Mechanical ventilation during extracorporeal life support (ECLS): a systematic review

Extracorporeal Membrane Oxygenation for Respiratory Failure: A Narrative Review

Extracorporeal membrane oxygenation support for respiratory failure in the intensive care unit continues to have an expanded role in select patients. While acute respiratory distress syndrome remains the most common indication, extracorporeal membrane oxygenation may be used in other causes of refractory hypoxemia and/or hypercapnia. The most common configuration is veno-venous extracorporeal membrane oxygenation; however, in specific cases of refractory hypoxemia or right ventricular failure, some patients may benefit from veno-pulmonary extracorporeal membrane oxygenation or veno-venoarterial extracorporeal membrane oxygenation. Patient selection and extracorporeal circuit management are essential to successful outcomes. This narrative review explores the physiology of extracorporeal membrane oxygenation, indications and contraindications, ventilator management, extracorporeal circuit management, troubleshooting hypoxemia, complications, and extracorporeal membrane oxygenation weaning in patients with respiratory failure. As the footprint of extracorporeal membrane oxygenation continues to expand, it is essential that clinicians understand the underlying physiology and management of these complex patients.

Mechanical ventilation during extracorporeal membrane oxygenation support - New trends and continuing challenges

BACKGROUND

The impact of mechanical ventilation on the survival of patients supported with veno-venous extracorporeal membrane oxygenation (V-V ECMO) due to severe acute respiratory distress syndrome (ARDS) remains still a focus of research.

METHODS

Recent guidelines, randomized trials, and registry data underscore the importance of lung-protective ventilation during respiratory and cardiac support on ECMO.

RESULTS

This approach includes decreasing mechanical power delivery by reducing tidal volume and driving pressure as much as possible, using low or very low respiratory rate, and a personalized approach to positive-end expiratory pressure (PEEP) setting. Notably, the use of ECMO in awake and spontaneously breathing patients is increasing, especially as a bridging strategy to lung transplantation. During respiratory support in V-V ECMO, native lung function is of highest importance and adjustments of blood flow on ECMO, or ventilator settings significantly impact the gas exchange. These interactions are more complex in veno-arterial (V-A) ECMO configuration and cardiac support. The fraction on delivered oxygen in the sweep gas and sweep gas flow rate, blood flow per minute, and oxygenator efficiency have an impact on gas exchange on device side. On the patient side, native cardiac output, native lung function, carbon dioxide production (VCO2), and oxygen consumption (VO2) play a role. Avoiding pulmonary oedema includes left ventricle (LV) distension monitoring and prevention, pulse pressure >10 mm Hg and aortic valve opening assessment, higher PEEP adjustment, use of vasodilators, ECMO flow adjustment according to the ejection fraction, moderate use of inotropes, diuretics, or venting strategies as indicated and according to local expertise and resources.

CONCLUSION

Understanding the physiological principles of gas exchange during cardiac support on femoro-femoral V-A ECMO configuration and the interactions with native gas exchange and haemodynamics are essential for the safe applications of these techniques in clinical practice. Proning during ECMO remains to be discussed until further data is available from prospective, randomized trials implementing individualized PEEP titration during proning.

Respiratory extracorporeal membrane oxygenation : From rescue therapy to standard tool for treatment of acute respiratory distress syndrome?

BACKGROUND

The use of extracorporeal membrane oxygenation (ECMO) for patients with acute respiratory distress syndrome (ARDS) has increased substantially. With modern trials supporting its efficacy, ECMO has become an important tool in the management of severe ARDS.

OBJECTIVES

The objectives of this paper are to discuss ECMO physiology and configurations used for patients with ARDS, review evidence supporting the use of ECMO for ARDS, and discuss aspects of management during ECMO.

CONCLUSION

Current evidence supports the use of ECMO, combined with an ultra-lung-protective approach to mechanical ventilation, in patients with ARDS who have refractory hypoxemia or hypercapnia with severe respiratory acidosis. Furthermore, data suggest that center volume and experience are important factors in the care of patients receiving ECMO. The use of extracorporeal technologies in expanded patient populations and the optimal management of patients during ECMO remain areas of investigation. This article is freely available.

Ventilation during extracorporeal gas exchange in acute respiratory distress syndrome

PURPOSE OF REVIEW

Accumulating evidence ascribes the benefit of extracorporeal gas exchange, at least in most severe cases, to the provision of a lung healing environment through the mitigation of ventilator-induced lung injury (VILI) risk. In spite of pretty homogeneous criteria for extracorporeal gas exchange application (according to the degree of hypoxemia/hypercapnia), ventilatory management during extracorporeal membrane oxygenation (ECMO)/carbon dioxide removal (ECCO 2 R) varies across centers. Here we summarize the recent evidence regarding the management of mechanical ventilation during extracorporeal gas exchange for respiratory support.

RECENT FINDINGS

At present, the most common approach to protect the native lung against VILI following ECMO initiation involves lowering tidal volume and driving pressure, making modest reductions in respiratory rate, while typically maintaining positive end-expiratory pressure levels unchanged.Regarding ECCO 2 R treatment, higher efficiency devices are required in order to reduce significantly respiratory rate and/or tidal volume.

SUMMARY

The best compromise between reduction of native lung ventilatory load, extracorporeal gas exchange efficiency, and strategies to preserve lung aeration deserves further investigation.

