Alveolar recruitment maneuver attenuates extravascular lung water in acute respiratory distress syndrome

ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies

The aim of these guidelines is to update the 2017 clinical practice guideline (CPG) of the European Society of Intensive Care Medicine (ESICM). The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19). These guidelines were formulated by an international panel of clinical experts, one methodologist and patients' representatives on behalf of the ESICM. The review was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations and the quality of reporting of each study based on the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network guidelines. The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS). In addition, the CPG includes expert opinion on clinical practice and identifies the areas of future research.

ARDS Clinical Practice Guideline 2021

Background

The joint committee of the Japanese Society of Intensive Care Medicine/Japanese Respiratory Society/Japanese Society of Respiratory Care Medicine on ARDS Clinical Practice Guideline has created and released the ARDS Clinical Practice Guideline 2021.

Methods

The 2016 edition of the Clinical Practice Guideline covered clinical questions (CQs) that targeted only adults, but the present guideline includes 15 CQs for children in addition to 46 CQs for adults. As with the previous edition, we used a systematic review method with the Grading of Recommendations Assessment Development and Evaluation (GRADE) system as well as a degree of recommendation determination method. We also conducted systematic reviews that used meta-analyses of diagnostic accuracy and network meta-analyses as a new method.

Results

Recommendations for adult patients with ARDS are described: we suggest against using serum C-reactive protein and procalcitonin levels to identify bacterial pneumonia as the underlying disease (GRADE 2D); we recommend limiting tidal volume to 4–8 mL/kg for mechanical ventilation (GRADE 1D); we recommend against managements targeting an excessively low SpO₂ (PaO₂) (GRADE 2D); we suggest against using transpulmonary pressure as a routine basis in positive end-expiratory pressure settings (GRADE 2B); we suggest implementing extracorporeal membrane oxygenation for those with severe ARDS (GRADE 2B); we suggest against using high-dose steroids (GRADE 2C); and we recommend using low-dose steroids (GRADE 1B). The recommendations for pediatric patients with ARDS are as follows: we suggest against using non-invasive respiratory support (non-invasive positive pressure ventilation/high-flow nasal cannula oxygen therapy) (GRADE 2D), we suggest placing pediatric patients with moderate ARDS in the prone position (GRADE 2D), we suggest against routinely implementing NO inhalation therapy (GRADE 2C), and we suggest against implementing daily sedation interruption for pediatric patients with respiratory failure (GRADE 2D).

Conclusions

This article is a translated summary of the full version of the ARDS Clinical Practice Guideline 2021 published in Japanese (URL: https://www.jsicm.org/publication/guideline.html). The original text, which was written for Japanese healthcare professionals, may include different perspectives from healthcare professionals of other countries.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40560-022-00615-6.

ARDS clinical practice guideline 2021

BACKGROUND

The joint committee of the Japanese Society of Intensive Care Medicine/Japanese Respiratory Society/Japanese Society of Respiratory Care Medicine on ARDS Clinical Practice Guideline has created and released the ARDS Clinical Practice Guideline 2021.

METHODS

The 2016 edition of the Clinical Practice Guideline covered clinical questions (CQs) that targeted only adults, but the present guideline includes 15 CQs for children in addition to 46 CQs for adults. As with the previous edition, we used a systematic review method with the Grading of Recommendations Assessment Development and Evaluation (GRADE) system as well as a degree of recommendation determination method. We also conducted systematic reviews that used meta-analyses of diagnostic accuracy and network meta-analyses as a new method.

RESULTS

Recommendations for adult patients with ARDS are described: we suggest against using serum C-reactive protein and procalcitonin levels to identify bacterial pneumonia as the underlying disease (GRADE 2D); we recommend limiting tidal volume to 4-8 mL/kg for mechanical ventilation (GRADE 1D); we recommend against managements targeting an excessively low SpO₂ (PaO₂) (GRADE 2D); we suggest against using transpulmonary pressure as a routine basis in positive end-expiratory pressure settings (GRADE 2B); we suggest implementing extracorporeal membrane oxygenation for those with severe ARDS (GRADE 2B); we suggest against using high-dose steroids (GRADE 2C); and we recommend using low-dose steroids (GRADE 1B). The recommendations for pediatric patients with ARDS are as follows: we suggest against using non-invasive respiratory support (non-invasive positive pressure ventilation/high-flow nasal cannula oxygen therapy) (GRADE 2D); we suggest placing pediatric patients with moderate ARDS in the prone position (GRADE 2D); we suggest against routinely implementing NO inhalation therapy (GRADE 2C); and we suggest against implementing daily sedation interruption for pediatric patients with respiratory failure (GRADE 2D).

