Tilt-evoked, breathing-driven blood pressure oscillations: Independence from baroreflex-sympathoneural function

Abstract

Abstract Purpose Orthostasis often increases blood pressure (BP) variability. Low-frequency (LF) BP oscillations (Mayer waves) are related to baroreflex-mediated alterations in sympathetic cardiovascular outflow. Effects of orthostasis on high frequency (HF) BP oscillations at the periodicity of respiration (Traube-Hering waves) have received relatively little research attention. A previously reported patient with post-neurosurgical orthostatic hypotension (OH) and baroreflex-sympathoneural failure had large tilt-evoked, breathing-driven BP oscillations, suggesting such oscillations can occur independently of baroreflex-sympathoneural modulation. We therefore assessed effects of orthostasis on BP variability in the frequency domain in patient cohorts with or without OH. Methods Power spectral analysis of systolic BP variability was conducted on physiological recordings from a total of 73 research participants, 42 with neurogenic OH (nOH) (13 pure autonomic failure, 14 Parkinson’s disease (PD) with OH, 12 parkinsonian multiple system atrophy, 3 status post brainstem neurosurgery) and 31 without OH (No OH group of 16 healthy volunteers and 15 PD patients), before, during, and after 5’ of head-up tilt at 90 degrees from horizontal. The data were log transformed for statistical testing. Results Across all subjects, head-up tilting increased HF power of systolic BP variability (p = 0.0008), without a difference between the nOH and No OH groups. LF power during tilt was higher in the No OH than nOH groups (p = 0.0094), with the extent of increase in LF power greater in the No OH group (p = 0.046). Conclusion Head-up tilt can increase HF power of BP variability even in the setting of baroreflex-sympathoneural failure. nOH is associated with attenuated Mayer waves.