Extracorporeal lung support for advanced lung failure: a new era in thoracic surgery and translational science

A Reduced Resistance, Concentric-Gated Artificial Membrane Lung for Pediatric End-Stage Lung Failure

The goal of the low-resistance pediatric artificial lung (PAL-LR) is to serve as a pumpless bridge-to-transplant device for children with end-stage lung failure. The PAL-LR doubles the exposed fiber length of the previous PAL design. In vitro and in vivo studies tested hemocompatibility, device flow, gas exchange and pressure drop performance. For in vitro tests, average rated blood flow (outlet SO2 of 95%) was 2.56 ± 0.93 L/min with a pressure drop of 25.88 ± 0.90 mm Hg. At the targeted pediatric flow rate of 1 L/min, the pressure drop was 8.6 mm Hg compared with 25 mm Hg of the PAL. At rated flow, the average O2 and CO2 transfer rates were 101.75 ± 10.81 and 77.93 ± 8.40 mL/min, respectively. The average maximum O2 and CO2 exchange efficiencies were 215.75 ± 22.93 and 176.99 ± 8.40 mL/(min m2), respectively. In vivo tests revealed an average outlet SO2 of 100%, and average pressure drop of 2 ± 0 mm Hg for a blood flow of 1.07 ± 0.02 L/min. Having a lower resistance, the PAL-LR is a promising step closer to a pumpless artificial membrane lung that alleviates right ventricular strain associated with idiopathic pulmonary hypertension.

Oxygenation performance assessment of an artificial lung in different central anatomic configurations

OBJECTIVES

Aim of this work was to characterize possible central anatomical configurations in which a future artificial lung (AL) could be connected, in terms of oxygenation performance.

METHODS

Pulmonary and systemic circulations were simulated using a numerical and an in vitro approach. The in vitro simulation was carried out in a mock loop in three phases: (1) normal lung, (2) pulmonary shunt (50% and 100%), and (3) oxygenator support in three anatomical configurations: right atrium-pulmonary artery (RA-PA), pulmonary artery-left atrium (PA-LA), and aorta-left atrium (Ao-LA). The numerical simulation was performed for the oxygenator support phase. The oxygen saturation (SO₂) of the arterial blood was plotted over time for two percentages of pulmonary shunt and three blood flow rates through the oxygenator.

RESULTS

During the pulmonary shunt phase, SO₂ reached a steady state value (of 68% for a 50% shunt and of nearly 0% for a 100% shunt) 20 min after the shunt was set. During the oxygenator support phase, physiological values of SO₂ were reached for RA-PA and PA-LA, in case of a 50% pulmonary shunt. For the same conditions, Ao-LA could reach a maximum SO₂ of nearly 60%. Numerical results were congruous to the in vitro simulation ones.

CONCLUSIONS

Both in vitro and numerical simulations were able to properly characterize oxygenation properties of a future AL depending on its placement. Different anatomical configurations perform differently in terms of oxygenation. Right to right and right to left connections perform better than left to left ones.

Association of pulmonary arterial pressure with volume status in patients with acute respiratory distress syndrome receiving extracorporeal membrane oxygenation

Background

Data on pulmonary hemodynamic parameters in patients with acute respiratory distress syndrome (ARDS) receiving extracorporeal membrane oxygenation (ECMO) are scarce.

Methods

The associations between pulmonary artery catheter parameters for the first 7 days of ECMO, fluid balance, and hospital mortality were investigated in adult patients (aged ≥19 years) who received venovenous ECMO for refractory ARDS between 2015 and 2017.

Results

Twenty patients were finally included in the analysis (median age, 56.0 years; interquartile range, 45.5-68.0; female, n=10). A total of 140 values were collected for each parameter (i.e., 7 days×20 patients). Net fluid balance was weakly but significantly correlated with systolic and diastolic pulmonary arterial pressures (PAPs; r=0.233 and P<0.001; r=0.376 and P<0.001, respectively). Among the mechanical ventilation parameters, above positive end-expiratory pressure was correlated with systolic PAP (r=0.191 and P=0.025), and static compliance was negatively correlated with diastolic PAP (r=-0.169 and P=0.048). Non-survivors had significantly higher systolic PAPs than in survivors. However, in multivariate analysis, there was no significant association between mean systolic PAP and hospital mortality (odds ratio, 1.500; 95% confidence interval, 0.937-2.404; P=0.091).

Conclusion

Systolic PAP was weakly but significantly correlated with net fluid balance during the early ECMO period in patients with refractory ARDS receiving ECMO.

Artificial lungs--Where are we going with the lung replacement therapy?

Lung transplantation may be a final destination therapy in lung failure, but limited donor organ availability creates a need for alternative management, including artificial lung technology. This invited review discusses ongoing developments and future research pathways for respiratory assist devices and tissue engineering to treat advanced and refractory lung disease. An overview is also given on the aftermath of the coronavirus disease 2019 pandemic and lessons learned as the world comes out of this situation. The first order of business in the future of lung support is solving the problems with existing mechanical devices. Interestingly, challenges identified during the early days of development persist today. These challenges include device-related infection, bleeding, thrombosis, cost, and patient quality of life. The main approaches of the future directions are to repair, restore, replace, or regenerate the lungs. Engineering improvements to hollow fiber membrane gas exchangers are enabling longer term wearable systems and can be used to bridge lung failure patients to transplantation. Progress in the development of microchannel-based devices has provided the concept of biomimetic devices that may even enable intracorporeal implantation. Tissue engineering and cell-based technologies have provided the concept of bioartificial lungs with properties similar to the native organ. Recent progress in artificial lung technologies includes continued advances in both engineering and biology. The final goal is to achieve a truly implantable and durable artificial lung that is applicable to destination therapy.

Extracorporeal Membrane Oxygenation and Lung Transplantation: Initial Experience at a Single Brazilian Center

OBJECTIVE

To report initial experience from the use of extracorporeal membrane oxygenation (ECMO) in patients who received lung transplantation.

METHODS

Retrospective study of a single tertiary center in the Brazilian state of São Paulo, a national reference in lung transplantation, based on the prospective collection of data from electronic medical records. The period analyzed extended from January 2009 (beginning of the program) until December 2018.

RESULTS

A total of 75 lung transplants were performed, with ECMO used in 8 (10.7%) cases. Of the patients, 4 (50%) were female. The mean age was 46.4±14.3 years. The causes of the end-stage lung disease that led to transplantation were pulmonary arterial hypertension in 3 (37.5%) patients, bronchiectasis in 2 (25%) patients, pulmonary fibrosis in 2 (25%) patients, and pulmonary emphysema in 1 (12.5%) patient. In our series, 7 (87.5%) cases were sequential bilateral transplantations. Prioritization was necessary in 4 (50%) patients, and in 1 patient, ECMO was used as a bridge to transplantation. The ECMO route was central in 4 (50%), peripheral venovenous in 2 (25%) and peripheral venoarterial in 2 (25%) patients. The mean length of the intensive care unit (ICU) stay was 14±7.5 days and of the hospital stay was 34.1±34.2 days. The mean ECMO duration was 9.3±6.6 days with a 50% decannulation rate. Three patients were discharged (37.5%).

CONCLUSION

Lung transplantation requires complex treatment, and ECMO has allowed extending the indications for transplantation and provided adjuvant support in the clinical management of these patients.