CONCLUSIONS

This article is a translated summary of the full version of the ARDS Clinical Practice Guideline 2021 published in Japanese (URL: https://www.jrs.or.jp/publication/jrs_guidelines/). The original text, which was written for Japanese healthcare professionals, may include different perspectives from healthcare professionals of other countries.

The Impact of Sample Size Misestimations on the Interpretation of ARDS Trials: Systematic Review and Meta-analysis

BACKGROUND

Indeterminate randomized controlled trials (RCTs) in ARDS may arise from sample size misspecification, leading to abandonment of efficacious therapies.

RESEARCH QUESTIONS

If evidence exists for sample size misspecification in ARDS RCTs, has this led to rejection of potentially beneficial therapies? Does evidence exist for prognostic enrichment in RCTs using mortality as a primary outcome?

STUDY DESIGN AND METHODS

We identified 150 ARDS RCTs commencing recruitment after the 1994 American European Consensus Conference ARDS definition and published before October 31, 2020. We examined predicted-observed sample size, predicted-observed control event rate (CER), predicted-observed average treatment effect (ATE), and the relationship between observed CER and observed ATE for RCTs with mortality and nonmortality primary outcome measures. To quantify the strength of evidence, we used Bayesian-averaged meta-analysis, trial sequential analysis, and Bayes factors.

RESULTS

Only 84 of 150 RCTs (56.0%) reported sample size estimations. In RCTs with mortality as the primary outcome, CER was overestimated in 16 of 28 RCTs (57.1%). To achieve predicted ATE, interventions needed to prevent 40.8% of all deaths, compared with the original prediction of 29.3%. Absolute reduction in mortality ≥ 10% was observed in 5 of 28 RCTs (17.9%), but predicted in 21 of 28 RCTs (75%). For RCTs with mortality as the primary outcome, no association was found between observed CER and observed ATE (pooled OR: β = -0.04; 95% credible interval, -0.18 to 0.09). We identified three interventions that are not currently standard of care with a Bayesian-averaged effect size of > 0.20 and moderate strength of existing evidence: corticosteroids, airway pressure release ventilation, and noninvasive ventilation.

INTERPRETATION

Reporting of sample size estimations was inconsistent in ARDS RCTs, and misspecification of CER and ATE was common. Prognostic enrichment strategies in ARDS RCTs based on all-cause mortality are unlikely to be successful. Bayesian methods can be used to prioritize interventions for future effectiveness RCTs.

Association of PEEP and Lung Recruitment Selection Strategies with Mortality in Acute Respiratory Distress Syndrome: A Systematic Review and Network Meta-Analysis

RATIONALE

The most beneficial positive end-expiratory pressure (PEEP) selection strategy in patients with acute respiratory distress syndrome (ARDS) is unknown and current practice is variable.

OBJECTIVES

To compare the relative effects of different PEEP selection strategies on mortality in adults with moderate to severe ARDS.

METHODS

We conducted a network meta-analysis using a Bayesian framework. Certainty of evidence was evaluated using GRADE methodology.

RESULTS

We included 18 randomized trials (4646 participants). In comparison to a lower PEEP strategy, the posterior probability of mortality benefit from a higher PEEP without lung recruitment maneuver (LRM) strategy was 99% (RR 0.77, 95% Crl 0.60-0.96, high certainty), the posterior probability of benefit of the Pes-guided strategy was 87% (RR 0.77, 95% CrI 0.48-1.22, moderate certainty), the posterior probability of benefit of a higher PEEP with brief LRM strategy was 96% (RR 0.83, 95% CrI 0.67-1.02, moderate certainty), and the posterior probability of increased mortality from a higher PEEP with prolonged LRM strategy was 77% (RR 1.06, 95% Crl 0.89-1.22, low certainty). In comparison to a higher PEEP without LRM strategy, the posterior probability of increased mortality from a higher PEEP with prolonged LRM strategy was 99% (RR 1.37, 95% CrI 1.04-1.81, moderate certainty).

