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S R Seydnejad

Publications and source records attributed to S R Seydnejad.

5 recordsLinked to original sources
PubMed2001

Time-varying threshold integral pulse frequency modulation.

Several methods have been proposed so far for the analysis of the integral pulse frequency modulation (IPFM) model and detecting its corresponding physiological information. Most of these methods rely on the low-pass filtering method to extract the modulating signal of the model. In this paper, we present an entirely new approach based on vector space theory. The new method is developed for a more comprehensive form of the IPFM model, namely the time-varying threshold integral pulse frequency modulation (TVTIPFM) model. The new method decomposes the driving signals of the TVTIPFM model into a series of orthogonal basis functions and constructs a matrix identity through which the input signals can be obtained by a parametric solution. As a particular case, we apply this method to R-R intervals of the SA node to discriminate between its autonomic nervous modulation and the stretch induced effect.

Heart Rate↗
PubMed2000

Transient phase locking patterns among respiration, heart rate and blood pressure during cardiorespiratory synchronisation in humans.

The interactions between respiration, heart rate and blood pressure variability (HRV, BPV), are considered to be of paramount importance for the study of the functional organisation of the autonomic nervous system (ANS). The aim of the reported study is to detect and classify the intermittent phase locking (PL) phenomena between respiration, HRV and BPV during cardiorespiratory synchronisation experiments, by using the following time-domain techniques: Poincaré maps, recurrence plots, time-space separation plots and frequency tracking locus. The experimental protocol consists of three stages, with normal subjects in paced breathing at 15, 12 and 8 breaths min-1. Transient phenomena of coordination between respiration and the major rhythms of HRV and BPV (low and high frequency, LF and HF) have been detected and classified: no interaction between LF and HF rhythms at 15 breaths min-1; short time intervals of stable 1:2 frequency and phase synchronisation during the 12 breaths min-1 stage; 1:1 PL during the 8 breaths min-1 stage. 1:1 and 1:2 PL phenomena occurred when the respiration frequency was quite close to the LF frequency or when it was about twice the LF frequency, respectively. The complex organisation of the ANS seems to provoke transient rather than permanent PL phenomena between the co-ordinating components of respiration and cardiovascular variability series.

Adult↗
PubMed1999

Impact of periodic breathing on V(O2) and V(CO2): a quantitative approach by Fourier analysis.

Oscillations in oxygen uptake (V(O2)) and carbon dioxide production (V(CO2)) in patients with chronic heart failure differ in amplitude and phase from the oscillations in ventilation (periodic breathing, PB), leading some to doubt whether they result from PB. We applied Fourier transforms to a pulmonary gas exchange model to quantify the effects of fluctuations in alveolar ventilation (V(A)). We found that PB causes oscillations in V(O2) and V(CO2), but their amplitude and phase are complex, and vary with workload. At low workloads, the relative oscillations in V(O2) and V(CO2) closely mirror the relative oscillations in V(A). But at high workloads, the metabolic oscillations are attenuated (V(O2) most severely), and the V(O2) peaks precede the ventilatory peaks significantly. This study also explains why normal controls simulating PB at higher workloads fail to reproduce the V(O2) and V(CO2) oscillations seen in spontaneous PB of heart failure.

Carbon Dioxide↗
PubMed1997

Real-time heart rate variability extraction using the Kaiser window.

A new method for real-time heart rate variability (HRV) detection from the R-wave signal, based on the integral pulse frequency modulation (IPFM) model and its similarity to pulse position modulation, is presented. The proposed method exerts low-pass filtering with a Kaiser window. It can also be used for off-line HRV analysis in both the time and frequency domains. Real-time bandpass filtering as a new HRV investigation method and as a by-product of the proposed algorithm is also introduced. Furthermore, the discrete time domain version of the French-Holden algorithm is developed, and it is thoroughly proved that low-pass filtering is an ideal method for detection of HRV.

Algorithms↗