Management of severe acute respiratory distress syndrome: a primer

This narrative review explores the physiology and evidence-based management of patients with severe acute respiratory distress syndrome (ARDS) and refractory hypoxemia, with a focus on mechanical ventilation, adjunctive therapies, and veno-venous extracorporeal membrane oxygenation (V-V ECMO). Severe ARDS cases increased dramatically worldwide during the Covid-19 pandemic and carry a high mortality. The mainstay of treatment to improve survival and ventilator-free days is proning, conservative fluid management, and lung protective ventilation. Ventilator settings should be individualized when possible to improve patient-ventilator synchrony and reduce ventilator-induced lung injury (VILI). Positive end-expiratory pressure can be individualized by titrating to best respiratory system compliance, or by using advanced methods, such as electrical impedance tomography or esophageal manometry. Adjustments to mitigate high driving pressure and mechanical power, two possible drivers of VILI, may be further beneficial. In patients with refractory hypoxemia, salvage modes of ventilation such as high frequency oscillatory ventilation and airway pressure release ventilation are additional options that may be appropriate in select patients. Adjunctive therapies also may be applied judiciously, such as recruitment maneuvers, inhaled pulmonary vasodilators, neuromuscular blockers, or glucocorticoids, and may improve oxygenation, but do not clearly reduce mortality. In select, refractory cases, the addition of V-V ECMO improves gas exchange and modestly improves survival by allowing for lung rest. In addition to VILI, patients with severe ARDS are at risk for complications including acute cor pulmonale, physical debility, and neurocognitive deficits. Even among the most severe cases, ARDS is a heterogeneous disease, and future studies are needed to identify ARDS subgroups to individualize therapies and advance care.

Extracorporeal membrane oxygenation for COVID-19 and influenza associated acute respiratory distress syndrome: a systematic review

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) has been used extensively for H1N1 influenza and coronavirus disease 2019 (COVID-19)-related acute respiratory distress syndrome (ARDS) to improve gas exchange and quickly correct hypoxemia and hypercapnia. This systematic review summarized the evidence on ECMO for the treatment of COVID-19 and influenza-associated ARDS.

RESEARCH DESIGN AND METHODS

This is a systematic review and meta-analysis of studies to compare the efficacy and safety of ECMO with conventional mechanical ventilation in adults with COVID-19 and influenza-associated ARDS. The study performed a structured search on PubMed, Embase, Web of Science, Scopus and The Cochrane Library. The primary outcome was hospital mortality.

RESULTS

The study included 15 observational studies with 5239 patients with COVID-19 and influenza-associated ARDS. The use of ECMO significantly reduced in-hospital mortality in COVID-19-associated ARDS (OR = 0.40; 95% CI = 0.27-0.58; P < 0.00001) but did not reduce influenza-related mortality (OR = 1.08; 95% CI = 0.41-2.87; P = 0.87). Moreover, ECMO treatment meaningfully increased the incidence of bleeding complications (OR = 7.66; 95% CI = 2.47-23.72; P = 0.0004).

CONCLUSION

The use of ECMO significantly reduced in-hospital mortality in COVID-19- associated ARDS, which may be related to the advances in ECMO-related techniques and the increased experience of clinicians. However, the incidence of bleeding complications remains high. [Figure: see text].

Extracorporeal membrane oxygenation (ECMO) and beyond in near fatal asthma: A comprehensive review

The treatment of choice in severe asthma exacerbations with respiratory failure includes ventilatory support, both invasive and/or non-invasive, along with different kinds of asthma medication. Of note, the rate of mortality of patients with asthma has decreased substantially in recent years mainly due to significant advances in pharmacological treatment and other management strategies. However, the risk of death in patients with severe asthma who require invasive mechanical ventilation has been estimated between 6.5% and 10.3%. When conventional measures fail, rescue strategies, such as extracorporeal membrane oxygenation (ECMO) or extracorporeal CO2 removal (ECCO2R) may need to be implemented. While ECMO does not constitute a definitive treatment per se, it can minimize further ventilator associated lung injury (VALI) and can enable diagnostic-therapeutic maneuvers that cannot be performed without ECMO such as bronchoscopy and transfer for diagnostic imaging. Asthma is one of the diseases that is associated with excellent outcomes for patients with refractory respiratory failure requiring ECMO support, as shown by the Extracorporeal Life Support Organization (ELSO) registry. Moreover, in such situations, the use of ECCO2R for rescue has been described and utilized in both children and adults and is more widely spread in different hospitals than ECMO. In this article, we aim to review the evidence for the usefulness of extracorporeal respiratory support measures in the management of severe asthma exacerbations that lead to respiratory failure.

Influence of confirmed viral infection on adult acute fulminant myocarditis supported with extracorporeal membrane oxygenation

BACKGROUND

The impact of etiologies of acute fulminant myocarditis (AFM), which requires extracorporeal membrane oxygenation (ECMO), on clinical outcomes remains unknown. This study aimed to investigate the risk factors for ECMO weaning and mortality among patients with AFM due to viral etiologies in a tertiary referral medical center.

METHODS

We included 33 adults with AFM who received ECMO and were admitted between January 2002 and January 2021. General demographics, laboratory data, echocardiography findings, and long-term outcomes were analyzed for confirmed viral etiology and unconfirmed etiology groups.

RESULTS

The overall hospital survival rate was 54.5%. The age, sex, severity of the hemodynamic condition, and cardiac rhythm were similar between the two groups. Multivariate Cox regression analysis revealed that a confirmed viral etiology (HR 4.201, 95% CI 1.061-16.666), peri-ECMO renal replacement therapy (RRT) (HR 9.804, 1.140-83.333) and a high positive end-expiratory pressure (PEEP) in the ventilator settings at 24 h after ECMO (HR 1.479, 1.020-2.143) were significant prognostic factors for in-hospital mortality. Peri-ECMO RRT was also a significant negative prognostic factor for successful ECMO weaning (OR 0.061, 0.006-0.600) in the multivariate logistic model.

CONCLUSIONS

Among AFM patients receiving ECMO support, RRT use was associated with a decreased chance of survival to ECMO weaning. Multiple organ dysfunction and a high PEEP were also predictive of a lower chance of hospital survival. Those with a confirmed diagnosis of viral myocarditis may require more medical attention due to the higher risk of hospital mortality than those without a definite diagnosis.

