title: Valsalva maneuver unveils central baroreflex dysfunction with altered blood pressure control in persons with a history of mild traumatic brain injury.
abstract: BACKGROUND
  Patients with a history of mild TBI (post-mTBI-patients) have an unexplained increase in long-term mortality which might be related to central autonomic dysregulation (CAD). We investigated whether standardized baroreflex-loading, induced by a Valsalva maneuver (VM), unveils CAD in otherwise healthy post-mTBI-patients.
  
  
  METHODS
  In 29 healthy persons (31.3 ± 12.2 years; 9 women) and 25 post-mTBI-patients (35.0 ± 13.2 years, 7 women, 4-98 months post-injury), we monitored respiration (RESP), RR-intervals (RRI) and systolic blood pressure (BP) at rest and during three VMs. At rest, we calculated parameters of total autonomic modulation [RRI-coefficient-of-variation (CV), RRI-standard-deviation (RRI-SD), RRI-total-powers], of sympathetic [RRI-low-frequency-powers (LF), BP-LF-powers] and parasympathetic modulation [square-root-of-mean-squared-differences-of-successive-RRIs (RMSSD), RRI-high-frequency-powers (HF)], the index of sympatho-vagal balance (RRI LF/HF-ratios), and baroreflex sensitivity (BRS). We calculated Valsalva-ratios (VR) and times from lowest to highest RRIs after strain (VR-time) as indices of parasympathetic activation, intervals from highest systolic BP-values after strain-release to the time when systolic BP had fallen by 90 % of the differences between peak-phase-IV-BP and baseline-BP (90 %-BP-normalization-times), and velocities of BP-normalization (90 %-BP-normalization-velocities) as indices of sympathetic withdrawal. We compared patient- and control-parameters before and during VM (Mann-Whitney-U-tests or t-tests; significance: P < 0.05).
  
  
  RESULTS
  At rest, RRI-CVs, RRI-SDs, RRI-total-powers, RRI-LF-powers, BP-LF-powers, RRI-RMSSDs, RRI-HF-powers, and BRS were lower in patients than controls. During VMs, 90 %-BP-normalization-times were longer, and 90 %-BP-normalization-velocities were lower in patients than controls (P < 0.05).
  
  
  CONCLUSIONS
  Reduced autonomic modulation at rest and delayed BP-decrease after VM-induced baroreflex-loading indicate subtle CAD with altered baroreflex adjustment to challenge. More severe autonomic challenge might trigger more prominent cardiovascular dysregulation and thus contribute to increased mortality risk in post-mTBI-patients.
authors.affiliation: Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany. max.hilz@uk-erlangen.de.
authors.forename: Max J
authors.initials: MJ
authors.lastname: Hilz
authors.affiliation: Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany.
authors.forename: Mao
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Koehn
authors.affiliation: Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany.
authors.forename: Ruihao
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Ammon
authors.affiliation: Department of Rehabilitation Medicine, New York University School of Medicine, 240 East 38th Street, New York, NY, 10016, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Flanagan
authors.affiliation: Department of Psychiatry and Psychotherapy, Paracelsus Medical University Nuremberg, Prof.-Ernst-Nathan-Strasse 1, 90419, Nuremberg, Germany.
authors.forename: Katharina M
authors.initials: KM
authors.lastname: Hösl
mesh_terms: D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology*; D017704:Baroreflex; D001794:Blood Pressure; D001924:Brain Concussion / Q000503:physiopathology*; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D012119:Respiration; D014636:Valsalva Maneuver
keywords: Baroreflex dysfunction; Blood pressure overshoot; Central autonomic network; Mild traumatic brain injury; Sympathetic dysregulation; Valsalva maneuver