EIT Assessment of Lung Volume and Tidal Distribution: A Comparison of Non-Invasive Ventilation Devices
Phase: NA
Conditions: Spontaneous Ventilation
Sponsor: University of Michigan

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EIT Assessment of Lung Volume and Tidal Distribution:  
A Comparison of Non-Invasive Ventilation Devices 
 
February 11, 2019 
 
 
NCT02930174 
 
PI: Carl Haas 
 
 

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EIT Assessment of Lung Volume and Tidal Distribution:  
A Comparison of Non-Invasive Ventilation Devices 
Protocol v. 2.6 
2/11/19  
 
 
Principal Investigator:  
Carl Haas, MLS, RRT-ACCS 
 
Co-Investigators:  
 
Anthony Courey, MD 
Pauline Park, MD  
Ric Eakin, RRT-ACCS, RN 
Kimberly Fecteau, RRT-ACCS 
Allan Andrews, MS, RRT 
Paul Loik, RRT 
Andrew Weirauch, BSRT, RRT-ACCS 
Chris Culter, BS, RRT-ACCS 
Aleksandar Tomas, MS, RPFT, RCE 
Brian Barnes, RRT 
Jessica Cusac, MA, RRT 
Ronald Dechert, DrPH, RRT 
 
1.0 Background and Significance 
Mechanical ventilation is life-saving technology but it can also inadvertently induce lung 
injury and increase morbidity and mortality.  There currently is not an easy method of 
assessing the impact ventilator settings have on the degree of lung inflation.  Computed 
tomography (CT), the gold standard for visually monitoring lung function, can provide 
detailed regional information of the lung (Figure 1).  Unfortunately, it necessitates moving 
critically ill patients to a special diagnostic room and involves exposure to radiation.  
A technique introduced in the 1980’s, electrical impedance tomography (EIT) can non-
invasively provide similar monitoring of lung function.  However, while CT provides 
information on the air content, EIT monitors ventilation-related changes of lung volume 
and changes of EELV.  Over the past several decades EIT has moved from the research lab 
to commercially available devices that are used at the bedside.  One such system 
manufactured by Draeger Medical (Lubeck, Germany) is available in Europe and Canada 
but is not yet FDA approved for use in the United States.1  Draeger Medical has agreed to 
provide this system to the Adult Respiratory Care Department at the University of 
Michigan Health System for use in research.  Our plan is to develop a series of research 

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protocols that build upon each other to provide us experience with the technology and 
insight on our practice of providing mechanical ventilation. 
The EIT system consists of a 1.6-inch wide belt containing 16 electrodes, which is wrapped 
around the chest (Figure 2), generally at the level of the 4th - 6th rib.  As an electrode pair 
emits a low alternating current (approximately 8 - 9 mA, depending on the frequency which 
can be set at 80 - 130 Hz), the resultant surface potential is measured by the remaining 
electrode pairs, and the impedance is determined.  The adjacent electrode pair then emits a 
signal and the remaining pairs measure the potential.  This sequence continues as the 
triggering of electrical emissions moves around the chest, via the belt, in a very rapid 
manner. One complete rotation creates voltage profiles at 16 positions of current emission, 
each consisting of 13 voltage measurements. The resultant 208 measurement values are 
reconstructed to provide one cross-sectional EIT image (Figure 3).  
An exciting application for EIT is to monitor the regional and global distribution of tidal 
ventilation during positive pressure ventilation.  Clinical studies have shown the value of 
EIT to quantify the effects of suctioning and ventilator disconnection2,3, during placement 
of double-lumen endotracheal tubes4, and to detect an incidental pneumothorax5 or 
pulmonary edema6.  Most importantly is the ability of EIT to assess lung recruitment and 
derecuitment7,8,9 as well as to assess for alveolar overdistension9, 10 in an attempt to provide 
a lung protective ventilation strategy. 
EIT has also been applied to study the effects of various devices used to provide 
noninvasive ventilation.  Noninvasive ventilation (NIV) is a form of mechanical ventilation 
which does not involve placement of and attachment to an artificial airway.  Rather the 
ventilator is attached to the subject via a face mask or other noninvasive interface.  Pelosi 
evaluated three devices used to provide a form of NIV, continuous positive airway pressure 
(CPAP), that create airway pressure using different methods (high flow CPAP, low-flow 
CPAP and an ICU ventilator) and detected differences in breathing pattern, end-expiratory 
lung volume (EELV) and airway pressures between the devices.11  Andersson evaluated 
three CPAP systems using EIT in 14 healthy volunteers.  They found different airway 
pressure profiles resulting in varying levels of EELV and noted that EELV increased more 
in ventral lung regions with increasing CPAP levels, independent of the system used, and a 
redistribution of tidal ventilation toward dorsal lung regions.12  EIT may prove useful to 
optimally adjust NPPV settings to improve ventilation and oxygenation. 
Our plan is to perform a study similar to that described by Andersson12 as an initial project 
on the use of EIT. 
 

