Time-varying respiratory system elastance: a physiological model for patients who are spontaneously breathing

Yeong Shiong Chiew; Christopher Pretty; Paul D Docherty; Bernard Lambermont; Geoffrey M Shaw; Thomas Desaive; J Geoffrey Chase

doi:10.1371/journal.pone.0114847

Time-varying respiratory system elastance: a physiological model for patients who are spontaneously breathing

PLoS One. 2015 Jan 22;10(1):e0114847. doi: 10.1371/journal.pone.0114847. eCollection 2015.

Authors

Yeong Shiong Chiew¹, Christopher Pretty¹, Paul D Docherty¹, Bernard Lambermont², Geoffrey M Shaw³, Thomas Desaive², J Geoffrey Chase¹

Affiliations

¹ Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
² GIGA Cardiovascular Science, University of Liege, Liege, Belgium.
³ Department of Intensive Care, Christchurch Hospital, Christchurch, New Zealand.

Abstract

Background: Respiratory mechanics models can aid in optimising patient-specific mechanical ventilation (MV), but the applications are limited to fully sedated MV patients who have little or no spontaneously breathing efforts. This research presents a time-varying elastance (E(drs)) model that can be used in spontaneously breathing patients to determine their respiratory mechanics.

Methods: A time-varying respiratory elastance model is developed with a negative elastic component (E(demand)), to describe the driving pressure generated during a patient initiated breathing cycle. Data from 22 patients who are partially mechanically ventilated using Pressure Support (PS) and Neurally Adjusted Ventilatory Assist (NAVA) are used to investigate the physiology relevance of the time-varying elastance model and its clinical potential. E(drs) of every breathing cycle for each patient at different ventilation modes are presented for comparison.

Results: At the start of every breathing cycle initiated by patient, E(drs) is < 0. This negativity is attributed from the E(demand) due to a positive lung volume intake at through negative pressure in the lung compartment. The mapping of E(drs) trajectories was able to give unique information to patients' breathing variability under different ventilation modes. The area under the curve of E(drs) (AUCE(drs)) for most patients is > 25 cmH2Os/l and thus can be used as an acute respiratory distress syndrome (ARDS) severity indicator.

Conclusion: The E(drs) model captures unique dynamic respiratory mechanics for spontaneously breathing patients with respiratory failure. The model is fully general and is applicable to both fully controlled and partially assisted MV modes.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Elasticity*
Humans
Models, Biological*
Respiratory Distress Syndrome / physiopathology*
Respiratory Mechanics*
Time

Grants and funding

This work was supported in part by the FNRS 474 (Belgium), the FRST (New Zealand), the University of Liege, the 475, Belgian French Community (ARC—Academie Wallonie Europe). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.