Extracorporeal Membrane Oxygenation in Acute Respiratory Failure

Venovenous (VV) extracorporeal membrane oxygenation (ECMO) is a form of mechanical life support that provides full respiratory bypass in patients with severe respiratory failure as a bridge to recovery or lung transplantation. The use of ECMO for respiratory failure and capable centers offering ECMO has expanded over the years, increasing its availability. As VV-ECMO provides an artificial mechanism for oxygenation and decarboxylation of native blood, it allows for an environment in which safer mechanical ventilatory care may be provided, allowing for treatment and resolution of underlying respiratory pathologies. Landmark clinical trials have provided a framework for better understanding patient selection criteria, resource utilization, and outcomes associated with ECMO when applied in settings of refractory respiratory failure. Maintaining close vigilance and management of complications during ECMO as well as identifying strategies post-ECMO (e.g., recovery, transplantation, etc.), are critical to successful ECMO support. In this review, we examine considerations for candidate selection for VV-ECMO, review the evidence of utilizing VV-ECMO in respiratory failure, and provide practical considerations for managing respiratory ECMO patients, including complication identification and management, as well as assessing for the ability to separate from ECMO support and the procedures for decannulation.

Effect of Hypoxemia on Outcome in Respiratory Failure Supported With Extracorporeal Membrane Oxygenation: A Cardinality Matched Cohort Study

Venovenous extracorporeal membrane oxygenation (ECMO) is recommended in adult patients with refractory acute respiratory failure (ARF), but there is limited evidence for its use in patients with less severe hypoxemia. Prior research has suggested a lower PaO 2 /FiO 2 at cannulation is associated with higher short-term mortality, but it is unclear whether this is due to less severe illness or a potential benefit of earlier ECMO support. In this exploratory cardinality-matched observational cohort study, we matched 668 patients who received venovenous ECMO as part of a national severe respiratory failure service into cohorts of "less severe" and "very severe" hypoxemia based on the median PaO 2 /FiO 2 at ECMO institution of 68 mmHg. Before matching, ICU mortality was 19% in the 'less severe' hypoxemia group and 28% in the "very severe" hypoxemia group (RR for mortality = 0.69, 95% CI 0.54-0.88). After matching on key prognostic variables including underlying diagnosis, this difference remained statistically present but smaller: (23% vs. 30%, RR = 0.76, 95% CI 0.59-0.99). This may suggest the observed survival benefit of venovenous ECMO is not solely due to reduced disease severity. Further research is warranted to examine the potential role of ECMO in ARF patients with less severe hypoxemia.

Transesophageal Echocardiography-Guided Extracorporeal Membrane Oxygenation Cannulation in COVID-19 Patients

OBJECTIVES

A paucity of data supports the use of transesophageal echocardiography (TEE) for bedside extracorporeal membrane oxygenation (ECMO) cannulation. Concerns have been raised about performing TEEs in patients with COVID-19. The authors describe the use and safety of TEE guidance for ECMO cannulation for COVID-19.

DESIGN

Single-center retrospective cohort study.

SETTING

The study took place in the intensive care unit of an academic tertiary center.

PARTICIPANTS

The authors included 107 patients with confirmed SARS-CoV-2 infection who underwent bedside venovenous ECMO (VV ECMO) cannulation under TEE guidance between May 2020 and June 2021.

INTERVENTIONS

TEE-guided bedside VV ECMO cannulation.

MEASUREMENTS

Patient characteristics, physiologic and ventilatory parameters, and echocardiographic findings were analyzed. The primary outcome was the number of successful TEE-guided bedside cannulations without complications. The secondary outcomes were cannulation complications, frequency of cannula repositioning, and TEE-related complications.

MAIN RESULTS

TEE-guided cannulation was successful in 99% of the patients. Initial cannula position was adequate in all but 1 patient. Fourteen patients (13%) required cannula repositioning during ECMO support. Forty-five patients (42%) had right ventricular systolic dysfunction, and 9 (8%) had left ventricular systolic dysfunction. Twelve patients (11%) had intracardiac thrombi. One superficial arterial injury and 1 pneumothorax occurred. No pericardial tamponade, hemothorax or intraabdominal bleeding occurred in the authors' cohort. No TEE-related complications or COVID-19 infection of healthcare providers were reported during this study.

CONCLUSIONS

Bedside TEE guidance for VV ECMO cannulation is safe in patients with severe respiratory failure due to COVID-19. No tamponade or hemothorax, nor TEE-related complications were observed in the authors' cohort.

When is tamponade not an echocardiographic diagnosis… Or is it ever?

Although cardiac tamponade remains a clinical diagnosis, echocardiography is an essential tool to detect fluid in the pericardial space. Interpretation of echocardiographic findings and assessment of physiologic and hemodynamic consequences of a pericardial effusion require a thorough understanding of pathophysiologic processes. Certain echocardiographic signs point toward the presence of cardiac tamponade: a dilated inferior vena cava (IVC), collapse of the cardiac chambers, an inspiratory bulge of the interventricular septum into the left ventricle (LV) (the "septal bounce"), and characteristic respiratory variations of Doppler flow velocity recordings. However, in certain circumstances (e.g., mechanical ventilation, post-surgical patients, and pulmonary hypertension), these echocardiographic signs can be missing, despite the presence of clinical tamponade. Failure to recognize a potentially life-threatening clinical condition due to the absence of corresponding echocardiographic findings can delay both diagnosis and life-saving treatment. Thus, in the context of critical care, echocardiography should only be used to confirm the presence of pericardial fluid or localized hematoma, and the diagnosis of tamponade should rely on clinical criteria.

Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Acute Respiratory Distress Syndrome: A Narrative Review

Acute respiratory distress syndrome (ARDS) is a life-threatening condition involving acute hypoxemic respiratory failure. Mechanical ventilation remains the cornerstone of management for ARDS; however, potentially injurious mechanical forces introduce the risk of ventilator-induced lung injury, multiple organ failure, and death. Extracorporeal membrane oxygenation (ECMO) is a salvage therapy aimed at ensuring adequate gas exchange for patients suffering from severe ARDS with profound hypoxemia where conventional mechanical ventilation has failed. ECMO allows for lower tidal volumes and airway pressures, which can reduce the risk of further lung injury, and allow the lungs to rest. However, the collateral effect of ECMO should be considered. Recent studies have reported correlations between mechanical ventilator settings during ECMO and mortality. In many cases, mechanical ventilation settings should be tailored to the individual; however, researchers have yet to establish optimal ventilator settings or determine the degree to which ventilation load can be decreased. This paper presents an overview of previous studies and clinical trials pertaining to the management of mechanical ventilation during ECMO for patients with severe ARDS, with a focus on clinical findings, suggestions, protocols, guidelines, and expert opinions. We also identified a number of issues that have yet to be adequately addressed.

Procollagen I and III as Prognostic Markers in Patients Treated with Extracorporeal Membrane Oxygenation: A Prospective Observational Study

Background: Procollagen peptides have been associated with lung fibroproliferation and poor outcomes in patients with acute respiratory distress syndrome (ARDS). Therefore, serum procollagen concentrations might have prognostic value in ARDS patients treated with extracorporeal membrane oxygenation (ECMO). Methods: In a prospective cohort study, serum N-terminal procollagen I-peptide (PINP) and N-terminal procollagen III-peptide (PIIINP) concentrations in twenty-three consecutive patients with severe ARDS treated with ECMO were measured at the time of ECMO initiation and during the course of treatment. The predictive value of PINP and PIIINP at the time of ECMO initiation was tested with a univariable logistic regression and a receiver operating characteristic (ROC) curve analysis. Results: Thirteen patients survived to intensive care unit (ICU) discharge. Non-survivors had higher serum PINP and PIIINP concentrations at all points in time during the course of treatment. Serum PIIINP at the day of ECMO initiation showed an odds ratio of 1.37 (95% CI 1.10–1.89, p = 0.017) with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.87 (95% CI 0.69–1.00, p = 0.0029) for death during the course of treatment. Conclusions: PINP and PIIINP concentrations differ between survivors and non-survivors in ARDS treated with ECMO. This exploratory hypothesis generating study suggests an association between PIIINP serum concentrations at ECMO initiation and an unfavorable clinical outcome.

The Evolution of the Use of Extracorporeal Membrane Oxygenation in Respiratory Failure

Extracorporeal membrane oxygenation (ECMO) has been used with increasing frequency to support patients with acute respiratory failure, most commonly, and severe forms of acute respiratory distress syndrome (ARDS). The marked increase in the global use of ECMO followed the publication of a large randomized trial in 2009 and the experience garnered during the 2009 influenza A (H1N1) pandemic, and has been further supported by the release of a large, randomized clinical trial in 2018, confirming a benefit from using ECMO in patients with severe ARDS. Despite a rapid expansion of ECMO-related publications, optimal management of patients receiving ECMO, in terms of patient selection, ventilator management, anticoagulation, and transfusion strategies, is evolving. Most recently, ECMO is being utilized for an expanding variety of conditions, including for cases of severe pulmonary or cardiac failure from coronavirus disease 2019 (COVID-19). This review evaluates modern evidence for ECMO for respiratory failure and the current challenges in the field.

Rest ventilator management in children on veno-venous extracorporeal membrane oxygenation

BACKGROUND

We aimed to use the Extracorporeal Life Support Organization registry to describe the current practice of rest mechanical ventilation setting in children receiving veno-venous extracorporeal membrane oxygenation (V-V ECMO) and to determine if relationships exist between ventilator settings and mortality.

METHODS

Data for patients 14 days to 18 years old who received V-V ECMO from 2012-2016 were reviewed. Mechanical ventilation data available includes mode and settings at 24 h after ECMO cannulation. Multivariable logistic regression analysis was performed to determine if rest settings were associated with mortality.

RESULTS

We reviewed 1161 subjects, of which 1022 (88%) received conventional mechanical ventilation on ECMO. Rest settings, expressed as medians (25th%, 75th%), are as follows: rate 12 breaths/minute (10, 17); peak inspiratory pressure (PIP) 22 cmH₂O (20,27); positive end expiratory pressure (PEEP) 10 cmH₂O (8, 10); and fraction of inspired oxygen (F_iO₂) 0.4 (0.37, 0.60). Survival to discharge was 68%. Higher ventilator F_iO₂ (odds ratio:1.13 per 0.1 increase, 95% confidence interval:1.04, 1.23), independent of arterial oxygen saturation, was associated with mortality.

CONCLUSIONS

Current rest ventilator management for children receiving V-V ECMO primarily relies on conventional mechanical ventilation with moderate amounts of PIP, PEEP, and FiO₂. Further study on the relationship between FiO₂ and mortality should be pursued.

Extracorporeal Life Support Organization (ELSO): 2020 Pediatric Respiratory ELSO Guideline

DISCLAIMER

This guideline describes prolonged extracorporeal life support (ECLS) and extracorporeal membrane oxygenation (ECMO), applicable to Pediatric respiratory failure. These guidelines describe useful and safe practice, prepared by ELSO and based on extensive experience and are considered consensus guidelines. These guidelines are not intended to define standard of care and are revised at regular intervals as new information, devices, medications, and techniques become available.

