Spontaneous Baroreflex detection

Spontaneous baroreflex occurs to maintain blood pressure (BP) homeostasis. This reflex mechanism counteracts BP deviations from a reference set point by modulating heart rate (HR), peripheral vascular tone and other cardiovascular variables through autonomic paths.
A traditional approach to estimate the spontaneous baroreflex is between the Systolic Blood Pressure (SBP) and RR or Pulse Interval (PI) in either the time domain or the frequency domain.

The time domain approach relies on the identification of consecutive beats where progressive increases in SBP are followed by a progressive lengthening in PI or vice versa2 (also called the sequence method). The baroreflex sensitivity is then expressed in term of slope (in ms/mmHg) corresponding to the linear relationship between SBP and PI.

NOTOCORD®'s baroreflex sequence analyzer BRS10a detects spontaneous baroreflex using an automated sequence method. BRS10a only needs a SBP signal and discriminates type 1 (ascending) and type 2 (decreasing) baroreflex sequences. Slope and Baroreflex Effectiveness Index are extracted for both sequence types. It is also possible to set a synchronization delay between BP and PI if the baroreflex impairment induces a delayed response.

Example analysis

In the example below, baroreflex sequence is analyzed with BRS10a on a freely-moving mouse.

Baroreflex sequence analysis with BRS10a

Extracted, calculated and displayed data include systolic blood pressure (SBP), pulse interval (PI, slope, correlation coefficient between SBP and PI, number of sequences, Baroreflex Effectiveness Index (BEI).

BP and PI fluctuate at regular frequencies and the magnitude can be accurately quantified using power spectral analysis3. Frequency domain methods are therefore the most widely used approaches for investigating HR and BP variabilities in humans and conscious animals. In particular, baroreflex efficiency can be assessed using cross-spectral analysis between BP and PI or RR interval.

Our cross-spectrum analyzer CSA10a computes coherence, gain and phase spectra between two signals and on specific bandwidths. Baroreflex sensitivity is estimated using the gain in bandwidths known for representing sympatho-vagal contributions to oscillations of BP and HR. The phase allows to assess the delay between the stimulus (BP variability) and the response (PI or RR interval fluctuations) at specific frequencies.

Example analysis

In the example below, baroreflex is analyzed with CSA10a on a freely-moving mouse.

Cross-spectrum analysis for baroreflex studies with CSA10a

Extracted, calculated and displayed data include systolic blood pressure (SBP), pulse interval (PI), power spectral density (in dB), cross-spectrum coherence and maximal coherence, gain and maximal gain, phase and maximal phase in the frequency bands.

BRS10a Baroreflex sequence analyzer
CSA10a Cross-spectrum analyzer

 

Keywords

  • Spontaneous baroreflex
  • BP homeostasis
  • Sequence method
  • BEI
  • Spectral analysis
  • Coherence
  • Gain
  • Phase spectra