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.

Lung Rest with Femoro-Femoral Veno-Venous Extracorporeal Membrane Oxygenation for COVID-19 Severe Pneumonia with Pneumomediastinum

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sometimes causes severe coronavirus disease 2019 (COVID-19) pneumonia. Here, we report the case of a 35-year-old man with obesity who showed severe respiratory failure from SARS-CoV-2 infection. Immediate high-resolution computed tomography (HRCT) of the chest after endotracheal intubation revealed a significant pneumomediastinum with diffuse ground-glass opacity and consolidation. Ventilator management was difficult with low tidal volume and low positive end expiratory pressure. Therefore, we administered extracorporeal membrane oxygenation (ECMO) to allow lung rest and prevent further progression of the pneumomediastinum and maintain oxygenation. Since implementing ECMO, the patient's oxygenation has stabilized and follow-up HRCT of the chest revealed dramatic improvement of the pneumomediastinum. We gradually tapered off ECMO and employed a pressure-control mode. He was extubated on day 11. To our knowledge, this is the first reported patient who showed complete pneumomediastinum recovery from COVID-19 pneumonia with ECMO.

Optimal timing of tracheostomy in patients on veno-venous extracorporeal membrane oxygenation for coronavirus 2019: a case series

Aim

An early tracheostomy is often considered for patients with veno‐venous extracorporeal membrane oxygenation (VV‐ECMO). However, there is no consensus on the timing of a tracheostomy in patients on VV‐ECMO for coronavirus disease 2019 (COVID‐19). The present report described the optimal timing of tracheostomy for these patients.

Method

The present study was a single‐center case series. We retrospectively reviewed the medical records of nine consecutive patients who underwent tracheostomy either during or after VV‐ECMO treatment in our center between January 1, 2020 and December 31, 2020.

Results

All the patients received a percutaneous dilatational tracheostomy, which was performed during VV‐ECMO in four patients. Three of these patients experienced hemorrhagic complications, and the remaining patient required a circuit change on the day after the operation. Heparin was discontinued 8 h preoperatively and resumed 1–14 h later. The platelet count was below normal in two patients, but no transfusion was performed. APTT was almost normal, and D‐dimer was elevated postoperatively. The remaining five patients received a tracheostomy after weaning off VV‐ECMO, and no complication was observed. Eight patients were deeply sedated during VV‐ECMO to prioritize lung rest and prevent infecting the healthcare workers.

Conclusion

In the present study, patients who underwent a tracheostomy during VV‐ECMO tended to have more hemorrhagic complications. Because an early tracheostomy during ECMO has little benefit for patients with COVID‐19, it should be performed after weaning off VV‐ECMO to protect the safety of the healthcare workers concerned.

EMPROVING outcomes: Evaluating the effect of an ultralung protective strategy for patients with ARDS treated with ECMO

OBJECTIVE

Since the initiation of an adult extracorporeal membrane oxygenation (ECMO) program at our institution, the program has managed well over 200 patients with ECMO in a 3-year time frame. While there is a plethora of research evaluating ECMO for acute respiratory distress syndrome (ARDS), few studies have evaluated the impact that ventilator management after cannulation might have on outcomes. We hypothesized that failure to properly protect the lungs after cannulation would lead to higher mortality.

MATERIALS AND METHODS

This was a retrospective observational study performed from 1 January 2014 to 8 July 2018.

RESULTS

A total of 196 patients were treated with ECMO, 57 of whom were diagnosed with ARDS and treated with venovenous ECMO. The univariable analysis revealed a statistically higher total serum bilirubin and lower total days on ECMO in those who died vs those who lived. During ECMO, higher mean peak inspiratory pressures (PIP) and higher FiO₂ were found in those who died vs those who lived. In multivariable analysis, increasing age (odds ratio [OR] = 1.2; confidence interval [CI] = 1.04-1.39, P = .02), increasing mean PIP, and increasing mean FiO₂ concentration during ECMO (PIP: OR = 1.40, CI = 1.03-1.89, P = .03; FiO₂ : OR = 1.16, CI = 1.02-1.32, P = .02) were all associated with increased mortality.

