Identification of open-loop transfer functions in closed-loop baroreflex system using random breathing in humans

Yingthawomsuk, T.; Kawada, Toru; Sato, Tatsuharu; Inagaki, Masumi; Sunagawa, Kenji; Cox, James F.; Shiavi, Richard; Diedrich, A.

doi:10.1109/cic.2002.1166809

Cited by 1 publication

(2 citation statements)

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“…We show that the temporal correlation between HF SBP and HF spike rate is low (r ϭ Ϫ0.22 Ϯ 0.04), meaning that vessels act as a neural low-pass filter (55), blocking transmission of the HF oscillations in MSNA to the arterial pressure. On the other hand, respiration has a strong mechanical influence on BP, evidenced by the high temporal correlation (r ϭ Ϫ0.79 Ϯ 0.04) between HF SBP and HF Resp at rest in the supine position.…”

Section: Hf Sbp -Hf Resp Relationmentioning

confidence: 99%

“…On the other hand, the HF component of BP (HF BP ) fluctuations is unaffected by ganglionic blockade (15,32,56) and remains after thoracic sympathectomy in transplant patients (27). Additionally, the neurovascular interface has been suggested to possess low-pass characteristics that effectively filter out the HF components of sympathetic activity (12,25,43,55). These findings indicate that the HF BP rhythm is not neurally mediated but, instead, largely the result of the mechanical interaction between BP and respiration or cardiac output (CO).…”

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confidence: 99%

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A simplified two-component model of blood pressure fluctuation

Brychta

Shiavi²,

Robertson³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

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September 29, 2006; doi:10.1152/ajpheart.00645.2006.-We propose a simple moving-average (MA) model that uses the low-frequency (LF) component of the peroneal muscle sympathetic nerve spike rate (LFspike rate) and the high-frequency (HF) component of respiration (HFResp) to describe the LF neurovascular fluctuations and the HF mechanical oscillations in systolic blood pressure (SBP), respectively. This method was validated by data from eight healthy subjects (23-47 yr old, 6 male, 2 female) during a graded tilt (15°increments every 5 min to a 60°angle). The LF component of SBP (LFSBP) had a strong baroreflex-mediated feedback correlation with LFspike rate (r ϭ Ϫ0.69 Ϯ 0.05) and also a strong feedforward relation to LFspike rate [r ϭ 0.58 Ϯ 0.03 with LFSBP delay () ϭ 5.625 Ϯ 0.15 s]. The HF components of spike rate (HFspike rate) and SBP (HFSBP) were not significantly correlated. Conversely, HFResp and HFSBP were highly correlated (r ϭ Ϫ0.79 Ϯ 0.04), whereas LFResp and LFSBP were significantly less correlated (r ϭ 0.45 Ϯ 0.08). The mean correlation coefficients between the measured and model-predicted LFSBP (r ϭ 0.74 Ϯ 0.03) in the supine position did not change significantly during tilt. The mean correlation between the measured and model-predicted HFSBP was 0.89 Ϯ 0.02 in the supine position. R 2 values for the regression analysis of the model-predicted and measured LF and HF powers indicate that 78 and 91% of the variability in power can be explained by the linear relation of LFspike rate to LFSBP and HFResp to HFSBP. We report a simple two-component model using neural sympathetic and mechanical respiratory inputs that can explain the majority of blood pressure fluctuation at rest and during orthostatic stress in healthy subjects. wavelet transform; blood pressure variability; Mayer waves; respiration; muscle sympathetic nerve activity VARIOUS RHYTHMIC OSCILLATIONS in human blood pressure (BP) have been proposed to reflect the action of different physiological mechanisms on BP regulation. For instance, it has been suggested that very low-frequency (VLF) trends (period Ͼ25 s, frequency Ͻ0.04 Hz) in BP represent the influence of hormonal regulation and thermoregulation and that high-frequency (HF, 0.15-0.4 Hz) fluctuations mark the effect of respiration on BP. A more hotly debated issue is the idea that low-frequency (LF, 0.04 -0.14 Hz) BP oscillations with a 10-s periodicity, generally referred to as Mayer waves, reflect sympathetically mediated vasomotor BP modulation. It has been proposed that the origin of these waves is a resonance phenomenon of the baroreflex pathway (12), and the LF power has been used as a marker of sympathetic activity (34,35,37), although this practice remains controversial (31, 48).Several lines of indirect evidence have been used to associate the oscillations in BP with oscillations in these other physiological rhythms. For example, physiological maneuvers have identified changes in the oscillatory patterns of sympathetic nerve activity and respiration that correspond to those in BP ...

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Section: Hf Sbp -Hf Resp Relationmentioning

confidence: 99%