Das, Anup, Cole, Oana, Chikhani, Marc, Wang, Wenfei, Ali, Tayyba, Haque, Mainul, Bates, Declan and Hardman, Jonathan G. (2015) Evaluation of lung recruitment maneuvers in acute respiratory distress syndrome using computer simulation. Critical Care, Volume 19 (Number 1). Article number 8. doi:10.1186/s13054-014-0723-6

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Abstract

Introduction
Direct comparison of the relative efficacy of different recruitment maneuvers (RMs) for patients with acute respiratory distress syndrome (ARDS) via clinical trials is difficult, due to the heterogeneity of patient populations and disease states, as well as a variety of practical issues. There is also significant uncertainty regarding the minimum values of positive end-expiratory pressure (PEEP) required to ensure maintenance of effective lung recruitment using RMs. We used patient-specific computational simulation to analyze how three different RMs act to improve physiological responses, and investigate how different levels of PEEP contribute to maintaining effective lung recruitment.

Methods
We conducted experiments on five ‘virtual’ ARDS patients using a computational simulator that reproduces static and dynamic features of a multivariable clinical dataset on the responses of individual ARDS patients to a range of ventilator inputs. Three recruitment maneuvers (sustained inflation (SI), maximal recruitment strategy (MRS) followed by a titrated PEEP, and prolonged recruitment maneuver (PRM)) were implemented and evaluated for a range of different pressure settings.

Results
All maneuvers demonstrated improvements in gas exchange, but the extent and duration of improvement varied significantly, as did the observed mechanism of operation. Maintaining adequate post-RM levels of PEEP was seen to be crucial in avoiding cliff-edge type re-collapse of alveolar units for all maneuvers. For all five patients, the MRS exhibited the most prolonged improvement in oxygenation, and we found that a PEEP setting of 35 cm H2O with a fixed driving pressure of 15 cm H2O (above PEEP) was sufficient to achieve 95% recruitment. Subsequently, we found that PEEP titrated to a value of 16 cm H2O was able to maintain 95% recruitment in all five patients.

Conclusions
There appears to be significant scope for reducing the peak levels of PEEP originally specified in the MRS and hence to avoid exposing the lung to unnecessarily high pressures. More generally, our study highlights the huge potential of computer simulation to assist in evaluating the efficacy of different recruitment maneuvers, in understanding their modes of operation, in optimizing RMs for individual patients, and in supporting clinicians in the rational design of improved treatment strategies.

Item Type:	Journal Article
Subjects:	R Medicine > RC Internal medicine
Divisions:	Faculty of Science > Engineering
Library of Congress Subject Headings (LCSH):	Respiratory distress syndrome, Adult -- Treatment -- Computer simulation
Journal or Publication Title:	Critical Care
Publisher:	BioMed Central Ltd.
ISSN:	1466-609X
Official Date:	12 January 2015
Dates:	Date Event 12 January 2015 Published 16 December 2014 Accepted 8 July 2014 Submitted
Volume:	Volume 19
Number:	Number 1
Article Number:	Article number 8
DOI:	10.1186/s13054-014-0723-6
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), Medical Research Council (Great Britain) (MRC)
Grant number:	EP/F057016/2 (EPSRC), EP/F057059/1 (EPSRC), EP/1036680/2 (EPSRC), G1002017 (MRC), MR/K019783 (MRC)

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