CONCLUSION

Failing to protect the lungs with a lung protective strategy such as the EMPROVE protocol after ECMO cannulation was associated with mortality. For every 1 mm Hg increase in the mean PIP, the odds of dying increased 1.4 times, and for every 1% increase in the mean FiO₂ , the odds of dying increased 1.16 times. For lung rest to truly be effective, the lungs must be relieved of the burden of gas exchange.

Applied Uses of Extracorporeal Membrane Oxygenation Therapy

Extracorporeal membrane oxygenation (ECMO) therapy has been around since the 1970s and has completely changed how critical care physicians view supportive therapy for certain patients. ECMO therapy is a supportive therapy provided by a mechanical extracorporeal circuit that is able to directly oxygenate and remove carbon dioxide from the blood. By performing this, ECMO can provide cardiac, respiratory, or combined cardiopulmonary supportive therapy in cases of failure. ECMO therapy also places less emphasis on invasive mechanical ventilation, which prevents barotrauma and gives rest to the lungs. Therefore, they are used for several different conditions. This review article focuses on the definition, principles, types, and practical applications of ECMO therapy.

Lung Rest During Extracorporeal Membrane Oxygenation for Neonatal Respiratory Failure-Practice Variations and Outcomes

OBJECTIVE

Describe practice variations in ventilator strategies used for lung rest during extracorporeal membrane oxygenation for respiratory failure in neonates, and assess the potential impact of various lung rest strategies on the duration of extracorporeal membrane oxygenation and the duration of mechanical ventilation after decannulation.

DATA SOURCES

Retrospective cohort analysis from the Extracorporeal Life Support Organization registry database during the years 2008-2013.

STUDY SELECTION

All extracorporeal membrane oxygenation runs for infants less than or equal to 30 days of life for pulmonary reasons were included.

DATA EXTRACTION

Ventilator type and ventilator settings used for lung rest at 24 hours after extracorporeal membrane oxygenation initiation were obtained.

DATA SYNTHESIS

A total of 3,040 cases met inclusion criteria. Conventional mechanical ventilation was used for lung rest in 88% of cases and high frequency ventilation was used in 12%. In the conventional mechanical ventilation group, 32% used positive end-expiratory pressure strategy of 4-6 cm H2O (low), 22% used 7-9 cm H2O (mid), and 43% used 10-12 cm H2O (high). High frequency ventilation was associated with an increased mean (SEM) hours of extracorporeal membrane oxygenation (150.2 [0.05] vs 125 [0.02]; p < 0.001) and an increased mean (SEM) hours of mechanical ventilation after decannulation (135 [0.09] vs 100.2 [0.03]; p = 0.002), compared with conventional mechanical ventilation among survivors. Within the conventional mechanical ventilation group, use of higher positive end-expiratory pressure was associated with a decreased mean (SEM) hours of extracorporeal membrane oxygenation (high vs low: 136 [1.06] vs 156 [1.06], p = 0.001; mid vs low: 141 [1.06] vs 156 [1.06]; p = 0.04) but increased duration of mechanical ventilation after decannulation in the high positive end-expiratory pressure group compared with low positive end-expiratory pressure (p = 0.04) among survivors.

CONCLUSIONS

Wide practice variation exists with regard to ventilator settings used for lung rest during neonatal respiratory extracorporeal membrane oxygenation. Use of high frequency ventilation when compared with conventional mechanical ventilation and use of low positive end-expiratory pressure strategy when compared with mid positive end-expiratory pressure and high positive end-expiratory pressure strategy is associated with longer duration of extracorporeal membrane oxygenation. Further research to provide evidence to drive optimization of pulmonary management during neonatal respiratory extracorporeal membrane oxygenation is warranted.