Assessment of Electrical Impedance Tomography to Set Optimal Positive End-Expiratory Pressure for Venoarterial Extracorporeal Membrane Oxygenation-Treated Patients

OBJECTIVES

Patients on venoarterial extracorporeal membrane oxygenation have many risk factors for pulmonary complications in addition to their heart failure. Optimal positive end-expiratory pressure is unknown in these patients. The aim was to evaluate the ability of electrical impedance tomography to help the physician to select the optimal positive end-expiratory pressure in venoarterial extracorporeal membrane oxygenation treated and mechanically ventilated patients during a positive end-expiratory pressure trial.

DESIGN

Observational prospective monocentric.

SETTING

University hospital.

PATIENTS

Patients (n = 23) older than 18 years old, on mechanical ventilation and venoarterial extracorporeal membrane oxygenation.

INTERVENTIONS

A decreasing positive end-expiratory pressure trial (20-5 cm H2O) in increments of 5 cm H2O was performed and monitored by a collection of clinical parameters, ventilatory and ultrasonographic (cardiac and pulmonary) to define an optimal positive end-expiratory pressure according to respiratory criteria (optimal positive end-expiratory pressure selected by physician with respiratory parameters), and then adjusted according to hemodynamic and cardiac tolerances (optimal positive end-expiratory pressure selected by physician with respiratory, hemodynamic, and echocardiographic parameters). At the same time, electrical impedance tomography data (regional distribution of ventilation, compliance, and overdistension collapse) were recorded and analyzed retrospectively to define the optimal positive end-expiratory pressure.

MEASUREMENTS AND MAIN RESULTS

The median of this optimal positive end-expiratory pressure was 10 cm H2O in our population. Electrical impedance tomography showed that increasing positive end-expiratory pressure promoted overdistention of ventral lung, maximum at positive end-expiratory pressure 20 cm H20 (34% [interquartile range, 24.5-40]). Decreasing positive end-expiratory pressure resulted in collapse of dorsal lung (29% [interquartile range, 21-45.8]). The optimal positive end-expiratory pressure selected by physician with respiratory parameters was not different from the positive end-expiratory pressure chosen by the electrical impedance tomography. However, there is a negative impact of a high level of intrathoracic pressure on hemodynamic and cardiac tolerances.

CONCLUSIONS

Our results support that electrical impedance tomography appears predictive to define optimal positive end-expiratory pressure on venoarterial extracorporeal membrane oxygenation, aided by echocardiography to optimize hemodynamic assessment and management.

Low Spontaneous Breathing Effort during Extracorporeal Membrane Oxygenation in a Porcine Model of Severe Acute Respiratory Distress Syndrome

BACKGROUND

A lung rest strategy is recommended during extracorporeal membrane oxygenation in severe acute respiratory distress syndrome (ARDS). However, spontaneous breathing modes are frequently used in this context. The impact of this approach may depend on the intensity of breathing efforts. The authors aimed to determine whether a low spontaneous breathing effort strategy increases lung injury, compared to a controlled near-apneic ventilation, in a porcine severe ARDS model assisted by extracorporeal membrane oxygenation.

METHODS

Twelve female pigs were subjected to lung injury by repeated lavages, followed by 2-h injurious ventilation. Thereafter, animals were connected to venovenous extracorporeal membrane oxygenation and during the first 3 h, ventilated with near-apneic ventilation (positive end-expiratory pressure, 10 cm H2O; driving pressure, 10 cm H2O; respiratory rate, 5/min). Then, animals were allocated into (1) near-apneic ventilation, which continued with the previous ventilatory settings; and (2) spontaneous breathing: neuromuscular blockers were stopped, sweep gas flow was decreased until regaining spontaneous efforts, and ventilation was switched to pressure support mode (pressure support, 10 cm H2O; positive end-expiratory pressure, 10 cm H2O). In both groups, sweep gas flow was adjusted to keep Paco2 between 30 and 50 mmHg. Respiratory and hemodynamic as well as electric impedance tomography data were collected. After 24 h, animals were euthanized and lungs extracted for histologic tissue analysis.

RESULTS

Compared to near-apneic group, the spontaneous breathing group exhibited a higher respiratory rate (52 ± 17 vs. 5 ± 0 breaths/min; mean difference, 47; 95% CI, 34 to 59; P < 0.001), but similar tidal volume (2.3 ± 0.8 vs. 2.8 ± 0.4 ml/kg; mean difference, 0.6; 95% CI, -0.4 to 1.4; P = 0.983). Extracorporeal membrane oxygenation settings and gas exchange were similar between groups. Dorsal ventilation was higher in the spontaneous breathing group. No differences were observed regarding histologic lung injury.

CONCLUSIONS

In an animal model of severe ARDS supported with extracorporeal membrane oxygenation, spontaneous breathing characterized by low-intensity efforts, high respiratory rates, and very low tidal volumes did not result in increased lung injury compared to controlled near-apneic ventilation.

EDITOR’S PERSPECTIVE

Ventilatory management of patients on ECMO

Extracorporeal membrane oxygenation (ECMO) is the final treatment offered to patients of acute respiratory distress syndrome (ARDS). The survival (to discharge) of patients on veno-venous ECMO is approximately 59% with an average duration of 8 days. The ventilatory management of lungs during the ECMO may have an impact on mortality. An ideal ventilation modality should promote recovery, prevent further damage to the alveoli, and enable weaning from mechanical ventilation. This article reviews the concept of “baby lung” in ARDS and the current evidence for the use of lung protective ventilation, prevention of ventilator-induced lung injury, recommended modes of mechanical ventilation, ideal ventilatory parameters (tidal volume, positive end expiratory pressure, plateau pressure, respiratory rate, fractional inspired oxygen concentration), and use of adjuncts (prone positioning, neuromuscular blocking agents) during the ECMO course.

