The document discusses the development and testing of portable ambulatory devices designed to measure cardiorespiratory activity, including respiratory patterns and heart activity, using impedance pneumography. It describes two devices, Pneumonitor 2 and Pneumonitor 3, intended for physiological analysis and sleep studies, respectively, highlighting their features and calibration methods. Results indicate that the devices achieve high accuracy in tidal volume calculation and are effective in natural settings, such as during sleep and physical activity.

1. Ambulatory Devices Measuring
Cardiorespiratory Activity with Motion
Marcel Młyńczak, MSc, Marek Żyliński, MSc,
Wiktor Niewiadomski, PhD, Gerard Cybulski, PhD
Warsaw University of Technology, Faculty of Mechatronics,
Institute of Metrology and Biomedical Engineering
Porto, February 21, 2017

2. Introduction
Traditional respiratory monitoring
Mesh grid of
known pneumatic
resistance
• The most reliable
• Direct measurements
• Cannot be performed in an outpatient setting
• In clinical practice, there are no natural daily and nightly parameters
Figures adapted from chat.stackexchange.com and legio24.pl
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3. Introduction
Ambulatory respiratory monitoring
Continuous
measurements
Traditional examination captures a single point in time.
The registrations carried out under more natural conditions and taking into
account activity, circadian rhythms could expand early diagnosis.
Sleep
Indirect methods
PSG could mark snoring and central or obstructive sleep apnea episodes.
The breathing patterns are usually measured indirectly by
a belt and a cannula, which make sleep less natural and comfortable.
Acoustical approaches, respiratory plethysmography or
impedance pneumography.
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4. Introduction
Impedance pneumography
Basic idea
Based on the measurement of the changes of transthoracic
bioimpedance, which could be linearily connected with changes
of the amount of air in the lungs.
Taking
measurements
Processing
remarks
Usually carried out using current tetrapolar method.
Voltage electrodes are usually positioned on the
midaxillary line at about 5th-rib level.
The signal is volume-related.
In order to obtain flows impedance pneumography signals
should be differentiated.
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5. Introduction
Motion and heart activity
• Based on the present guidelines, each
sleep study device should be equipped
with pulse oximetry and heart activity
registration unit.
• Simultaneous analysis of heart activity
along with respiratory one could allow
assessment of the autonomic nervous
system operation. Such experiments
are rarely carried out under natural
conditions.
• The calibration coefficients converting
impedance to volume are dependent
mainly upon subjects and body
positions.
• It seems also very important with
regards to sleep studies, e.g., for
hypnogram estimation.
• The motion-associated artifacts could
be adaptively removed, smoothed,
or marked using a synchronized
motion signal.
Motion tracking Cardiorespiratory coupling
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6. Objective
Development and pilot testing of portable devices which would register:
• respiratory activity (using impedance pneumography)
• ECG
• motion
• pulse oximetry (saturation, pulse wave)
1. 3.2.
Sleep studies
Sport
applications
Physiological
applications
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7. The devices
Pneumonitor 2
• ECG signal to estimate heart rate
and tachogram
• Impedance signal relating to
main breathing activity
• Portable
• Recording on SD card
• Rechargeable battery
• Motion signal from 3-axis
accelerometer to indicate
subject’s activity and body position
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8. The devices
Pneumonitor 3
• ECG signal to estimate heart rate
and tachogram
• Impedance signal relating to
main breathing activity
• Analog, SD and BT outputs
• Handling improved
• Rechargeable battery
• Wireless pulse oximeter to
acquire saturation level and
pulse wave
• Motion signal from 3-axis
accelerometer to indicate
subject’s activity and body position
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9. Electrode configurations
Pneumonitor 2 with 7 electrodes configurations
IP electrodes
Single-lead
ECG electrodes
IP electrode placement proposed by Seppa et al. likely provides
the best linearity between impedance and volume changes.
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Physiological applications Sport applications

10. Electrode configurations
Pneumonitor 3 with 5 electrodes configurations
IP & ECG
electrodes
Neutral
electrode
Seppa’s electrode configuration Classical electrode configuration
It is considered worse in terms of
transition linearity, yet most likely
optimal in terms of motion artifacts.
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Sleep applications

11. Methodology
• Calibration procedure - free 30-second-lasting breathing in supine, sitting and
standing body positions.
• Test procedure consisting of 6 normal breaths and then 6 deep breaths (with the
subjective difference), for three breathing rates (6, 10 and 15 BPM) and for the same
three body positions as during calibration.
• Reference: Flow Measurement System with a Spirometer Unit and a Fleisch-type
Heatable Flow Transducer 5530, with a Conical Mouthpiece (Medikro Oy, Finland).
• Qualitative assessment of acquired signals and the usability from subjects’
perspective were tested during walking, climbing stairs, exercising on a cycle
ergometer for 90 seconds with the increasing load (from 50W to 200W).
• The activity and changing of body positions on a bed were tested during sleep.
• MATLAB 2016b software was used to review and analyze the results.
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12. Methodology
Subjects - generally healthy students, 10 males
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Minimum Mean Maximum
Weight [kg] 65.0 77.4 100.0
Height [cm] 171.0 179.3 187.0
BMI 20.75 24.14 33.41
Age 19 23 27

13. Sample results
Free breathing in static conditions
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14. Sample results
Sleep signals with two changes of body position
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15. Results
Mean 86.5% accuracy of tidal volume calculating for
simple short recording of free breathing calibration procedure,
in three body positions.
No artifacts (except quick, motion-related) or errors that might
preclude analysis were shown during pilot evaluation in natural
situations, e.g., changing positions on a bed or walking.
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16. Final discussion
Pneumonitor 2 is designed for the environment physiology analyses (registering
ventilation and cardiac functioning in subjects with obesity or nervous-muscle-related
illnesses) and sports medicine (for ambulatory diagnostics, monitoring training, and
determining exercise capacity).
Pneumonitor 3 is intended mainly for sleep studies to monitor breathing disorders and
the treatment progress.
The first ambulatory system was described by Vuorela et al. in 2010.
In contrary to their construction:
• we removed most of the analog blocks for signal conditioning and processing,
• we added the ability to measure blood saturation and pulse wave,
• we reduced the number of electrodes from 7 to 5.
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17. Porto, February 21, 2017
Ambulatory Devices Measuring
Cardiorespiratory Activity with Motion
Marcel Młyńczak, MSc
mlynczak@mchtr.pw.edu.pl