Download Ambulatory Impedance Cardiography - The Systems and Their Applications - G. Cybulski (Springer, 2011) WW PDF

TitleAmbulatory Impedance Cardiography - The Systems and Their Applications - G. Cybulski (Springer, 2011) WW
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Total Pages128
Table of Contents
Lecture Notes in Electrical Engineering
Volume 76
Ambulatory Impedance
	ISBN 9783642119866
	List of Abbreviations
1 Introduction
	1.1…The Importance of Monitoring Transient Changes
	1.2…Non-invasive Recording of the Cardiac Parameters and its Significance
	1.3…Ambulatory Monitoring and Implementations of it
	1.4…Ambulatory Monitoring Using Impedance Cardiography Signals
2 Impedance Cardiography
	2.1…Bioimpedance Measurement: Applications and Importance
	2.2…Electrical Properties of the Biological Tissues
	2.3…Tissue as a Conductor
	2.4…Frequency and Current Values
	2.5…Bioimpedance Measurement Methods
		2.5.1 Biopolar and Tetrapolar Method
		2.5.2 Alternating Constant-Current Source
		2.5.3 Receiving Unit
		2.5.4 Demodulation Unit
		2.5.5 Automatic Balance Systems
	2.6…Electrodes Types and Topography
		2.6.1 Band Electrodes, Spot Electrodes and Mixed Spot/Band Electrodes
		2.6.2 Other Solutions
	2.7…Signal Description and Analysis
		2.7.1 Impedance Cardiography Traces
		2.7.2 Characteristic Points on Impedance Cardiography Curves
		2.7.3 Characteristic Periods in Impedance Cardiography
		2.7.4 Hemodynamic Indices
		2.7.5 The Influence of Breathing
		2.7.6 The Origin of the Impedance Cardiography Signals
		2.7.7 The Methods of Stroke Volume Calculation
			Nyboer Formula
			Kubicek Formula
			Sramek Formula
			Sramek-Bernstein Formula
			TaskForce Monitor Method
			PhysioFlow Method
		2.7.8 Blood Resistivity Impact
	2.8…Signal Conditioning
		2.8.1 Ensemble Averaging Method
		2.8.2 Large-Scale Ensemble Averaging Method
	2.9…Technical Aspects of ICG-Limitations, Errors and Patients’ Safety
	2.10…Modifications of ICG, and Other Impedance Techniques
	2.11…Physiological and Clinical Applications of Impedance Cardiography
3 Ambulatory Impedance Cardiography
	3.1…The Idea of Ambulatory Impedance Cardiography
	3.2…ReoMonitor: The Research System
		3.2.1 The Ambulatory Recorder
		3.2.2 The Analogue Unit
		3.2.3 The Digital Unit
		3.2.4 The User Interface
		3.2.5 Software for Hemodynamics Parameters Calculations
	3.3…VU-AMS: The Vrije Universiteit Ambulatory Monitoring System
	3.4…MW1000A: The MindWare System
	3.5…PhysioFlow Enduro System
	3.6…AIM-8-V3: Wearable Cardiac Performance Monitor
	3.7…Ambulatory Impedance Cardiograph: AZCG
	3.8…Other Systems
4 Validation of the Ambulatory Impedance Cardiography Method
	4.2…Validation using Reference Methods
		4.2.1 Background and Motivation
		4.2.2 Experimental Studies
		4.2.3 Results of the Own Experimental Studies
			Stroke Volume
			Ejection Time
			Pre-ejection Period
		4.2.4 Discussion and Conclusions
	4.3…The Quality of the Ambulatory Impedance Cardiography Recordings
		4.3.1 Background and Motivation
		4.3.2 Experimental Studies
		4.3.3 Results of the Experimental Studies
		4.3.4 Discussion and Conclusions
5 Clinical and Physiological Applications of Impedance Cardiography Ambulatory Monitoring
	5.2…Atrial Fibrillation
	5.3…Ventricular Extrasystole Beats (VEB) Monitoring
	5.4…Ambulatory ICG and Pacemaker Monitoring
		5.4.1 Cardiac Pacing Optimisation
		5.4.2 Pacemaker Syndrome Detection
	5.5…Cardiac Parameters Monitoring During the Tilt Test
	5.6…Other Applications
6 Final Conclusions and Future Directions
	6.1…Prospects for Impedance Ambulatory Monitoring
	6.2…Clinical Importance of the Ambulatory Impedance Cardiography Monitoring
	Ambulatory Impedance Cardiography System: Reomonitor
	The Vrije Universiteit Ambulatory Monitoring System: Specifications and Features
	The MindWare MW1000A System: Specification and Features
	The PhysioFlow Enduro System: Specification and Features
	AIM-8-V3 Wearable Cardiac Performance Monitor
	Ambulatory Impedance Cardiograph: AZCG
	The Useful Links to Ambulatory Monitoring and Impedance Cardiography Web Pages
Document Text Contents
Page 2