Mechanical Ventilation Management during Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome. An International Multicenter Prospective Cohort

Rationale: Current practices regarding mechanical ventilation in patients treated with extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome are unknown.Objectives: To report current practices regarding mechanical ventilation in patients treated with ECMO for severe acute respiratory distress syndrome (ARDS) and their association with 6-month outcomes.Methods: This was an international, multicenter, prospective cohort study of patients undergoing ECMO for ARDS during a 1-year period in 23 international ICUs.Measurements and Main Results: We collected demographics, daily pre- and per-ECMO mechanical ventilation settings and use of adjunctive therapies, ICU, and 6-month outcome data for 350 patients (mean ± SD pre-ECMO Pa_O2/Fi_O2 71 ± 34 mm Hg). Pre-ECMO use of prone positioning and neuromuscular blockers were 26% and 62%, respectively. Vt (6.4 ± 2.0 vs. 3.7 ± 2.0 ml/kg), plateau pressure (32 ± 7 vs. 24 ± 7 cm H₂O), driving pressure (20 ± 7 vs. 14 ± 4 cm H₂O), respiratory rate (26 ± 8 vs. 14 ± 6 breaths/min), and mechanical power (26.1 ± 12.7 vs. 6.6 ± 4.8 J/min) were markedly reduced after ECMO initiation. Six-month survival was 61%. No association was found between ventilator settings during the first 2 days of ECMO and survival in multivariable analysis. A time-varying Cox model retained older age, higher fluid balance, higher lactate, and more need for renal-replacement therapy along the ECMO course as being independently associated with 6-month mortality. A higher Vt and lower driving pressure (likely markers of static compliance improvement) across the ECMO course were also associated with better outcomes.Conclusions: Ultraprotective lung ventilation on ECMO was largely adopted across medium- to high-case volume ECMO centers. In contrast with previous observations, mechanical ventilation settings during ECMO did not impact patients' prognosis in this context.

Extracorporeal membrane oxygenation support in adult patients with acute respiratory distress syndrome

Introduction: The global number of patients receiving extracorporeal membrane oxygenation (ECMO) support has been growing after several studies highlighted the favorable results attained in cases of severe respiratory failure. However, evidence-based guidelines for optimal use of ECMO are lacking.Areas covered: This review covers optimal candidates, timing of initiation, strategies for patient management including mechanical ventilation, and decision-making regarding discontinuation of ECMO based on its potential role in treatment of patients with acute respiratory distress syndrome.Expert opinion: Early initiation of ECMO should be considered if hypoxemia and uncompensated hypercapnia do not respond to optimal conventional treatment. Use of a comprehensive management approach for preventing additional lung injury and extrapulmonary organ failure is critical during ECMO support to ensure the best outcome. The possibility of weaning from ECMO should be fully assessed by a multidisciplinary team during ECMO support. Futility should not be determined solely by duration of ECMO, and use of prolonged ECMO for lung recovery may be worthwhile.

Extracorporeal membrane oxygenation: a literature review

Extracorporeal membrane oxygenation is a modality of extracorporeal life support that allows for temporary support in pulmonary and/or cardiac failure refractory to conventional therapy. Since the first descriptions of extracorporeal membrane oxygenation, significant improvements have occurred in the device and the management of patients and, consequently, in the outcomes of critically ill patients during extracorporeal membrane oxygenation. Many important studies about the use of extracorporeal membrane oxygenation in patients with acute respiratory distress syndrome refractory to conventional clinical support, under in-hospital cardiac arrest and with cardiogenic refractory shock have been published in recent years. The objective of this literature review is to present the theoretical and practical aspects of extracorporeal membrane oxygenation support for respiratory and/or cardiac functions in critically ill patients.

Bedside troubleshooting during venovenous extracorporeal membrane oxygenation (ECMO)

In this review, we discuss common difficulties that clinicians may encounter while managing patients treated with venovenous (VV) extracorporeal membrane oxygenation (ECMO). ECMO is an increasingly important tool for managing severe respiratory failure that is refractory to conventional therapies. Its overall goal is to manage respiratory failure-induced hypoxemia and hypercarbia to allow "lung rest" and promote recovery. Typically, by the time VV-ECMO is initiated, the patient's pulmonary condition requires conventional ventilator settings that are detrimental to lung recovery or that exceed the remaining functional lung's ability to maintain acceptable physiological conditions. Standard mechanical ventilation can activate inflammation and worsen the pulmonary damage caused by the underlying disease, leading to ventilator-induced lung injury. In contrast, VV-ECMO facilitates lung-protective ventilation, decreasing further ventilator-induced lung injury and allowing lung recovery. Such lung-protective ventilation seeks to avoid barotrauma (by monitoring transpulmonary pressure), volutrauma (by reducing excessive tidal volume to promote lung rest), atelectotrauma [by maintaining adequate positive end-expiratory pressure (PEEP)], and oxygen toxicity (by decreasing ventilator oxygen levels when PEEP is adequate). ECMO for adult respiratory failure was associated with overall survival of 62% in 2018, according to the Extracorporeal Life Support Organization (ELSO) January 2019 registry report. Difficulties that may arise during VV-ECMO require timely diagnosis and optimal management to achieve the most favorable outcomes. These difficulties include ventilation issues, hypoxemia (especially as related to recirculation or low ECMO-flow-to-cardiac-output ratio), sepsis, malfunctioning critical circuit components, lack of clarity regarding optimal hemoglobin levels, hematological/anticoagulation complications, and right ventricular (RV) dysfunction. A culture of safety should be emphasized to optimize patient outcomes. A properly functioning team-not only the bedside clinician, but also nurses, perfusionists, respiratory therapists, physical therapists, pharmacists, nutritionists, and other medical specialists and allied health personnel-is vital for therapeutic success.

