Journal of Clinical Monitoring and Computing

, Volume 30, Issue 4, pp 467–473 | Cite as

A mainstream monitoring system for respiratory CO2 concentration and gasflow

  • Jiachen Yang
  • Bobo Chen
  • Kyle Burk
  • Haitao Wang
  • Jianxiong Zhou
Original Research


Continuous respiratory gas monitoring is an important tool for clinical monitoring. In particular, measurement of respiratory \(\hbox {CO}_2\) concentration and gasflow can reflect the status of a patient by providing parameters such as volume of carbon dioxide, end-tidal \(\hbox {CO}_2,\) respiratory rate and alveolar deadspace. However, in the majority of previous work, \(\hbox {CO}_2\) concentration and gasflow have been studied separately. This study focuses on a mainstream system which simultaneously measures respiratory \(\hbox {CO}_2\) concentration and gasflow at the same location, allowing for volumetric capnography to be implemented. A non-dispersive infrared monitor is used to measure \(\hbox {CO}_2\) concentration and a differential pressure sensor is used to measure gasflow. In developing this new device, we designed a custom airway adapter which can be placed in line with the breathing circuit and accurately monitor relevant respiratory parameters. Because the airway adapter is used both for capnography and gasflow, our system reduces mechanical deadspace. The finite element method was used to design the airway adapter which can provide a strong differential pressure while reducing airway resistance. Statistical analysis using the coefficient of variation was performed to find the optimal driving voltage of the pressure transducer. Calibration between variations and flows was used to avoid pressure signal drift. We carried out targeted experiments using the proposed device and confirmed that the device can produce stable signals.


Respiratory gas monitoring \(\hbox {CO}_2\) Gasflow  Capnography NDIR Differential pressure FEM 



This research is partially supported by the National Natural Science Foundation of China (No. 61471260), Natural Science Foundation of Tianjin (No. 12jcqnjc00500), Supported by Program for New Century Excellent Talents in University (NCET-12-0400).

Compliance with ethical standards

Conflicts of interest

The authors declare that they have no conflict of interest.

Ethical standard

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  • Jiachen Yang
    • 1
    • 2
  • Bobo Chen
    • 1
  • Kyle Burk
    • 3
  • Haitao Wang
    • 1
  • Jianxiong Zhou
    • 1
  1. 1.School of Electronic Information EngineeringTianjin UniversityTianjinPeople’s Republic of China
  2. 2.Tianjin Yaan Polytron Technologies IncTianjinPeople’s Republic of China
  3. 3.Departments of Anesthesiology and BioengineeringUniversity of UtahSalt Lake CityUSA

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