Acute worsening of native lung fibrosis after single lung transplantation for pulmonary fibrosis: two case reports

Background In patients receiving single lung transplantation for idiopathic pulmonary fibrosis, worsening of fibrosis of the native lung is usually progressive over time, with no significant effects on gas exchange. Case presentation Here, we describe the cases of two Caucasian male recipients of single lung transplants for idiopathic pulmonary fibrosis, 65 and 62 years of age, who exhibited acute worsening of lung fibrosis after an episode of serious viral infection (cytomegalovirus primo-infection in one case and COVID-19 in the other). In both cases, along with opacification of the native lung over several days, the patients presented acute respiratory failure that required the use of high-flow nasal oxygen therapy. Eventually, hypoxemic respiratory failure resolved, but with rapid progression of fibrosis of the native lung. Conclusion We conclude that acute worsening of fibrosis on the native lung secondary to a severe viral infection should be added to the list of potential complications developing on the native lung after single lung transplantation for idiopathic pulmonary fibrosis.

The Association of Oxygenation, Carbon Dioxide Removal, and Mechanical Ventilation Practices on Survival During Venoarterial Extracorporeal Membrane Oxygenation

Introduction: Oxygenation and carbon dioxide removal during venoarterial extracorporeal membrane oxygenation (VA ECMO) depend on a complex interplay of ECMO blood and gas flows, native lung and cardiac function as well as the mechanical ventilation strategy applied.Objective: To determine the association of oxygenation, carbon dioxide removal, and mechanical ventilation practices with in-hospital mortality in patients who received VA ECMO.Methods: Single center, retrospective cohort study. All consecutive patients who received VA ECMO in a tertiary ECMO referral center over a 5-year period were included. Data on demographics, ECMO and ventilator support details, and blood gas parameters for the duration of ECMO were collected. A multivariable logistic time-series regression model with in-hospital mortality as the primary outcome variable was used to analyse the data with significant factors at the univariate level entered into the multivariable regression model.Results: Overall, 52 patients underwent VA ECMO: 26/52 (50%) survived to hospital discharge. The median PaO2 for the duration of ECMO support was 146 mmHg [IQR 131–188] and PaCO2 was 37.2 mmHg [IQR 35.3, 39.9]. Patients who survived to hospital discharge had a significantly lower median PaO2 (117 [98, 140] vs. 154 [105, 212] mmHg, P = 0.04) and higher median PaCO2 (38.3 [36.1, 41.1] vs. 36.3 [34.5, 37.8] mmHg, p = 0.03). Survivors also had significantly lower median VA ECMO blood flow rate (EBFR, 3.6 [3.3, 4.2] vs. 4.3 [3.8, 5.2] L/min, p = < 0.001) and greater measured minute ventilation (7.04 [5.63, 8.35] vs. 5.32 [4.43, 6.83] L/min, p = 0.01). EBFR, PaO2, PaCO2, and minute ventilation, however, were not independently associated with death in a multivariable analysis.Conclusion: This exploratory analysis in a small group of VA ECMO supported patients demonstrated that hyperoxemia was common during VA ECMO but was not independently associated with increased mortality. Survivors also received lower EBFR and had greater minute ventilation, but this was also not independently associated with survival. These findings highlight that interactions between EBFR, PaO2, and native lung ventilation may be more relevant than their individual association with survival. Further research is indicated to determine the optimal ECMO and ventilator settings on outcomes in VA ECMO.

Successful use of veno-venous extracorporeal membrane oxygenation for acute chest syndrome in a child with sickle cell disease and SARS-CoV-2

Children with sickle cell disease (SCD) are at increased risk for severe illness due to severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2). We describe the successful native lung recovery of a child with SCD referred for lung transplant (LTx) evaluation who was on prolonged veno-venous extracorporeal membrane oxygenation (VV-ECMO). He initially presented with acute chest syndrome complicated by SARS-CoV-2 infection that ultimately required dual-lumen, single bicaval VV-ECMO cannulation for respiratory support. Despite increased risk of hemolysis and thrombosis from SCD and SARS-CoV-2 infection, he was successfully supported on VV-ECMO for 71 days without complications leading to native lung recovery with meticulous management of his SCD therapy. This report provides new insight on our approach to VV-ECMO support in a child with SCD and SARS-CoV-2 infection. With a successful outcome, the patient has returned home but still on mechanical ventilation with LTx still an option if he is not eventually liberated from invasive respiratory support.