Lung Compliance and Outcomes in Patients With Acute Respiratory Distress Syndrome Receiving ECMO

BACKGROUND

Limited data are available regarding mechanical ventilation strategies in patients with acute respiratory distress syndrome receiving extracorporeal membrane oxygenation (ECMO).

METHODS

A retrospective analysis of acute respiratory distress syndrome patients on ECMO was conducted in 9 hospitals in Korea. Data on ventilator settings (pre-ECMO and 0, 4, 24, and 48 hours after ECMO) were collected. Based on the effect of the duration and intensity of mechanical ventilator on outcomes, time-weighted average values were calculated for ventilator parameters.

RESULTS

The 56 patients included in the study had a mean age of 55.5 years. The hospital and 6-month mortality rates were 48.1% and 54.0%, respectively, with a median ECMO duration of 9.4 days. After initiation of ECMO, peak inspiratory pressure, above positive end-expiratory pressure, tidal volume, and respiration rate were reduced, while lung compliance did not change significantly. Before and during ECMO support, tidal volume and lung compliance were higher in 6-month survivors than in nonsurvivors. In Cox proportional models, both lung compliance (odds ratio, 0.961; 95% confidence interval, 0.928 to 0.995) and time-weighted average-lung compliance (odds ratio, 0.943; 95% confidence interval, 0.903 to 0.986) were significantly associated with 6-month mortality. Kaplan-Meier curves revealed that patients with higher lung compliance before ECMO had a longer survival time at the 6-month follow-up than did those with lower lung compliance.

CONCLUSIONS

Lung compliance, whether before or during ECMO, may be an important predictor of outcome in acute respiratory distress syndrome patients receiving ECMO. However, this result requires confirmation in larger clinical studies.

Venovenous extracorporeal membrane oxygenation for acute respiratory distress syndrome: a systematic review and meta-analysis

BACKGROUND

Use of extracorporeal membrane oxygenation (ECMO) in adults with severe acute respiratory distress syndrome has increased in the past 10 years. However, the efficacy of venovenous ECMO in people with acute respiratory distress syndrome is uncertain according to the most recent data. We aimed to estimate the effect of venovenous ECMO on mortality from acute respiratory distress syndrome.

METHODS

In this systematic review and meta-analysis, we searched MEDLINE (including MEDLINE In-Process and Epub Ahead of Print), Embase and the Wiley search platform in the Cochrane database for randomised controlled trials and observational studies with matching of conventional mechanical ventilation with and without venovenous ECMO in adults with acute respiratory distress syndrome. Titles, abstracts, and full-text articles were screened in duplicate by two investigators. Data for study design, patient characteristics, interventions, and study outcomes were abstracted independently and in duplicate. Studies were weighted with the inverse variance method and data were pooled via random-effects modelling. We calculated risk ratios (RRs) and 95% CIs to summarise results. The primary outcome was 60-day mortality across randomised controlled trials. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines were used to rate the quality of evidence FINDINGS: We included five studies, two randomised controlled trials and three observational studies with matching techniques (total N=773 patients). In the primary analysis, which included two randomised controlled trials with a total population of 429 patients, 60-day mortality was significantly lower in the venovenous ECMO group than in the control group (73 [34%] of 214 vs 101 [47%] of 215; RR 0·73 [95% CI 0·58-0·92]; p=0·008; I² 0%). The GRADE level of evidence for this outcome was moderate. Three studies included data for the incidence of major haemorrhage in the ECMO group. 48 (19%) of the 251 patients in these three studies had major haemorrhages.

INTERPRETATION

Compared with conventional mechanical ventilation, use of venovenous ECMO in adults with severe acute respiratory distress syndrome was associated with reduced 60-day mortality. However, venovenous ECMO was also associated with a moderate risk of major bleeding. These findings have important implications surrounding decision making for management of severe acute respiratory distress syndrome at centres providing venovenous ECMO.

FUNDING

None.

Mechanical ventilation and respiratory monitoring during extracorporeal membrane oxygenation for respiratory support

Over the past decade, the use of veno-venous extracorporeal membrane oxygenation (VV-ECMO) for respiratory support has widely expanded as a treatment strategy for patients with acute respiratory distress syndrome (ARDS). Despite considerable attention has been given to the indications, the timing and the management of patients undergoing ECMO for refractory respiratory hypoxemic failure, little is known regarding the management of mechanical ventilation (MV) in this group of patients. ECMO enables to minimize ventilatory induced lung injury (VILI) and it has been successfully used as rescue therapy in patients with ARDS when conventional ventilator strategies have failed. However, literature is lacking regarding the best strategies and MV settings, including positive end expiratory pressure (PEEP), tidal volume (VT), respiratory rate (RR) and plateau pressure (PPLAT). The aim of this review is to summarize current evidence, the rationale and provide recommendations about the best ventilator strategy to adopt in patients with ARDS undergoing VV-ECMO support.

When the momentum has gone: what will be the role of extracorporeal lung support in the future?

PURPOSE OF REVIEW

There has been expanding interest in and use of extracorporeal support in respiratory failure concurrent with technological advances and predominantly observational data demonstrating improved outcomes. However, until there is more available data from rigorous, high-quality randomized studies, the future of extracorporeal support remains uncertain.

RECENT FINDINGS

Outcomes for patients supported with extracorporeal devices continue to show favorable trends. There are several large randomized controlled trials that are in various stages of planning or completion for extracorporeal membrane oxygenation (ECMO) and extracorporeal carbon dioxide removal (ECCO2R) in the acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD), which may help clarify the role of this technology for these disease processes, and which stand to have a significant impact on a large proportion of patients with acute respiratory failure. Novel applications of extracorporeal lung support include optimization of donor organ quality through ex-vivo perfusion and extracorporeal cross-circulation, allowing for multimodal therapeutic interventions.

