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BMC Neurol. 2016 May 4;16:61. doi: 10.1186/s12883-016-0584-5.

Valsalva maneuver unveils central baroreflex dysfunction with altered blood pressure control in persons with a history of mild traumatic brain injury.

Author information

1
Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany. max.hilz@uk-erlangen.de.
2
Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054, Erlangen, Germany.
3
Department of Rehabilitation Medicine, New York University School of Medicine, 240 East 38th Street, New York, NY, 10016, USA.
4
Department of Psychiatry and Psychotherapy, Paracelsus Medical University Nuremberg, Prof.-Ernst-Nathan-Strasse 1, 90419, Nuremberg, Germany.

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.

KEYWORDS:

Baroreflex dysfunction; Blood pressure overshoot; Central autonomic network; Mild traumatic brain injury; Sympathetic dysregulation; Valsalva maneuver

PMID:
27146718
PMCID:
PMC4857428
DOI:
10.1186/s12883-016-0584-5
[Indexed for MEDLINE]
Free PMC Article
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