Broad-band neck suction in the assessment of the dynamics of the baroreflex-heart rate transfer in humans

In this study we applied broad-band neck suction (NES) stimulation to 11 healthy individuals and 10 chronic heart failure (CHF) patients, and performed a closed-loop estimation of the transfer magnitude characteristics (Gain) of the carotid sinus baroreceptor-RR interval (RRI) reflex using a non-parametric frequency domain approach. The suction pressure, obtained through a servo-controlled pump, was 0÷ -35 mmHg in the band 0÷0.35 Hz. We found a marked difference in the pattern of the Gain between the two groups. Particularly, normal subjects showed a band-pass behavior centered at 0.1±0.01 Hz, whereas CHF patients showed a marked low-pass response in the VLF band with a progressive attenuation in the LF and HF bands. The coherence between NES and RRI was typically <0.5, which would imply a low precision of gain point estimates.