title: Regularity of cardiac rhythm as a marker of sleepiness in sleep disordered breathing.
abstract: OBJECTIVE
  The present study aimed to analyse the autonomic nervous system activity using heart rate variability (HRV) to detect sleep disordered breathing (SDB) patients with and without excessive daytime sleepiness (EDS) before sleep onset.
  
  
  METHODS
  Two groups of 20 patients with different levels of daytime sleepiness -sleepy group, SG; alert group, AG- were selected consecutively from a Maintenance of Wakefulness Test (MWT) and Multiple Sleep Latency Test (MSLT) research protocol. The first waking 3-min window of RR signal at the beginning of each nap test was considered for the analysis. HRV was measured with traditional linear measures and with time-frequency representations. Non-linear measures -correntropy, CORR; auto-mutual-information function, AMIF- were used to describe the regularity of the RR rhythm. Statistical analysis was performed with non-parametric tests.
  
  
  RESULTS
  Non-linear dynamic of the RR rhythm was more regular in the SG than in the AG during the first wakefulness period of MSLT, but not during MWT. AMIF (in high-frequency and in Total band) and CORR (in Total band) yielded sensitivity > 70%, specificity >75% and an area under ROC curve > 0.80 in classifying SG and AG patients.
  
  
  CONCLUSIONS
  The regularity of the RR rhythm measured at the beginning of the MSLT could be used to detect SDB patients with and without EDS before the appearance of sleep onset.
authors: Multidisciplinary Unit of Sleep Disorders, Hospital Clinic, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
authors: Marc
authors: M
authors: Guaita
authors: Dept. ESAII, Centre for Biomedical Engineering Research, BarcelonaTech, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
authors: Umberto
authors: U
authors: Melia
authors: Dept. ESAII, Centre for Biomedical Engineering Research, BarcelonaTech, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
authors: Montserrat
authors: M
authors: Vallverdú
authors: Dept. ESAII, Centre for Biomedical Engineering Research, BarcelonaTech, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
authors: Pere
authors: P
authors: Caminal
authors: Multidisciplinary Unit of Sleep Disorders, Hospital Clinic, Barcelona, Spain; Department of Otorhinolaryngology, Hospital Clinic, Barcelona, Spain; Ciber Enfermedades Respiratorias (CIBERES), Madrid, Spain; Medical School, University of Barcelona, Barcelona, Spain.
authors: Isabel
authors: I
authors: Vilaseca
authors: Multidisciplinary Unit of Sleep Disorders, Hospital Clinic, Barcelona, Spain; Ciber Enfermedades Respiratorias (CIBERES), Madrid, Spain; Medical School, University of Barcelona, Barcelona, Spain; Department of Pneumology, Hospital Clinic, Barcelona, Spain.
authors: Josep M
authors: JM
authors: Montserrat
authors: Multidisciplinary Unit of Sleep Disorders, Hospital Clinic, Barcelona, Spain; Department of Neurology, Hospital Clinic, Barcelona, Spain; Ciber Enfermedades Neurológicas (CIBERNED), Barcelona, Spain.
authors: Carles
authors: C
authors: Gaig
authors: Multidisciplinary Unit of Sleep Disorders, Hospital Clinic, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Medical School, University of Barcelona, Barcelona, Spain; Department of Psychiatry, Hospital Clinic, Barcelona, Spain.
authors: Manel
authors: M
authors: Salamero
authors: Multidisciplinary Unit of Sleep Disorders, Hospital Clinic, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Medical School, University of Barcelona, Barcelona, Spain; Department of Neurology, Hospital Clinic, Barcelona, Spain; Ciber Enfermedades Neurológicas (CIBERNED), Barcelona, Spain.
authors: Joan
authors: J
authors: Santamaria
mesh_terms: D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D017286:Polysomnography; D012890:Sleep / Q000502:physiology; D012891:Sleep Apnea Syndromes / Q000175:diagnosis*; D012894:Sleep Stages; D014851:Wakefulness / Q000502:physiology