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Ambulatory Devices Measuring Cardiorespiratory Activity with Motion

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BIODEVICES 2017 Presentation - Publication by Marcel Młyńczak, Marek Żyliński, Wiktor Niewiadomski and Gerard Cybulski

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Ambulatory Devices Measuring Cardiorespiratory Activity with Motion

  1. 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. 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 2
  3. 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. 3
  4. 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. 4
  5. 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 5
  6. 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 6
  7. 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 7
  8. 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 8
  9. 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. 9 Physiological applications Sport applications
  10. 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. 10 Sleep applications
  11. 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. 11
  12. 12. Methodology Subjects - generally healthy students, 10 males 12 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. 13. Sample results Free breathing in static conditions 13
  14. 14. Sample results Sleep signals with two changes of body position 14
  15. 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. 15
  16. 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. 16
  17. 17. Porto, February 21, 2017 Ambulatory Devices Measuring Cardiorespiratory Activity with Motion Marcel Młyńczak, MSc mlynczak@mchtr.pw.edu.pl

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