A Global Experience of Donation after Circulatory Death for Pediatric Lung Transplantation.

OBJECTIVE: Donation after circulatory death (DCD) lung transplantation has increased, but there is limited data in children. We sought to characterize the international experience of pediatric DCD lung transplant (LT) in comparison to donation after brain death (DBD) to address extreme donor organ shortages in children needing LT. METHODS: Using the International Society for Heart and Lung Transplantation (ISHLT) Thoracic Organ Transplant Registry, 1453 children (<18yo) LT recipients from January 2004 to June 2018 were identified: 34 (3%) were DCD and 1419 (97%) were DBD recipients. Post-transplant outcomes were compared between groups. Propensity score method was used to derive matched cohorts and were compared between groups. RESULTS: DCD and DBD recipients were of similar age, with cystic fibrosis being the most frequent indication for LT in both groups (64.5% vs. 57.5%, respectively). Kaplan-Meier analysis demonstrated similar survival between DCD and DBD cohorts, whereas propensity score-matched recipients also identified similar post-transplant survival in both groups (P=0.098). Secondary analysis found that DCD LT recipients had a longer post-transplant length of hospital stay (unmatched cohorts: 36.5d vs. 20d, p=0.022; matched cohort: 26d vs. 19d, p=0.016), and shorter time to acute cellular rejection (ACR) (unmatched cohorts: 248d vs. 560d, p=0.039; matched cohorts: 248d vs. 1650d,p=0.059). CONCLUSIONS: Due to DCD being a key contributor to the increasing number of lung transplants being performed worldwide, the results of this analysis support this organ donation approach in children requiring LT, which would increase access to donor organs. The identification of a potential shorter time to ACR needs further exploration as more DCD pediatric LTs are performed.

Distinct Non-Human Leukocyte Antigen Antibody Signatures Correlate with Endothelial Crossmatch Status in Lung and Renal Transplant Recipients.

Non-HLA antibodies against heterogeneous targets on endothelial cells have been associated with allograft injuries. The endothelial cell crossmatch (ECXM) is used in the detection of non-HLA antibodies but remains non-discriminatory for specific antibody identification. The primary objective of this study was to delineate the specific non-HLA antibody signatures associated with ECXM positivity and to determine the correlation of ECXM status and non-HLA antibody signatures on allograft health. Serum specimens from 25 lung transplant recipients (LTRs) and 13 renal transplant recipients (RTRs) were collected as part of clinical evaluation, and testing for angiotensin II receptor type 1 (AT1R) and donor-specific MHC class I chain-related gene A (MICA) antibodies and ECXM was performed. Remnant sera were tested for non-HLA antibodies using the LABScreen™ Autoantibody (LSAUT) Group 1, 2, and 3 kits (One Lambda, Inc., Los Angeles, CA, USA). In both cohorts, the concordance of AT1R and MICA together or individually with ECXM+ status was poor (<0.7), suggesting the presence of other unaccounted antibodies. Autoantibody profiling revealed three distinct clusters targeting fibrotic products, cytoskeletal proteins, and cell signaling molecules. A comparative analysis of ECXM+ and ECXM- specimens identified nine and five differentially expressed antibodies in the LTR and RTR cohorts, respectively. Employing machine learning techniques (variable importance, feature selection, ROC-AUC), we derived a five-antibody panel (TNFα, collagen V, CXCL11, GDNF, GAPDH) and a two-antibody panel (TNFα, CXCL9) that effectively discriminated between ECXM+ and ECXM- status in the LTR and RTR cohorts, respectively. Distinct antibody signatures were identified in LTR and RTR cohorts that correlated with ECXM+ status and were associated with allograft dysfunction.

Impact of Functional Status at the Time of Transplant on Short-Term Pediatric Lung Transplant Outcomes in the USA.

PURPOSE: Poor functional status is associated with pediatric lung transplant (LTx) waitlist mortality. We investigate how pre-transplant functional status affects post-LTx survival. METHODS: A retrospective analysis was performed using The United Network for Organ Sharing (UNOS) Registry data. Pediatric first-time lung transplant candidates between ages 1 and 18 years with reported Lansky Play-Performance Scores (LPPS) at the time of waitlist and/or transplant were included from 2005 and 2021. Functional status by the LPPS scores is defined as severe limitation for LPPS score 10-40, mild limitation for LPPS score 50-70, and normal activity for LPPS score 80-100. Univariate analyses, multivariable Cox regression, and Kaplan-Meier plots were used to assess the impact of functional status on 1-year post-LTx survival. RESULTS: There were 913 and 610 patients at the time of LTx listing and transplant with LPPS scores, respectively. Poor functional status as determined by the LPPS score at the time of LTx, but not at the time of waitlist, was associated with worse 1-year post-LTx outcome (p value 0.0025 vs. 0.071). Multivariable survival analysis using Cox proportional hazards regression identified that a severely limited functional status at the time of LTx was the most profound risk factor for worse 1-year post-LTx survival outcomes when compared to a normal functional status (HR 2.16; 95% CI 1.15-4.07, p value 0.017). CONCLUSIONS: Children with severely limited functional status at the time of LTx have worse 1-year post-LTx outcome. It is important to develop strategies to optimize the functional status of children for improved post-LTx outcomes.

Inhaled Nanoparticulate Systems: Composition, Manufacture and Aerosol Delivery.

An increasing growth in nanotechnology is evident from the growing number of products approved in the past decade. Nanotechnology can be used in the effective treatment of several pulmonary diseases by developing therapies that are delivered in a targeted manner to select lung regions based on the disease state. Acute or chronic pulmonary disorders can benefit from this type of therapy, including respiratory distress syndrome (RDS), chronic obstructive pulmonary disease (COPD), asthma, pulmonary infections (e.g. tuberculosis, Yersinia pestis infection, fungal infections, bacterial infections, and viral infections), lung cancer, cystic fibrosis (CF), pulmonary fibrosis, and pulmonary arterial hypertension. Modification of size and surface property renders nanoparticles to be targeted to specific sites, which can serve a vital role in innovative pulmonary drug delivery. The nanocarrier type chosen depends on the intended purpose of the formulation and intended physiological target. Liquid nanocarriers and solid-state nanocarriers can carry hydrophilic and hydrophobic drugs (e.g. small molecular weight drug molecules, large molecular weight drugs, peptide drugs, and macromolecular biological drugs), while surface modification with polymer can provide cellular targeting, controlled drug release, and/or evasion of phagocytosis by immune cells, depending on the polymer type. Polymeric nanocarriers have versatile architectures, such as linear, branched, and dendritic forms. In addition to the colloidal dispersion liquid state, the various types of nanoparticles can be formulated into the solid state, offering important unique advantages in formulation versatility and enhanced stability of the final product. This chapter describes the different types of nanocarriers, types of inhalation aerosol device platforms, liquid aerosols, respirable powders, and particle engineering design technologies for inhalation aerosols.

Pseudomonas aeruginosa Infection and Inflammation in Cystic Fibrosis: A Pilot Study With Lung Explants and a Novel Histopathology Scoring System.

PURPOSE: Pseudomonas aeruginosa is the predominant bacterial pathogen colonizing the cystic fibrosis (CF) lung. Mixed populations of nonmucoid and mucoid variants of P. aeruginosa have been isolated from the CF airway. While the association between mucoid variants and pulmonary function decline is well-established, their impact on inflammation and tissue damage in advanced CF lung disease remains unclear. METHODS: This pilot study utilized 1 non-CF and 3 CF lung explants to examine lobar distribution, inflammation, and histopathology related to nonmucoid and mucoid P. aeruginosa infection. To study tissue damage, we developed a novel lung histopathology scoring system, the first applied to human CF lung biopsies, which is comprised of five indicators: bronchiolar epithelial infiltrate, luminal inflammation, peribronchial/bronchiolar infiltrate, peribronchiolar fibrosis, and alveolar involvement. RESULTS: Mucoid P. aeruginosa variants were distributed throughout the CF lung but associated with greater concentrations of proinflammatory cytokines, IL-1ß, TNF-α, IL-6, IL-8, and IFN-γ, and one anti-inflammatory cytokine, IL-10, compared to nonmucoid variants. CF lung explants exhibited higher histopathology scores compared to a non-CF lung control. In mixed-variant infection, nonmucoid constituents associated with increased bronchiolar epithelial infiltration, one indicator of histopathology. CONCLUSION: This pilot study suggests ongoing interplay between host and bacterial elements in late-stage CF pulmonary disease. Mucoid P. aeruginosa infection correlates with inflammation regardless of lung lobe, whereas nonmucoid P. aeruginosa is associated with increased inflammatory cell infiltration. The development of a novel lung histopathology scoring system lays the groundwork for future large-cohort investigations.

Outcomes of Concomitant Cardiac Surgical Procedures Performed During Pediatric Lung Transplantation in the United States.

Data on concomitant cardiac surgery (CCS) performed during pediatric lung transplantation (LTx) is limited. Therefore, we conducted a multi-institutional analysis to identify the incidence and outcomes of CCS in pediatric (< 18 years) LTx recipients by merging data (2004-2023) from the United Network for Organ Sharing (UNOS) and Pediatric Health Information System (PHIS) databases. Of the total of 596 pediatric LTx recipients, 87 (15%) underwent CCS. The majority of these cardiac surgeries were atrial septal defect (ASD) closure (90%) followed by aortic arch/descending aortic repair (3%), atrial repair (3%), ventricular septal defect closure (2%), patent ductus arteriosus ligation (2%), and tricuspid valve repair (2%). The median age at LTx was 3 years (IQR: 0-12). Pulmonary hypertension (PHT) was the predominant indication for LTx (54%). Survival to discharge was 94% and 5-years survival was 64%. Our findings indicate CCS in children undergoing LTx has acceptable outcomes.

xTrends in racial and ethnic disparities in pediatric lung transplantation in the United States.

BACKGROUND: Racial and ethnic disparities in pediatric lung transplantation (LTx) related to the shifting cystic fibrosis (CF) population receiving highly effective modulator therapy (HEMT) has not been well investigated. METHODS: The UNOS Registry was queried for patients age 1-25 years undergoing bilateral LTx between 1 January 2012 and 31 December 2021. Race and ethnicity were classified as non-Hispanic White, non-Hispanic Black, Hispanic, or none of the above. The primary outcome was posttransplant mortality. Trends in the association between race/ethnicity and mortality were examined using transplant year as a continuous variable and stratifying year based on introduction of HEMT (triple combination therapy) in November 2019. RESULTS: In the study sample (N = 941), 7% of patients were non-Hispanic Black, 15% were Hispanic, and 2% were some other racial or ethnic group. One hundred (11%) received LTx after approval of triple combination therapy, and 407 (43%) died during follow-up. We identified a statistically significant disparity in mortality hazard (hazard ratio: 1.91; 95% confidence interval: 1.31, 2.80) in non-Hispanic Black compared to non-Hispanic White patients in the pre-triple combination therapy era. CONCLUSIONS: We found higher mortality hazard among non-Hispanic Black compared to non-Hispanic White children undergoing LTx in the United States. Further monitoring of LTx outcomes to identify and address disparities is needed in the current era of triple combination therapy for CF.

ECMO Bridge to Lung Transplant in Children with Idiopathic Pulmonary Arterial Hypertension.

Idiopathic pulmonary arterial hypertension (IPAH) represents an important clinical indication for lung transplant (LTx) in children. Recent trends show fewer children with IPAH are undergoing LTx nowadays compared to previous time periods, including those with most severe form of the disease. Using the UNOS Registry, we investigated if ECMO at the time of transplant impacts post-transplant survival in children with IPAH. A total of 74 LTx recipients while on ECMO at the time of transplant were identified (IPAH: N = 12). Children with IPAH who underwent LTx while on ECMO had shown comparable survival rates to those who were on ECMO for other conditions. This analysis provides encouraging results, supporting the potential expansion of LTx for this patient population. Given the low number of children undergoing LTx, we think there should be a consensus document to provide better guidance for referring and selecting the high-risk pediatric population with IPAH on ECMO for lung transplant.

Flexible bronchoscopy in pediatric lung transplantation.

Pediatric lung transplantation represents a treatment option for children with advanced lung disease or pulmonary vascular disorders who are deemed an appropriate candidate. Pediatric flexible bronchoscopy is an important and evolving field that is highly relevant in the pediatric lung transplant population. It is thus important to advance our knowledge to better understand how care for children after lung transplant can be maximally optimized using pediatric bronchoscopy. Our goals are to continually improve procedural skills when performing bronchoscopy and to decrease the complication rate while acquiring adequate samples for diagnostic evaluation. Attainment of these goals is critical since allograft assessment by bronchoscopic biopsy is required for histological diagnosis of acute cellular rejection and is an important contributor to establishing chronic lung allograft dysfunction, a common complication after lung transplant. Flexible bronchoscopy with bronchoalveolar lavage and transbronchial lung biopsy plays a key role in lung transplant graft assessment. In this article, we discuss the application of bronchoscopy in pediatric lung transplant evaluation including historical approaches, our experience, and future directions not only in bronchoscopy but also in the evolving pediatric lung transplantation field. Pediatric flexible bronchoscopy has become a vital modality for diagnosing lung transplant complications in children as well as assessing therapeutic responses. Herein, we review the value of flexible bronchoscopy in the management of children after lung transplant and discuss the application of novel techniques to improve care for this complex pediatric patient population and we provide a brief update about new diagnostic techniques applied in the growing lung transplantation field.

Magnetic Resonance Elastography and Computational Modeling Identify Heterogeneous Lung Biomechanical Properties during Cystic Fibrosis.

The lung is a dynamic mechanical organ and several pulmonary disorders are characterized by heterogeneous changes in the lung's local mechanical properties (i.e. stiffness). These alterations lead to abnormal lung tissue deformation (i.e. strain) which have been shown to promote disease progression. Although heterogenous mechanical properties may be important biomarkers of disease, there is currently no non-invasive way to measure these properties for clinical diagnostic purposes. In this study, we use a magnetic resonance elastography technique to measure heterogenous distributions of the lung's shear stiffness in healthy adults and in people with Cystic Fibrosis. Additionally, computational finite element models which directly incorporate the measured heterogenous mechanical properties were developed to assess the effects on lung tissue deformation. Results indicate that consolidated lung regions in people with Cystic Fibrosis exhibited increased shear stiffness and reduced spatial heterogeneity compared to surrounding non-consolidated regions. Accounting for heterogenous lung stiffness in healthy adults did not change the globally averaged strain magnitude obtained in computational models. However, computational models that used heterogenous stiffness measurements predicted significantly more variability in local strain and higher spatial strain gradients. Finally, computational models predicted lower strain variability and spatial strain gradients in consolidated lung regions compared to non-consolidated regions. These results indicate that spatial variability in shear stiffness alters local strain and strain gradient magnitudes in people with Cystic Fibrosis. This imaged-based modeling technique therefore represents a clinically viable way to non-invasively assess lung mechanics during both health and disease.

Preventive service utilization among adults with cystic fibrosis covered by private insurance is comparable to the general population.

BACKGROUND: As the life expectancy of the cystic fibrosis (CF) population is lengthening with modulator therapies, diligent age-appropriate screening and preventive care are increasingly vital for long-term health and wellbeing. METHODS: We performed a retrospective analysis comparing rates of receiving age- and sex-appropriate preventive services by commercially insured adult people with CF (PwCF) and adults without CF from the general population (GP) via the Truven Health MarketScan database (2012-2018). RESULTS: We captured 25,369 adults with CF and 488,534 adults from the GP in the United States. Comparing these groups, we found that 43% versus 39% received an annual preventive visit, 28% versus 28% were screened for chlamydia, 38% versus 37% received pap smears every 3 years (21-29-year-old females), 33% versus 31% received pap smears every 5 years (30-64-year-old females), 55% versus 44% received mammograms, 23% versus 21% received colonoscopies, and 21% versus 20% received dyslipidemia screening (all screening rates expressed per 100 person-years). In age-stratified analysis, 18-27-year-old PwCF had a lower rate of annual preventive visits compared to adults in the same age group of the GP (27% versus 42%). CONCLUSIONS: We discovered a comparable-to-superior rate of preventive service utilization in adults with CF relative to the GP, except in young adulthood from 18-27 years. Our findings establish the importance of meeting the primary care needs of adults with CF and call for development of strategies to improve preventive service delivery to young adults.

Lung Transplantation for Pulmonary Vascular Disease in Children: A United Network for Organ Sharing Analysis.

Pulmonary vascular disease (PVD) represents an important clinical indication for lung transplant (LTx) in infants, children, and adolescents. There is limited information on LTx outcomes in these patients. We explored LTx volumes and post-LTx survival in children with PVD compared to other diagnoses. The UNOS Registry was queried from 1989 to 2020 to identify first-time pediatric LTx recipients (< 18 yo). PVD was categorized as idiopathic pulmonary arterial hypertension (IPAH) and non-idiopathic arterial hypertension (non-IPAH) and compared to all other patients as other diagnoses. Univariate and multivariate regression models were performed. 984 pediatric LTx patients (593 before 2010 and 391 during/after 2010) were identified, of which 145 (14.7%) had PVD. There has been no significant change in annual rate of all LTxs over comparative eras. However, there has been a decrease in rate of LTxs for PVD patients. Children with PVD had similar survival to other LTx groups in the early era (p = 0.2) and the latter era (p = 0.9). Univariate Cox models, showed that LTx in patients with PVD was associated with a significantly less risk of mortality for children aged 6-11 years compared to younger and older cohorts (HR = 0.4 [0.17-0.98]; p = 0.045), whereas multivariate analysis showed a trend toward higher mortality in 11-17-year-olds (HR = 1.54 [0.97-2.45]; p = 0.06). For PVD patients, oxygen supplementation and ventilator support at LTx were associated with worse post-transplant survival (p = 0.029 and p = 0.01). There has been a decrease in LTx volume for pediatric patients with PVD in the modern era. Post-LTx outcomes for children with PVD are similar to those of other diagnoses in both eras, with children aged 6-11 years having the best survival. Given these findings, LTx should be considered for this patient population.

Improved donor lung size matching by estimation of lung volumes based on chest X-ray measurements.

RATIONALE: Organ size matching is an important determinant of successful allocation and outcomes in lung transplantation. While computed tomography (CT) is the gold standard, it is rarely used in an organ-donor context, and chest X-ray (CXR) may offer a practical and accurate solution in estimating lung volumes for donor and recipient size matching. We compared CXR lung measurements to CT-measured lung volumes and traditional estimates of lung volume in the same subjects. METHODS: Our retrospective study analyzed clinically obtained CXR and CT lung images of 250 subjects without evidence of lung disease (mean age 9.9 ± 7.8 years; 129 M/121F). From CT, each lung was semi-automatically segmented and total lung volumes were quantified. From anterior-posterior CXR view, each lung was manually segmented and areas were measured. Lung lengths from the apices to the mid-basal regions of each lung were measured from CXR. Quantified CT lung volumes were compared to the corresponding CXR lung lengths, CXR lung areas, height, weight, and predicted total lung capacity (pTLC). RESULTS: There are strong and significant correlations between CT volumes and CXR lung areas in the right lung (R2 = .89, p < .0001), left lung (R2 = .87, p < .0001), and combined lungs (R2 = .89, p < .0001). Similar correlations were seen between CT volumes and CXR measured lung lengths in the right lung (R2 = .79, p < .0001) and left lung (R2 = .81, p < .0001). This correlation between anatomical lung volume (CT) and CXR was stronger than lung-volume correlation to height (R2 = .66, p < .0001), weight (R2 = .43, p < .0001), or pTLC (R2 = .66, p < .0001). CONCLUSION: CXR measures correlate much more strongly with true lung volumes than height, weight, or pTLC. The ability to obtain efficient and more accurate lung volume via CXR has the potential to change our current listing practices of using height as a surrogate for lung size, with a case example provided.

Lung Transplantation for Pulmonary Vascular Disease in Children: A United Network for Organ Sharing Analysis.

Background: Pulmonary vascular disease (PVD) represents an important clinical indication for lung transplant (LTx) in infants, children, and adolescents. There is limited information on LTx outcomes in these patients. We explored LTx volumes and post-LTx survival in children with PVD compared to other diagnoses. Methods: The UNOS Registry was queried from 1989-2020 to identify first-time pediatric LTx recipients (<18 yo). PVD was categorized as idiopathic pulmonary arterial hypertension (IPAH) and non-idiopathic arterial hypertension (non-IPAH) and compared to all other patients as other diagnoses. Univariate and multivariate regression models were performed. Results: 984 pediatric LTx patients (593 before 2010 and 391 during/after 2010) were identified, of which 145 (14.7%) had PVD. There has been no significant change in annual rate of all LTxs over comparative eras. However, there has been a decrease in rate of LTxs for PVD patients. Children with PVD had similar survival to other LTx groups in the early era (p=0.2) and the latter era (p=0.9). Univariate Cox models, showed that LTx in patients with PVD was associated with a significantly less risk of mortality for children aged 6-11 years compared to younger and older cohorts (HR=0.4 [0.17-0.98];p=0.045), whereas multivariate analysis showed a trend towards higher mortality in 11-17-year-olds (HR=1.54 [0.97-2.45];p=0.06). For PVD patients, oxygen supplementation and ventilator support at LTx were associated with worse post-transplant survival (p=0.029 and p=0.01). Conclusions: There has been a decrease in LTx volume for pediatric patients with PVD in the modern era. Post-LTx outcomes for children with PVD are similar to those of other diagnoses in both eras, with children aged 6-11 years having the best survival. Given these findings, LTx should be considered for this patient population.