Relationship between blood pressure, sleep K-complexes, and muscle sympathetic nerve activity in humans.
Stage 2 sleep is characterized by the EEG appearance of "K-complexes" and blood pressure oscillations. K-complexes may be directly related to blood pressure changes or they may reflect central sympathetic activation. We analyzed the temporal relationship among K-complexes, heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA) during sleep in eight healthy volunteers (3 men and 5 women, age 22-41 yr). Most K-complexes presented as single large complexes (56 +/- 20%), followed by single small complexes (15 +/- 14%) and as couplets or triplets (13 +/- 6%). Single large K-complexes were preceded by a baroreflex-mediated increase of MSNA in approximately one-half (55%) of the cases. Detailed analysis of HR, BP, and MSNA was possible in 63 (45%) large single K-complexes not disturbed by preceding baroreflex-related changes. Systolic and diastolic BP and MSNA increased significantly after single events (22.5 +/- 13, 5.2 +/- 2.1, and 6.5 +/- 3.0%). Mean sympathetic baroreflex latency was similar after the single large K-complexes compared with the mean value during stage 2 sleep (1,290 +/- 126 vs. 1,279 +/- 61 ms). The area under the burst was significantly increased after single large K-complexes (median 3.9 vs. 9.0 arbitrary units, P < 0.03). The results support the hypothesis that K-complexes express cortical activation leading to temporary facilitation of sympathetic outflow in a graded fashion. Their functional effects appear to be independent of baroreflex modulation of MSNA in approximately 50% of the cases.
Tank
Jens
J
Helios Klinikum Berlin, Clinical Research Center, Franz Volhard Clinic, Charité Campus-Buch, Humboldt Univ. Berlin, Wiltberg Str. 50, 13125 Berlin, Germany. tank@fvk-berlin.de
Diedrich
Andre
A
Hale
Nanette
N
Niaz
Faiz E
FE
Furlan
Raffaello
R
Robertson
Rose Marie
RM
Mosqueda-Garcia
Rogelio
R
D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D004562:Electrocardiography; D004569:Electroencephalography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation*; D011930:Reaction Time / Q000502:physiology; D012894:Sleep Stages / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*