Benign Metastasizing Leiomyoma in the Lung Presenting in a Phyllodes-Like Pattern Mimicking a Biphasic Tumor: A Case Report

Primary biphasic tumors of the lung are rare. Lung lesions with a biphasic pattern are far more commonly primary or metastatic soft tissue tumors with entrapped native respiratory epithelium, giving the false impression of a biphasic tumor. We report a case of bilateral benign metastasizing leiomyomas in a 69-year-old female where the tumor cells diffusely entrapped native respiratory glands in a phyllodes-like pattern. The radiographic characteristics and histologic appearance were not immediately diagnostic and covered a wide differential. Reaching the final diagnosis required the use of immunohistochemical studies as well as correlation with the patient's history and radiographic findings. To the best of our knowledge, this is the first report of pulmonary benign metastasizing leiomyoma presenting in a phyllodes-like pattern. This case illustrates the importance of considering entrapment of native lung epithelium in the differential diagnosis of biphasic-appearing lung tumors.

Bioengineering Progress in Lung Assist Devices

Artificial lung technology is advancing at a startling rate raising hopes that it would better serve the needs of those requiring respiratory support. Whether to assist the healing of an injured lung, support patients to lung transplantation, or to entirely replace native lung function, safe and effective artificial lungs are sought. After 200 years of bioengineering progress, artificial lungs are closer than ever before to meet this demand which has risen exponentially due to the COVID-19 crisis. In this review, the critical advances in the historical development of artificial lungs are detailed. The current state of affairs regarding extracorporeal membrane oxygenation, intravascular lung assists, pump-less extracorporeal lung assists, total artificial lungs, and microfluidic oxygenators are outlined.

The influence of the native lung on early outcomes and survival after single lung transplantation

Objective To determine whether problems arising in the native lung may influence the short-term outcomes and survival after single lung transplantation (SLT), and therefore should be taken into consideration when selecting the transplant procedure. Patients and methods Retrospective review of 258 lung transplants performed between June 2012 and June 2019. Among them, 161 SLT were selected for the analysis. Complications in the native lung were recorded and distributed into two groups: early and late complications (within 30 days or after 30 days post-transplant). Donor and recipient preoperative factors, 30-day mortality and survival were analysed and compared between groups by univariable and multivariable analyses, and adjusting for transplant indication. Results There were 161 patients (126M/35F; 57±7 years) transplanted for emphysema (COPD) (n = 72), pulmonary fibrosis (IPF) (n = 77), or other indications (n = 12). Forty-nine patients (30%) presented complications in the native lung. Thirty-day mortality did not differ between patients with or without early complications (6% vs. 12% respectively; p = 0.56). Twelve patients died due to a native lung complication (7.4% of patients; 24% of all deaths). Survival (1,3,5 years) without vs. with late complications: COPD (89%, 86%, 80% vs. 86%, 71%, 51%; p = 0.04); IPF (83%, 77%, 72% vs. 93%, 68%, 58%; p = 0.65). Among 30-day survivors: COPD (94%, 91%, 84% vs. 86%, 71%, 51%; p = 0.01); IPF (93%, 86%, 81% vs. 93%, 68%, 58%; p = 0.19). Native lung complications were associated to longer ICU stay (10±17 vs. 33±96 days; p<0.001), longer postoperative intubation (41±85 vs. 99±318 hours; p = 0.006), and longer hospital stay (30±24 vs. 45±34 days; p = 0.03). The presence of late native lung problems predicted survival in COPD patients (OR: 2.55; p = 0.07). Conclusion The native lung is a source of morbidity in the short-term and mortality in the long-term after lung transplantation. This should be taken into consideration when choosing the transplant procedure, especially in COPD patients.

Physiological Basis of Extracorporeal Membrane Oxygenation and Extracorporeal Carbon Dioxide Removal in Respiratory Failure

Extracorporeal life support (ECLS) for severe respiratory failure has seen an exponential growth in recent years. Extracorporeal membrane oxygenation (ECMO) and extracorporeal CO2 removal (ECCO2R) represent two modalities that can provide full or partial support of the native lung function, when mechanical ventilation is either unable to achieve sufficient gas exchange to meet metabolic demands, or when its intensity is considered injurious. While the use of ECMO has defined indications in clinical practice, ECCO2R remains a promising technique, whose safety and efficacy are still being investigated. Understanding the physiological principles of gas exchange during respiratory ECLS and the interactions with native gas exchange and haemodynamics are essential for the safe applications of these techniques in clinical practice. In this review, we will present the physiological basis of gas exchange in ECMO and ECCO2R, and the implications of their interaction with native lung function. We will also discuss the rationale for their use in clinical practice, their current advances, and future directions.