Showing posts with label Noninvasive Cardiac Output. Show all posts
MEAP and its Implications for Cardiovascular Research
Ensemble analysis averages raw waveform signals through lining up their peaks, allowing researchers to mitigate noise or potential outside artifacts. Researchers Cieslak et al. (2017) from University of California, Santa Barbara, identified and assessed a new open source tool that conducts ensemble analysis of cardiovascular data. The moving ensemble analysis pipeline (MEAP) builds on classic collection and analysis tools; not only in detecting cardiovascular state during an experiment, but also in measuring how cardiovascular cycles change overtime.Cardiovascular measurements are typically averaged to reduce noise, but traditional measurement methods made capturing changes in cardiovascular cycles restricted to a select window of time. This makes it difficult to assess fast changes with traditional cardiovascular ICG data. With MEAP, variability is better analyzed, allowing it to become a more accurate dimension of assessment.
In assessing MEAP’s viability, researchers measured two participants as they completed four different tasks. The experiment began and ended with a random dot kinetogram task allowing for a baseline control of cardiovascular activity. This was followed by the “cold presser” and “Valsalva,” two tasks that were expected to induce strong physiological reactions. Another task included a video game, seen as having less predictive effects.
Two subjects were measured for ECG and other physiological signals as they completed the four physical and cognitive tasks. BIOPAC’s research solutions included ECG100C utilized for ECG, NICO100C-MRI to collect ICG signals, and NIBP100D CNAP Monitor 500 to record blood pressure. Data was gathered and measured with MP Research System with AcqKnowledge software.
The results pointed to changes typical cardiovascular measures wouldn’t be able to describe. This was seen during the Valsalva maneuver, where rapid baroflex changes occurred. It was also found cardiovascular data varied immensely while performing repetitive tasks.
The paper recognizes MEAP’s potential for rapidly advancing findings that use cardiovascular data. The authors point to this tool’s potential ability for exploring new areas of study that have been difficult to quantify in the past, such as linking cardiovascular reactivity to motivation. In acknowledging the benefits of MEAP, the authors stress the importance of not overstepping smaller aspects of acquisition, such as poorly attached electrodes or imbalanced experiment design. Overall, this paper recognizes, analyzes, and validates this exciting new development in the field of cardiovascular research.
Noninvasive Cardiac Output | Data Acquisition
Noninvasive
Cardiac Output (NICO) measures can be determined by employing electrical
bioimpedance (EBI) measurement techniques. Electrical bioimpedance is the
characteristic impedance of a volume
of tissue and fluid. For Cardiac Output measures, the
relevant tissue includes the heart and the immediate surrounding volume of the
thorax, and the relevant fluid is blood.
The electrical
impedance of the thorax (Zt) can be thought of as composed of two impedance
types:
- The base impedance (Zo) corresponding to non-time varying tissues, such as muscle, bone and fat. Zo is measured when the pulsatile volume is minimal.
- The delta impedance (dZ) corresponding to time-varying fluid volume (blood).
Zt drops with
each pulsatile volume of blood ejected from the heart. dZ/dt is the magnitude
of the largest impedance change during systole.
Noninvasive
cardiac output amplifiers incorporate a precision high-frequency current
source, which injects a very small (400 microamp rms) current through the
measurement tissue volume defined by the placement of a set of current source
electrodes. A separate set of monitoring electrodes measures the voltage
developed across the tissue volume. Because the current is constant, the
voltage measured is proportional to the characteristics of the biological
impedance of the tissue volume.
BIOPAC data
acquisition hardware for recording real-time Noninvasive Cardiac Output
parameters include tethered amplifiers such as the NICO100C (or NICO100C-MRI
for fMRI environments), EBI100C, or SS31L, or the wireless BioNomadix BN-NICO.
Hardware
simultaneously measures impedance magnitude and phase, and may
incorporate an internal derivative function to output dZ/dt simultaneously with
Z; an AcqKnowledge calculation channel can also be used to determine
dZ/dt. The internal derivative function inverts the polarity of the dZ/dt
signal so that it displays a positive-going peak, coincident with negative
slopes indicated in Z, as per academic research convention.
Disposable
Ag/AgCl Paired Electrodes (EL500) are recommended for bioimpedance and cardiac
output studies. Paired electrodes provide fixed spacing between the dual
contacts and are pre-gelled with hypo-allergenic, wet liquid gel electrolyte
(10% chloride salt); the gel cavity is situated between electrode and skin
surfaces and helps reduce motion artifact.
The impact of
movement artifacts on recorded data is a significant methodological concern in
impedance cardiography; Ensemble Averaging tools in AcqKnowledge provide
an automated strategy to remove these artifacts. Watch a demo now!