Non-invasive Tidal Volume Monitoring Using the Linshom Respiratory Monitoring Device
Phase: NA
Conditions: Pulmonary Ventilation, Capnography
Sponsor: University of Mississippi Medical Center

 
 
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6/21/2017 
RESEARCH PROTOCOL  
 NCT03279458 
 
Title 
 
Non-invasive tidal volume monitoring using the Linshom 
Respiratory Monitoring Device  
 
 
Faculty Sponsor 
 
Madhankumar Sathyamoorthy, MD 
 
Principle 
Investigator/Co-
investigators 
Madhankumar Sathyamoorthy, MD 
George E. Abraham III, MD 
Abstract 
Many post-operative complications arise from patients who breathe 
inadequately. Inadequate respiration, whether the result of surgery or the 
anesthesia, causes a decrease in blood oxygen saturation and an increase 
in carbon dioxide partial pressure. Both of these surrogate 
measurements of respiration may pose a challenge to measure. Some 
administer exogenous oxygen to all patients as they leave the operating 
room in order to maintain the blood oxygen saturation. This renders the 
oximeter a less sensitive metric of depressed respiration. In the face of 
decreased respiration, the carbon dioxide levels continue to increase 
slowly and often go undetected unless blood gases are measured. Indeed 
carbon dioxide blood levels are the only metric to detect inadequate 
ventilation using this surrogate index.  
 
Monitoring ventilation is a serious challenge outside of critical care 
settings. In fact, there are no monitors available that can measure tidal 
volume or relative tidal volume outside of these settings.  
 
Linshom is a novel instrument that tracks relative respiration by 
measuring the excursions of the temperature swings between inspiration 
and expiration and normalizing them to the patient’s breathing. This 
monitor may be the first non-invasive monitor to measure relative tidal 
volume in non-critical care settings.  
 

 
 
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Background  
 
 
 
Oxygenation – the process of delivering oxygen to the lungs – is often 
much simpler to achieve than ventilation, since only a small volume of 
oxygen must be delivered to oxygenate the patient and provide a 
reserve. Carbon dioxide, however, constantly accumulates and depends 
on ongoing ventilation to eliminate it from the lungs.  
 
Direct automatic ventilation monitors tend to be cumbersome. They 
typically require chest straps or EKG-type stickers to be placed on the 
patient’s chest. EKG signals themselves can be used to detect inhalation 
and exhalation, but the noise of EKG monitors tends to make this 
method unreliable. In most cases, the patient needs to be lying quite still 
in order for accurate ventilation monitoring and even then they measure 
respiratory rate and not tidal volume.  
 
The gold standard method to measure the adequacy of ventilation is to 
measure the exhaled carbon dioxide concentration. Exhaled gas almost 
always contains carbon dioxide that may be measured using either 
sidestream or mainstream capnography. However, the carbon dioxide 
tension is only a surrogate measure of ventilation since it is the changes 
in tidal volume per breath or minute ventilation that determines the 
adequacy of respiration and therefore the carbon dioxide tension. 
Capnography accurately measures the respiratory rate and the net effect 
of ventilation without reporting the tidal volume. Knowing the tidal 
volume before the carbon dioxide tension begins to increase provides an 
opportunity to intervene before the clinical situation has deteriorated too 
much. Linshom is a reliable, effective patient ventilation monitor that is 
minimally invasive, simple, inexpensive, fast responding and tracks 
relative tidal volume outside of critical care settings.  
Purpose 
 
 
To determine whether a non-invasive, temperature-based respiratory 
instrument could track tidal volume (Vt) in patients. 
Specific Aim(s) 
The primary purpose of this investigation is to evaluate whether a non-
invasive, thermodynamic temperature-based instrument, Linshom, can 
accurately and consistently track tidal volume as measured by closed 
loop mechanical ventilator.  
Study Period 
(inclusive years) 
The study will be completed over a period of one week. 

 
 
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Study Design 
Flyers advertising the study will be placed around campus on designated 
bulletin boards.  Individuals interested in the study will be able to call 
the number (PI Office Number: 601 815 7066).  If the individual meets 
the study criteria, then he or she will be scheduled for a study session, 
which will take place in room N200-13 of the respiratory therapy 
department.  After completing the visit, the volunteer will receive a 
$10.00 gift card. 
 
The Linshom detector, which is comprised of two rapid responding 
medical-grade thermistors in close proximity to the mouth/nose (sensor) 
and a thermistor remote to the airway, will be mounted in the CPAP 
facemask to measure the temperature during breathing. The CPAP will 
be connected to a Servo-I ventilator (Maquet) with a circuit and 
disposable filter. The volunteers will be instructed to breathe normal 
through the CPAP mask on room air. The excursions of the thermistor 
tracings (from valley to peak) will be recorded by the Linshom device 
and displayed continuously on a laptop monitor in a waveform.  The 
tidal volume will also be measured by the ventilator and the data 
downloaded in a Compact Flash card. The temperature profiles from the 
sensors and the relative tidal volume will be correlated with the tidal 
volumes measured by the ventilator.  
Inclusion Criteria 
 
Healthy volunteers 18 years of age or older will be recruited from the 
Medical School at the University of Mississippi.  
 
 
Exclusion Criteria 
 
 
Individuals who are pregnant, suffer from claustrophobia, or who have 
had a recent respiratory or gastrointestinal illness will be excluded.  
Volunteers deemed not to have the capacity to provide informed consent 
will not be enrolled.   
Number of Subjects 
(anticipated) 
40.  
 
Outcome Measures 
 
 
Every volunteer recruited in this study will be monitored by the study 
investigators during data collection. Linshom readings showing the 
temperature changes and tidal volume measured by ventilator will be 
collected. 
 
Study Endpoints 
 
 
The subjects will breathe through the mask for about 5  minutes, and 
will be observed during this time by the study investigators. Continuous 
data for tidal volume and temperature will be collected during this time 
and the data will be analyzed post-hoc. 

 
 
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Private Health 
Information 
 
 
No medical record information will be collected – no other volunteer 
information will be recorded. Volunteer numbers will be paired with 
study numbers in a single Microsoft Excel spreadsheet. All study 
information will thereafter refer to study numbers. 
Statistical 
Methodology  
 
 
 
We shall correlate the tidal volumes measured with the Linshom 
detector with the respective tidal volumes from the mechanical 
ventilator. A least squares regression analysis (with the coefficient of 
determination r-squared) and a Bland Altman plot will be prepared. 
P<0.05 will be accepted.  

 
 
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References  
 
 
 
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Funding Source 
 
 
Departmental Funds (Department of Anesthesia)