Chemical instability, state instability and arousals in the pathogenesis of Periodic Breathing in heart failure patients

Periodic Breathing (PB, cyclic waxing and waning of tidal volume) is very common in heart failure patients. It is commonly thought that PB is caused by an instability in the closed-loop chemical control of ventilation. Some investigators, however, have suggested that it may also result from fluctuations in sleep/wake state, namely state instability. The aim of this study was i) to set up a methodology for semi-automated state fluctuation analysis and ii) to assess whether state instability is a necessary condition for the development of PB. We carried out daytime and nighttime standard polysomnographic recordings in 9 patients. During daytime, 86% of state transitions were synchronous with an apneic event. Synchronous state and ventilatory changes were also observed during nighttime, but during the deeper stages of sleep PB occurred without concurrent state transitions. We conclude that state instability is not necessary for the development of PB.