Positive end-expiratory pressure-induced recruited lung volume measured by volume-pressure curves in ARDS:
a physiologic systemic review and meta-analysis
The rationale for using positive end-expiratory pressure (PEEP) is to prevent lung decruitment during expiration and thereby improving oxygenation and distribution of ventilation. A tool that can be used to measure recruited lung volume at the bedside is the volume-pressure (VP) curve on the ventilator. So far, no studies have proven a relationship between recruited lung volume measured by VP curves to set PEEP and mortality in ARDS patients.
In this systematic review, Turbil et al. tried to assess PEEP-induced recruitment measured by the VP curve defined as >150 ml in ARDS patients in association with mortality.
After a literature search on Pubmed and using study references to find additional papers, a total number of 21 papers were retrieved. These papers were all observational studies. All papers were assessed for risk of bias using a protocolised tool.
The obtained data were analysed into two parts. In the first part, the pooled data directly obtained from the published papers were analysed. In the second part, individual patient level data were analysed.
308 patients from 16 papers were included for the pooled data meta-analysis. The overall prevalence of recruitment was 74% (95% CI 64-84%). There were no differences in independent variables, including mortality, between recruiters and non-recruiters, except for compliance at baseline (difference 13.83 ml/cmH2O).
In the second part, individual patient level data were analysed. These data were available for a total of 384 patients (14 papers). The prevalence of recruiters was 70% (266/380 patients). ICU mortality was 44% (152/344 patients). The relative risk (RR) of mortality for recruiters vs. non-recruiters was not significant (RR 1.05, 95% CI 0.86-1.3). Recruited volume was used as a continuous variable instead of a dichotomous data to predict ICU mortality using a ROC curve. This relationship was poor (AUC ROC 0.52, 95% CI 0.46-0.58) however.
STUDY STRENGTHS & LIMITATIONS
- First systematic review and meta-analysis to assess PEEP-induced recruited lung volume and mortality in ARDS patients.
- The assessment of certainty of evidence using the GRADE methodology for mortality was regarded as very low.
- There was a significant publication bias in studies reporting in favour of significant associations between recruited lung volume and patient outcomes.
- The analysis was based on observational data.
- Some papers included were dated before the ARMA trial.
- Recruited lung volume might be affected by airway opening pressure and the data did not enable investigation of this parameter.
- Authors were unable to assess the effect of time after diagnosis of ARDS and recruitability.
- Missing data might have affected the results.
TAKE HOME MESSAGE
Decruitment of lung volume (>150 ml) using increment of PEEP using the VP curve is not associated with improved mortality. However, no prospective studies exist and more research is needed.
This article review was prepared and submitted by Dr Anna Hall, Zorg Saam Hospital, Terneuzen (Netherlands) on behalf of the ESICM Journal Review Club.
Turbil, E., Terzi, N., Cour, M. et al. Positive end-expiratory pressure-induced recruited lung volume measured by volume-pressure curves in acute respiratory distress syndrome: a physiologic systematic review and meta-analysis. Intensive Care Med(2020)