title: Respiratory induced heart rate variability during slow mechanical ventilation : Marker to exclude brain death patients.
abstract: BACKGROUND
  Respiratory induced heart rate variability (rHRV) was analysed in mechanically ventilated patients during two levels of sedation and brain death. Our aim was to determine whether rHRV can distinguish between different levels of sedation and especially between brain death and sedated patients.
  
  
  METHODS
  In this study 30 critically ill and 23 brain death patients were included and four respiratory rates of 15, 12, 8 and 6 breaths per minute, each lasting 5 min were used. Two sedation levels, basal and deep, were performed in the critically ill patients. Heart rate and blood pressure changes induced by ventilation were subsequently detected and analysed.
  
  
  RESULTS
  Significant differences were found in rHRV and rHRV adjusted for tidal volume (rHRV/VT) between critically ill and brain death patients during slow breathing at 6 or 8 breaths per minute. The rHRV at 6 breaths per minute was below 15 ms in all brain death subjects except one. The rHRV/VT was lower than 25 ms/l at both 6 and 8 breaths per minute in all brain death patients and simultaneously at 75% of non-brain death patients was higher (specificity 1, sensitivity 0.24). Differences in rHRV and rHRV/VTs between basal and deep sedation were not significant.
  
  
  CONCLUSIONS
  The main clinical benefit of the study is the finding that rHRV and rHRV/VT during 6 and 8 breaths per minute can differentiate between critically ill and brain death patients. An rHRV/VT exceeding 25 ms/l reliably excludes brain death.
authors.affiliation: Institute of Scientific Instruments, The Czech Academy of Sciences, Brno, Czech Republic.|International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jurak
authors.affiliation: Institute of Scientific Instruments, The Czech Academy of Sciences, Brno, Czech Republic.|International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Halamek
authors.affiliation: Institute of Scientific Instruments, The Czech Academy of Sciences, Brno, Czech Republic.|International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic.
authors.forename: Vlastimil
authors.initials: V
authors.lastname: Vondra
authors.affiliation: Laboratory of Structural Biology and Proteomis, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences, Palackeho tr. 1946/1, 612 42, Brno, Czech Republic. kruzliakpeter@gmail.com.
authors.forename: Peter
authors.initials: P
authors.lastname: Kruzliak
authors.affiliation: Department of Anaesthesiology and Intensive Care, St. Anne's University Hospital and Masaryk University, Pekarska 53, 656 91, Brno, Czech Republic.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Sramek
authors.affiliation: Department of Anaesthesiology and Intensive Care, St. Anne's University Hospital and Masaryk University, Pekarska 53, 656 91, Brno, Czech Republic.
authors.forename: Ivan
authors.initials: I
authors.lastname: Cundrle
authors.affiliation: International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Leinveber
authors.affiliation: Department of Thoracic Surgery, Faculty of Medicine and Dentistry, Medical University of Silesia, Katowice, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Adamek
authors.affiliation: Department of Anaesthesiology and Intensive Care, St. Anne's University Hospital and Masaryk University, Pekarska 53, 656 91, Brno, Czech Republic.
authors.forename: Vaclav
authors.initials: V
authors.lastname: Zvonicek
mesh_terms: D015415:Biomarkers; D001926:Brain Death / Q000175:diagnosis* / Q000503:physiopathology*; D016638:Critical Illness; D003937:Diagnosis, Differential; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012121:Respiration, Artificial / Q000379:methods*; D015656:Respiratory Mechanics; D056152:Respiratory Rate; D012680:Sensitivity and Specificity; D013990:Tidal Volume
chemical_list: D015415:Biomarkers
keywords: Brain death; Critical illness; Heart rate variability; Mechanical ventilation; Respiratory rate variability; Sedation