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2.0 Hypothesis 
We hypothesize that the distribution of ventilation and EELV in healthy adult subjects will 
not be different when NPPV is applied via different devices set to identical pressure 
settings.  Also, when applying increasing NPPV pressures, the distribution of ventilation 
will shift from the ventral to dorsal regions and be similar between devices. 
3.0 Subject Selection and Enrollment 
3.1 Subjects:  Twenty adult healthy volunteers will be recruited for this study.  They will 
be solicited from within the University of Michigan Health System (e.g. students, 
staff, and employees).  No financial incentive will be provided. 
3.2 Inclusion Criteria: 
 
3.2.1 Age 18 years or older 
 
3.3 Exclusion Criteria: 
  
3.3.1 Use of a cardiac pacemaker, an implantable cardioverter-defibrillator (ICD) or 
any other active implants [electrical current may interfere with EIT signal] 
4.0 Study Procedures 
4.1 Written informed consent will be obtained on all subjects prior to enrollment in the 
study and before any research procedures are performed.  Subjects can withdraw from 
the study at any time. 
4.2 Subjects will undergo testing by applying NPPV via 2 different BiPAP devices that 
are currently used in standard of care for patients at the University of Michigan 
Health System.  The decision of which device to begin with will be determined by 
random allocation of a coin toss.   
4.3 BiPAP Systems:   
4.3.1 The Respironics V-60 (Phillips, Carlsbad CA) device is continuous 
high flow, blower type of generator.   
4.3.2 The Drager V-500 (Drager Medical, Lubeck, Germany) is our primary 
critical care ventilator that has a specific NPPV mode.  

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4.4 EIT System: The Drager PulmoVista 500 EIT system (Drager Medical, Lubeck, 
Germany) consists of an electrode belt connected to the EIT monitor.  Before using 
the system it will be reviewed and approved for use by our Biomedical Department.   
4.5 Subjects will be placed in the supine position.  This position will be maintained for 
the entire procedure. An electrode belt will be placed on the subject at the 5th 
intercostal space and connected to the EIT monitor.  Prior to initiating a study session, 
the EIT system will be calibrated per manufacturer’s instruction.  
4.6 Each study device will be applied in the following manner: 
4.6.1 Four steps (series of device setting changes) will be applied, as such: 
4.6.1.1 A baseline will be established breathing without the NPPV mask 
attached 
4.6.1.2 Following mask attachment, a pressure support of 0 cm H2O and 
PEEP of 5 cm H2O will be applied, then 
4.6.1.3 A pressure support of 5 cm H2O and PEEP of 5 cm H2O, then 
4.6.1.4 A pressure support of 5 cm H2O and PEEP of 10 cm H2O. 
4.6.2 Each step will consist of a 5-minute stabilization period, and then readings 
will be taken over the next two minutes before proceeding to the next step. 
4.6.3 Following all four steps with the initial device, the second device will be 
applied and steps 1-4 repeated. 
4.7 Primary Outcomes: Global Tidal Variation (see figures 4-6) 
4.8 Secondary Outcomes:  
4.8.1 Regional Tidal Variations  
4.8.2 Global and Regional changes in End-Expiratory Lung Impedance (EELI)  
4.9 Exploratory Outcomes:  
4.9.1 A pneumotachometer (NM3 monitor, Phillips Healthcare, Andover MA), will 
be placed between the mask and inspiratory hose and the following 
measurements obtained: respiratory rate, tidal volume, peak inspiratory 

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pressure, PEEP.  A pulse oximeter (RAD8, Masimo, Irvine CA) will provide 
SpO2 and heart rate.  
4.9.2 Change in regional and global distribution in subjects with a BMI less than or 
greater than 25 kg/m2  
4.9.3 Change in global and regional distribution for subjects at 0 degrees,45 
degrees, and 90 degrees’ body positions.  
4.10 In addition to device testing, baseline demographics such as age and gender will be 
recorded for each subject.   
5.0 Statistical Analysis 
A two-way ANOVA will be the first step of analysis to determine the influence of the 
BiPAP systems on the NPPV. Regional distribution of tidal volume will be analyzed using 
four ventral to dorsal regions of interest (ROI) by EIT.   The relative distribution of tidal 
volume between regions will be displayed as a percentage. Regional change in end-
expiratory lung impedance (EELI) will be similarly expressed as a percent for each ROI.  
These parameters will be treated as functions of each individual step outlined in 4.6, with 
particular attention paid to the pressure support and PEEP. Values will be presented as 
mean ± standard deviation and initial comparisons will be made using paired t-tests against 
baseline. Given the factorial design of experiment, if further analysis becomes warranted, a 
multivariate ANOVA will be utilized to determine the time, pressure, and total tidal 
volume relationship to relative distribution of tidal volume within the regions of interest. 
Potential conflating parameters such as patient size, weight, and health status will be 
screened in a similar manner. 
6.0 Risks 
The total procedure should be completed within 90-120 minutes.  There is minimal risk or 
discomfort to the subject.  The electrode belt will not be applied long enough for any 
chafing or skin breakdown to occur.  Although hyperventilation (i.e. lightheadedness, 
tingling in the hands) may occur as airway pressure is applied, the subject will be 
monitored continuously and the pressures used are relatively low compared to those used 
clinically or at home for sleep apnea. 
7.0 Benefits 
There will be no direct benefit to the study subjects. This research will 1) provide an 
opportunity to learn the EIT system in a nonclinical application on healthy volunteers 