SUMMARY

Despite the ongoing rise in ECMO use for acute respiratory failure, its true value will not be known until more information is gleaned from prospective randomized controlled trials. Additionally, there are modalities beyond the current considerations for extracorporeal support that have the potential to revolutionize respiratory failure, particularly in the realm of chronic lung disease and lung transplantation.

Should we use driving pressure to set tidal volume?

PURPOSE OF REVIEW

Ventilator-induced lung injury (VILI) can occur despite use of tidal volume (VT) limited to 6 ml/kg of predicted body weight, especially in patients with a smaller aerated compartment (i.e. the baby lung) in which, indeed, tidal ventilation takes place. Because respiratory system static compliance (CRS) is mostly affected by the volume of the baby lung, the ratio VT/CRS (i.e. the driving pressure, ΔP) may potentially help tailoring interventions on VT setting.

RECENT FINDINGS

Driving pressure is the ventilatory variable most strongly associated with changes in survival and has been shown to be the key mediator of the effects of mechanical ventilation on outcome in the acute respiratory distress syndrome. Observational data suggest an increased risk of death for patients with ΔP more than 14 cmH2O, but a well tolerated threshold for this parameter has yet to be identified. Prone position along with simple ventilatory adjustments to facilitate CO2 clearance may help reduce ΔP in isocapnic conditions. The safety and feasibility of low-flow extracorporeal CO2 removal in enhancing further reduction in VT and ΔP are currently being investigated.

SUMMARY

Driving pressure is a bedside available parameter that may help identify patients prone to develop VILI and at increased risk of death. No study had prospectively evaluated whether interventions on ΔP may provide a relevant clinical benefit, but it appears physiologically sound to try titrating VT to minimize ΔP, especially when it is higher than 14 cmH2O and when it has minimal costs in terms of CO2 clearance.

ARDS: challenges in patient care and frontiers in research

This review discusses the clinical challenges associated with ventilatory support and pharmacological interventions in patients with acute respiratory distress syndrome (ARDS). In addition, it discusses current scientific challenges facing researchers when planning and performing trials of ventilatory support or pharmacological interventions in these patients.

Noninvasive mechanical ventilation is used in some patients with ARDS. When intubated and mechanically ventilated, ARDS patients should be ventilated with low tidal volumes. A plateau pressure <30 cmH₂O is recommended in all patients. It is suggested that a plateau pressure <15 cmH₂O should be considered safe. Patient with moderate and severe ARDS should receive higher levels of positive end-expiratory pressure (PEEP). Rescue therapies include prone position and neuromuscular blocking agents. Extracorporeal support for decapneisation and oxygenation should only be considered when lung-protective ventilation is no longer possible, or in cases of refractory hypoxaemia, respectively. Tracheotomy is only recommended when prolonged mechanical ventilation is expected.

Of all tested pharmacological interventions for ARDS, only treatment with steroids is considered to have benefit.

Proper identification of phenotypes, known to respond differently to specific interventions, is increasingly considered important for clinical trials of interventions for ARDS. Such phenotypes could be defined based on clinical parameters, such as the arterial oxygen tension/inspiratory oxygen fraction ratio, but biological marker profiles could be more promising.

Treatment of ARDS is mainly through the prevention of ventilation-induced lung injuryhttp://ow.ly/DeJC30hGWfi

Perioperative Management of the Adult Patient on Venovenous Extracorporeal Membrane Oxygenation Requiring Noncardiac Surgery

The use of venovenous extracorporeal membrane oxygenation is increasing worldwide. These patients often require noncardiac surgery. In the perioperative period, preoperative assessment, patient transport, choice of anesthetic type, drug dosing, patient monitoring, and intraoperative and postoperative management of common patient problems will be impacted. Furthermore, common monitoring techniques will have unique limitations. Importantly, patients on venovenous extracorporeal membrane oxygenation remain subject to hypoxemia, hypercarbia, and acidemia in the perioperative setting despite extracorporeal support. Treatments of these conditions often require both manipulation of extracorporeal membrane oxygenation settings and physiologic interventions. Perioperative management of anticoagulation, as well as thresholds to transfuse blood products, remain highly controversial and must take into account the specific procedure, extracorporeal membrane oxygenation circuit function, and patient comorbidities. We will review the physiologic management of the patient requiring surgery while on venovenous extracorporeal membrane oxygenation.

Pathophysiology and Management of Acute Respiratory Distress Syndrome in Children

Acute respiratory distress syndrome (ARDS) is a syndrome of noncardiogenic pulmonary edema and hypoxia that accompanies up to 30% of deaths in pediatric intensive care units. Pediatric ARDS (PARDS) is diagnosed by the presence of hypoxia, defined by oxygenation index or Pao₂/Fio₂ ratio cutoffs, and new chest infiltrate occurring within 7 days of a known insult. Hallmarks of ARDS include hypoxemia and decreased lung compliance, increased work of breathing, and impaired gas exchange. Mortality is often accompanied by multiple organ failure. Although many modalities to treat PARDS have been investigated, supportive therapies and lung protective ventilator support remain the mainstay.

Respiratory support in patients with acute respiratory distress syndrome: an expert opinion

Acute respiratory distress syndrome (ARDS) is a common condition in intensive care unit patients and remains a major concern, with mortality rates of around 30–45% and considerable long-term morbidity. Respiratory support in these patients must be optimized to ensure adequate gas exchange while minimizing the risks of ventilator-induced lung injury. The aim of this expert opinion document is to review the available clinical evidence related to ventilator support and adjuvant therapies in order to provide evidence-based and experience-based clinical recommendations for the management of patients with ARDS.