3 research outputs found
Differentiation of skin incision and laparoscopic trocar insertion via quantifying transient bradycardia measured by electrocardiogram
Background. Most surgical procedures involve structures deeper than the skin.
However, the difference in surgical noxious stimulation between skin incision
and laparoscopic trocar insertion is unknown. By analyzing instantaneous heart
rate (IHR) calculated from the electrocardiogram, in particular the transient
bradycardia in response to surgical stimuli, this study investigates surgical
noxious stimuli arising from skin incision and laparoscopic trocar insertion.
Methods. Thirty-five patients undergoing laparoscopic cholecystectomy were
enrolled in this prospective observational study. Sequential surgical steps
including umbilical skin incision (11 mm), umbilical trocar insertion (11 mm),
xiphoid skin incision (5 mm), xiphoid trocar insertion (5 mm), subcostal skin
incision (3 mm), and subcostal trocar insertion (3 mm) were investigated. IHR
was derived from electrocardiography and calculated by the modern time-varying
power spectrum. Similar to the classical heart rate variability analysis, the
time-varying low frequency power (tvLF), time-varying high frequency power
(tvHF), and tvLF-to-tvHF ratio (tvLHR) were calculated. Prediction probability
(PK) analysis and global pointwise F-test were used to compare the performance
between indices and the heart rate readings from the patient monitor. Results.
Analysis of IHR showed that surgical stimulus elicits a transient bradycardia,
followed by the increase of heart rate. Transient bradycardia is more
significant in trocar insertion than skin incision. The IHR change quantifies
differential responses to different surgical intensity. Serial PK analysis
demonstrates de-sensitization in skin incision, but not in laparoscopic trocar
insertion. Conclusions. Quantitative indices present the transient bradycardia
introduced by noxious stimulation. The results indicate different effects
between skin incision and trocar insertion.Comment: One table and 4 figure
An Efficient Forecasting Approach to Reduce Boundary Effects in Real-Time Time-Frequency Analysis
Time-frequency (TF) representations of time series are intrinsically subject
to the boundary effects. As a result, the structures of signals that are
highlighted by the representations are garbled when approaching the boundaries
of the TF domain. In this paper, for the purpose of real-time TF information
acquisition of nonstationary oscillatory time series, we propose a numerically
efficient approach for the reduction of such boundary effects. The solution
relies on an extension of the analyzed signal obtained by a forecasting
technique. In the case of the study of a class of locally oscillating signals,
we provide a theoretical guarantee of the performance of our approach.
Following a numerical verification of the algorithmic performance of our
approach, we validate it by implementing it on biomedical signals
Wave-shape function analysis -- when cepstrum meets time-frequency analysis
We propose to combine cepstrum and nonlinear time-frequency (TF) analysis to
study mutiple component oscillatory signals with time-varying frequency and
amplitude and with time-varying non-sinusoidal oscillatory pattern. The concept
of cepstrum is applied to eliminate the wave-shape function influence on the TF
analysis, and we propose a new algorithm, named de-shape synchrosqueezing
transform (de-shape SST). The mathematical model, adaptive non-harmonic model,
is introduced and the de-shape SST algorithm is theoretically analyzed. In
addition to simulated signals, several different physiological, musical and
biological signals are analyzed to illustrate the proposed algorithm