CONCLUSIONS AND RELEVANCE

In patients with moderate to severe ARDS, higher PEEP without LRM is associated with a lower risk of death as compared to lower PEEP. A higher PEEP with prolonged LRM strategy is associated with increased risk of death when compared to higher PEEP without LRM.

Impact of differences in acute respiratory distress syndrome randomised controlled trial inclusion and exclusion criteria: systematic review and meta-analysis

BACKGROUND

Control-arm mortality varies between acute respiratory distress syndrome (ARDS) RCTs.

METHODS

We systematically reviewed ARDS RCTs that commenced recruitment after publication of the American-European Consensus (AECC) definition (MEDLINE, Embase, and Cochrane central register of controlled trials; January 1994 to October 2020). We assessed concordance of RCT inclusion criteria to ARDS consensus definitions and whether exclusion criteria are strongly or poorly justified. We estimated the proportion of between-trial difference in control-arm 28-day mortality explained by the inclusion criteria and RCT design characteristics using meta-regression.

RESULTS

A literature search identified 43 709 records. One hundred and fifty ARDS RCTs were included; 146/150 (97.3%) RCTs defined ARDS inclusion criteria using AECC/Berlin definitions. Deviations from consensus definitions, primarily aimed at improving ARDS diagnostic certainty, frequently related to duration of hypoxaemia (117/146; 80.1%). Exclusion criteria could be grouped by rationale for selection into strongly or poorly justified criteria. Common poorly justified exclusions included pregnancy related, age, and comorbidities (infectious/immunosuppression, hepatic, renal, and human immunodeficiency virus/acquired immunodeficiency syndrome). Control-arm 28-day mortality varied between ARDS RCTs (mean: 29.8% [95% confidence interval: 27.0-32.7%; I²=88.8%; τ²=0.02; P<0.01]), and differed significantly between RCTs with different Pao₂:FiO₂ ratio inclusion thresholds (26.6-39.9 kPa vs <26.6 kPa; P<0.01). In a meta-regression model, inclusion criteria and RCT design characteristics accounted for 30.6% of between-trial difference (P<0.01).

CONCLUSIONS

In most ARDS RCTs, consensus definitions are modified to use as inclusion criteria. Between-RCT mortality differences are mostly explained by the Pao₂:FiO₂ ratio threshold within the consensus definitions. An exclusion criteria framework can be applied when designing and reporting exclusion criteria in future ARDS RCTs.

Between-trial heterogeneity in ARDS research

Purpose

Most randomized controlled trials (RCTs) in patients with acute respiratory distress syndrome (ARDS) revealed indeterminate or conflicting study results. We aimed to systematically evaluate between-trial heterogeneity in reporting standards and trial outcome.

Methods

A systematic review of RCTs published between 2000 and 2019 was performed including adult ARDS patients receiving lung-protective ventilation. A random-effects meta-regression model was applied to quantify heterogeneity (non-random variability) and to evaluate trial and patient characteristics as sources of heterogeneity.

Results

In total, 67 RCTs were included. The 28-day control-group mortality rate ranged from 10 to 67% with large non-random heterogeneity (I² = 88%, p < 0.0001). Reported baseline patient characteristics explained some of the outcome heterogeneity, but only six trials (9%) reported all four independently predictive variables (mean age, mean lung injury score, mean plateau pressure and mean arterial pH). The 28-day control group mortality adjusted for patient characteristics (i.e. the residual heterogeneity) ranged from 18 to 45%. Trials with significant benefit in the primary outcome reported a higher control group mortality than trials with an indeterminate outcome or harm (mean 28-day control group mortality: 44% vs. 28%; p = 0.001).

Conclusion

Among ARDS RCTs in the lung-protective ventilation era, there was large variability in the description of baseline characteristics and significant unexplainable heterogeneity in 28-day control group mortality. These findings signify problems with the generalizability of ARDS research and underline the urgent need for standardized reporting of trial and baseline characteristics.

Supplementary Information

The online version of this article (10.1007/s00134-021-06370-w) contains supplementary material, which is available to authorized users.

