Mechanism of sleep-induced periodic breathing in convalescing stroke patients and healthy elderly subjects.

Cerebral vascular ischemic strokes are known to precipitate Cheyne-Stokes periodic breathing. Interestingly, Cheyne-Stokes-like breathing during sleep may be associated with obstructive sleep apnea (OSA) in some individuals. Therefore, it was reasoned that stroke patients with periodic breathing in sleep would be susceptible to OSA. Because oscillations in upper airway resistance can occur as a component of sleep-induced periodic breathing, we hypothesized that stroke patients with sleep-induced periodic breathing would have oscillations in upper airway resistance. These oscillations in resistance would be expected to contribute to OSA. We studied stroke patients with sleep-induced periodic breathing and control subjects to evaluate the relationship between upper airway resistance and ventilation in periodic breathing in sleep. Ventilation and upper airway resistance were measured in presleep wakefulness and in stage 2 NREM sleep. Mean tidal volume, minute ventilation, respiratory cycle timing variables, and upper airway resistance were not different between stroke and control subjects, either awake or asleep. Upper airway resistance increased and ventilation volume decreased from wakefulness to sleep in both groups. In an equivalent number of subjects from each group, reciprocal patterned oscillations in tidal volume and upper airway resistance were present at a 5 to 12.5 breath frequency during sleep. As upper airway resistance increased, tidal volume decreased. Stroke patients had wider fluctuations in upper airway resistance than control subjects, likely contributing to the higher number of sleep-disordered breathing events observed in the stroke patients.