title: Long-term CPAP treatment partially improves the link between cardiac vagal influence and delta sleep.
abstract: BACKGROUND
  Continuous positive airway pressure (CPAP) treatment improves the risk of cardiovascular events in patients suffering from severe sleep apnea-hypopnea syndrome (SAHS) but its effect on the link between delta power band that is related to deep sleep and the relative cardiac vagal component of heart rate variability, HF(nu) of HRV, is unknown. Therefore, we tested the hypothesis that CPAP restores the link between cardiac autonomic activity and delta sleep across the night.
  
  
  METHODS
  Eight patients suffering from severe SAHS before and after 4 ± 3 years of nasal CPAP treatment were matched with fourteen healthy controls. Sleep EEG and ECG were analysed to obtain spectral sleep and HRV components. Coherence analysis was applied between HF(nu) and delta power bands across the first three sleep cycles.
  
  
  RESULTS
  Sleep characteristics and spectral HRV components were similar between untreated patients, treated patients and controls, with the exception of decreased Rapid Eye Movement duration in untreated patients. Coherence and gain values between HF(nu) and delta EEG variability were decreased in untreated patients while gain values normalized in treated patients. In patients before and during long-term CPAP treatment, phase shift and delay between modifications in HF(nu) and delta EEG variability did not differ from controls but were not different from zero. In healthy men, changes in cardiac vagal activity appeared 9 ± 7 minutes before modifications in delta sleep.
  
  
  CONCLUSIONS
  Long-term nasal CPAP restored, in severe SAHS, the information between cardiovascular and sleep brainstem structures by increasing gain, but did not improve its tightness or time shift.
authors.affiliation: Sleep Laboratory and Laboratory of Psychiatric Research, Department of Psychiatry, Erasme Academic Hospital - ULB, Brussels, Belgium. fabrice.jurysta@erasme.ulb.ac.be
authors.forename: Fabrice
authors.initials: F
authors.lastname: Jurysta
authors.forename: Chantal
authors.initials: C
authors.lastname: Kempenaers
authors.forename: Jean-Pol
authors.initials: JP
authors.lastname: Lanquart
authors.forename: André
authors.initials: A
authors.lastname: Noseda
authors.forename: Philippe
authors.initials: P
authors.lastname: van de Borne
authors.forename: Paul
authors.initials: P
authors.lastname: Linkowski
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D016022:Case-Control Studies; D045422:Continuous Positive Airway Pressure; D003700:Delta Rhythm / Q000502:physiology*; D004562:Electrocardiography; D004569:Electroencephalography; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008134:Long-Term Care; D008297:Male; D008875:Middle Aged; D012891:Sleep Apnea Syndromes / Q000503:physiopathology / Q000628:therapy*; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology