Airway Complications Following Lung Transplantation

Machine learning model predicts airway stenosis requiring clinical intervention in patients after lung transplantation: a retrospective case-controlled study

BACKGROUND

Patients with airway stenosis (AS) are associated with considerable morbidity and mortality after lung transplantation (LTx). This study aims to develop and validate machine learning (ML) models to predict AS requiring clinical intervention in patients after LTx.

METHODS

Patients who underwent LTx between January 2017 and December 2019 were reviewed. The conventional logistic regression (LR) model was fitted by the independent risk factors which were determined by multivariate LR. The optimal ML model was determined based on 7 feature selection methods and 8 ML algorithms. Model performance was assessed by the area under the curve (AUC) and brier score, which were internally validated by the bootstrap method.

RESULTS

A total of 381 LTx patients were included, and 40 (10.5%) patients developed AS. Multivariate analysis indicated that male, pulmonary arterial hypertension, and postoperative 6-min walking test were significantly associated with AS (all P < 0.001). The conventional LR model showed performance with an AUC of 0.689 and brier score of 0.091. In total, 56 ML models were developed and the optimal ML model was the model fitted using a random forest algorithm with a determination coefficient feature selection method. The optimal model exhibited the highest AUC and brier score values of 0.760 (95% confidence interval [CI], 0.666-0.864) and 0.085 (95% CI, 0.058-0.117) among all ML models, which was superior to the conventional LR model.

CONCLUSIONS

The optimal ML model, which was developed by clinical characteristics, allows for the satisfactory prediction of AS in patients after LTx.

[Airway complications after lung transplantation]

Lung transplantations have been regularly performed in the Russian Federation since 2010. Therefore, the number of lung transplant recipients, as well as the number of patients with airway complications following lung transplantation has been increasing. Treatment of these patients takes place not only in transplantation centers, but also in other hospitals. This review is devoted to risk factors, clinical manifestations, treatment and prevention of airway complications after lung transplantation. We analyzed literature data over the last 15 years. It was confirmed that bronchoscopy is a «gold standard» for diagnosis of airway complications while bronchoscopic interventions are preferred for treatment. Balloon and rigid bronchodilation and endoscopic airway stenting are the most effective interventions. Silicone stents are the most optimal. Antimicrobial prophylaxis and timely use of antiproliferative immunosuppressive drugs are important factors in prevention and treatment of airway complications after lung transplantation.

Early Sirolimus-Based Immunosuppression is Safe for Lung Transplantation Patients: Retrospective, Single Arm, Exploratory Study

Background

Sirolimus, a mechanistic target of sirolimus inhibitor, is an immunosuppression medication for patients undergoing heart and abdominal transplantation. Sirolimus-based immunosuppression administered de novo post-lung transplantation is associated with bronchial anastomosis healing-related complications. We hypothesized that sirolimus administration within the first postoperative month in selected lung transplant recipients is safe and may be associated with favorable short-term and long-term outcomes due to its anti-proliferative properties and minimal adverse side effects.

Material/Methods

Thirteen patients (13.3%; mean age, 46.8±11.9 years) received early sirolimus-based immunosuppression along with cyclosporine and prednisone; 10 patients received single-lung transplantation, 3 received double-lung transplantation, and all received induction immunosuppressants. Patients received early sirolimus-based immunosuppression after an uncomplicated postoperative course and detailed bronchoscopic assessment.

Results

Sirolimus was begun on a mean of 20.6±4.7 days postoperatively (range, 14–32 days). The in-hospital and 30-day mortality rate was 0%. At long-term follow-up, 5 patients died (due to bacterial infection in 4 patients and pneumocystis jiroveci pneumonia in 1 patient). The mean overall survival was 4.4±2.53 (range, 0.8–10.0) years, 1-year survival was 92%, and 5-year survival was 62%. In 4 patients (30.8%), sirolimus was stopped due to infection in 3 patients and re-transplantation in 1 patient. Only one of the 13 patients developed bronchiolitis obliterans syndrome. In patients still taking sirolimus, renal function, systolic blood pressure, and lipid profile were within normal ranges; however, these patients required statin therapy.

Conclusions

In selected lung transplant recipients, early sirolimus-based immunosuppression is safe and associated with beneficial short-term and long-term outcomes.

Transplanted fibroblasts proliferate in host bronchial tissue and enhance bronchial anastomotic healing in a rodent model

INTRODUCTION

Healing of airway anastomoses after preoperative irradiation can be a significant clinical problem. The augmentation of bronchial anastomoses with a fibroblast-seeded human acellular dermis (hAD) was shown to be beneficial, although the underlying mechanism remained unclear. Therefore, in this study we investigated the fate of the fibroblasts transplanted to the scaffold covering the anastomosis.

MATERIAL AND METHODS

32 Fisher rats underwent surgical anastomosis of the left main bronchus. In a 2 × 2 factorial design, they were randomized to receive preoperative irradiation of 20 Gy and augmentation of the anastomosis with a fibroblast-seeded transplant. Fibroblasts from subcutaneous fat of Fischer-344 rat were transduced retrovirally with tdTomato for cell tracking. After 7 and 14 days, animals were sacrificed and cell concentration of transplanted and nontransplanted fibroblasts in the hAD as well as in the bronchial tissue was measured using RT-PCR.

RESULTS

Migration of transplanted fibroblasts from dermis to bronchus were demonstrated in both groups, irradiated and nonirradiated. In the irradiated groups, there was a cell count of 7 × 104 ± 1 × 104 tomato+-fibroblasts in the bronchial tissue at day 7, rising to 1 × 105 ± 1 × 104 on day 14 (p <0.0001). Tomato+-cell concentration in hAD increased from 6 × 103 ± 1 × 103 at day 7 to 6 × 104 ± 1 × 104 at day 14 (p <0.0001). In the nonirradiated groups, tomato+-cell concentration in bronchus was 4 × 103 ± 1 × 103 on day 7 and 4 × 103 ± 1 × 103 at day 14. In the hAD tomato+ cell concentration rising from 1 × 104 ± 1 × 103 at day 7 to 2 × 104 ± 3 × 103 cells at day 14 (p = 0.0028).

CONCLUSIONS

Transplanted fibroblasts in the irradiated groups proliferate and migrate into the irradiated host bronchial tissue, but not in the nonirradiated groups.

Airway anastomosis for lung transplantation

Lung transplantation (LT) is the only viable option for a selected group of patients with end stage pulmonary diseases. During the recent years satisfactory results in terms of long-term survival and quality of life have been achieved with improvements in surgical technique, immunosuppression and perioperative management. Since the beginning, the airway anastomosis has been considered crucial and significant efforts have been made to understand the healing process. A number of experimental studies allowed improving the surgical technique by modifying the technique of suturing, the anastomotic protection and type and dose of immunosuppression, reducing the risk of airway complications. Furthermore, a huge progress has been made in the management of such complications. Early diagnosis of bronchial complications and their prompt and correct management are crucial to achieve long-term survival.

Airway complications after lung transplantation

Airway complications after lung transplantation present a formidable challenge to the lung transplant team, ranging from mere unusual images to fatal events. The exact incidence of complications is wide-ranging depending on the type of event, and there is still evolution of a universal characterization of the airway findings. Management is also wide-ranging. Simple observation or simple balloon bronchoplasty is sufficient in many cases, but vigilance following more severe necrosis is required for late development of both anastomotic and nonanastomotic airway strictures. Furthermore, the impact of coexisting infection, rejection, and medical disease associated with high-level immunosuppression further complicates care.

MECHANICAL VENTILATION FOR THE LUNG TRANSPLANT RECIPIENT

Mechanical ventilation (MV) is an important aspect in the intraoperative and early postoperative management of lung transplant (LTx)-recipients. There are no randomized-controlled trials of LTx-recipient MV strategies; however there are LTx center experiences and international survey studies reported. The main early complication of LTx is primary graft dysfunction (PGD), which is similar to the adult respiratory distress syndrome (ARDS). We aim to summarize information pertinent to LTx-MV, as well as PGD, ARDS, and intraoperative MV and to synthesize these available data into recommendations. Based on the available evidence, we recommend lung-protective MV with low-tidal-volumes (≤6 mL/kg predicted body weight [PBW]) and positive end-expiratory pressure for the LTx-recipient. In our opinion, the MV strategy should be based on donor characteristics (donor PBW as a parameter of actual allograft size), rather than based on recipient characteristics; however this donor-characteristics-based protective MV is based on indirect evidence and requires validation in prospective clinical studies.

Practical guidelines: lung transplantation in patients with cystic fibrosis

There are no European recommendations on issues specifically related to lung transplantation (LTX) in cystic fibrosis (CF). The main goal of this paper is to provide CF care team members with clinically relevant CF-specific information on all aspects of LTX, highlighting areas of consensus and controversy throughout Europe. Bilateral lung transplantation has been shown to be an important therapeutic option for end-stage CF pulmonary disease. Transplant function and patient survival after transplantation are better than in most other indications for this procedure. Attention though has to be paid to pretransplant morbidity, time for referral, evaluation, indication, and contraindication in children and in adults. This review makes extensive use of specific evidence in the field of lung transplantation in CF patients and addresses all issues of practical importance. The requirements of pre-, peri-, and postoperative management are discussed in detail including bridging to transplant and postoperative complications, immune suppression, chronic allograft dysfunction, infection, and malignancies being the most important. Among the contributors to this guiding information are 19 members of the ECORN-CF project and other experts. The document is endorsed by the European Cystic Fibrosis Society and sponsored by the Christiane Herzog Foundation.

A comparative analysis of bronchial stricture after lung transplantation in recipients with and without early acute rejection

BACKGROUND

Risk factors and outcomes of bronchial stricture after lung transplantation are not well defined. An association between acute rejection and development of stricture has been suggested in small case series. We evaluated this relationship using a large national registry.

METHODS

All lung transplantations between April 1994 and December 2008 per the United Network for Organ Sharing (UNOS) database were analyzed. Generalized linear models were used to determine the association between early rejection and development of stricture after adjusting for potential confounders. The association of stricture with postoperative lung function and overall survival was also evaluated.

RESULTS

Nine thousand three hundred thirty-five patients were included for analysis. The incidence of stricture was 11.5% (1,077/9,335), with no significant change in incidence during the study period (P=0.13). Early rejection was associated with a significantly greater incidence of stricture (adjusted odds ratio [AOR], 1.40; 95% confidence interval [CI], 1.22-1.61; p<0.0001). Male sex, restrictive lung disease, and pretransplantation requirement for hospitalization were also associated with stricture. Those who experienced stricture had a lower postoperative peak percent predicted forced expiratory volume at 1 second (FEV1) (median 74% versus 86% for bilateral transplants only; p<0.0001), shorter unadjusted survival (median 6.09 versus 6.82 years; p<0.001) and increased risk of death after adjusting for potential confounders (adjusted hazard ratio 1.13; 95% CI, 1.03-1.23; p=0.007).

CONCLUSIONS

Early rejection is associated with an increased incidence of stricture. Recipients with stricture demonstrate worse postoperative lung function and survival. Prospective studies may be warranted to further assess causality and the potential for coordinated rejection and stricture surveillance strategies to improve postoperative outcomes.

Postoperative complications in the intensive care unit following lung transplantation in adults: results in University Hospital Reina Sofia

The postoperative period following lung transplantation remains critical because of several complications. Infection, primary graft failure, acute rejection, and surgical complications are risk factors for mortality and morbidity. The recognition and early treatment of these complications is important to optimize outcomes. This article provides an overview of postoperative complications observed in our center during the last year. We were particularly interested in the influence of variables, such as inotrope usage and Acute Physiology and Chronic Health Evaluation (APACHE II) score, a well-known, and validated mortality prediction model for general intensive care unit (ICU) patients only infrequently reported in the transplantation literature. High APACHE II scores were significantly associated with prolonged mechanical ventilation (P = 0.041) and a tracheostomy requirement (P = .035). The factors significantly associated with an early postoperative death were older donor age (P = .005), prolonged donor ICU period (P = .004), need for cardiopulmonary bypass (CB; P = .005), and high inotrope requirements in the ICU (P = .034). CB data were biased because we selected the worst case patients. Donor age and high inotrope requirements in the ICU have been reported previously to be prognostic factors for poor graft function. We believe that control of these variables may improve outcomes.

Tracheobronchial transplantation with a stem-cell-seeded bioartificial nanocomposite: a proof-of-concept study

BACKGROUND

Tracheal tumours can be surgically resected but most are an inoperable size at the time of diagnosis; therefore, new therapeutic options are needed. We report the clinical transplantation of the tracheobronchial airway with a stem-cell-seeded bioartificial nanocomposite.

METHODS

A 36-year-old male patient, previously treated with debulking surgery and radiation therapy, presented with recurrent primary cancer of the distal trachea and main bronchi. After complete tumour resection, the airway was replaced with a tailored bioartificial nanocomposite previously seeded with autologous bone-marrow mononuclear cells via a bioreactor for 36 h. Postoperative granulocyte colony-stimulating factor filgrastim (10 μg/kg) and epoetin beta (40,000 UI) were given over 14 days. We undertook flow cytometry, scanning electron microscopy, confocal microscopy epigenetics, multiplex, miRNA, and gene expression analyses.

FINDINGS

We noted an extracellular matrix-like coating and proliferating cells including a CD105+ subpopulation in the scaffold after the reseeding and bioreactor process. There were no major complications, and the patient was asymptomatic and tumour free 5 months after transplantation. The bioartificial nanocomposite has patent anastomoses, lined with a vascularised neomucosa, and was partly covered by nearly healthy epithelium. Postoperatively, we detected a mobilisation of peripheral cells displaying increased mesenchymal stromal cell phenotype, and upregulation of epoetin receptors, antiapoptotic genes, and miR-34 and miR-449 biomarkers. These findings, together with increased levels of regenerative-associated plasma factors, strongly suggest stem-cell homing and cell-mediated wound repair, extracellular matrix remodelling, and neovascularisation of the graft.

INTERPRETATION

Tailor-made bioartificial scaffolds can be used to replace complex airway defects. The bioreactor reseeding process and pharmacological-induced site-specific and graft-specific regeneration and tissue protection are key factors for successful clinical outcome.

FUNDING

European Commission, Knut and Alice Wallenberg Foundation, Swedish Research Council, StratRegen, Vinnova Foundation, Radiumhemmet, Clinigene EU Network of Excellence, Swedish Cancer Society, Centre for Biosciences (The Live Cell imaging Unit), and UCL Business.