The Nature of Recruitment and De-Recruitment and Its Implications for Management of ARDS

Recruitment maneuvers in ARDS are used to improve oxygenation and lung mechanics by applying high airway pressures to reopen collapsed or obstructed peripheral airways and alveoli. In the early 1990s, recruitment maneuvers became a central feature of a variant form of lung-protective ventilation known as open-lung ventilation. This strategy is based on the belief that repetitive opening and closing of distal airspaces induces shear injury and therefore contributes both to ventilator-induced lung injury and ARDS-associated mortality. However, the largest multi-center randomized controlled trial of open-lung ventilation in moderate to severe ARDS reported that recruitment maneuver plateau pressures of 50-60 cm H₂O were associated with significantly higher mortality compared to traditional lung-protective ventilation. Despite being based on well conducted preclinical and clinical recruitment maneuver studies, the higher mortality associated with the open-lung ventilation strategy requires re-examining the assumptions and conclusions drawn from those previous studies. This narrative review examines the evidence used to design recruitment maneuver strategies. We also review the radiologic, rheologic, and histopathologic evidence regarding the nature of lung injury and the phenomena of recruitment and de-recruitment as it informs our perceptions of recruitment potential in ARDS. Major lung-protective ventilation clinical trial data and other clinical data are also examined to assess the practical necessity of recruitment maneuvers in ARDS and whether a subset of cases might benefit from pursuing recruitment maneuver therapy. Finally, a less a radical approach to recruitment maneuvers is offered that might achieve the goals of recruitment maneuvers with less risk of harm.

Non-specialist therapeutic strategies in acute respiratory distress syndrome

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is associated with significant morbidity and mortality. We undertook a meta-analysis of randomized controlled trials (RCTs) to determine the mortality benefit of non-specialist therapeutic interventions for ARDS available to general critical care units.

EVIDENCE ACQUISITION

A systematic search of MEDLINE, Embase, and the Cochrane Central Register for RCTs investigating therapeutic interventions in ARDS including corticosteroids, fluid management strategy, high PEEP, low tidal volume ventilation, neuromuscular blockade, prone position ventilation, or recruitment maneuvers. Data was collected on demographic information, treatment strategy, duration and dose of treatment, and primary (28 or 30-day mortality) and secondary (P<inf>a</inf>O<inf>2</inf>:FiO<inf>2</inf> ratio at 24-48 hours) outcomes.

EVIDENCE SYNTHESIS

No improvement in 28-day mortality could be demonstrated in three RCTs investigating high PEEP (28.0% vs. 30.2% control; risk ratio [confidence interval] 0.93 [0.82-1.06]; eight assessing prone position ventilation (39.3% vs. 44.5%; RR 0.83 [0.68-1.01]; seven investigating neuromuscular blockade (37.8% vs. 42.0%; RR 0.91 [0.81-1.03]); ten investigating recruitment maneuvers (42.4% vs. 42.1%; RR 1.01 [0.91-1.12]); eight investigating steroids (34.8% vs. 41.1%; RR 0.81 [0.59-1.12]); and one investigating conservative fluid strategies (25.4% vs. 28.4%; RR 0.90 [0.73-1.10]). Three studies assessing low tidal volume ventilation (33.1% vs. 41.9%; RR 0.79 (0.68-0.91); P=0.001), and subgroup analyses within studies investigating prone position ventilation greater than 12 hours (33.1% vs. 44.4%; RR 0.75 [0.59-0.95), P=0.02) did reveal outcome benefit.

CONCLUSIONS

Among non-specialist therapeutic strategies available to general critical care units, low tidal volumes and prone position ventilation for greater than 12 hours improve mortality in ARDS.

Effect of lung recruitment maneuver on oxygenation, physiological parameters and mortality in acute respiratory distress syndrome patients: a systematic review and meta-analysis

PURPOSE

Among acute respiratory distress syndrome (ARDS) patients in intensive care units, the efficacy of lung recruitment maneuver (LRM) use is uncertain taking into account the most recent randomized controlled trials (RCTs). We aimed to estimate the effect of LRMs on mortality from ARDS.

METHODS

In this systematic review and meta-analysis, we searched for RCTs comparing mechanical ventilation with and without LRMs in adults with ARDS. We generated pooled relative risks (RR), mean difference, performed trial-sequential-analysis and cumulative meta-analysis. The primary outcome was 28-day mortality. The secondary outcomes were oxygenation evaluated by PaO₂/FiO₂ ratio, rate of rescue therapy and rate of hemodynamic compromise.

