimulus applied during inspiration had no effect on respiratory phase durations; SN activity during stimulation is attenuated due to baroreflex. In (A2, A3), the stimuli during expiration prolonged expiration, slightly when applied in post-inspiration or substantially, in late expiration. (B) After removal of the pontine compartment in the model, the applied stimulation does not prolong the expiratory period, but shorten the “apneustic” PN bursts if applied during inspiration. SN activity respiratory modulation is abolished. Traces are as Fig. 1. The phases of barostimulation are chosen approximately the same as in experimental examples in Fig. 1.