Relation of respiratory system elastance and expiratory time constant: are they from the same lung?

Nor Salwa Damanhuri, Paul D. Docherty, Yeong Shiong Chiew, Erwin J. Van Drunen, Nor Azlan Othman, Thomas Desaive, J. Geoffrey Chase

Research output: Chapter in Book/Report/Conference proceedingConference PaperOther


Modeling the respiratory system can aid clinical decision making during mechanical ventilation (MV) in the intensive care. However, most lung models only use airway pressure and flow data during inspiration phase of the breathing, and the data from expiration are often neglected. In this study, we hypothesized that the airway pressure and flow data during expiration have equal important information as the inspiratory data for respiratory mechanics modeling. In particular, expiratory time constant parameter, K, can provide unique information and relation with respiratory system elastance in MV patients. Two different respiratory models were investigated, with one model focusing on data from inspiratory cycle (Single compartment model) and the other focusing on expiratory cycle (Time constant model). The expiratory time constant model and single compartment model were evaluated based on 22 retrospective datasets of acute respiratory distress syndrome (ARDS) patients from two different cohorts. The expiration time constant model captured a moderate correlation with the lung elastance with R2= 0.568 in Cohort 1 and weak correlation with R2= 0.184 in Cohort 2, resulting in an overall of R2 = 0.435. Significant variations in lung resistance may lead to a poor correlation between K and lung elastance, Elung. Thus, the application of K as a surrogate to the respiratory elastance warrants further investigation.

Original languageEnglish
Title of host publication19th IFAC World Congress IFAC 2014, Proceedings
EditorsEdward Boje, Xiaohua Xia
PublisherElsevier - International Federation of Automatic Control (IFAC)
Number of pages6
ISBN (Electronic)9783902823625
Publication statusPublished - 2014
Externally publishedYes
EventInternational Federation of Automatic Control World Congress 2014 - Cape Town International Convention Centre, Cape Town, South Africa
Duration: 24 Aug 201429 Aug 2014
Conference number: 19th

Publication series

NameIFAC Proceedings Volumes (IFAC-PapersOnline)
ISSN (Print)1474-6670


ConferenceInternational Federation of Automatic Control World Congress 2014
Abbreviated titleIFAC 2014
Country/TerritorySouth Africa
CityCape Town
Internet address

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