Cardiovascular changes associated with spontaneous and evoked K-complexes

This study examines the relationship between blood pressure and spontaneous and sound-evoked K-complexes (KCs) during stage 2 NREM sleep, in 8 volunte ers studied by intraarterial blood pressure (BP) monitoring and polysomnogr aphy. A robust oscillation of blood pressure with a period of 16-30 s (Maye r waves) was seen in all subjects. Spontaneous KCs predominantly occurred d uring a drop (downward slope) in blood pressure. Randomly administered soun d stimuli were more likely to evoke a KC if the stimulus was given during a downward slope of BP. During the last 20 s prior to a sound-evoked KC, the mean drop in systolic BP was 0.3 mmHg, and evoked and spontaneous K-comple xes were preceded by a mean drop in BP of 1.9 and 2.7 mmHg, respectively. F inally, K-complexes, either spontaneous or evoked, during the first 6 s, in duced a rise in systolic BP. The results indicate that if the BP falls duri ng stage 2 NREM sleep, there is a greater likelihood that an external stimu lus will evoke a K-complex and that spontaneous K-complexes may occur more frequently as well. Spontaneous and evoked K-complexes may play a role in t he control of BP during NREM sleep. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.