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before using it in a clinical protocol, and 2) allow comparison of NPPV systems that are 
routinely used clinically to hopefully show equivalence in important measures.  
8.0 Safety Monitoring/Reporting 
8.1 Due to the minimal risk of this study, only related adverse events will be reported.   
8.1.1 Serious, related adverse events will be reported to the IRB within 7 calendar 
days  
8.1.2 Non-serious, related adverse events grade 3 or higher will be reported to the 
IRB prior to SCR  
8.1.3 Any serious, unanticipated problems that are related to the study and indicate 
risks to subjects will be reported to the IRB within 7 calendar days.  Non-
serious problems will be reported within 14 days.  
8.1.4 Privacy violation or breach of confidentiality will be reported to the IRB 
within 7 calendar days, and to the UMHS Privacy Office within 24 hours.  
9.0 References: 
1. Teschner E, Imhoff M. Electrical impedance tomography: the realization of regional ventilation 
monitoring. A Drager Technical Monograph; 2011; Draeger Medical GmbH, Lubeck Germany 
2. Lindgren S, et al. Regional lung derecruitment after endotracheal tube suction during volume- 
or pressure-controlled ventilation: a study using electric impedance tomography. Intensive Care 
Med 2007; 33:172-180 
3. Wolf GK, et al. Regional lung volume changes in children with acute respiratory distress 
syndrome during a derecruitment maneuver. Crit Care Med 2007; 35:1972-1978 
4. Steinmann D, et al. Electircal impedance tomography to confirm correct placement of double-
lumen tube: a feasibility study. Br J Anaesth 2008; 101:411-418 
5. Costa EL, et al. Real-time detection of pneumothorax using electrical impedance tomography. 
Crit Care Med 2008; 36:1230-1238 
6. Arad M, et al. The detection of pleural effusion using a parametric EIT technique. Physiol Meas 
2009; 30:421-48 
7. Kunst PW, et al. Evaluation of electrical impedance tomography in the measurement of PEEP-
induced changes in lung volume. Chest 1999; 115:1102-1106 
8. Lowhagen K, et al. A new nonradiological method to assess potential lung recruitability: a pilot 
study of ALI patients. Acta Anaesthesiol Scand 2011; 55:165-174  
9. Costa EL, et al. Bedside estimation of recruitable alveolar collapse and hyper-distension by 
electrical impedance tomography. Intensive Care Med 2009; 35:1132-1137 

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10. Gomez-Laberge C. A unified approach for EIT imaging of regional overdistension and 
atelectasis in acute lung injury. IEEE Trans Med Imaging 2012; 31:834-842 
11. Pelosi P, et al. Effects of different continuous positive airway pressure devices and periodic 
hyperinflation on respiratory function.  Crit Care Med 2001; 29:1683-1689 
12. Andersson B, et al. End-expiratory lung volume and ventilation distribution with different 
continuous positive airway pressure systems in volunteers. Acta Anesthesiol Scand 2010; 
55:157-164 
 

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Acknowledgement: all figures are taken from the Drager monograph by Teschner 
Figure 1.  CT image showing four distinct lung regions (manually colorized to highlight the distinction) 
 
 
Figure 2. Electrode belt containing 16 electrodes wrapped around a patient’s chest 
 
 
 

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Figure 3.  Example of an EIT image 
 
 
Figure 4.  Main Screen 
This screen depicts: 1) on the left: Dynamic Image (showing impedance changes over time) and Status 
Image (image used to derive waveforms and percentages) of the lungs, 2) in the center: a global 
impedance wave form at the top and 4 regional impedance waveforms (one for each ROI) and 3) on the 
right: the Tidal Rate, the global Tidal Variation (100%) and the regional Tidal variation percentages for 
each ROI 
 
 
 

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Figure 5. Trend View 
Two status images are displayed (baseline and following an intervention) to graphically represent 
regional ventilation distribution over a time period of up to 120 minutes. 
 
 
Figure 6.  Delta EELV Trend View 
Figure shows waveforms of the global (top center) and four regional changes in end-expiratory lung 
impedance.  Corresponding numeric values are shown on the right.