Lecture Notes in Electrical Engineering

Volume 76

For further volumes:

Page 64

chest are placed two electrodes receiving the voltage difference over the thorax.
Two other electrodes are placed on the both sides of the lower part of the chest.
The topology of the electrodes placement could be found in the VU-AMS manual

Below is a quotation from that manual describing the method of the
impedance signal generation an analysis. ‘‘The thorax impedance measurement
uses a 4-spot electrode technique. Two electrodes supply a constant current
through the subject of 50 kHz, 350 lA. The remaining two electrodes pick up
the impedance signal. This signal is amplified and led to a precision rectifier.
The rectified signal is filtered at 72 Hz to give thorax impedance ZQ. Filtering
ZQ at 0.1 Hz supplies A _Z, which in return is filtered at 30.0 Hz to determine dz/
dt. Z0, DZ and dz/dt are led to the AD-converter of the microprocessor. The DZ
is sampled default at 100 ms yielding the respiration signal. This sample rate
can be set between 100 and 1,000 ms. AMS stores the respiration signal for
later off-line processing. This off-line processing can be used to obtain inspi-
ration time, expiration time and total cycle time off all recorded breaths. Signal
dz/dt is sampled at 250 Hz to yield the ICG. dz/dt values are sampled only
during a short period (512 ms) around each R-wave. These R-wave locked dz/dt
data blocks are ensemble averaged over a default period of 60 s. The user may
change this from 30 to 120 s. The entire ensemble average is written to AMS
memory, including the average Z0 value measured at the beginning of the
block. Off-line processing of the ensemble averages of the dz/dt signal allows
the computation of systolic time intervals like the left ventricular ejection
ctime (LVET), the PEP and the Heather index’’ (
manuals/index.html). VU-AMS does not record the full 3-channel ECG. Instead
a series of R–R intervals is stored [20]. The R-wave is used as a trigger
allowing the synchronisation necessary to perform the ICG signal averaging.
The ensemble averaging is performed over a certain period (e.g. 60 s) by
summing the digitised samples gated by R-wave peak and dividing by the
numbers of beats in the analysed period. It is used to reduce the influence of
natural beat-to-beat variability and the disturbing effect of the respiration on
impedance signal.

Another method used in analysis of the ambulatory ICG is the large scale
ensemble averaging. This method is a way of longer averaging than over the
60 s period. It was introduced by the group who developed the VU-AMS device
[18]. This method was applied as an off-line analysis for a period of the similar
type of the patient activity but lasting not longer than 1 h. If the activity type
lasted longer than 1 h (sleeping) it was divided into several periods shorter than
1 h. The periods were selected using the entries from patient diaries describing
the activity, physical load, posture, location (home, work, etc.), and social sit-
uation. The full description of the categories is given by Riese et al. [18]. The
morphology analysis of the large-scale ensemble averaging was performed in a
similar way to a 60 s averaging. The technical specification data are presented
in Appendix.