RESULTS

In 14 RCTs including 3185 patients, LRMs were not associated with reduced 28-day mortality (RR = 0.92, 95% confidence interval (95% CI) 0.82-1.04, P = 0.21), compared to no-LRM. Trial-sequential-analysis showed that the required information size has been accrued. PaO₂/FiO₂ ratio was significantly higher in the LRMs group in comparison to the no-LRM group (mean difference = 47.6 mmHg, 95% CI 33.4-61.8, P < 0.001). LRMs were associated with a decreased rate of rescue therapy (RR = 0.69 95% CI 0.56-0.84, P < 0.001), and an increased rate of hemodynamic compromise (RR = 1.19, 95% CI 1.06-1.33, P = 0.002), compared to no-LRM group. Using cumulative meta-analysis, a significant change for effect on mortality was observed after 2017.

CONCLUSIONS

The results suggest that in ARDS patients, systematic use of LRMs does not significantly improve 28-day mortality. However, LRM use was associated with positive effects such as an oxygenation improvement and a less frequent use of rescue therapy. Nevertheless, LRM use was associated with negative effects such as hemodynamic impairment.

Recruitment manoeuvres for adults with acute respiratory distress syndrome receiving mechanical ventilation: a systematic review and meta-analysis

PURPOSE

To determine if recruitment manoeuvres (RMs) would decrease 28-day mortality of patients with acute respiratory distress syndrome (ARDS) compared with standard care.

MATERIALS AND METHODS

Relevant randomized controlled trials (RCTs) published prior to April 26, 2018 were systematically searched. The primary outcome was mortality. The secondary outcomes were oxygenation, barotrauma or pneumothorax, the need for rescue therapies. Data were pooled using the random effects model. And the quality of evidence was assessed by the GRADE system.

RESULTS

Of 3180 identified studies, 15 were eligibly included in our analysis (N = 2755 participants). In the primary outcome, RMs were not associated with reducing 28-day mortality (RR 0.90; 95% CI 0.74-1.09), ICU mortality (RR 0.92; 95% CI 0.74-1.1), and the in-hospital mortaliy (RR 1.02; 95% CI 0.93-1.12). In the secondary outcomes, RMs could improve oxygenation (MD 37.85; 95% CI 11.08-64.61), the rates of barotrauma (RR 1.42; 95% CI 0.83-2.42) and the need for rescue therapies (RR 0.69; 95% CI 0.42-1.12) did not show any difference in the ARDS patients with RMs.

CONCLUSIONS

Earlier meta-analyses found decreased mortality with RMs, in the contrary, our results indicate that RMs could improve oxygenation without detrimental effects, but it does not appear to reduce mortality.

Extravascular lung water measurements in acute respiratory distress syndrome: why, how, and when?

PURPOSE OF REVIEW

Increase in pulmonary vascular permeability accompanied with accumulation of excess extravascular lung water (EVLW) is the hallmark of acute respiratory distress syndrome (ARDS). Currently, EVLW and pulmonary vascular permeability index (PVPI) can be quantitatively measured using the transpulmonary thermodilution (TPTD) technique. We will clarify why, how, and when EVLW and PVPI measurements should be performed.

RECENT FINDINGS

Although the Berlin criteria of ARDS are simple and widely used, several criticisms of them have been published. The last 2 decades have witnessed the introduction and evolution of the TPTD technique for measuring EVLW and PVPI. Several publications have recommended to evaluate EVLW and the PVPI during the treatment of critically ill patients. Accurate and objective diagnoses can be made for ARDS patients using EVLW and PVPI. EVLW more than 10 ml/kg is a reasonable criterion for pulmonary edema, and EVLW more than 15 ml/kg for a severe condition. In addition to EVLW more than 10 mL/kg, PVPI more than three suggests increased vascular permeability (i.e., ARDS), and PVPI less than 2 represent normal vascular permeability (i.e., cardiogenic pulmonary edema).

SUMMARY

EVLW and PVPI measurement will open the door to future ARDS clinical practice and research, and have potential to be included in the future ARDS definition.