48 3 Ambulatory Impedance Cardiography

Page 65

3.4 MW1000A: The MindWare System

The MindWare MW1000A Ambulatory Impedance Cardiograph (Mindware
Technologies LTD, Gahanna, OH 43230, USA, is a
battery powered, portable, small impedance device combined with a PDA based
data acquisition system. The impedance signal detector is design as a tetra-polar
system using two application and two receiving electrodes. The application part of
MW1000A injects a high precision frequency alternating current (l00 kHz) of
constant amplitude at 400 mA. This allows measurement of the impedance changes
across the thorax. The detection part contains an ECG receiving and amplification
channel. The four continuous output signals—impedance (Z0), its derivative (dz/dt),
ECG, and a galvanic skin conductance (GSC)—are digitized by the high-resolution
(16 bits) A/D card. Data can be streamed to local storage on the PDA (512 MB SD)
or transmitted Wi-Fi to a host PC using a wireless router and MindWare’s Wi-Fi
acquisition application (ACQ). This data can then be analyzed real-time (using so
called ICG RT) or offline with MindWare’s suite of analysis applications. Real time
measurements are stored in a tab delimited text file for offline processing. File
format is compatible with MindWare desktop analysis applications IMP, HRV, and
EDA. The system has very low power consumption and is powered by internal PDA
battery. The device of a size 45 9 95 9 160 mm weights 400 g. The system
enables to compute and display real time cardiac and systolic measures such as:
LVET, PEP, SV, CO, HR, dz/dt, Z0, mean inter beat interval (IBI) and RSA for hear
rate variability, and skin conductance.

The system is supplied complete with the PDA, rugged case with Impedance
Electronics, Acquisition Card, SD Card (for memory storage), patient leads and
harness, charger, and acquisition software. The wireless router essential to use the
included Wi-Fi ACQ acquisition software should be bought separately. The
technical data and features are presented in the appendices chapter. Figure 3.7
presents the MindWare MW1000A Ambulatory Impedance Cardiograph (Mind-
ware Technologies LTD, Gahanna, OH 43230, USA). Some technical data of that
device are presented in Appendices part.

3.5 PhysioFlow Enduro System

The PhysioFlow Enduro is a Holter-type version of a system offered also by the
producer in a stationary version. It is very light (200 g with AA batteries) and
offers a long time recording in a field conditions. The crucial difference between
this system and other available on the market is associated with the way of cal-
culating the SV from an impedance signals. It is the only system that does not use
geometrical parameters of the thorax (or a distance between the electrodes) to
calculate every cycle SV values. Due to some legal and commercial reasons the
method of calculation was never revealed in the scientific paper. According to the

3.4 MW1000A: The MindWare System 49

Page 127


Application electrodes, 11, 12, 21, 41–42, 54
Arrhythmia, 1–4, 33, 47, 73, 75–80, 81, 83, 99,

Atrial fibrillation, 2, 16, 57, 65–67, 73, 76–77,


Bernstein formula, 25–26
Bipolar method, 11
Blood resistivity, 9, 22–23, 28, 31, 60, 63

Cardiac output, 2, 16, 18–19, 29, 31, 40, 58,

68, 82, 84, 87–90, 100
Current source, 11, 12
Cylindrical model, 22, 26

Demodulator, 12
dz/dt, 15–16, 18, 20, 24–25, 28, 31, 33, 45,

48–49, 51–55, 74–76, 81, 85–86, 99
dz/dtmax, 3, 16–17, 20–21, 24–25, 27, 29, 31,

33, 45–46, 52, 74–78

Hypertension, 2, 40, 100

Kubicek formula, 24, 26, 28, 60, 63

Left ventricular ejection time, 2, 16, 18, 23,

30, 48, 59
LVET, 2, 15, 18, 20, 24, 30, 48–49, 52, 54, 68

Model, 7, 9–10, 21–22, 26, 31–32, 44

Orthostatic syndrome, 85

Pacemaker, 2, 4, 32, 73, 82–86, 101
Pacemaker optimisation, 32, 73, 82, 84, 101
Pacemaker syndrome, 73, 84–86, 101
PEP, 2, 17, 30, 40, 59–60, 62, 79, 87–88
Pre-ejection period, 2, 15, 17, 30, 30, 40,

45–49, 52, 59–63, 79, 87–88

Receiving electrodes, 11–14, 21, 24–25, 41,

43, 49, 54


Page 128

Sramek formula, 24
Stroke volume, 3, 12, 16, 20–24, 27, 29,

31–33, 51, 58, 60–62, 68, 73–74,
76–77, 79, 81–83, 85–87, 91, 100

Systolic time intervals, 2, 13, 16, 18, 40, 48,
59, 68, 100

Tetrapolar method, 11
Tilt test, 1, 26, 59, 73, 85, 87–91, 101
Tissue resistivity, 9
Total impedance, 11

VEB, 76, 79–80, 82
Ventricular extrasystole beats, 73, 76, 100

112 Index

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